PIT Crew Design Concepts

1
PIT Crew Design Concepts
By Dan Chapman, Tim Wilson, and Jon
Miller December 11, 2002
2
Design Alternative 1

• Experimental Data
• Air consumption for a given torque of lug nut
• Pressure vs. volume of tank assuming a constant
  mass of air
• Pressure and torque vs. breaking time
• Modification
• Review

3
Air consumption and torque data
4
(contd)
5
Total amount of air required for 6 lug nuts
Solution
6
Pressure vs. Volume of Tank
Assumes constant mass of air (1.214 lbm found
from previous slide, 100 ftlb of torque)
7
Pressure vs. Breaking torque
8
Breaking time at 5 psi increments(constant
torque of 80ft-lb)
psi
9
Modified Chicago Pneumatic Impact Wrench
Developed to experimentally determine the effect
of changing the moment of inertia of the Hammer
on wrench performance.
10
Review of Alternative 1

• Strengths
• Impact design requires very little strength by
  user
• Impacting mechanism has already been designed

• Concerns
• Consumes a large amount of air
• Will need pressures approaching 6000 psi to
  contain the needed amount of air in a standard
  bottle for 6 lug nuts
• Will need more air to remove bolts torqued higher
  than 100 ftlb

11
Design Alternative 2
Features

• Pressurized Air Canister
• Air Piston with spring return
• Moment Arm
• Ratchet
• Bracing Attachment

12
Pressurized Air Canister

• Could contain up to 2000 psi of air
• Would be able to push piston about 90 times
• Enough air for 6 lug nuts
• Already designed by Autoliv
• Would also incorporate a pressure regulating
  device

13
Air piston

• With a bore of 2.5 in and a pressure of 90 psi
  piston will deliver 400 lb of force
• It will also have a spring return that will force
  the air out and pull the piston arm back

14
Moment arm

• Will be about 5 in long
• Using the 400 lb force from the piston, it will
  deliver a 170 ftlb torque on the lug nut

15
Ratchet

• Allows piston to return to starting position
  without retightening the lug nut
• Attaches to moment arm

16
Bracing attachment

• It will attach to another lug nut
• The whole tool will now be attached to two lug
  nuts
• This will allow the piston to apply a large
  torque to the tightened lug nut without the user
  having to hold on and resist the torque

17
Review of Alternative 2

• Strengths
• Requires very little physical strength
• With adjustable attachment, user does not have to
  resist applied torque
• 3 step usage
• Attach air canister
• Attach to lug nut
• Activate

• Concerns
• Manufactured piston is relatively expensive
• Safety issues involved with pressures of 2000 psi

18
Design Alternative 3
Piston is 50mm diameter, outputs 441lbf at 145
psi Consumes about 55 in3 of air per stroke

• Components
• Air canister
• Valve
• Piston
• Rack pinion
• Stand

Rack and pinion transmits about 160 ft-lbs torque
to lug
19
Rack and piston

• Piston will be 50mm bore with 100mm stroke, and
  provide about 440lbf output.

20
Rack and pinion

• Rack and pinion will provide a moment arm of
  4.75 and deliver a torque of about 175 ft-lbs.
• The output will be a 0.5 or 0.375 square drive
  (like the impact wrench).

Torque 175ftlb
Socket driver
21
Stand

• Keeps components accurately positioned
• (dimensions are in inches)
• Eliminates need for customer to provide the
  necessary resisting torque by an adjustable lug
  nut attachment

22
Review of Alternative 3

• Strengths
• No need for user applied resistant torque.
• 3 step usage attach canister, lug nut, activate

• Concerns
• Removes 6 lugs per canister of air (if canister
  is at 3000 psig)
• Much larger than existing equipment

23
Design Alternative 4

• Pneumatic Torque Actuator
• Pressurized air canister
• Torque actuator
• Gearing to turn all lugs at once

double-acting cylinder
24
Internal rack and pinion

• Single piston would activate a rack and pinion
• At a regulated pressure of 75 psi, it will
  deliver about 200 ftlb shaft torque
• Displaced volume is about 365 in3
• At an initial bottle pressure of 1500 psi there
  would be just enough air to remove 1 lug nut

Calculations were performed with a single
cylinder model similar to the annotated one above
25
Review of Alternative 4

• Concerns
• Air consumption quite high (7 bore and a 9
  stroke)
• Would require a starting pressure of about 11,000
  psi to remove 6 lug nuts
• Safety issues involved with using pressures
  around 11,000 psi
• Larger than existing equipment

• Strengths
• Could potentially turn all four to six lug nuts
  at once (the actuator has very high torques but
  at cost of much higher pressure)
• Removal of all lug nuts at once would require an
  adapter that would only fit certain
  wheelsspecialized product for each car
  manufacturer
• Simple design mainly uses existing components but
  could be redesigned for a limited use application
• Compact design
• Current models available on the market

26
Appendix

• Current Market Concepts and Products
• Geared Air Motors
• Torque multipliers
• Electric Impact Wrench
• EZ-Lug
• Impact wrench modification and description
• Energy required to remove a lug nut
• Order numbers for air piston and torque actuator

27
Geared Air Motors
LZB 46 AV0012-11
LZB 42 AR0004-11
28
Other Torque Multipliers
Industrial duty torque tools available.
Eliminator HG by etorque.com which uses gears
Square drive Hydraulic Torque Machine by TorcUp,
which is attached to a hydraulic compressor
29
Electric Impact Wrench
30
EZ-LugMechanical Advantage using Gears

• Uses 321 Gearing
• Low Cost (50 to 60)
• Light Weight (3 pounds)
• Very Compact

31
Assembly of existinghammer design
32
Assembly of Modified Hammer Design
Steel Collar (increases moment of inertia)
33
Assembly of Current Rotor (Gas Turbine)
34
Final Assembly as Shown in Design Alternative 1
35
Energy Required to Remove a Lug Nut
36
Component callouts
Piston cylinder for design alternative 2 FESTO
160655, (2½ bore)
Piston cylinder for design alternative 3 Bimba
A-50-100-D
Torque Actuator FLO-TORK A-4000-184-OO-ET-MS1-X
-CCW-SR