Title: PIT Crew Design Concepts
1PIT Crew Design Concepts
By Dan Chapman, Tim Wilson, and Jon
Miller December 11, 2002
2Design 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
3Air consumption and torque data
4(contd)
5Total amount of air required for 6 lug nuts
Solution
6Pressure vs. Volume of Tank
Assumes constant mass of air (1.214 lbm found
from previous slide, 100 ftlb of torque)
7Pressure vs. Breaking torque
8Breaking time at 5 psi increments(constant
torque of 80ft-lb)
psi
9Modified Chicago Pneumatic Impact Wrench
Developed to experimentally determine the effect
of changing the moment of inertia of the Hammer
on wrench performance.
10Review 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
11Design Alternative 2
Features
- Pressurized Air Canister
- Air Piston with spring return
- Moment Arm
- Ratchet
- Bracing Attachment
12Pressurized 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
13Air 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
14Moment 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
15Ratchet
- Allows piston to return to starting position
without retightening the lug nut - Attaches to moment arm
16Bracing 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
17Review 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
18Design 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
19Rack and piston
- Piston will be 50mm bore with 100mm stroke, and
provide about 440lbf output.
20Rack 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
21Stand
- Keeps components accurately positioned
- (dimensions are in inches)
- Eliminates need for customer to provide the
necessary resisting torque by an adjustable lug
nut attachment
22Review 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
23Design Alternative 4
- Pneumatic Torque Actuator
- Pressurized air canister
- Torque actuator
- Gearing to turn all lugs at once
double-acting cylinder
24Internal 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
25Review 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
26Appendix
- 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
27Geared Air Motors
LZB 46 AV0012-11
LZB 42 AR0004-11
28Other 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
29Electric Impact Wrench
30EZ-LugMechanical Advantage using Gears
- Uses 321 Gearing
- Low Cost (50 to 60)
- Light Weight (3 pounds)
- Very Compact
31Assembly of existinghammer design
32Assembly of Modified Hammer Design
Steel Collar (increases moment of inertia)
33Assembly of Current Rotor (Gas Turbine)
34Final Assembly as Shown in Design Alternative 1
35Energy Required to Remove a Lug Nut
36Component 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