2017 CRW: Breakout Session 2: Unbreakable Laws: Physics of a Move

Don Mahnke P.Eng
President
Hydra-Slide Ltd.

2011-present
DESIGN – MANUFACTURING - SALES
• Heavy Track Skidding Systems
• Low Profile Skidding Systems
• Synchronous Power Units
• Hydraulic Turntables
• Ekki Jacking Timbers
• Alignment Shoes
• Climbing Jacks

Why do we care about Physics?
• We generally think only of weight and size.
What happens when we start to move things?

• Forensic Engineers use the Laws of Physics to
look at the underlying causes of accidents

• Laws of Physics can be used to predict what will
happen in order to prevent occurrences

• Laws of Physics can be used to predict what will
happen in order to prevent occurrences
• Let’s look at what happens when you try to break
laws of physics

What We’ll Cover
• Newton’s Laws of Motion

What We’ll Cover
• Types of Forces
• Weight (gravity)
• Inertia/Momentum (Kinetic Energy)
• Centrifugal Force
• Impact Force
• Wind Force

What We’ll Cover
• Types of Forces
• Impact Force
• Wind Force
• Stability
• Airplanes/Barges/Railcars/Trucks/Cranes

What We’ll Cover
• Types of Forces
• Impact Force
• Wind Force
• Stability
• Force – Work – Power

What We’ll Cover
• Types of Forces
• Impact Force
• Wind Force
• Stability
• Choosing the right equipment

What We’ll Cover
• Types of Forces
• Impact Force
• Wind Force
• Stability
• Choosing the right equipment
• First Hydra-Slide Skid System

LAWS OF PHYSICS (Newton’s Laws of Motion)
Sir Isaac Newton
1643 - 1727
First law:
?
Second law:
?
Third law:
?

First law:
An object will remain at rest or move at a constant
velocity, unless acted upon by an external force.
Second law:
?
Third law:
?

First law:
Second law:
Acceleration and force are vectors; an object will
accelerate in the same direction as the direction of
the net force applied. (F = ma).
Third law:
?
A Force acts on an object

First law:
Second law:
Third law:
?
The Force has both Magnitude
and Direction

First law:
Second law:
Third law:
?
The object moves in the
direction of the Force

First law:
Second law:
Third law:
?
The Force can be broken down into
Its Horizontal and Vertical components

First law:
Second law:
Third law:
For every action there is an equal and opposite
reaction.

Force as a Vector
Example:
• Spreader Bars
Estimate Sling Forces

Force as a Vector
Example:
• Spreader Bars
Typical Spreader Bar

Force as a Vector
Example:
• Spreader Bars
Measure Bar Length
and Sling length.
Draw to scale

Force as a Vector
Example:
• Spreader Bars
Draw load weight vectors
To scale
50,000 lbs 50,000 lbs
x

Force as a Vector
Example:
• Spreader Bars
Vertical component in top
Slings must be same as
load weight vectors.
(Equilibrium)
x
x

Force as a Vector
Example:
• Spreader Bars
Force in sling is along sling axis

Force as a Vector
Example:
• Spreader Bars
Measure length of sling Force
(using same scale)
50,000 lbs 50,000 lbs
57,350 lbs

Weight
• Weight is a Force that is a result of
Gravity acting on a Mass.

Weight
• It never changes unless the Mass changes

Weight
• The Force can be considered acting at its
Center of Gravity (or Center of Mass)

Weight
• The Force can be considered acting at its
Center of Gravity (or Center of Mass)
• It always acts straight down

Inertia and Momentum
• Inertia is a tendency to do nothing or
to remain unchanged.

• Momentum is the quantity of motion
of a moving body, measured as a
product of its mass and velocity.
p = m v

• Momentum is the quantity of motion
of a moving body, measured as a
product of its mass and velocity.
p = m v
• Kinetic Energy is the energy that a
body possesses by virtue of being in
motion.
KE = ½mv2

Centrifugal Force
• Centrifugal Force is known as a
“fictitious” force

Centrifugal Force
• It is a reaction to the pull towards the
center of the curve (Newton’s Third Law)

Centrifugal Force
• It is a reaction to the pull towards the
center of the curve (Newton’s Third Law)
• The object wants to continue moving in
a straight line (Newton’s First Law) but is
being pulled towards the center of the
curve. It is being accelerated towards
the center. a = v2
r

Centrifugal Force
Example:
80,000 lb. truck going around a 100’ radius
curve at 30 mph (44 ft/sec)

Centrifugal Force
Example:
80,000 lb. truck going around a 100’ radius
curve at 30 mph (44 ft/sec)
F = m x a
Force = Wt x v2
= 80,000 x (44)2
g r 32.2 100
= 48,000 lbs

When stationary, the total force in the sling is equal
to the weight of the object.
But what if the load falls?
The impact force generated when the load is
stopped depends on three factors:
• The load’s weight
• The distance of the fall (which determines
time and velocity)
• The stopping distance
Impact Forces

Example: A one-ton load falls for one foot and
when it’s caught, the sling stretches by one
inch while arresting the load.
Impact Forces

______
t = √2h/g where g = 32.2 ft/s2
= 0.25 s
_____
V = √2gh = 8.1 ft/s
Impact Forces

______
t = √2h/g where g = 32.2 ft/s2
= 0.25 s
_____
V = √2gh = 8.1 ft/s
The load takes a quarter of a second to
travel one foot, and is moving at 8.1 ft/s.
(about 5.5 mph)
Impact Forces

The load’s kinetic energy is:
KE = 1/2mv2
= 65600 lb∙ft2/s2
and all this energy is absorbed by the slings in one inch:
F = KE = 65600 lb∙ft2/s2
d 0.083 ft
F = 790500 lb∙ft/s2
The equivalent of 24500 lbs
about 12 times the weight of the load.
Impact Forces
12 ton

Wind
Forces
Fw = .0035(v)2
Fw (lbs/ft2)
V (mph)

Wind
Forces
Example: Wind Force on a 15’ x 20’ panel
Gentle Breeze 10 mph Force = 105 lbs
Strong Breeze 30 mph Force = 945 lbs
Storm 70 mph Force = 5,145 lbs

Wind Forces
How much wind would
be needed to blow over
this truck?

Wind Forces
How much wind would
be needed to blow over
this truck?
Truck Righting Moment = 15,000 x 4’-0”
= 60,000 ft-lbs
Wind Force must be more than this
Wind x 8’6” > 60,000
Wind Force > 7,058 lbs
If projected area is about 53’ x 8’-6” = 450 ft2
Wind Pressure = 7058/450
= 15.7 psf (more than 67 mph)

STABILITY
• All forces are in
Equilibrium

STABILITY
Equilibrium
• Righting moment
exceeds the
overturning moment

STABILITY
Equilibrium
• Righting moment
exceeds the
overturning moment
• Lift is within capacity

STABILITY
Unstable
• Overturning moment
exceeds the righting
moment
• Over Capacity

Aircraft Stability
(Roll Stability)
Why are the wings angled up?
Dihedral Angle

Aircraft Stability
(Roll Stability)

Aircraft Stability
(Roll Stability)
Inherent Stability

Aircraft Stability
(Roll Stability)
In some Cargo and Military Aircraft,
stability comes from a low center of gravity.

Barge Stability
A barge floats because
of buoyancy.
The buoyancy force
Is equal to the weight
of water displaced.

Barge Stability
When a load is applied
to the barge, it is pushed
down into the water

Barge Stability
When a load is applied
to the barge, it is pushed
down into the water
and the buoyancy
increases

Barge Stability
If the weight is moved
off center, the barge
tilts.
The buoyancy force
moves to balance the
off center weight.
Inherent Stability

Barge Stability Ballasting to maintain
Stability during roll-on.

Pre-ballast
Water is added into the
barge equivalent to the
weight coming on

Pre-ballast
weight coming on
Water is added to the wing
tanks to be used for leveling
barge

Pre-ballast
weight coming on
Water is added to the wing
tanks to be used for leveling
barge
Additional water can be
added to bring the barge
level to the dock

Barge Stability Roll-on
Place Ro-Ro ramps

Barge Stability Roll-on
Water is moved from one
side tank to the other to
keep barge level
Water is pumped out of
center tank to offset the
weight coming on

Barge Stability
With weight fully on barge
and moving towards center
water is pumped back to
first wing tank to keep
barge level

Barge Stability
With load centered
on barge, all water
is pumped out of
barge

Barge Stability
A potentially dangerous
condition if water is left
in barge during transit
The ballast water can
slosh from side to side
causing decreased
stability

Railcar Stability
Railways move a lot of high volume cargo and their track systems
are designed for high speed movement
Movement of large and heavy objects often presents particular
problems for the Railways

Normal maximum
CCG is 98” ATR
without special handing

Schnabel Railcars
with Side Shift

Transporter Stability
ESTA Recommendations
on 3 or 4 Point suspension groupings

• Load weight not exceed 75% of rated capacity

• Load weight not exceed 75% of rated capacity
• Tipping angle not exceed 9° (7 ° + 2 °)

3 Point suspension groupings
CCG

• Statically Determinant

3 Point suspension groupings – 75% capacity

• Statically Indeterminant

4 Point suspension groupings – 75% capacity

Crane Stability
Force from Load
is applied at boompoint

Crane Stability
“Effective”
Combined Center of Gravity

Crane Stability
Effect of Levelness

Crane Stability
Effect of Levelness
140’ Boom

Crane Swinging a Load
Use Laws of Physics
to predict path of Load

Use Laws of Physics
Crane starts to swing
but load lags behind
due to Inertia.
(Newton’s first Law)

Use Laws of Physics
Crane continues to swing
And load starts to move.
As it picks up speed
Centrifugal Force causes it
to move outward

Use Laws of Physics
Crane continues to swing.
Load moves in a circular path
but at a larger radius

Use Laws of Physics
Crane stops swinging.
Load continues to move
in a circular path at
a larger radius.

Use Laws of Physics
Load continues to move
in a pendulum motion
causing various side loads
on crane.

Use Laws of Physics
Load lags behind crane and
Then swings at a wider radius.
Thanks to NCSG for Simulator Video

Use Laws of Physics
Load lags behind crane
causing sideload on boom

Use Laws of Physics
Load swings at a wider radius
Causing potential overload

Centrifugal
Forces
Centrifugal Force can
increase effective lift
radius and cause side-
loading on boom.

Wind
Forces
A Wind Force away
from Crane can increase
effective lift radius.
A Wind Force from the
side can cause side
loading on boom.

FORCE – WORK - POWER
Force - a Force is defined as any external effort that can cause an object with mass to change its
velocity.
Force can also be described as a push or a pull that has both magnitude and direction, making it a
vector quantity.
The man in the picture below is applying a push Force on the car in a forward direction.

Work - a force is said to do Work when it acts on a body, and causes a displacement in the direction of
the force.
If, as a result of his pushing Force, the car moved forward a certain distance, he has done Work.

Power - Power is the rate of doing work.
It is equivalent to an amount of energy consumed per unit time.
If you consider the time it took to move the car a certain distance, you can calculate the Power.

Application in hydraulics:
If you want to raise an object to a height
• The Force required will be equal to its weight
• The Work required will be equal to its weight times the height of the lift.
(For any given situation these quantities will be fixed)
• The Power required to do it can vary and will depend solely on how fast you want to do it.

Example:
• If you want to lift a 100,000 lb. load up 1 foot
the Work required will be 1 x 100,000 = 100,000 ft-lbf
• If it is done in 2 seconds,
the Power required will be 100,000/2 = 50000 ft-lbsf/sec (or about 100 HP)
• If the same lift is done over 30 seconds,
the Power required will be 100,000/30 = 3330 ft-lbsf/sec (or about 6 HP)
In Hydraulics, it is possible to produce very high Forces and do a large amount of Work with
relatively low Power (but taking a longer time)

Cranes are one of the most common and useful pieces of equipment on a
construction site but may not always be the best choice for moving loads
horizontally.
Choosing the right equipment for the job
Often more than one “right” choice

horizontally.
• Technical Constraints
• Crane availability
• Limits on crane setup space
• Limits on pick and set area
• Overhead clearances and obstructions

horizontally.
• Safety & Risk Assessment

horizontally.
• Safety & Risk Assessment
• Financial
• Crane costs vs. benefits

A 145 ton transformer needs to be
placed on the pad in the foreground.
What is the best way to do it?.......Is
this a job for a crane?
Consider
• Suitability and capacity of
available equipment
• Work space availability
• Safety considerations
• Schedule constraints
• Crew expertise

Transformer 290,000 lbs
Block/Rigging 10,000 lbs
Total Lift 300,000 lbs
• Let’s look at the information for an
800 ton Demag mobile crane to see
if it can do the job.
• Find the operating range in the load
chart for placing the 145 ton
transformer.

• In this case it is determined that the crane has sufficient capacity to lift and place the
transformer and there was sufficient access.
• However, the crane was not chosen…..Why?
• Other considerations:
• The crane was not available at the required time
• The crane would be very expensive to mobilize
• When the Power Station is complete there will not be overhead clearances for the
crane, so it could not be used for a change-out.
• The contractor had just purchased a skid system
• Skidding was considered less disruptive to other operations at the construction
site.

A hydraulic skidding system, sometimes referred to as
a Jack and Slide System
It is a horizontal load handling method that involves hydraulic
cylinders pushing (or pulling) shoes that carry a load over a
controlled friction surface on a guided track.
The force is applied directly to the skid shoe and is completely
contained within the system.
A Case for Skidding Systems

• The ability to move extremely heavy loads.
• The load sits on skid shoes which are
pushed by hydraulic cylinders.
• The load is never freely suspended
• High friction reduces risk of uncontrolled
movement
• No "external forces" and no holdbacks are
required.
• Simple setup.
• Low height for optimum stability

• Newton’s First Law
• Load moves slowly so no appreciable Momentum or Kinetic
Energy. Run away is restricted by friction force.

• Newton’s Second Law
• Forces are inline with direction of move and load moves in
same direction. No centrifugal forces.

• Newton’s Second Law
• Forces are inline with direction of move and load moves in
same direction. No centrifugal forces.
• Newton’s Third Law
• Reaction to pushing force is contained within track and no
external forces.

First “Hydra-Slide” skid system

2017 CRW: Breakout Session 2: Unbreakable Laws: Physics of a Move

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2017 CRW: Breakout Session 2: Unbreakable Laws: Physics of a Move