Related Resources: calculators
Plastic Spur Gearing Design Hp and Operating Stress Equations and Calculator
Plastics Engineering and Design
Mechanical Gear Design and Engineering
Plastic Spur Gearing Rated Design Hp, Operating Stress Equations and Calculator
Choice of plastics gear material depends on requirements for size and nature of loads to be transmitted, designated speeds, required life, working environment, type of cooling, lubrication, and operating precision. Because of cost plastics gears are sometimes not enclosed in sealed housings, so are often given only a single coating of lubricant grease. Overloading of lubricated plastics gear teeth will usually cause tooth fracture, and unlubricated teeth often suffer excessive wear. Thermoplastics strength varies with temperature, with higher temperatures reducing root stress and permitting tooth deformation. In calculating power to be transmitted by spur, helical, and straight bevel gearing, the following formulas should be used with the factors given in tables below.
Preview Plastic Spur Gearing Rated Design Hp, Calculator
Internal and External Spur Gears Rated Hp in US Customary Units
HP = ( Ss F Y V ) / ( ( 55 ( 600 + V ) P Cs )
Internal and External Spur Gears Rated Hp in Metric Units
KW = ( F Y m Ss V ) / ( 327 ( 3.05 + V ) Cs )
Operating Stress Ss in US Customary Units Internal and External Spur Gears
Ss = [ HP ( ( 55 ( 600 + V ) P Cs ) ] / ( F Y V )
Operating Stress Ss in Metric Units Internal and External Spur Gears
Ss = [ KW ( 327 ( 3.05 + V ) Cs ) ] / ( F Y m V )
Where:
Ss = safe stress in bending (lbs/in2, (from Table 2);
F = face width in inches (mm);
Y = tooth form factor (from Table 1);
m = module, (mm); = Ref. Dia / No. teeth
C = pitch cone distance in inches (mm);
Cs = service factor (from Table 3);
P = diametral pitch in inches (mm);
Pn = normal diametral pitch in inches (mm);
V = velocity at pitch circle diameter in ft/min (m/s).
V = ( rpm π D ) / 12 = ft/min
Table 1 Tooth Form Factors Y for Plastic Gears
|
Number
of Teeth |
14 - 1⁄2° Involute
or Cycloidal |
20° Full Depth
Involute |
20° Stub Tooth
Involute |
20° Internal
Full Depth |
|
|
Pinion
|
Gear
|
||||
|
12
|
0.210
|
0.245
|
0.311
|
0.327
|
…
|
|
13
|
0.220
|
0.261
|
0.324
|
0.327
|
…
|
|
14
|
0.226
|
0.276
|
0.339
|
0.330
|
…
|
|
15
|
0.236
|
0.289
|
0.348
|
0.330
|
…
|
|
16
|
0.242
|
0.259
|
0.361
|
0.333
|
…
|
|
17
|
0.251
|
0.302
|
0.367
|
0.342
|
…
|
|
18
|
0.261
|
0.308
|
0.377
|
0.349
|
…
|
|
19
|
0.273
|
0.314
|
0.386
|
0.358
|
…
|
|
20
|
0.283
|
0.320
|
0.393
|
0.364
|
…
|
|
21
|
0.289
|
0.327
|
0.399
|
0.371
|
…
|
|
22
|
0.292
|
0.330
|
0.405
|
0.374
|
…
|
|
24
|
0.298
|
0.336
|
0.415
|
0.383
|
…
|
|
26
|
0.307
|
0.346
|
0.424
|
0.393
|
…
|
|
28
|
0.314
|
0.352
|
0.430
|
0.399
|
0.691
|
|
30
|
0.320
|
0.358
|
0.437
|
0.405
|
0.679
|
|
34
|
0.327
|
0.371
|
0.446
|
0.415
|
0.660
|
|
38
|
0.336
|
0.383
|
0.456
|
0.424
|
0.644
|
|
43
|
0.346
|
0.396
|
0.462
|
0.430
|
0.628
|
|
50
|
0.352
|
0.480
|
0.474
|
0.437
|
0.613
|
|
60
|
0.358
|
0.421
|
0.484
|
0.446
|
0.597
|
|
75
|
0.364
|
0.434
|
0.496
|
0.452
|
0.581
|
|
100
|
0.371
|
0.446
|
0.506
|
0.462
|
0.565
|
|
150
|
0.377
|
0.459
|
0.518
|
0.468
|
0.550
|
|
300
|
0.383
|
0.471
|
0.534
|
0.478
|
0.534
|
|
Rack
|
0.390
|
0.484
|
0.550
|
…
|
…
|
- These values assume a moderate temperature increase and some initial lubrication.
- With bevel gearing, divide the number of teeth by the cosine of the pitch angle and use the data in the table.
- For example, if a 20-deg PA bevel gear has 40 teeth and a pitch angle of 58 deg, 40 divided by the cosine of 58 deg = 40 ÷ 0.529919 ≈ 75, and Y = 0.434.
Table 2 Recommended Bending Stress Values for Plastic Gears
| Plastic Type |
Recommended Stress | |||
| Unfilled | Glass-Filled | |||
| (lb/in2) | (MPa) | (lb/in2) | (MPa) | |
| ABS | 3,000 | 20.68 | 6,000 | 41.37 |
| Acetal | 5,000 | 34.47 | 7,000 | 48.26 |
| Nylon | 6,000 | 41.37 | 12,000 | 82.74 |
| Polycarbonate | 6,000 | 41.37 | 9,000 | 62.05 |
| Polyester | 3,500 | 24.13 | 8,000 | 55.16 |
| Polyurethane | 2,500 | 17.24 | ... | ... |
Table 3 Service Factors Plastic Gears
| Load | 8-10 hr/day | 24 hr/day | Intermittent 3 hr/day |
Occasional 1/2 hr/day |
| Steady | 1.00 | 1.25 | 0.80 | 0.50 |
| Light Shock | 1.25 | 1.50 | 1.00 | 0.80 |
| Medium Shock | 1.50 | 1.75 | 1.25 | 1.00 |
| Heavy Shock | 1.75 | 2.00 | 1.50 | 1.25 |
References:
Machinerys Handbook, 29th Edition
Link to this Webpage:
© Copyright 2000 -
2024, by Engineers Edge, LLC
www.engineersedge.com
All rights reserved
Disclaimer |
Feedback
Advertising
| Contact
