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

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

Air consumption and torque data

(cont’d)

Total amount of air required for 6 lug nuts Solution:

Pressure vs. Volume of Tank Assumes constant mass of air (1.214 lbm found from previous slide, [100 ft*lb of torque])

Pressure vs. Breaking torque

Breaking time at 5 psi increments (constant torque of 80ft-lb) psi

Modified Chicago Pneumatic Impact Wrench Developed to experimentally determine the effect of changing the moment of inertia of the “Hammer” on wrench performance.

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 ft*lb

Design Alternative 2 Pressurized Air Canister Air Piston with spring return Moment Arm Ratchet Bracing Attachment Features:

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

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

Moment arm Will be about 5 in long Using the 400 lb force from the piston, it will deliver a 170 ft*lb torque on the lug nut

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

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

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

Design Alternative 3 Components Air canister Valve Piston Rack & pinion Stand Rack and pinion transmits about 160 ft-lbs torque to lug Piston is 50mm diameter, outputs 441lbf at 145 psi Consumes about 55 in 3 of air per stroke

Rack and piston Piston * will be 50mm bore with 100mm stroke, and provide about 440lbf output. * Actuation direction F out = 440lbf

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 = 175ft*lb Socket driver

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

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

Design Alternative 4 Pneumatic Torque Actuator** Pressurized air canister Torque actuator Gearing to turn all lugs at once double-acting cylinder

Internal rack and pinion Single piston would activate a rack and pinion At a regulated pressure of 75 psi, it will deliver about 200 ft*lb shaft torque* Displaced volume is about 365 in 3 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

Review of Alternative 4 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 wheels—specialized 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 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

Appendix Current Market Concepts and Products –Geared Air MotorsGeared Air Motors –Torque multipliersTorque multipliers –Electric Impact WrenchElectric Impact Wrench –EZ-LugEZ-Lug Impact wrench modification and description Energy required to remove a lug nut Order numbers for air piston and torque actuatorOrder numbers

Geared Air Motors LZB 46 AV LZB 42 AR

Other Torque Multipliers Eliminator HG by etorque.com which uses gears Square drive Hydraulic Torque Machine by TorcUp, which is attached to a hydraulic compressor Industrial duty torque tools available.

Electric Impact Wrench Connects to cigarette lighter Max. torque: 150 ft. lbs. 10 to 20 impacts per minute 3.8 amps at peak load Reversible rotation Socket sizes: 11/16'', 3/4'', 13/16'' and 7/8''. $19.95 at Harbor Freight

EZ-Lug Mechanical Advantage using Gears Uses 32:1 Gearing Low Cost ($50 to $60) Light Weight (3 pounds) Very Compact

Assembly of existing hammer design Hammer Dog Socket Adaptor Anvil Hammer Cage

Assembly of Modified Hammer Design Steel Collar (increases moment of inertia)

Assembly of Current Rotor (Gas Turbine)

Final Assembly as Shown in Design Alternative 1

Energy Required to Remove a Lug Nut

Component callouts Piston cylinder for design alternative 3: Bimba: A D Torque Actuator: FLO-TORK: A OO-ET-MS1-X-CCW-SR Piston cylinder for design alternative 2: FESTO: , (2½” bore)