1. HORSEPOWER
• Defined as the amount of energy or work required to raise a weight of 33,000
pounds a height of one foot in one minute.
• 1 hp = 33,000 ft-lbs/min
INDICATED HP
• Is the power developed in the engine cylinder.
• This does not represent the actual useful power delivered by the engine.
• Ihp = PLANn/2C
Tractor Engine Indicated and Brake Horsepower Formula
IHP = [P L A N n ] / [ 2c ]
BHP = IHP – FHP
= IHP x ξe
Where:
IHP - indicated horsepower, hp
BHP - brake horsepower, hp
FHP - friction horsepower, hp
ξe - engine efficiency, decimal
BRAKE & EFFECTIVE HP
• BP is the actual horsepower delivered by the engine to the drive shaft.
• BP = IHP – FRICTION
• EFFECTIVE HP is the final power delivered to the equipment. The difference
between IHP & EHP should be only around 25%.
• FRICTION POWER - is the power absorbed by the engine in generating itself
with a given speed and without any load.
• Mechanical efficiency – ratio of the BP over the IP x 100.
ME = (BP/IP) x 100
Sample Problem:
• Given: BP = 75 KW ME = 84%
N = 400 rpm
P = 760 KPa
4-stroke, cycle single cylinder
a) Determine the IP and
b) Size of the engine if B = S
B = bore (diameter of the piston);
S = stroke (length of travel of piston)
P - mean effective pressure, psi
L - piston stroke, ft
A - area of the piston, in2
N - crankshaft speed, rpm
n - number of cylinders
2. • Piston Displacement = the volume displaced by the piston in one stoke.
• Clearance Volume = volume left in the cylinder when the piston is at the TDC.
Sample Problem:
• What is the bore & stroke of an engine that has a CV of 160,000 mm^3, a
compression ratio of 5:1, a 575 mm flywheel, a piston speed of 5 m/s & a rim
speed of 45 m/s.
DRAWBAR POWER
• The power available at the drawbar hitch located at the rear of the tractor.
• Use for pulling, dragging, and other tractive works.
DP = Pw – Pl
= Pw – (Ps + Pr
• DP = Drawbar Power
• F = Force
• S = Speed
FSDP =
Pw - wheel axle power
Pl - power loss
Ps - power lost due to slip
Pr - power lost due to rolling
resistance
![HORSEPOWER
• Defined as the amount of energy or work required to raise a weight of 33,000
pounds a height of one foot in one minute.
• 1 hp = 33,000 ft-lbs/min
INDICATED HP
• Is the power developed in the engine cylinder.
• This does not represent the actual useful power delivered by the engine.
• Ihp = PLANn/2C
Tractor Engine Indicated and Brake Horsepower Formula
IHP = [P L A N n ] / [ 2c ]
BHP = IHP – FHP
= IHP x ξe
Where:
IHP - indicated horsepower, hp
BHP - brake horsepower, hp
FHP - friction horsepower, hp
ξe - engine efficiency, decimal
BRAKE & EFFECTIVE HP
• BP is the actual horsepower delivered by the engine to the drive shaft.
• BP = IHP – FRICTION
• EFFECTIVE HP is the final power delivered to the equipment. The difference
between IHP & EHP should be only around 25%.
• FRICTION POWER - is the power absorbed by the engine in generating itself
with a given speed and without any load.
• Mechanical efficiency – ratio of the BP over the IP x 100.
ME = (BP/IP) x 100
Sample Problem:
• Given: BP = 75 KW ME = 84%
N = 400 rpm
P = 760 KPa
4-stroke, cycle single cylinder
a) Determine the IP and
b) Size of the engine if B = S
B = bore (diameter of the piston);
S = stroke (length of travel of piston)
P - mean effective pressure, psi
L - piston stroke, ft
A - area of the piston, in2
N - crankshaft speed, rpm
n - number of cylinders](https://image.slidesharecdn.com/horsepower-180822025542/85/horsepower-1-320.jpg)
