Transcript Design Alternative 1 - University of Idaho
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
Regulator Pressure: Breaking Time (seconds) Volumetric Flow Rate:[SCFM]
85 85 85 85 85 4.07
2.46
4.60
7.60
2.23
4.19
6.5
6.5
6.5
6.5
6.5
Volume of air needed: ft^3 Lug Torque: [ft-lbf]
2.6455
1.599
2.99
4.94
1.4495
2.7248
80 80 80 80 80
Average
90 90 90 95 95 95 95 1.41
1.41
2.26
1.69
7.57
2.48
3.36
2.37
3.95
6.5
6.5
6.5
6.5
6.5
6.5
6.5
0.9165
0.9165
1.469
1.100666667
4.9205
1.612
2.184
1.5405
2.56425
80 80 80 80 80 80 80
Average Average
100 100 100 100 3.13
1.87
1.76
1.59
2.09
6.5
6.5
6.5
6.5
2.0345
1.2155
1.144
1.0335
1.356875
80 80 80 80
Average
105 105 105 105 110 110 110 110 100 100 100 100 100 105 105 105 105 105 105 2.80
1.50
1.47
1.53
1.83
1.45
1.59
1.35
1.35
1.44
3.15
4.20
3.69
2.83
4.06
3.59
2.88
2.50
2.15
2.17
1.85
1.77
2.22
6.5
6.5
6.5
6.5
6.5
6.5
7.5
7.5
7.5
7.5
7.5
7.5
7.5
7.5
(cont’d)
2.1
1.125
1.1025
1.1475
1.36875
1.0875
1.1925
1.0125
1.0125
1.07625
6.5
6.5
6.5
6.5
6.5
2.0475
2.73
2.3985
1.8395
2.639
2.3309
1.872
1.625
1.3975
1.4105
1.2025
1.1505
1.44
80 80 80 80 80 80 80 80 100 100 100 100 100 100 100 100 100 100 100
Average Average Average Average
Total amount of air required for 6 lug nuts
Solving for total mass of air needed for the impact wrench for 6 lug nuts Air flow from experiment assumes an average flow of 7.5 scfm Q = 7.5
60 [ft 3 /s] = ('Air' , T=T1, P=P1) T1 = 70 [F] mass air = 1.284 [lb Q = 0.125 [ft 3 /s] m ] time = 18 [s] P1 = 112 [psig] m = · Q [lb m /s] Finding total mass of air required assuming 3 seconds per lug and 6 lugs time = 3 · 6 [s] mass air = m · time [lb m ]
Solution:
mass air = 1.284 [lb Q = 0.125 [ft 3 /s] m ] time = 18 [s] m = 0.07135 [lb m /s] = 0.5708 [lb m /ft 3 ] Volume = 2.25 [ft 3 ] m = 0.07135 [lb m /s] = 0.5708 [lb m /ft 3 ] Volume = 2.25 [ft 3 ] P1 = 112 [psia] T1 = 70 [F] P1 = 112 [psia] T1 = 70 [F]
Pressure vs. Volume of Tank
0.6
0.55
0.5
0.45
0.4
0.35
0.3
0.25
0.2
0.15
0.1
0.05
0 0 1000 2000 Real Air Density Properties 3000 4000 5000 6000
P [PSIA]
Assumes constant mass of air (1.214 lbm found from previous slide, [100 ft*lb of torque])
Pressure vs. Breaking torque
4.50
4.00
3.50
3.00
2.50
2.00
1.50
1.00
0.50
0.00
0 1 2 3 4 run number 5 breaking time at 105 psi and 80 ft-lb breaking time at 100 psi and 80 ft-lb 6 7 breaking time at 105 psi and 100 ft-lb breaking time at 100 psi and 100 ft-lb 8
8.00
Breaking time at 5 psi increments (constant torque of 80ft-lb)
psi 7.00
6.00
5.00
4.00
3.00
2.00
85 90 95 100 105 110 1.00
0.00
0 1 2 3 Run 4 5 6
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
Features:
• Pressurized Air Canister • Air Piston with spring return • Moment Arm • Ratchet • Bracing Attachment
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
Piston is 50mm diameter, outputs 441lbf at 145 psi Consumes about 55 in 3 of air per stroke
Components
• Air canister • Valve • Piston • Rack & pinion • Stand Rack and pinion transmits about 160 ft-lbs torque to lug
Rack and piston
• Piston
will be 50mm bore with 100mm stroke, and provide about 440lbf output.
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
• Impact wrench modification and description
• Energy required to remove a lug nut
actuator for air piston and torque
Geared Air Motors
LZB 46 AV0012-11 LZB 42 AR0004-11
Atlas Copco Air Motors
Model
LZB 33 AR0003-11 LZB 42 AR0006-11 LZB 42 AR0004-11 LZB 42 AV0008-11 LZB 46 AR0006-11 LZB 46 AV0012-11 LZB 54 AR0009-11 LZB 54 AV0012-11 Product data at air pressure 6.3 bar (91 psi)
Min. starting torque [lbf. Ft] Air consumption at max. power [scfm] Weight [lb] Free speed [rpm] Direction
170 18 11 25 Reversible 125 199 200 140 150 122 180 28 28 28 30.7
35 37 53 10.7
10.7
10.7
10.8
6 10.3
10.3
55 35 75 62 120 90 125 Reversible Reversible Counter Reversible Counter Reversible Counter
Cost Obs.
$1,640.00
$1,640.00
$1,640.00
$1,700.00
$1,300.00
$1,680.00
Obs.
Cost data from: Productive Tool Products, Inc.
WWW.ProductiveTool.Com
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
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 Cage Hammer Dog Anvil Socket Adaptor
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
Theoretical Energy to Remove a Lug Nut Dimensions from a Typical Passenger Vehicle 1200 1100 1000 900 800 700 600 500 400 300 200 100 50 60 70 80 90 100 110 Torque Applied to Nut [ft*lbf] 120 130 140 150
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