This document evaluates vehicle performance through three tasks:
1) It calculates the gear ratios, maximum gradeability of 22.5% in 1st gear and 5.5% in top gear, and determines the road speed changes from 3rd to 4th gear.
2) It analyzes a graph showing maximum road speed of 115 km/h and maximum gradeability of 30% in 1st gear.
3) It discusses power-to-weight ratio, number of gears, range changes, vehicle body aerodynamics, and trailer design impacts on heavy goods vehicles.
The team designed a robot to lift and transport cubes in zone 4. It must lift 3 cubes (207 grams) at once and travel between zones 3 and 4 within 1 minute while reaching a goal height of 12 inches. It must also be able to push the largest block. The key challenges are stability with weight on the front and ensuring blocks don't fall off the table. Risks include turning the dustpan without a motor and pushing blocks into an area needed for travel. Analysis showed gears and a planetary motor could lift the required weights efficiently.
The document describes a project to optimize car performance through interpolation of design values. It provides vehicle specifications for a BMW 740li, including dimensions, engine specs, and transmission ratios. Formulas are given for calculating forces, velocity, acceleration, resistance and other parameters. Linear interpolation, Newton's interpolating polynomial, and spline methods are used to predict unknown performance values and optimize design parameters like weight and frontal area. The goal is to improve acceleration and fuel efficiency through analysis and design changes.
The document analyzes a quarter-car suspension system using equations of motion, block diagrams, and Simulink modeling. It derives the equation of motion from a free body diagram. Natural frequency and damping coefficients are calculated using the given spring and damping constants. A block diagram models the system and is implemented in Simulink. Simulink plots show the displacement, velocity, and forces over time, validating the dynamic behavior of the suspension system.
This document provides solutions to problems involving belt drives. It first solves for the tensions and power transmission in a belt drive system connecting two pulleys of different diameters, one running at 200 rpm. Taking into account centrifugal tension, friction, and a maximum tension of 2 kN, it finds the transmitted power is 13.588 kW. It also calculates the efficiencies lost to friction in the system.
Aco mmpecahreasn iac arlo ttaorryq uien ptruatn sshmaifsts aiodna pptreodd ufocri nagt taanch omuetpnut tt ow itthhe vraortiaarbyl ep coownetrr oslolaubrlcee scpoenende tcotreqdu teo c ah amraacitne rsihstaifcts.
This invention relates to a mechanism transferring torque from one rotating shaft to another and in particular to a
ltreavneslsm. iCssoinotnr oml eccahna nbies mut itlhizaet dw tioll aecntaivbalete a onr ednegaicnteiv oart em tohteo rc ltuot cdhe laivlseor p ocwhaenrg teo a tlhoea d paht aospet i m ruemlat tioornqsuheip a n do fs p etehde
driven eccentric masses device in order to vary the transmission output under varying load condition.
Continuous variable transmission system plays a crucial role in order to guarantee the overall vehicle
performance in different working conditions.
This research paper presents a new technique called nomogram-based synthesis for synthesizing complex planar mechanisms without needing to solve nonlinear equations or use optimization techniques. The author applies this technique to synthesize a 6 bar-2 slider planar mechanism. A nomogram is constructed using four performance measures: time ratio, normalized stroke, minimum transmission angle, and maximum transmission angle. A five-step procedure utilizes the nomogram to synthesize the mechanism for desired time ratio and stroke values while maintaining transmission angle within recommended ranges. As an example, the technique is used to synthesize a mechanism with a time ratio of 2 and normalized stroke of 1.5, obtaining transmission angles between 108.5-112 degrees.
Design and Fabrication of a Tricycle for Municipal Waste Collectioninventionjournals
Β
ABSTRACT: The use of inappropriate technology for the primary collection of municipal wastes in general is a common problem. A tricycle was designed and fabricated with a carriage to be used for doorstep collection of waste. The tricycle was designed to be human powered for the purpose of primary collection of municipal solid waste in locations and communities where the existing collection trucks could not cover due to narrow, poor quality roads and a high density population and congested areas. The final result shows that the tricycle is stable, strong, durable, and the dynamic test conducted has confirmed the stability, easy maneuvering, and the effectiveness of the braking system. This research work is applicable to the reduction in the inefficiency with the existing methods and equipment used in the collection of municipal waste.
Optimum Design of 1st Gear Ratio for 4WD Vehicles Based on Vehicle Dynamic Be...yarmohammadisadegh
Β
This paper presents an approach that allows optimizing gear ratio and vehicle dimension to achieve optimum gear transmission. Therefore,augmented Lagrangian multiplier method, defined as classical method, is utilized to find the optimum gear ratios and the corresponding number of gear teeth applied to all epicyclical gears. The new method is able to calculate and also to optimize the gear ratio based on dynamics of 4WD vehicles. Therefore, 4WD vehicles dynamic equations are employed as suming that the rear wheels or the front wheels are at the point of slip. In addition, a genetic algorithm is modified to preserve feasibility of the encountered solutions. The basic dimension of a sample commercial vehicle (2009 hummer H34 dr AWDSUV) and its gear box are optimized, and then the effects of changing slip angle, wheelbase, and engine torque on optimum vehicle dimension are analyzed.
The team designed a robot to lift and transport cubes in zone 4. It must lift 3 cubes (207 grams) at once and travel between zones 3 and 4 within 1 minute while reaching a goal height of 12 inches. It must also be able to push the largest block. The key challenges are stability with weight on the front and ensuring blocks don't fall off the table. Risks include turning the dustpan without a motor and pushing blocks into an area needed for travel. Analysis showed gears and a planetary motor could lift the required weights efficiently.
The document describes a project to optimize car performance through interpolation of design values. It provides vehicle specifications for a BMW 740li, including dimensions, engine specs, and transmission ratios. Formulas are given for calculating forces, velocity, acceleration, resistance and other parameters. Linear interpolation, Newton's interpolating polynomial, and spline methods are used to predict unknown performance values and optimize design parameters like weight and frontal area. The goal is to improve acceleration and fuel efficiency through analysis and design changes.
The document analyzes a quarter-car suspension system using equations of motion, block diagrams, and Simulink modeling. It derives the equation of motion from a free body diagram. Natural frequency and damping coefficients are calculated using the given spring and damping constants. A block diagram models the system and is implemented in Simulink. Simulink plots show the displacement, velocity, and forces over time, validating the dynamic behavior of the suspension system.
This document provides solutions to problems involving belt drives. It first solves for the tensions and power transmission in a belt drive system connecting two pulleys of different diameters, one running at 200 rpm. Taking into account centrifugal tension, friction, and a maximum tension of 2 kN, it finds the transmitted power is 13.588 kW. It also calculates the efficiencies lost to friction in the system.
Aco mmpecahreasn iac arlo ttaorryq uien ptruatn sshmaifsts aiodna pptreodd ufocri nagt taanch omuetpnut tt ow itthhe vraortiaarbyl ep coownetrr oslolaubrlcee scpoenende tcotreqdu teo c ah amraacitne rsihstaifcts.
This invention relates to a mechanism transferring torque from one rotating shaft to another and in particular to a
ltreavneslsm. iCssoinotnr oml eccahna nbies mut itlhizaet dw tioll aecntaivbalete a onr ednegaicnteiv oart em tohteo rc ltuot cdhe laivlseor p ocwhaenrg teo a tlhoea d paht aospet i m ruemlat tioornqsuheip a n do fs p etehde
driven eccentric masses device in order to vary the transmission output under varying load condition.
Continuous variable transmission system plays a crucial role in order to guarantee the overall vehicle
performance in different working conditions.
This research paper presents a new technique called nomogram-based synthesis for synthesizing complex planar mechanisms without needing to solve nonlinear equations or use optimization techniques. The author applies this technique to synthesize a 6 bar-2 slider planar mechanism. A nomogram is constructed using four performance measures: time ratio, normalized stroke, minimum transmission angle, and maximum transmission angle. A five-step procedure utilizes the nomogram to synthesize the mechanism for desired time ratio and stroke values while maintaining transmission angle within recommended ranges. As an example, the technique is used to synthesize a mechanism with a time ratio of 2 and normalized stroke of 1.5, obtaining transmission angles between 108.5-112 degrees.
Design and Fabrication of a Tricycle for Municipal Waste Collectioninventionjournals
Β
ABSTRACT: The use of inappropriate technology for the primary collection of municipal wastes in general is a common problem. A tricycle was designed and fabricated with a carriage to be used for doorstep collection of waste. The tricycle was designed to be human powered for the purpose of primary collection of municipal solid waste in locations and communities where the existing collection trucks could not cover due to narrow, poor quality roads and a high density population and congested areas. The final result shows that the tricycle is stable, strong, durable, and the dynamic test conducted has confirmed the stability, easy maneuvering, and the effectiveness of the braking system. This research work is applicable to the reduction in the inefficiency with the existing methods and equipment used in the collection of municipal waste.
Optimum Design of 1st Gear Ratio for 4WD Vehicles Based on Vehicle Dynamic Be...yarmohammadisadegh
Β
This paper presents an approach that allows optimizing gear ratio and vehicle dimension to achieve optimum gear transmission. Therefore,augmented Lagrangian multiplier method, defined as classical method, is utilized to find the optimum gear ratios and the corresponding number of gear teeth applied to all epicyclical gears. The new method is able to calculate and also to optimize the gear ratio based on dynamics of 4WD vehicles. Therefore, 4WD vehicles dynamic equations are employed as suming that the rear wheels or the front wheels are at the point of slip. In addition, a genetic algorithm is modified to preserve feasibility of the encountered solutions. The basic dimension of a sample commercial vehicle (2009 hummer H34 dr AWDSUV) and its gear box are optimized, and then the effects of changing slip angle, wheelbase, and engine torque on optimum vehicle dimension are analyzed.
The document summarizes the kinematic analysis of an epicyclic gear train using a tabular method. It shows three conditions of the arm movement and calculates the speed of the gears and arm. In condition 1, the arm is fixed as gear A rotates 1 turn, giving gear B a speed of -TA/TB. In condition 2, gear A rotates x turns with arm fixed, giving gear B a speed of -x*TA/TB. Condition 3 adds a +y rotation of the arm. The tabular method is used to calculate the speeds by adding the individual steps.
Here are the steps to solve this problem:
a) Power of the engine
- Power stroke area = 6000 mm2 = 6000 x 10 Nm = 60,000 Nm
- Resisting torque is uniform, so work done = Area x Resisting torque
- Assuming resisting torque is 10 Nm, work done per cycle = 60,000 Nm
- Work done per cycle x rpm = Power
- Given: Work done per cycle is 60,000 Nm
- Assuming rpm is N
- Then, Power = 60,000 x N W
b) Energy to be stored by flywheel
- Total area under the diagram = Power stroke + Exhaust + Suction + Compression
NEW APPROACH FOR COMPUTER-AIDED STATIC BALANCING OF TURBINES ROTORSBarhm Mohamad
Β
The balancing operation consists in improving the distribution of the rotor masses so that the free centrifugal forces around the rotor axis, imposed by the manufacturer, do not exceed the tolerances allowed by the standards. In this paper we propose algorithms for the distribution of the turbine blades from data from an electronic scale which allows to measure the static moment of the blades, these algorithms aim to find the correction weight and the angle of position of the correction mass, we also propose a simulation of the distribution of the blades of a turbine to get an idea on the assembly. This operation is necessary in the case of a repair of the rotors or in the assembly of the new flexible rotors. Using a MATLAB calculation code.
This document discusses various types of brakes and dynamometers used in mechanical engineering. It describes shoe brakes, internally expanding shoe brakes, and how braking works when applied to rear wheels only, front wheels only, or all wheels of a vehicle. It also covers different types of dynamometers used to measure power including pony brake, rope brake, epicyclic train, belt transmission, and torsion dynamometers. Example problems are provided to calculate braking torque and distance required to stop a vehicle under different braking conditions.
SAIF ALDIN ALI MADIN
Ψ³ΩΩ Ψ§ΩΨ―ΩΩ ΨΉΩΩ Ω Ψ§ΨΆΩ
S96aif@gmail.com
Torsion tesd
MECHANICS OF MATERIALS
The objective of this experiment is to study the linearly elastic behavior
of metallic material under a torsion test. Torsion test measures the
strength of any material against maximum twisting forces. During this
experiment, a failure testing is done to our testing material which is a
steel. This failure testing involves twisting the material until it breaks
which helps demonstrates how materials undergo during testing
condition by measuring the applied torque with respect to the angle of
twist, the shear modulus, shear stress
At the limit of proportionality. The shear modulus of elasticity G and
Poisson's Ratio are determined for the specimen using torsional stressstrain relationship from the data collected during the experiment. The
fraction surface of our material at the end of the experiment is used to
stablish characteristics of the material,
1. The document contains information about flywheel design including formulas for centrifugal stress, energy variation, and determining the necessary mass and dimensions of a flywheel.
2. Key parameters that must be determined from the problem information include the energy variation, mean resisting torque, angular velocity, and coefficient of fluctuation of speed.
3. The mass and dimensions of the flywheel can then be calculated using the density of the material, maximum safe centrifugal stress, energy variation, and other specified parameters such as diameter.
The document discusses the fundamentals of theory of machines and its subdivisions. It covers the following key points:
1. Theory of machines deals with the study of relative motion between machine parts and forces acting on them. It is subdivided into kinematics, dynamics, kinetics, and statics.
2. Kinematics studies relative motion, dynamics studies forces and their effects on moving parts, kinetics studies inertia forces, and statics studies forces on stationary parts.
3. Fundamental concepts like space, time, matter, body, mass, and force are defined. Newton's laws of motion are also summarized.
4. Methods for analyzing reciprocating engines like graphical and analytical methods are outlined. Forces
This document discusses the 3-4-5 polynomial cam, which uses five coefficients (C0, C1, C2, C3, C4, C5) to define the cam profile as a fifth-order polynomial equation relating displacement x to angular displacement ΞΈ. It derives the boundary conditions for x, velocity v, and acceleration a at ΞΈ = 0 and ΞΈ = Ξ². By solving the simultaneous equations from the boundary conditions, it determines the values of the coefficients to be C3 = 10h, C4 = -15h, C5 = 6h, resulting in equations for x, v, and a as fifth-order polynomial functions of ΞΈ/Ξ².
The document discusses different types of gear trains used to transmit motion between rotating shafts in machines. It describes simple gear trains which use a single gear on each shaft, compound gear trains which use multiple gears on a shaft, reverted gear trains where the first and last gears share a common axis of rotation, and epicyclic gear trains where gears move in an orbital path relative to a fixed axis. Epicyclic gear trains are useful for achieving high speed ratios within a compact space and are used in applications like lathes, differentials, hoists, and watches.
The document discusses worm gears and provides definitions and equations related to their design and operation. It defines worm gears as having large gear reductions from 20:1 up to 300:1. Worm gears are used widely in machinery because the worm can easily turn the gear but the gear cannot turn the worm. Key terms defined include lead, lead angle, velocity ratio, center distance, efficiency, and force equations. Design considerations like helix angle, module, and pitch are also addressed.
A punching press punches 38mm holes in 32mm thick plates, requiring 7 N-m of energy per square mm of sheared area. It punches one hole every 10 seconds. The mean flywheel speed is 25 m/s.
To calculate the motor power required, the energy per hole is calculated based on the sheared area of the hole. The mass of the flywheel required to limit speed fluctuations to 3% of the mean is then calculated using the energy variation and flywheel properties.
This document describes an experiment conducted to determine the moment of inertia of a flywheel. It includes sections on the objective, theory, apparatus, calculations and results, and discussion. The results show the angular acceleration of the flywheel, calculated moment of inertia, and percentage error between calculated and experimental values. The discussion comments on the relationship between moment of inertia and friction torque, and factors that affect moment of inertia such as mass distribution and applied torque. It also defines the kinetic energy stored in a flywheel based on its rotational speed and mass.
In an epicyclic gear train with gears A and B on an arm C, the arm rotates at -150 rpm. Gear A is fixed. Using a tabular kinematic analysis method:
1) Arm C is fixed, gear A completes 1 rotation so gear B speed is -TA/TB
2) Gear A completes x rotations, so gear B speed is -x*TA/TB
3) Arm C adds y rotations, so final speeds are: gear A = x+y, gear B = y - x*TA/TB
Solving the equations gives: x = 150, y = -150, so gear B speed is -270 rpm.
97th transportation research board meeting presentation-poster session 583Ozgur Bezgin
Β
This presentation introduces the concept of impact reduction factor and a method both developed by Dr. Niyazi ΓzgΓΌr Bezgin that can estimate vertical impact forces on railways due to changes in track profile. The Bezgin Impact Factors KB1 and KB2 are introduced.
This document describes the design of a steel staircase with 12 steps to provide access between two floors of a household. Key details include:
- The design concept uses 12 steel steps connected by brackets to a central 6" diameter pole.
- Analysis shows the welds and fasteners will withstand the intended 300 lb load capacity with safety factors above 1.
- Features include pre-welded construction for easy assembly using bolts, and durable all-steel design.
This document discusses the analysis of a cantilevered L4x4 aluminum beam. It includes:
1. Computing section properties like centroid, moments of inertia, and flexibility matrix of the beam. Values from SolidWorks were compared.
2. Calculating stresses from bending, shear, and torsion at various points on the cross section.
3. Determining displacements and rotations of the beam tip under an applied load using the flexibility matrix in MATLAB and comparing to an Abaqus model. Percentage errors between analysis methods were reported.
1) A 4-bar linkage mechanism is used to design a recumbent elliptical trainer to rehabilitate people with lower extremity mobility restrictions. The linkage converts rotational motion to an elliptical trajectory.
2) The 4-bar linkage mechanism has one degree of freedom according to Grubler's equation. An elliptical trajectory is achieved by connecting the legs to the point that traces an ellipse during the linkage's back-and-forth motion.
3) Velocity and acceleration are derived using velocity and acceleration diagrams from the 4-bar linkage mechanism. The slider's velocity is calculated as 1.6756 m/s and acceleration is -3.5975 m/s2 using D'Alembert's principle
The document summarizes a finite element analysis of a torque arm performed in Abaqus to optimize the design. It includes:
1) A preliminary analysis using mechanics of materials approximations to estimate stress and displacement.
2) An analysis of different element types to determine appropriate meshing.
3) A convergence study to determine optimal mesh size.
4) A parameter study that varies arm dimensions to minimize mass while meeting stress constraints.
The analysis aims to find the lightest torque arm design that keeps stresses below 240 MPa.
Measuring Axle Weight of Moving Vehicle Based on Particle Swarm OptimizationIJRES Journal
Β
The dynamic tire forces are the important factor influencing weigh-in-motion of vehicle. This paper presents a method to separate the dynamic tire forces contained in axle-weight signal. On the basis of analyzing the characteristic of axle-weight signal, the model of axle-weight signal and the objective function are constructed. After introducing the principle of particle swarm optimization (PSO), an improved PSO is employed to estimate the unknown parameters of the objective function. According to the obtained estimates of parameters, the dynamic tire forces contained in axle-weight signal are reconstructed. Subtract the reconstructed dynamic tire forces from the axle-weight signal, and get the estimate of axle weight of moving vehicle. Simulation and field experiments are conducted to demonstrate the performance of the proposed method.
This document provides information about a laboratory manual for a Mechanics of Machines course, including safety notices, report guidelines, and descriptions of 5 experiments involving gears, clutches, mechanisms, gyroscopes, and balancing. It introduces the laboratory coordinator and demonstrators, and provides details about the equipment and procedures for experiments on gears, clutches, and epicyclic gear systems.
Selection of powertrain for vehicle is depends upon vehicle type & application of vehicle. To achieve performance of vehicle, engine torque at maximum revolutions, Transmission ratio, Axle ratio & tire plays important role. In order to understand vehicle performance in theoretical calculation there should be proper selection of power train aggregates. All these aggregates technically will evaluate the actual vehicle performances. For example, trucks are seldom run at their rated maximum speed. In fact, they are usually operated with engine speed at maximum torque or at the speed where fuel consumption is minimized. In climbing hills, there may be occasions when the engine revolution is raised to its maximum to produce the maximum horsepower; however, the most efficient method of operation is to use the range of engine speed, which maximizes torque. If an engine's speed range, producing maximum torque, is extremely narrow, a slight increase of rpm will cause a substantial loss of power and sign of poor performance characteristic. In other words, engines with high maximum torque and horsepower are not necessarily the most "powerful engine." Factors other than the maximum values of the torque and horsepower must be evaluated in determining the practical performance of engines. Furthermore, a high performance engine must be combined with the correct transmission and differential in order to produce the desired running performance. It is necessary to understand the factors affecting its ease of operations. This Paper tells how to integrate powertrain and judge performance of vehicle according to application and type of vehicle by reading performance curves and calculation
The document discusses using OptimumT software to design the steering geometry for a small autocross car based on tire data. It describes using OptimumT to fit a tire model to test data, then analyzing the model to determine the ideal slip angles at different loads and cambers. Both a simplified method ignoring camber and a more advanced method including camber are presented. The advanced method uses OptimumT in Excel to iteratively calculate the lateral forces and weight transfer to determine the ideal difference in left and right steering angles for the car's tires. The results suggest adding a small amount of positive Ackermann and static toe-in.
The document summarizes the kinematic analysis of an epicyclic gear train using a tabular method. It shows three conditions of the arm movement and calculates the speed of the gears and arm. In condition 1, the arm is fixed as gear A rotates 1 turn, giving gear B a speed of -TA/TB. In condition 2, gear A rotates x turns with arm fixed, giving gear B a speed of -x*TA/TB. Condition 3 adds a +y rotation of the arm. The tabular method is used to calculate the speeds by adding the individual steps.
Here are the steps to solve this problem:
a) Power of the engine
- Power stroke area = 6000 mm2 = 6000 x 10 Nm = 60,000 Nm
- Resisting torque is uniform, so work done = Area x Resisting torque
- Assuming resisting torque is 10 Nm, work done per cycle = 60,000 Nm
- Work done per cycle x rpm = Power
- Given: Work done per cycle is 60,000 Nm
- Assuming rpm is N
- Then, Power = 60,000 x N W
b) Energy to be stored by flywheel
- Total area under the diagram = Power stroke + Exhaust + Suction + Compression
NEW APPROACH FOR COMPUTER-AIDED STATIC BALANCING OF TURBINES ROTORSBarhm Mohamad
Β
The balancing operation consists in improving the distribution of the rotor masses so that the free centrifugal forces around the rotor axis, imposed by the manufacturer, do not exceed the tolerances allowed by the standards. In this paper we propose algorithms for the distribution of the turbine blades from data from an electronic scale which allows to measure the static moment of the blades, these algorithms aim to find the correction weight and the angle of position of the correction mass, we also propose a simulation of the distribution of the blades of a turbine to get an idea on the assembly. This operation is necessary in the case of a repair of the rotors or in the assembly of the new flexible rotors. Using a MATLAB calculation code.
This document discusses various types of brakes and dynamometers used in mechanical engineering. It describes shoe brakes, internally expanding shoe brakes, and how braking works when applied to rear wheels only, front wheels only, or all wheels of a vehicle. It also covers different types of dynamometers used to measure power including pony brake, rope brake, epicyclic train, belt transmission, and torsion dynamometers. Example problems are provided to calculate braking torque and distance required to stop a vehicle under different braking conditions.
SAIF ALDIN ALI MADIN
Ψ³ΩΩ Ψ§ΩΨ―ΩΩ ΨΉΩΩ Ω Ψ§ΨΆΩ
S96aif@gmail.com
Torsion tesd
MECHANICS OF MATERIALS
The objective of this experiment is to study the linearly elastic behavior
of metallic material under a torsion test. Torsion test measures the
strength of any material against maximum twisting forces. During this
experiment, a failure testing is done to our testing material which is a
steel. This failure testing involves twisting the material until it breaks
which helps demonstrates how materials undergo during testing
condition by measuring the applied torque with respect to the angle of
twist, the shear modulus, shear stress
At the limit of proportionality. The shear modulus of elasticity G and
Poisson's Ratio are determined for the specimen using torsional stressstrain relationship from the data collected during the experiment. The
fraction surface of our material at the end of the experiment is used to
stablish characteristics of the material,
1. The document contains information about flywheel design including formulas for centrifugal stress, energy variation, and determining the necessary mass and dimensions of a flywheel.
2. Key parameters that must be determined from the problem information include the energy variation, mean resisting torque, angular velocity, and coefficient of fluctuation of speed.
3. The mass and dimensions of the flywheel can then be calculated using the density of the material, maximum safe centrifugal stress, energy variation, and other specified parameters such as diameter.
The document discusses the fundamentals of theory of machines and its subdivisions. It covers the following key points:
1. Theory of machines deals with the study of relative motion between machine parts and forces acting on them. It is subdivided into kinematics, dynamics, kinetics, and statics.
2. Kinematics studies relative motion, dynamics studies forces and their effects on moving parts, kinetics studies inertia forces, and statics studies forces on stationary parts.
3. Fundamental concepts like space, time, matter, body, mass, and force are defined. Newton's laws of motion are also summarized.
4. Methods for analyzing reciprocating engines like graphical and analytical methods are outlined. Forces
This document discusses the 3-4-5 polynomial cam, which uses five coefficients (C0, C1, C2, C3, C4, C5) to define the cam profile as a fifth-order polynomial equation relating displacement x to angular displacement ΞΈ. It derives the boundary conditions for x, velocity v, and acceleration a at ΞΈ = 0 and ΞΈ = Ξ². By solving the simultaneous equations from the boundary conditions, it determines the values of the coefficients to be C3 = 10h, C4 = -15h, C5 = 6h, resulting in equations for x, v, and a as fifth-order polynomial functions of ΞΈ/Ξ².
The document discusses different types of gear trains used to transmit motion between rotating shafts in machines. It describes simple gear trains which use a single gear on each shaft, compound gear trains which use multiple gears on a shaft, reverted gear trains where the first and last gears share a common axis of rotation, and epicyclic gear trains where gears move in an orbital path relative to a fixed axis. Epicyclic gear trains are useful for achieving high speed ratios within a compact space and are used in applications like lathes, differentials, hoists, and watches.
The document discusses worm gears and provides definitions and equations related to their design and operation. It defines worm gears as having large gear reductions from 20:1 up to 300:1. Worm gears are used widely in machinery because the worm can easily turn the gear but the gear cannot turn the worm. Key terms defined include lead, lead angle, velocity ratio, center distance, efficiency, and force equations. Design considerations like helix angle, module, and pitch are also addressed.
A punching press punches 38mm holes in 32mm thick plates, requiring 7 N-m of energy per square mm of sheared area. It punches one hole every 10 seconds. The mean flywheel speed is 25 m/s.
To calculate the motor power required, the energy per hole is calculated based on the sheared area of the hole. The mass of the flywheel required to limit speed fluctuations to 3% of the mean is then calculated using the energy variation and flywheel properties.
This document describes an experiment conducted to determine the moment of inertia of a flywheel. It includes sections on the objective, theory, apparatus, calculations and results, and discussion. The results show the angular acceleration of the flywheel, calculated moment of inertia, and percentage error between calculated and experimental values. The discussion comments on the relationship between moment of inertia and friction torque, and factors that affect moment of inertia such as mass distribution and applied torque. It also defines the kinetic energy stored in a flywheel based on its rotational speed and mass.
In an epicyclic gear train with gears A and B on an arm C, the arm rotates at -150 rpm. Gear A is fixed. Using a tabular kinematic analysis method:
1) Arm C is fixed, gear A completes 1 rotation so gear B speed is -TA/TB
2) Gear A completes x rotations, so gear B speed is -x*TA/TB
3) Arm C adds y rotations, so final speeds are: gear A = x+y, gear B = y - x*TA/TB
Solving the equations gives: x = 150, y = -150, so gear B speed is -270 rpm.
97th transportation research board meeting presentation-poster session 583Ozgur Bezgin
Β
This presentation introduces the concept of impact reduction factor and a method both developed by Dr. Niyazi ΓzgΓΌr Bezgin that can estimate vertical impact forces on railways due to changes in track profile. The Bezgin Impact Factors KB1 and KB2 are introduced.
This document describes the design of a steel staircase with 12 steps to provide access between two floors of a household. Key details include:
- The design concept uses 12 steel steps connected by brackets to a central 6" diameter pole.
- Analysis shows the welds and fasteners will withstand the intended 300 lb load capacity with safety factors above 1.
- Features include pre-welded construction for easy assembly using bolts, and durable all-steel design.
This document discusses the analysis of a cantilevered L4x4 aluminum beam. It includes:
1. Computing section properties like centroid, moments of inertia, and flexibility matrix of the beam. Values from SolidWorks were compared.
2. Calculating stresses from bending, shear, and torsion at various points on the cross section.
3. Determining displacements and rotations of the beam tip under an applied load using the flexibility matrix in MATLAB and comparing to an Abaqus model. Percentage errors between analysis methods were reported.
1) A 4-bar linkage mechanism is used to design a recumbent elliptical trainer to rehabilitate people with lower extremity mobility restrictions. The linkage converts rotational motion to an elliptical trajectory.
2) The 4-bar linkage mechanism has one degree of freedom according to Grubler's equation. An elliptical trajectory is achieved by connecting the legs to the point that traces an ellipse during the linkage's back-and-forth motion.
3) Velocity and acceleration are derived using velocity and acceleration diagrams from the 4-bar linkage mechanism. The slider's velocity is calculated as 1.6756 m/s and acceleration is -3.5975 m/s2 using D'Alembert's principle
The document summarizes a finite element analysis of a torque arm performed in Abaqus to optimize the design. It includes:
1) A preliminary analysis using mechanics of materials approximations to estimate stress and displacement.
2) An analysis of different element types to determine appropriate meshing.
3) A convergence study to determine optimal mesh size.
4) A parameter study that varies arm dimensions to minimize mass while meeting stress constraints.
The analysis aims to find the lightest torque arm design that keeps stresses below 240 MPa.
Measuring Axle Weight of Moving Vehicle Based on Particle Swarm OptimizationIJRES Journal
Β
The dynamic tire forces are the important factor influencing weigh-in-motion of vehicle. This paper presents a method to separate the dynamic tire forces contained in axle-weight signal. On the basis of analyzing the characteristic of axle-weight signal, the model of axle-weight signal and the objective function are constructed. After introducing the principle of particle swarm optimization (PSO), an improved PSO is employed to estimate the unknown parameters of the objective function. According to the obtained estimates of parameters, the dynamic tire forces contained in axle-weight signal are reconstructed. Subtract the reconstructed dynamic tire forces from the axle-weight signal, and get the estimate of axle weight of moving vehicle. Simulation and field experiments are conducted to demonstrate the performance of the proposed method.
This document provides information about a laboratory manual for a Mechanics of Machines course, including safety notices, report guidelines, and descriptions of 5 experiments involving gears, clutches, mechanisms, gyroscopes, and balancing. It introduces the laboratory coordinator and demonstrators, and provides details about the equipment and procedures for experiments on gears, clutches, and epicyclic gear systems.
Selection of powertrain for vehicle is depends upon vehicle type & application of vehicle. To achieve performance of vehicle, engine torque at maximum revolutions, Transmission ratio, Axle ratio & tire plays important role. In order to understand vehicle performance in theoretical calculation there should be proper selection of power train aggregates. All these aggregates technically will evaluate the actual vehicle performances. For example, trucks are seldom run at their rated maximum speed. In fact, they are usually operated with engine speed at maximum torque or at the speed where fuel consumption is minimized. In climbing hills, there may be occasions when the engine revolution is raised to its maximum to produce the maximum horsepower; however, the most efficient method of operation is to use the range of engine speed, which maximizes torque. If an engine's speed range, producing maximum torque, is extremely narrow, a slight increase of rpm will cause a substantial loss of power and sign of poor performance characteristic. In other words, engines with high maximum torque and horsepower are not necessarily the most "powerful engine." Factors other than the maximum values of the torque and horsepower must be evaluated in determining the practical performance of engines. Furthermore, a high performance engine must be combined with the correct transmission and differential in order to produce the desired running performance. It is necessary to understand the factors affecting its ease of operations. This Paper tells how to integrate powertrain and judge performance of vehicle according to application and type of vehicle by reading performance curves and calculation
The document discusses using OptimumT software to design the steering geometry for a small autocross car based on tire data. It describes using OptimumT to fit a tire model to test data, then analyzing the model to determine the ideal slip angles at different loads and cambers. Both a simplified method ignoring camber and a more advanced method including camber are presented. The advanced method uses OptimumT in Excel to iteratively calculate the lateral forces and weight transfer to determine the ideal difference in left and right steering angles for the car's tires. The results suggest adding a small amount of positive Ackermann and static toe-in.
This document presents a mathematical model of a vehicle experiencing a tire blowout. It describes developing a simplified four-wheel vehicle model using equations of motion and a Dugoff tire model. It then outlines modifying the model to account for factors during a tire blowout, such as decreasing tire radius and effective radius over 0.8 seconds, and increasing rolling resistance and decreasing cornering stiffness. Simulation results are presented to verify the basic model and behavior during a tire blowout. The goal is to model vehicle behavior during this scenario to assist with controller design for lane keeping.
Conceptual Design of a Light Sport AircraftDustan Gregory
Β
The document provides a conceptual design for a light sport aircraft. It defines key parameters for light sport aircraft and summarizes the design of several existing models. The design process described initializes parameters like wing area and airfoil selection. Equations are presented to calculate performance metrics like drag, power required, climb rate, endurance and range. Requirements for the conceptual design are specified, including taking off, cruising, and landing with sufficient fuel reserves.
Single Speed Transmission for Electric VehiclesSameer Shah
Β
This document summarizes Sameer Shah's seminar report on designing a single speed transmission for electric vehicles. The report describes the design process for a helical gear transmission with a gear ratio of 12.25:1 to meet the torque requirements of an electric vehicle. Structural simulation was performed on the gears to validate they could withstand the expected loads. The gears would be manufactured using hobbing or shaping and finished through grinding or honing. Lubrication would be provided by Omega 690 gear oil for its low temperature fluidity and high temperature strength.
6 ijaems jul-2015-11-design of a drivetrain for sae baja racing off-road vehicleINFOGAIN PUBLICATION
Β
This document discusses the design of a drivetrain for an off-road racing vehicle that will compete in SAE Baja competitions. It begins by outlining the importance of drivetrain design and lack of available literature on the topic. The document then evaluates the performance needs of a Baja vehicle and selects components for the powertrain including a 10 HP Briggs & Stratton engine. Calculations are shown for determining the vehicle's total tractive effort based on factors like rolling resistance, aerodynamic drag and grade resistance. Based on these calculations and the maximum adhesive force between tires and the road surface, the maximum gradient the vehicle can climb is determined to be 60%, or 30.7 degrees, without slipping.
The document discusses the design parameters of electric vehicles. It begins by outlining the presentation outcomes, which are to recognize the importance of EV design parameters, describe EV dynamics, and recall relations between tractive force, velocity, power, energy, torque, etc. It then provides background on EVs and discusses parameters like vehicle dynamics, capacity, motor type, speed, range, battery type, and power converters. Key equations for tractive effort, power required, aerodynamic drag, rolling resistance, and gradient force are also presented.
Behaviour of metals β problem for heat transfer from the automobile brakes sy...eSAT Journals
Β
Abstract We know that, The Braking action is the use of a controlled force to reduce the speed or to stop a moving vehicle or to keep a vehicle stationary , when braking is applied, it develop friction which does the braking i.e. Kinetic energy which is converted into heat energy on the application of brake. The biggest question today is, while the driver is going to brake applied, this force is increasing by 8 times of as per horse power. For example, one vehicle has 100 hp, after the braking applied is going to reached 800 hp. Therefore, in terms of behavior of metals, some time frequent accident by means of dragging. Because, this heat is transferred through the surrounding air. The weight of the vehicle is divided on its axle, and retarding force acts on the point of road contacts towards the rear and the inertia force of gravity towards the font. Let F= retarding force, ΞΌ = coefficient of friction, W = weight of the vehicle, h = height of centre of Gravity of the vehicle from road. Therefore, F = ΞΌW (inertia force) and couple = ΞΌW Γ h Keywords: Braking action, horse power, inertia
The document discusses gear ratios and transmissions. It explains that gearboxes are needed to allow engines to operate at their optimal speeds for power, torque, and efficiency over a vehicle's entire speed range from starting to maximum velocity. It describes how gear ratios are selected for different operating conditions like maximum speed, acceleration, traction, and fuel efficiency. Lower gears provide increased torque for starting and hill climbing while higher gears allow the engine to spin faster at high speeds. The document focuses on spur gear design and how gear ratios are calculated in multi-speed transmissions.
Design and performance Analysis of a 5 Speed Manual Transmission System for I...IRJET Journal
Β
This document summarizes a research paper that analyzed the design and performance of a 5-speed manual transmission system for an Indian drive cycle. The researchers obtained various gear ratio sets by varying final drive ratios, intermediate gear ratios, and gear stepping. They then used ADAMS CAR software to simulate the performance of the transmission designs under different conditions. Their results showed that increasing the final drive ratio from 4.467 to 4.8 improved acceleration performance by providing more wheel torque in first gear. They also found that increasing the first gear ratio from 3.72 to 4.2 further enhanced acceleration. The optimal transmission design was selected based on achieving the best acceleration performance.
1. The document provides information about the turning moment diagrams and calculations for determining flywheel properties for 6 different engines.
2. It includes details like turning moment scales, intercepted areas, engine speed, power output, work done during strokes, and equations to represent the turning moment curve.
3. The goal is to calculate properties like coefficient of fluctuation of speed, necessary flywheel mass, moment of inertia, mass of the flywheel rim, power developed, angular acceleration and diameter/cross-section of the flywheel rim.
This document discusses how aerodynamics can improve vehicle performance in various racing events by increasing downforce. Downforce pushes the tires into the road, allowing for increased cornering ability without a significant weight penalty. Analysis of the skid pad, slalom, and acceleration events shows that a car with an aerodynamic package could achieve faster lap times by producing higher lateral and transient lateral forces. While drag also increases with downforce, the calculations show the engine power is sufficient to overcome these forces for the speeds in these events. Therefore, an aerodynamic package has the potential to significantly improve performance.
The document summarizes the modeling and control of an automobile cruise control system. It develops a mathematical model that relates the velocity of the car to the throttle setting and slope of the road. A PI controller is designed using this model to maintain a constant velocity even when the road slope changes. Parameters for the PI controller are selected to provide critical damping and a response speed that balances minimizing velocity errors with smooth control signals. Simulation results demonstrate the cruise control system can effectively maintain the desired velocity when the road slope changes compared to an open loop system without control.
Traction is the force that allows a vehicle to move forward or backward on a surface. It is the result of friction between the tires and the ground. Traction is important for vehicle safety and performance, as it affects acceleration, braking, and cornering.
The theory predicts that failure occurs when the maximum tensile stress reaches a critical value. This critical value is determined by the same factors as in shear, namely the friction angle and the cohesion of the material.
The Mohr-Coulomb failure envelope in traction is a plot of the tensile stress versus the normal stress acting on the material. The slope of the envelope still represents the friction angle, while the intercept on the tensile stress axis represents the tensile strength of the material.
factors affecting
Tire type
Surface conditions
Vehicle weight
Driving style
Road grade and slope
Temperature
tire pressure
This document discusses flywheels and balancing of rotating masses. It defines a flywheel as an energy storage device that acts to smooth power transmission. Flywheels store excess energy from a motor and deliver it when needed. The kinetic energy of a flywheel depends on its moment of inertia and angular velocity. Flywheels are used to reduce torque fluctuations in machines like punch presses. The document also discusses balancing rotating masses to reduce vibrations by ensuring the system's center of gravity is at the axis of rotation.
The document describes research into optimizing the design of cam profiles for radial piston hydraulic motors. It develops equations to calculate displacement, pressure angle, torque, and cumulative torque at different points on the cam profile based on varying design parameters like roller radius, number of rollers, fluid pressure, etc. A computer code was created to automatically generate cam profiles by applying the equations, and analyze how changes to the input parameters affect the maximum and variation in cumulative torque output. The code found that 8 rollers produced the minimum variation in cumulative torque of 3.89% for their case.
Drivetrain was designed and manufacture in such a way that it provides good acceleration, top speed and is reliable on different terrains. To obtain an infinite range of gear ratios so as to obtain the highest torque and as well reach the maximum speed, a CVT along with a self-designed auxiliary reduction gearbox was incorporated. Also driver comfort and fuel economy were include by using CVT.
Vehicle Dynamics and Drive Control for Adaptive Cruise VehiclesIRJET Journal
Β
This document describes an adaptive cruise control system that uses hierarchical control architecture and PID/feedback controllers to maintain a desired distance and speed relative to a preceding vehicle.
The system uses a lower-level controller to compensate for nonlinear vehicle dynamics and track desired acceleration commands from an upper-level controller. The lower-level controller switches between a PID throttle controller and a feedback brake controller. Computer simulations validate that this hierarchical control approach enables the vehicle to accurately track the speed of the preceding vehicle and maintain the desired inter-vehicle distance.
Validation of Hydraulic brakes for Electric VehiclesIJAEMSJORNAL
Β
This document shows the validation of the hydraulic brakes occupied in a solar electric vehicle. The braking system evaluated consists of two components: the brake pedal with master cylinder and the wheel brake mechanism, together with the corresponding tubes or conduits and the clamping pieces. This validation is carried out through the analysis of forces, in the first part the braking force between the tire and the floor is determined; subsequently the force is calculated in the main braking system which is activated by a pedal The braking system with which it is suitable for the prototype in question is that of a Volkswagen sedan, because this brake system meets the needs of drivers in terms of efficiency.
Validation of Hydraulic brakes for Electric Vehicles
Β
evdp 4a
1. i
EVALUATE VEHICLE PERFORMANCE ...........................................................................................1
TASK 1.................................................................................................................................................1
First and Intermediate Ratios of the Gearbox .............................................................................1
Maximum Gradeability of the Vehicle..........................................................................................2
Road Speed When Changing from 3rd
to 4th
Gear ......................................................................3
3rd
Gear Road Speed...................................................................................................................3
TASK 2.................................................................................................................................................5
TASK 3.................................................................................................................................................7
Power to Weight Ratio.................................................................................................................7
Number of Gears .........................................................................................................................8
Range Change and Splitter Boxes ............................................................................................10
Vehicle Body Shape...................................................................................................................11
Aerodynamic Styling ..................................................................................................................14
Trailer Height and Design..........................................................................................................16
BIBLIOGRAPHY ...............................................................................................................................17
CONVERSION TABLE.....................................................................................................................A-1
2. i
Abbreviations
Cd Drag Coefficient
EU European Union
FDR Final Drive Ratio
GR Gear Ratio
HGV Heavy Goods Vehicle
Kmh Kilometres per hour
Kg Kilogram
KN Kilo newton
KW Kilo Watt
LPPV Light Protected Patrol Vehicle (Foxhound)
m/s Metres per second
PM Protected Mobility (Vehicle)
RPM Revolutions per Minute
Ra Air resistance
Rg Gradient Resistance
Rr Rolling Resistance
TE Tractive effort
TR Tractive Resistance
3. 1
EVALUATE VEHICLE PERFORMANCE
This assignment will cover calculations of vehicle gearing and its gradeabilty based on them, it will
establish the parameters of tractive effort versus tractive resistance and how they interrelate. The
third part of this assignment will focus on the choice of vehicle gearboxes and the impact of
aerodynamic resistance on Heavy Goods Vehicles (HGV). I will set myself a period of 3 weeks to
complete the first two tasks and use the remainder of the time available to research aerodynamic
issues as this is not something I have looked at in detail.
TASK 1
1. The data given in table 1 below is for an experimental vehicle that could be manufactured,
based on the information given we will calculate the first and intermediate ratios of the gearbox, the
vehicles maximum gradeability and gradeability in top gear and the road speed change that will
occur when going from 3rd
to 4th
gear. I will use student notes and formula books (Greer, 1989) for
equations as these are relevant to the tasks.
Table 1. Vehicle Information
First and intermediate ratios of the gearbox
2. Assuming geometric progression of gear ratios (a,ar,ar2
β¦..or n,nz,nz2
β¦..)1
. The gear ratio or
n in 5th
gear is n5=1:1, therefore n5 = n1 z4
. To conduct this equation we require our z value, this
is the engine speed ratio, the engine speed ratio is the area of engine rpm between maximum
torque and maximum power, this is also known as the engine operating speed range. It is
calculated by:
π§ =
πππ ππ‘ maxπ‘ππππ’π
πππ ππ‘maxπππ€ππ
2 π§ =
1540
2100
= 0.73
n5 = n1 x z4
or 1 = n1 x 0.734
Therefore n1 = n5 / z4
which is 1 / 0.734
= 3.52:1
n2 = 3.52 x 0.73 = 2.57:1
n3 = 3.52 x 0.732
= 1.88:1
n4 = 3.52 x 0.733
= 1.37:1
n5 = 3.52 x 0.734
= 0.999:1 or 1:1
1
(Greer, 1989)
2
(Defence Schoolof Electronic and Mechanical Engineering)
Mass 15tonne Final drive ratio 5.248:1
Max Power 165KW @2100rpm Efficiency of other ratios 90.50%
Max Torque 710Nm @ 1540rpm Transmission Efficiency 92%
5th gear ratio 01:01 Wheel rolling radius 0.328m
Vehicle Information
4. 2
3. To confirm our figures we can check that our r or z figure is correct by calculating:
π ππ π§ = 4β
1
3.52
= 0.73
4. These figures would be the ideal gear ratios to use in the gearbox based on the data given,
however, the gears must also fit inside the gearbox and if a constant mesh gearbox is to be used
than gears must be found that can all fit while running on the same central shafts, therefore the
actual gear ratioβs used may be altered to suit.
Maximum gradeability of the vehicle
Table 2. Vehicle Information
5. Gradeability is the amount of incline that a vehicle can drive up dependant on the torque and
gear ratios it is using, it is calculated by:
πππ₯ πππππ’π π₯ πππππ‘π¦ ππππ‘ππ π₯ πΊπππ πππ‘ππ π₯ πΉππππ ππππ£π πππ‘ππ π₯
ππβππππ πππππ ( π) π₯ π·πππ£πππ π‘π¦ππ πππππ’π
3
6. This equation includes a safety factor to ensure that we are always working within safe limits
and wonβt design a vehicle that is dangerous to use. By using a safety factor of 95% we can
calculate maximum gradeability in first gear and gradeability in top gear as:
πππ₯ πππππππππππ‘π¦ =
710 π₯ 0.95 π₯ 3.52 π₯ 5.248 π₯ 0.905
147150 π₯ 0.328
= π. ππππ
πΊππππππππππ‘π¦ ππ π‘ππ ππππ =
710 π₯ 0.95 π₯ 1 π₯ 5.248 π₯ 0.92
147150 π₯ 0.328
= π. ππππ
7. By taking these figures and comparing them against a conversion table at Annex A we reach
a tanΖ (%) figure of 22.5% in first gear and 5.5% in top gear, this shows that by using a higher
gear ratio we have lost the advantage of a lower gear and the tractive effort available to overcome
the tractive resistance of the gradient is insufficient, the driver must therefore shift down to a lower
gear.
3
(Defence Schoolof Electronic and Mechanical Engineering)
lowest gear ratio 3.52:1
transmission mech
efficiency (top gear)
0.92
top gear ratio 01:01
transmission mech
efficiency (other
0.905
max engine torque
(NM)
710 vehicle weight 147150
safety factor 95% driving wheel size 0.328
final drive ratio 5.248:1
Vehicle Data
5. 3
Road speed when changing from 3rd
to 4th
gear
Table 3. Vehicle Information
8. As the vehicle drives it will accelerate through the rev range until a point where it needs to
shift up to the next gear ratio, by shifting up a gear we will move down into the max torque area to
enable us to accelerate away in a new gear ratio that allows higher speed, this is shown below.
To calculate the change in speed we require the following equations:
π πππ π€βπππ π ππππ =
πΈπππππ π ππππ ππ‘ πππ₯πππ’π πππ€ππ
πΊπππ πππ‘ππ Γ πππππ ππππ£π πππ‘ππ
4
π πππ π ππππ = (
π πππ π€βπππ π ππππ Γ π Γ π·
60
) Γ 3.6
3rd
gear road speed
π πππ π€βπππ π ππππ =
2100
1.88 Γ 5.428
= 212.85 πππ
π πππ π ππππ = (
212.85 Γ π Γ 0.656
60
) Γ 3.6 = 26.32km/h
9. The above assumes that the driver is making a gear change as soon as the vehicle gets to
its maximum power point, however the vehicle could continue driving until engine maximum rpm,
despite being passed maximum power there would still be an increase in road speed, E.g:
π πππ π€βπππ π ππππ =
2500
1.88 Γ 5.428
= 244.99 πππ
π πππ π ππππ = (
244.99 Γ π Γ 0.656
60
) Γ 3.6 = 30.294km/h
10. The speed at which the vehicle changes from 3rd
to 4th
gear occurs at 26.32 km/h, when the
gear change is made the vehicle is shifted into a higher gear ratio, in this instance 1.37, when this
happens the engine rpm will drop down due to the increase in resistance now offered by the higher
gear ratio. By transposing our equation for road wheel speed and assuming the road wheel speed
does not change at the point of gear change we can calculate the effect on engine speed (n) of this
gear change:
πΉππππ’ππ π‘ππππ πππ ππ ππ π = 212.84 (1.88 π₯ 5.248) = 2100πππ
4
(Defence Schoolof Electronic and Mechanical Engineering)
3rd gear ratio 1.88
4th gear ratio 1.37
wheel rolling diameter 0.636
engine max power 2100rpm
engine max torque 1540 rpm
Vehicle Data
6. 4
If gear ratio is changed to 1.37:
π = 212.84 (1.37 π₯ 5.248) = 1530.27πππ
11. We can now see that by shifting up a gear we have gone from the point where our engine is
making maximum power (2100) to close to the point where our engine is making maximum torque
(1540), we now have maximum torque available for acceleration.
7. 5
TASK 2
12. The graph below contains information on a vehicles performance, by reading the graph we
can calculate max road speed, gradeability and tractive effort (TE). Again calculations are taken
from student notes and a formula book (Greer, 1989).
13. Maximum road speed of the vehicle. This is where the tractive effort and tractive
resistance meet, using the highest gear ratio of 5th
and the tractive resistance based on a gradient
of 0% we reach a figure of around 115 km/h.
Graph 1. Tractive effort and resistance v Speed5
14. The gradeability of the vehicle in 1st
gear. This is where the tractive effort in that gear ratio
is at its maximum, looking at the graph we can see that 1st
gear has a tractive effort curve that
reads at 23.5 KN at its maximum, the TE required to climb a 35% gradient is around 24KN,
therefore technically in this instance we do not have sufficient TE to do this, our maximum
gradeability is probably around 34%, reading from the graph we would say that maximum
gradeability is 30%.
15. Gear ratio to negotiate a 10% gradient. For this we would need to find a gear that has
enough TE to overcome the TR present, at 10% this ranges from 7.8KN at 20 km/h to 9KN at
130km/h, the TE in 3rd
gear is less than 7 KN so this gear ratio would be too high to allow the
vehicle to climb, the maximum TE in 2nd
gear is 13 KN so this gear ratio gives us enough TE to
climb the hill but also an extra 5 KN at 17km/h should the gradient increase, we would also be able
to use this extra TE to accelerate past a slower moving vehicle up to a speed of about 37.5km/h ( a
line drawn down from the TE curve would cut the 10% TR line at about 37.5 km/h).
5
Assignment Unit 25 Paper 11
8. 6
16. We could also use 1st
gear which has close to 24 KN of TE available but at a much reduced
speed, it can be seen that TE in lower gears drops of greatly for a small increase in speed while at
higher gear ratios (4 and 5) the curve drop is much shallower, this is due to where in the rev range
the engine produces most torque and this is dependent on engine design.
17. Surplus tractive effort. Travelling at 80km/h in 5th
gear on a 0% gradient we see from the
graph that approximately 1.8 KN is required but our available TE is around 3 KN, therefore we
have 1.2 KN surplus tractive effort. If we were travelling at 40 km/h on a 5% gradient in 3rd
gear
than we have a TR of 4.25 KN while our gear ratio and speed gives us a TE of 7 KN, our surplus
TE is 7 β 4.25 = 2.75 KN.
18. Acceleration. To work out the acceleration at 60 km/h on a 0% gradient in 5th
gear with a
vehicle with a mass of 3.6 tonnes (3600 kg). TE available is TE-TR = (3 β 1) 2 KN, mass of vehicle
is 3600 kg.
πΉ = πππ π π π΄ππππππππ‘πππ. πβπππππππ π΄πΆπΆπΈπΏπΈπ π΄ππΌππ =
πΉππ πΆπΈ
ππ΄ππ
=
2000π
3600πΎπΊ
= 0.556 π/π2
19. Based on the performance curves I would recommend that this engine be suitable for a small
to medium HGV, it offers a reasonably high speed in top gear and the tractive effort available in
gears 1 and 2 allow for steep hills to be climbed but also provide sufficient surplus power to
accelerate past slower moving vehicles. The spread of 5 gears would also be indicative of a small
truck such as a Leyland Daf 4 tonne.
9. 7
TASK 3
Power to weight ratio
20. This can be defined as the power developed divided by the weight of the laden vehicle. It is
based on the maximum brake power of the vehicle divided by its weight, the weight used is
normally the curb weight of the vehicle which is the vehicle weight minus the weight of drivers/crew
or additional load, but other ratios such as combat weight may be used to give a more accurate
figure. It is calculated by:
πππ€ππ π‘π ππππβπ‘ πππ‘ππ =
π΅ππππ πππ€ππ
ππππβπ‘ ππ π‘βπ π£πβππππ (πππππ)
6
21. As a comparison of these ratios we can look at 2 Army vehicles, the Ford Jeep light vehicle
from the 1940s and the Foxhound Light Protected Patrol Vehicle (LPPV) HGV from 2010, both
these vehicles are small combat vehicles used for reconnaissance and utility tasks and designed to
carry about four soldiers. I have used the combat weight of the vehicles as this provides a more
realistic power to weight ratio of the vehicles in actual service.
22. The Ford Jeep has a mass of 1530kg and a power output of 44.74 KW7
.
πππ€ππ π‘π ππππβπ‘ πππ‘ππ =
44.74 πΎπ
1.530 tonnes
= ππ. ππ π²πΎ πππ πππππ
23. The Foxhound Light Protected Patrol Vehicle (LPPV) has a mass of 7500 kg and a power
output of 145 KW8
.
πππ€ππ π‘π ππππβπ‘ πππ‘ππ =
145 πΎπ
7.5 π‘πππππ
= ππ. π π²πΎ πππ πππππ
Fig 1. Ford Jeep9
Fig 2. Foxhound LLPV10
24. This illustrates that although the Foxhound has over three times the power of the Ford Jeep,
because we have increased the weight nearly 5 times as much we have a much lower power to
weight ratio, the relationship between power and weight is not linear. A poor power to weight ratio
poses a particular problem when climbing a gradient, power is needed to drive the vehicle uphill,
gradient resistance and tractive effort required to overcome it is proportional to the weight of the
6
(Defence Schoolof Electronic and Mechanical Engineering)
7
(Ware, 2010)
8
(Genral Dynamics Land Systems, 2014)
9
(Wikipedia, 2014)
10
(Genral Dynamics Land Systems, 2014)
10. 8
vehicle and the steepness of the gradient, therefore a vehicle with a poor power to weight ratio has
less power in reserve to tackle the climb.
25. To counter the problem of low power to weight ratio we must first accept that the extra weight
will mean a generally slower vehicle, increasing engine power is possible but the increased weight
of a larger engine and chassis to hold/house it will mean we will only ever create slight
improvements. By knowing the gradients the vehicle is likely to climb along with its weight and
power the correct gearing can be produced for it.
Number of gears
26. Gears are required in order to allow engine torque to be multiplied at the road wheel, this is
crucial for accelerating, the first gear ratio must be low enough that the torque can overcome the
resistance offered by the vehicle and the ground. The trade-off is speed, a gear ratio (GR) low
enough to move the vehicle forward such as 4:1 will mean the engine is spinning quicker than the
road wheel (with further final drive reduction (FDR) of 5:1), therefore the engine will reach max rpm
while the vehicle is only travelling slowly. For example
Engine 4000 rpm / (GR) 4 = 1000rpm / (FDR) 5 =wheel spinning at 200rpm / 60 = 3.3 revs per
second
Wheel diameter of 0.5m means distance of 1.57m per revolution
1.57 x 3.3 =5.18 m/s or 18.66 km/h
27. So, if we need to increase speed we need to shift up to the next gear, however, we require
torque to accelerate further, max torque will occur at a set rpm and as explained earlier rpm will
drop on gear upshifts dependant on the gear ratio, from para 14:
π ππ (π) = 212.84 (1.88 π₯ 5.248) = 2100πππ
If gear ratio is changed to 1.37:
π = 212.84 (1.37 π₯ 5.248) = 1530.27πππ
28. It is therefore clear that if a heavy vehicle with a low revving diesel engine with a max torque
high up in the rev range, has a gearbox with few gears, then the upshifts will result in the engine
speed dropping below an acceptable torque figure and further acceleration will be sluggish (known
as torque recovery). To remedy this we require more gear ratios to ensure that each upshift
results in only a minor drop in rpm, the downside will be an increase in power losses through the
extra gears.
29. In order to minimise journey times it is beneficial to drive in top gear at the quickest speed
possible, this has the negative effect of increasing fuel consumption. Consider the graph below,
this displays the torque, power and specific fuel consumption (SFC) of an example vehicle, the
engine operating speed range lies between max torque and max power, SFC is at a minimum from
around peak torque to a point 200-400rpm further on the positive torque rise curve. This band is
known as the economy speed range and if engine rpm is kept within this range then maximum fuel
efficiency will be realised.
11. 9
Graph 2. Example vehicle data graph11
30. Let us consider that our vehicle has just 5 gears rather than the 8 indicated, in 5th
gear and
staying in the economy speed range we can achieve around 35 km/h, if we go to max engine rpm
we could achieve around 50 km/h but with massively increased fuel consumption. If we now βre-fitβ
our 8 speed gearbox we can achieve around 70 km/h but for the same fuel consumption as 35 in
5th
. By increasing the number of gears we can increase our speed while still remaining within our
economy speed range.
31. Example:
5th
gear inside economy range (2000 rpm) = SFG (kg/kWh) X Power (KW) X 1 hour
= 0.20 kg/kWh X 225 KW X 1 hour
= 45 kg/h
Relative density of fuel = 0.8
45 / 0.8 = 56.25 Litres per hour at 2000 rpm
Speed is 35 km/h for 8 hours = 280 km travelled plus 450 litres of fuel used
However, if we increase the number of gears but remain in the economy range at 2000 rpm:
Speed is now 70 km/h x 8 hours = 560 km/h plus 450 litres of fuel used
32. So it is clear to see that by increasing the number of gears we can travel further and faster
but remain within the most economic range, this is key for HGVβs. The limiting factor on number of
gears is likely to be the size of the gearbox. A standard gearbox will usually contain 4, 5 or 6 gears
but by using a splitter or range change box we can double that.
11
(Heisler, Advanced engine technology, 1995)
12. 10
Range change and Splitter boxes
33. As discussed previously an issue with HGVβs that have very poor power to weight ratios is
that when we change up a gear we must accept a drop in engine rpm, this drop in rpm could put
our rpm below that were maximum torque is produced. As we require that torque to accelerate
away we will find that with large changes between gearbox ratios our torque recovery or
acceleration will be sluggish. To counter this and increase fuel economy splitter or range
gearboxes can be fitted.
34. Splitter gearbox. In this arrangement the gear ratios are spread out wide as per a
conventional gearbox while the 2 speed auxiliary gearbox at the front has one gear in direct ratio
and the second gear is either a step up or step down ratio. The ratio is chosen so as to βsplitβ the
main gearbox ratios in half with a typical ratio being 1.25:1. As well as the normal gearstick to
select gears there would be another means to select either the high or the low ratio of the splitter
gearbox. (fig 3)
Figure 3. Splitter gearbox12
35. With this gearbox the procedure from moving off to top gear would be to select first gear and
low on the splitter box, then as speed increases select high on the splitter box, further acceleration
then requires the driver to select 2nd
gear and low on the splitter box. This is then repeated
through acceleration or, on deceleration, continually alternating between high and low on the
gearbox as shown in the figure 4.
Figure 4. Splitter gearbox gear selection13
12+12
(Heisler, Advanced engine technology, 1995)
13. 11
36. While this system addresses the requirement for a reduction in the ratio difference between
gears in a conventional gearbox it clearly is a somewhat complicated procedure and could cause a
grinding of the gears if the wrong high/low splitter ratio is selected, an improvement on this system
is the range change.
37. Range change. In this setup the gearbox has gear ratios set close together, the auxiliary
gearbox at the back has a 2 speed box with one gear again in direct ratio to the gearbox and one
at a ratio slightly larger than the gearbox gear ratio spread (fig 5).
Figure 5. Range change gearbox14
38. The procedure for gear change with this arrangement would be to engage first gear and low
on the range change box, accelerating further and shifting up gears through 2,3,4,5 etc until top
gear is reached, high ratio is then selected and the sequence is repeated through 1,2,3,4 and 5
only now they are in reality 6,7,8,9 and 10.
39. The principal difference in design between range change splitter gearboxes is that the splitter
box βsplitsβ the gear changes between high and low for each individual gear by having auxiliary
gears before the gearbox, whilst the range change uses the gear progression as normal with the
auxiliary gears changing the output from low to high after the gearbox. Certain specialised HGVβs
such as those that carry very heavy loads or climb severe gradients may be fitted with a third
auxiliary box which would allow for very low or crawler gears.
Vehicle Body Shape
40. When a vehicle drives forwards its speed will be dictated by many factors such as vehicle
power, gearing, and rolling and gradient resistance. Another form of resistance is from the air, air
resistance (Ra) is calculated as:
π π =
1
2
ππ΄π2 πΆπ15
14
(Heisler, Advanced engine technology, 1995)
15
(Defence Schoolof Electronic and Mechanical Engineering)
14. 12
41. Where π is air density, A is the projected frontal area, V is velocity of the air relative to the
vehicle and Cd is the drag coefficient of the vehicle shape. As A, Cd and π are relatively fixed it
can be seen that as velocity increases the air resistance will increase to the square of the velocity.
Although HGVβs are travelling at slower speeds then cars the large frontal area adds considerably
to the air resistance. An increase in air resistance can lead to an increase in fuel consumption.
βAerodynamic drag is responsible for 35-40% of a 40t lorryβs fuel consumption. Reducing
aerodynamic drag therefore offers a very promising way to reduce fuel consumption and GHG
emissions from HGVs.β16
42. At low speeds Ra will be minimal and other resistances such as gradient or rolling
resistances will have more of an impact, however as speed increases the increase in velocity
together with the large frontal area will cause Ra to become the dominant resisting force. Consider
the example below with air density of 1.23 Kg/m3
and Cd of 0.65:
Fig 6. HGV Frontal area17
Fig 7. Cd values of vehicles18
At 25 Km/h (6.9m/s) π π =
1
2
1.23(2.55π₯4) π₯6.92 π₯0.65 =194.13 N
At 100 Km/h (27.78m/s) π π =
1
2
1.23(2.55π₯4) π₯27.782 π₯0.65 =3146.68N
43. By increasing our speed by a factor of 4 we have caused an increase in air resistance of over
16 times the resistance at the slower speed. As we donβt really want to reduce our velocity and as
air density is (relatively) fixed we are left with trying to alter the frontal area of the vehicle and
decreasing its Cd.
44. Looking at it in closer detail air resistance can actually be classified as a drag force acting
on the vehicle and this can be broken down into the following areas:
a. Forebody Drag. Caused by the vehicle displacing the air molecules in front of it, the
faster the vehicle moves the less time there is for the air molecules to move out of the way
and so more energy is required to move them, this energy comes from the kinetic energy
created by the motion of the vehicle. This can be reduced with smooth surfaces.
b. Skin Friction Drag. Air consists of layers of molecules and those at the surface of the
vehicle attach themselves to it and move at the same speed as the vehicle, the next layer
above it moves a little slower, and this then repeats again and again until a point where the
vehicle no longer has an effect on the air, as each layer moves over the lower one shear
16,17,18
(Dings, 2012)
15. 13
forces are created, the sum of these is the skin friction drag. The volume in which these
layers act is called the boundary layer
c. Pressure or Base Drag. As the air separates from the rear of the vehicle it cannot fill
up the area behind it quickly enough, this creates an area of turbulent vortices known as
eddies which create an area of low pressure, the pressure acting against the front of the
vehicle is now higher than that at the back and causes a vacuum or suction effect on the
vehicle.
45. Of note now is that air resistance is dependent not just on the frontal area, but the sides, top
and back as well. In order to reduce air resistance on a HGV we can add some of these devices:
a. Rounded corners on the cab edges. This allows air to flow easily over the vehicle and
thereby reduce the drag coefficient. The effect of an increased radius on the corner is to
encourage the air flow to remain attached to the body rather than separating from it.
b. Ensure the cab and body are of equal height. This is to reduce the frontal area that air
will act on and reduce the disruption of the air flow. In order to maximise the load carried it
will be likely that the trailer height will be the maximum permissible by law, this is likely to
place it higher than the cab, in order to minimise this a deflector can be fitted above the cab
to push the airflow over the trailer and reduce the difference in height.
c. Ensure a minimal gap between the cab and trailer. This will reduce the vortices
between cab and trailer and reduce the effect of crosswinds being βcaughtβ in between the
gap, it can be reduced by fitting extended seals between cab and trailer which remain flexible
to allow for the vehicle turning.
d. Fit trailer skirts. In order to reduce any crosswind that may sweep under the vehicle and
create an increase in drag coefficient. These can however prove problematic for
inspection/servicing of the vehicle.
Fig 8. Effect of aerodynamic devices19
46. The effects of these items on air flow are illustrated in figure 8 and show the smoothing of air
flow lines over the cab and trailer, the reduction in the drag coefficient is illustrated below in figure
9 which also illustrates how these devices effect the βyaw angleβ, this is caused as a result of
19
(Heisler, 2002)
16. 14
crosswinds which can raise the drag coefficient, by knowing the direction of wind and the direction
of the vehicle a vector diagram can be drawn from which the angle of yaw can be calculated.
Fig 9. Effect of aerodynamic devices on Cd and Yaw angle20
Aerodynamic Styling
47. In order to reduce air resistance further we could alter the design of the cab and trailer itself.
Consider the effect of introducing a more curved structure to the cab as evaluated by a Transport
and Environment research paper by FKA automotive research, this is a justifiable source as it is an
independent research company acting on behalf of EU legislators and relates to this assignment.
Shown below is a computer simulated model of the air resistance on the front of a standard and
potential truck (fig 10+11).
Fig 10. Standard HGV21
Fig 11. Improved HGV22
48. By increasing the cab length (currently legislated at 2.35m) by 80 cm and allowing for a more
aerodynamic design incorporating a rounded and aerodynamic frontal area has led to a reduction
in aerodynamic drag by 12%, this is evidenced by the reduced high pressure zone on the improved
design.
49. As discussed under pressure drag we must also address the resistance caused as a result of
the trailer, because of its role the trailerβs most likely shape will be rectangular with an end
perpendicular to the body (a square back configuration), and this has the effect of increasing
pressure drag.
20
(Heisler, 2002)
21+20
(Dings, 2012)
17. 15
50. Pressure drag is caused by the airflow separating from the body at the back of the vehicle, a
highly aerodynamic shape such as a teardrop will mean that airflow separation occurs smoothly at
the back, the square back of the trailer prevents this and so flow separation is not smooth and
pressure drag is roughly equal to the height of the trailers end (base area wake), this creates a
large negative pressure area which has the effect of increasing drag.
51. In order to reduce this effect we can alter the shape of the trailer itself and/or the rear end
configuration, two options are to create a trailer that is physically more tear drop shaped (fig 12),
or, to fit a device at the back known as a boat tail which consist of angled boards at the back of the
vehicle (fig 13).
Fig. 12 Teardrop design23
Fig 13. Boat tail design24
52. The effect of the teardrop design is clear to see, because the airflow remains attached to the
trailer for longer it has a reduced area of negative pressure indicated by the white area between
the flow lines, note also the improved flow between cab and trailer due to the improved shape of
the trailer between it and the cab. The effect of a boat tail is to encourage the air to flow down and
fill the void created easier and so has a similar effect to that of the teardrop in that it reduces the
negative pressure at the back of the truck.
53. While both these designs have shown reductions in drag they are not without their
disadvantages, principle among these are the requirements for a trailer to be a practical item for
carrying loads. For the teardrop design to be aerodynamically efficient it should follow the fineness
ratio where the ratio between its length and height should be between 2 and 4 with the widest part
about a third of the total length from the front (consider the tear drop trailer and cab as one unit),
this therefore places design constraints on the height of the rear as the design requires an initial
increase in height to make the tear shape, height is regulated by law and so a genuine increase in
carrying capacity may prove difficult to achieve.
54. The constantly changing height could also make fitting and securing loads difficult while the
reduction in size of the rear doors can make loading/unloading operations difficult. The boat tail
would seem to negate these downsides however EU laws place strict rules on lengths, heights and
overhangs of vehicles and this could be prohibitive in this case. Further considerations of inter-
operability with other driving cabs must be taken into consideration
55. The ultimate driving goal in improving aerodynamics will be in the value for money it
represents, fuel will make up a large amount in the cost of fleet running and while reducing
aerodynamic drag is an appealing aspect it may not reduce fuel costs in proportion to the cost of
the design ideas. While the reduction of emissions is attractive it will not be fully considered until
legislation either enforces it or, allows it by authorising design alterations as alluded to by the
Transport and Environment FKA report from para 52.
23+24
(Carter, 2011)
18. 16
Trailer Height and Design
56. A critical aspect in aerodynamic drag is the height of the trailer in relation to the height of the
cab, this is known as the t/c ratio. Although the cab is a relatively poor aerodynamic shape it does
contain devices to improve the air flow over and around it, a standard box trailer has few of these
devices, therefore if the trailer height is much larger than the cab height the flow of air will be
hindered by these large area.
57. By dividing the trailer height by the height of the cab gives us the t/c ratio. Wind tunnel tests
have shown that a t/c ratio of less than 1.2 has a negligible effect on drag coefficient (Cd), however
after 1.2 Cd rose considerably due to this increase in surface area (fig 14). The increase is a
combination of the air hitting the surface area of exposed trailer and also that some of the air hitting
the trailer will be directed down between it and the cab, this increases negative pressure.
Fig 14. Effect of t/c ratio on Drag coefficient (Cd)25
58. This increase of Cd amounts to 0.23 which is considerable, the t/c ratio is stopped at 1.5 as
this represents the maximum trailer height allowed by law. In order to reduce this problem most
trucks are designed with a set trailer it can pull and these designs would ensure the t/c ratio to be
1.2 or less. However fleet managers may need to task cabs to pull or backhaul different trailers
depending on the needs of the company, in this instance a cab could be required to pull a trailer
outside of its ideal t/c ratio.
59. To counter this a cab roof deflector can be utilised, this was discussed briefly in para 49.
The deflector will direct the air to flow up and over the air gap between cab and trailer and flow
further down the trailer (fig 15). An adjustable deflector will allow the altering t/c ratios for different
trailers to be accounted for. As discussed previously deflectors are affected by crosswinds which
can sometimes increase Cd.
Fig 15. Effect of deflector on directing airflow26
25+26
(Heisler, 2002)
19. 17
Conclusion
60. The design of vehicles has changed considerably over time, it is still an evolving process
which changes in-line with our understanding of the physics of forces and the development of
materials to make vehicles lighter and stronger. As task 3 has shown a big push for altering
vehicle design comes from fuel efficiency savings and legal requirements for it.
61. This assignment covers a wide range of technical difficulties in vehicle design, by drawing on
lessons covered within the science modules I was able to produce the calculations required.
Because of this I was able to complete tasks 1 and 2 quickly and ahead of schedule which then
gave me more time to consider the effects of aerodynamic resistance, this is a large feature of
vehicle design and I have addressed how much more important it becomes as vehicles travel at
quicker speeds. I had initially underestimated how much work would be required for task 3 but
internet research provided me with an excellent report from the transport and environment agency
which helped a great deal.
62. This assignment was enjoyable to complete, the area of aerodynamics is very interesting to
me and is something I will look to study further at degree level, in hindsight I wouldβve liked to have
carried out some computer aided drawing to show the effect of changing a vehicle shape to reduce
drag.
BIBLIOGRAPHY
Carter, M. (2011). Aerodynamics in HGV's.
Defence School of Electronic and Mechanical Engineering. (n.d.). Engine and Vehicle Design and
Performance Student Notes Version 1.
Dings, J. (2012, February). www.transportenvironment.org. (J. Dings, Ed.) Retrieved November 17,
2014, from transportenvironment.
Genral Dynamics Land Systems. (2014, November 11). Retrieved from General Dynamics Land
Systems: http://www.gdls.com/index.php/products/other-vehicles/ocelot
Greer, A. &. (1989). Tables, Data and Formulae for Engineeers & Mathematicians. Cheltenham:
Stanley Thomas.
Heisler, H. (2002). advanced vehicle technology (2 ed.). Oxford: Butterworth Heineman.
Sully, F. (1974). Motor Vehicle Craft Studies 380 (Vol. 1). London: Butterworth & Co LTD.
Ware, P. (2010). Military Jeep. Yeovil: Haynes Publishing.
Wikipedia. (2014, December 16). Retrieved from Wikipedia: http://en.wikipedia.org/wiki/Jeep
Figures
All figures taken from the sources quoted.
Tables
Except where stated all tables produced by the author.
Annex:
A. Conversion table.