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Telephone+44(0)1246268080 Fax +44(0)1246260003Unit 14, Foxwood Ind. Park, Foxwood Rd. Chesterfield, Derbyshire S41 9RN
27. 48
MODULE IMPERIAL
Corrected PCD = (No. of Teeth + 1) x MOD[(No. of Teeth + 1) / DP]
Corrected ØD = (No. of Teeth + 3) x MOD[(No. of Teeth + 3) / DP]
Our SPUR GEARS are made to give 0.07-0.3*Approx. backlash at standard centres. Housingcentres should be nominal +0.00 +0.05mm.
PCD (A) + PCD (B)=
2 * Depends on pitch
CORRECTED TEETH FOR 8 - 17 TEETHON REQUEST OR WHERE LISTED Whole depth = Addendum + Dedendum
FROM NOMINALCENTRES mm
INCREASE IN BACKLASH mm
Tooth thicknessDedendum
AddendumWhole depth
PCD
A
PCD
B
Outside Diameter
CentredistanceNominal
+0.00+0.05
CP
TO FIND:-
PCD
ØD
DP
MODULE
No. of TEETH
CP
ADDENDUM
DEDENDUM
= No. of TEETH x MOD (mm)
= (No. of TEETH + 2) x MOD (mm)
25.4=
MODULECP
= (mm)π
= PCD ÷ MODULE (mm)= MODULE x π (mm)
= MODULE (mm)
= 1.4 x MOD = 1.25 x MOD(0.25-1 MOD) (1.25-8 MOD)
No. of TEETH= (ins)
DPNo. of TEETH + 2
= (ins)DP
π=
CP”25.4
=DP
= PCD” x DPπ
= (ins)DP1
= (ins)DP1.4 (100-24 DP) 1.25 (20-6 DP)
= =DP DP
Root clearance
0.0050.0100.0150.0200.0250.0300.0350.0400.0450.050
0.00370.00740.01110.01480.01850.02210.02590.02950.03280.0370
FORMULAS SPUR GEARS Technical Section
LH LH
LH LH
RH
RH RH
RH
DRIVEN
DRIVER
DRIVER
LH LH
LH
RH
RH
RH
LEFT hand runs with RIGHT hand.
TO FIND:- MODULE IMPERIAL
P.C.D.
ØD
DP (NORMAL)
MODULE
No. of TEETH
CP (NORMAL)
ADDENDUM
Lead
No. of TEETH = (ins)
DP x COS. HELIX )<PCD. + 2
=DP
π=
CP25.4
=DP
= (DP x COS. )<°) x PCD
π= (ins)
DP1
= (ins)DP
No. of TEETH x MOD= (mm)
COS. HELIX )<= PCD + (2 x MOD) (mm)
25.4=
MODULECP
= (mm)π
PCD x COS. )<°= (mm)
MODULE
= MODULE x π (mm)
= MODULE
PCD x π=
TAN )<
Made to give 0.07-0.3mm* approx. backlash at standard centres. Housing centres should benominal +0.00 - +0.05mm.
* dependent on pitch
General Direction of Force
LEFT hand runs with LEFT hand.RIGHT hand runs with RIGHT hand.
CROSSED AXIS
PARALLEL AXIS
RHLH
DRIVEN
DRIVER
DRIVEN
DRIVER
DRIVEN
DRIVER
DRIVEN
27. 49Telephone+44(0)1246268080 Fax +44(0)1246260003Unit 14, Foxwood Ind. Park, Foxwood Rd. Chesterfield, Derbyshire S41 9RN
Technical SectionFORMULAS HELICAL GEARS
Where HELIX )< = HELIX Angle
SPUR GEARS, BSI 436 : 1940
*for other helix anglesmultiply Z by 0.75 sec2 α
*for other helix anglesmultiply Y by 1.33 cos2 α
Cos = Cosine Sec = Secant
1.33 Cos2 17°45’ = 1.2060.75 Sec2 17°45’ = 0.862
ALLOWABLE TANGENTIAL LOAD OF 30° HELIX ANGLE, 20° P.A.
WEAR
Xc Z* Sc Flbs.
K
STRENGTH
Xb Y* Sb Flbs.
DP
Xb = Speed factor for strength
Xc = Speed factor for wear
Y = Strength factor
Z = Zone factor
Sc* = Material rating (surface stress)
Sb* = Material rating (bending stress)
K = Pitch factor DP 0.8 power
F = Face width (inches)
DP = 25.4MOD
ALLOWABLE TANGENTIAL LOAD, 20° P.A.
WEAR
Xc Z Sc Flbs.
K
STRENGTH
Xb Y Sb Flbs.
DP
1N = 0.2248 lbs
Allowable tangential teeth load lbs = Torque lbs ins x 2pcd”
The lowest of the four values for pinion and wheel gives the gearrating. The normal rating for gears is based on 12 hours/day.
Torque lbs ins x .113 = Torque Nm1kg
1 lb = 1N x .2248 =2.20462
Torque Nm= Torque lbs Ins
.113
Xb = Speed Factor for Strength
Xc = Speed Factor for Wear
Y = Strength Factor
Z = Zone Factor
Sc* = Material Rating (surface stress)
Sb* = Material Rating (bending stress)
K = Pitch Factor DP 0.8 Power
F = Face Width (inches)
α = Helix Angle
DP = 25.4MOD
LOAD CALCULATIONS SPUR & HELICAL
HELICAL GEARS, BSI 436 : 1940
Technical Section
* Please refer to Material Strength page for values.
27. 50Unit 14, Foxwood Ind. Park, Foxwood Rd. Chesterfield, Derbyshire S41 9RN
Telephone+44(0)1246268080 Fax +44(0)1246260003
27. 51Telephone+44(0)1246268080 Fax +44(0)1246260003Unit 14, Foxwood Ind. Park, Foxwood Rd. Chesterfield, Derbyshire S41 9RN
Rpm 1 2 4 6 8 12 18 24.5136
103060
100200400500600800
100020003000400050007000
10000
2.602.141.801.571.431.181.02
0.9350.8250.7300.7000.6800.6350.6100.5200.4500.4150.3800.3400.305
2.101.801.441.251.130.920.82
0.7350.6500.5800.5500.5300.5000.4800.4150.3550.3250.3050.2700.240
1.651.441.140.970.900.730.64
0.5850.5200.4600.4400.4250.4000.3800.3250.2800.2600.2400.2150.190
1.451.251.0
0.870.790.640.57
0.5150.4600.4000.3800.3700.3500.3350.2900.2500.2250.2100.1900.165
1.311.150.900.790.720.580.52
0.4700.4150.3600.3500.3400.3200.3050.2600.2250.2070.1900.1700.152
1.161.000.780.680.630.510.45
0.4100.3600.3200.3050.2900.2700.2600.2200.1950.1800.1650.1500.130
1.000.860.670.600.540.430.39
0.3500.3100.2700.2600.2500.2400.2300.2000.1700.1550.1450.1300.115
0.900.780.620.540.480.400.35
0.3200.2800.2500.2400.2300.2200.2100.1800.1550.1450.1320.1180.105
SPEED FACTORS SPUR & HELICALXc FOR WEAR
Xb FOR STRENGTH
RUNNING TIME (hours per day)
Rpm 1 3 6 12 24.614
10305080
100200400500600800
100020003000400050007000
10000
1.061.000.900.800.700.650.62
0.6000.5250.4350.4200.4150.4100.3850.3250.2850.2600.2400.2150.192
0.90.860.760.690.610.560.53
0.5100.4250.4000.3800.3700.3450.3300.2850.2450.2250.2080.1850.165
0.820.770.690.630.550.510.48
0.4300.4050.3600.3450.3300.3100.2950.2550.2200.2000.1850.1650.148
0.730.700.630.570.480.460.43
0.4100.3600.3200.3100.3000.2850.2700.2300.2000.1820.1680.1500.135
0.670.640.570.520.450.420.39
0.3750.3300.2950.2850.2750.2550.2450.2100.1800.1650.1520.1380.120
RUNNING TIME (hours per day)
Telephone+44(0)1246268080 Fax +44(0)1246260003Unit 14, Foxwood Ind. Park, Foxwood Rd. Chesterfield, Derbyshire S41 9RN
27. 52
No. ofTeeth
in Gear 400 200 150 100 80 60 50 40 30 26 20 15 12 1010121520263040506080
100150200400
Rack
1.091.401.842.483.093.504.274.955.607.008.00— ———
1.081.381.792.392.943.323.954.585.116.146.888.32———
1.081.361.752.322.853.163.794.304.815.626.347.448.32——
1.071.341.692.202.642.903.503.844.215.005.516.346.888.009.70
1.071.321.642.122.532.763.273.653.894.575.005.626.147.008.40
1.061.281.582.002.362.542.933.283.573.894.214.815.115.606.50
1.051.261.531.892.232.402.763.003.283.653.844.304.584.955.50
1.051.251.481.752.062.302.532.762.933.273.503.793.954.274.65
1.041.241.431.681.881.982.302.402.542.762.903.163.323.503.70
1.031.221.411.631.801.882.062.232.362.532.642.852.943.093.20
1.021.191.341.531.631.681.751.892.002.122.202.322.392.482.55
0.971.101.211.341.411.431.481.531.581.641.691.751.791.841.90
0.921.011.101.191.221.241.251.261.281.321.341.361.381.401.47
0.850.920.971.021.031.041.051.051.061.071.071.081.081.091.12
NUMBER OF TEETH ON PINION
No. ofTeeth
in Gear Rack 400 200 150 100 80 60 50 40 30 26 20 15 12 1010121520263040506080
100150200400
Rack
2.032.352.803.434.274.896.117.478.42
10.88—————
1.952.262.703.354.104.695.806.747.388.89
10.67————
1.882.192.613.243.904.475.486.306.837.949.26
11.30———
1.852.162.553.183.804.275.186.006.507.508.40
10.0011.20——
1.762.062.443.003.583.954.725.415.836.707.358.429.17
10.55—
1.741.992.362.903.423.764.444.945.356.156.717.508.009.11
10.92
1.641.892.252.703.143.463.984.474.765.425.886.506.887.488.50
1.581.812.162.562.963.223.704.184.394.945.365.926.206.677.34
1.501.712.012.392.742.933.343.703.934.424.675.075.335.686.00
1.451.611.832.162.442.612.923.203.383.743.944.244.374.634.91
1.401.551.742.032.292.442.722.943.123.413.603.843.964.144.36
1.291.441.611.822.022.172.382.552.662.872.973.173.253.353.44
1.181.281.431.601.731.832.002.142.222.362.432.522.682.692.81
1.091.171.291.431.541.601.721.811.871.982.052.142.192.262.36
1.001.091.181.271.381.451.521.581.641.751.781.841.881.94—
NUMBER OF TEETH ON PINION
HELICAL GEARS FOR 30° HELIX ANGLE, 20°P.A.
SPUR GEARS, 20°P.A. Z
ZFor other helix angles, multiply zone factor by 0.75 x Sec2 helix angle. NOTE 0.75 x Sec2 17° 45’ = 0.826
ZONE FACTORS SPUR & HELICAL Technical Section
27. 53Telephone+44(0)1246268080 Fax +44(0)1246260003Unit 14, Foxwood Ind. Park, Foxwood Rd. Chesterfield, Derbyshire S41 9RN
HELICAL GEARS WITH 30° HELIX ANGLE, 20° P.A. AND 20° P.A. SPUR GEARSFor other helix angles, multiply zone strength by 1.33 x Cos2 helix angle. NOTE: 1.33 x Cos2 17° 45’ = 1.206
No. ofTeeth
in Gear Rack 400 200 150 100 80 60 50 40 30 26 20 15 12 1010121520263040506080
100150200400
Rack
The zone factor (Z) is a factor dependent on the totalcontact between mating teeth and the radii of curvatureof the tooth surfaces.Internal Gears - The zone factor for internal gears shall beequal to that for the same combination of external teethmultiplied by:-
R + 1 0.8 Power( )R=Ratio R — 1
The Strength Factor (Y) is a factor dependent on thenumber of teeth in contact, the cantilever strength of anindividual tooth, and the distribution of load over the faceof the tooth.Internal Gears - The strength factor for the pinion gearingwith an internal gear shall be the same as that for a pinionof the same number of teeth gearing with a rack. Thestrength factor for the internal gear shall be the same asthat of a rack gearing with a pinion having the samenumber of teeth as the actual pinion, multiplied by:-
3(1 + – ) T
where T is the number of teeth in the internal gear.Idler Gears The idler gears in which the teeth makecontact on one side with the driving gears and on theother with the driven gears, should be calculated on the
normal basis for wear, but the speed co-efficient used incalculating the load capacity for strength must be half thenormal value.Multiple Contact - If a gear makes contact on the same setof flanks with more than one other gear, the equivalentrunning time per day is to be taken as the sum of thoseapplying to the separate mating gears.
Given the variety of gear types, service requirements,environmental influences and service temperatureranges, the choice of lubricant is an important factor forthe service reliability and service life of the machineconcerned. The following are recommended, on thebasis of DIN 51 509 (Selection of Lubricants for Gears):-1. At peripheral velocities up to v = 2 m/s:High-consistency adhesive lubricants are used on largeopen gears.2. At peripheral velocities up to v = 4 m/s:Here, splash-lubrication using a soft gear-grease iscustomary into which the gear wheel dips3. At peripheral velocities up to v = 15 m/s:Here it is oil splash-lubrication which predominates4. At peripheral velocities above v = 15 m/s:In this range, oil spray lubrication is required in most cases.
.600
.658
.714
.770
.813
.838
.876
.900
.913
.928
.931
.930
.928
.924—
.585.639.697.750.790.813.854.872.883.896.897.893.889.882.869
.580
.630
.687
.738
.776
.796
.837
.858
.865
.875
.875
.870
.867
.861
.850
.579
.625
.681
.731
.768
.788
.824
.848
.856
.863
.864
.858
.855
.850
.839
.575
.618
.670
.720
.753
.772
.803
.822
.833
.839
.840
.835
.833
.828
.820
.573
.614
.664
.713
.742
.759
.788
.806
.815
.821
.822
.820
.818
.814
.808
.568
.605
.653
.698
.725
.738
.761
.776
.783
.791
.793
.780
.793
.791
.789
.566
.600
.646
.686
.699
.716
.736
.752
.758
.765
.767
.770
.771
.772
.767
.563
.597
.638
.677
.671
.677
.693
.705
.716
.728
.734
.740
.743
.747
.755
.561
.593
.631
.652
.633
.623
.642
.644
.654
.673
.683
.697
.703
.713
.728
.558
.591
.626
.642
.627
.611
.607
.620
.630
.645
.661
.676
.681
.695
.714
.554
.585
.617
.626
.614
.602
.574
.582
.590
.602
.613
.628
.638
.654
.684
.548
.573
.598
.605
.595
.582
.555
.544
.549
.562
.571
.584
.591
.607
.642
.542
.562
.580
.579
.572
.560
.535
.517
.523
.533
.541
.552
.561
.576
.606
.533
.550
.563
.562
.551
.543
.518
.490
.500
.511
.518
.533
.537
.550
.582
NO. OF TEETH ON MATING GEAR OR PINION
GEAR LUBRICATION
STRENGTH FACTORS SPUR & HELICAL
Y
Telephone+44(0)1246268080 Fax +44(0)1246260003Unit 14, Foxwood Ind. Park, Foxwood Rd. Chesterfield, Derbyshire S41 9RN
27. 54
TO FIND:- PINION WHEEL
PCD
PITCH ANGLE(for 90° shaft angle)
PITCH ANGLE(for shaft angle <90°)
PITCH ANGLE(for shaft angle > 90°)
CONE DISTANCE
nd = or n x mod
DP(ins) (mm)
n = No. of teeth.-1 n
Y = tan (deg)N
-1 sin ΣY = tan
N + cos Σn
Σ = SHAFT ANGLE-1 sin (180 – Σ)
Y = tan N – cos (180 – Σ)n
DAo =
2 sin Γ
([ ][ ]
)
ND = or N x mod
DP(ins) (mm)
N = No. of teeth.
Γ = 90 – Y (deg)
Γ = Σ – Y
Γ = Σ – Y
See Pinion * see note
TO FIND:- MODULE IMPERIAL
ØD
TANGENT OF THE LEAD ANGLE
CENTRE DISTANCE
TO FIND:- MODULE IMPERIAL
THROAT Ø
TIP Ø
P.C.D.
REDUCTION RATIO
= (No. of TEETH + 2) x MOD (mm)
= (No. of TEETH + 3) x MOD (mm)
= No. of TEETH x MOD (mm)
No. of TEETH + 2= (inches)
DP
No. of TEETH + 3= (inches)
DP
No. of TEETH= (inches)
DP
No. of TEETH in WHEEL=
No. of STARTS in WORM
PCD (WORM) + PCD (WHEEL)CENTRE DISTANCE = 2
Our WORMS and WORMWHEELS are made to give 0.08 - 0.15mm backlash at standard centres.Housing centres should be nominal +0.00 +0.05mm.
FORMULAS - WORMS & WHEELS
(2 x MODULE) + PCDmm
MODULE x No. of STARTSPCD
PCD (Worm) + PCD (Wheel)in mm
2
2 + PCD”DP
CP” x No. of STARTSPCD x π
PCD” (Worm) + PCD” (Wheel)2
* A pitch angle (Σ) greater than 90° indicates an internal gear. Please contact Technical to determine if the gear can be cut.
FORMULAS BEVEL GEARS Technical Section
27. 55Telephone+44(0)1246268080 Fax +44(0)1246260003Unit 14, Foxwood Ind. Park, Foxwood Rd. Chesterfield, Derbyshire S41 9RN
ALLOWABLE TANGENTIAL LOAD AT PITCH RADIUS
WEAR
Xc Sc Z F C - Fx lbs.
K x 1.33 1.1 x C
STRENGTH
Xb Sb Y F C - Fx lbs.
P 1.1 x C
hrs per dayApprox.
Total hours life
Wear multiply by
Strengthmultiply by
Gear torque =allowable Tangential Load x PCD”
2
Allowable Tangential Load =Gear Torque x 2
PCD
0
0.5
1
3
6
12
24
0
100
1000
5000
10000
26000
52000
3.0
2.91
2.38
1.66
1.35
1.0
0.79
2.0
1.89
1.55
1.27
1.14
1.0
0.9
(
( )
)
Based on 12 hour day.
Cone Distance C = PCD" of Gear2 x Sin Pitch Angle of Gear
Allowable tangential load at PCR = Torque lbs ins x 2PCD”
Pitch Angle of Gear = 90° – Pitch Angle of Pinion
Pitch Angle of Pinion = tan –1 No. of Teeth PinionNo. of Teeth Gear
Xc = Speed factor for wear
Z = Zone factor (see chart)
Sc* = Material rating (surface stress)
Sb* = Material rating (bending stress)
K = Pitch factor DP 0.8 power
F = Face width (inches)
Xb = Speed for strength
Y = Strength factor
C = Cone distance (inches)
P = DP
lbs
The lowest of the fourvalues for pinion and wheelgives the gear rating. Thenormal rating for gears isbased on 12 hours/day.
BEVEL GEARS, BSI 545 : 1949
LOAD CALCULATIONS BEVELS
Technical Section
* Please refer to Material Strength page for values.
Telephone+44(0)1246268080 Fax +44(0)1246260003Unit 14, Foxwood Ind. Park, Foxwood Rd. Chesterfield, Derbyshire S41 9RN
27. 56
BEVEL GEARSmaximum ratio 4:1 Gleason
No. ofTeeth
in Gear 15 16 19 20 24 25 26 30 32 45 48 60 7215161920242526303245486072
1.8001.8502.0502.1002.2452.2502.2552.3502.3802.4502.5002.600
—
1.8501.9502.2352.2402.2602.2652.2652.4552.5002.6502.7002.740
—
2.0502.2352.3002.3552.6002.6002.6502.7502.7553.0003.0003.1003.150
2.1002.2402.3552.4502.7302.7402.7502.7702.7753.2003.3003.3503.400
2.2452.2602.6002.7302.8502.9002.9503.2003.2503.6003.6503.7503.800
2.2502.2652.6002.7402.9002.9003.0503.2503.3003.7503.7503.8003.950
2.2552.2652.6502.7502.9503.0503.2003.4003.4503.8003.8504.0004.100
2.3502.4552.7502.7703.2003.2503.4003.6503.7004.1004.2004.5004.700
2.3802.5002.7552.7553.2503.3003.4503.7003.7004.2004.3004.7004.850
2.4502.6503.0003.2003.6003.7503.8004.1004.2005.0005.2005.8005.950
2.5002.7003.0003.3003.6503.7503.8504.2004.3005.2005.4005.9006.100
2.6002.7403.1003.3503.7503.8004.0004.5004.7005.8005.9006.6007.000
——
3.1503.4003.8003.9504.1004.7004.8505.9506.1007.0007.700
NUMBER OF TEETH IN MATING GEAR
No. ofTeeth
in Gear 15 20 30 40 60 80152030406080
.625
.585
.570
.580
.600—
.660
.625
.620
.625
.640
.650
.670
.705
.710
.715
.720
.720
.705
.730
.765
.770
.765
.760
.710
.745
.795
.825
.830
.790
—.750.810.840.860.855
NUMBER OF TEETH IN MATING GEAR
Rpm Xc Rpm Xc Rpm Xc Rpm Xc12468
1.000.880.770.700.67
10204060
100
.635
.550
.485
.460
.425
200400600800
1000
.375
.330
.310
.285
.275
2000400060008000
10000
.230
.180
.165
.140
.125
Rpm Xc Rpm Xc Rpm Xc Rpm Xc12468
.66
.64
.62
.59
.58
10204060
100
.570
.525
.480
.460
.425
200400600800
1000
.375
.330
.310
.285
.275
2000400060008000
10000
.230
.180
.165
.140
.125
SPEED FACTORS Xb FOR STRENGTH
SPEED FACTORS Xc FOR WEAR
ZONE FACTORS Z
STRENGTH FACTORS Y
Technical Section
27. 57Telephone+44(0)1246268080 Fax +44(0)1246260003Unit 14, Foxwood Ind. Park, Foxwood Rd. Chesterfield, Derbyshire S41 9RN
O/D of Worm”
PCD of Worm” )
Rubbing Speed Feet/Minute = Worm pcd” x π x RPM12
(
LOAD CALCULATIONS WORMS & WHEELS
Xc = Speed factor for wear (see chart)
0.18 = Constant value
Sc = Material rating - surface stress (see tables)
Sb = Material rating - bending stress (see tables)
efw = Effective face width of wheel
Xb = Speed factor for strength
1.8 = Constant value
M = Addendum in inches
D = Wheel PCD”
Lr = Length at root of wheel teeth in inches
Cosα = Cosine of lead angle of worm
x secant lead angle
TORQUE CAPACITY (based on 12 hour day)WEAR
0.18 Sc Xc efw D1.8 lbs. Ins.
STRENGTH
1.8Sb Xb Lr M D Cosα lbs. ins.
BSI 721 : 1937
1/6 1/4 1/2 1 2 3 4 6 8 10 18 24WearStrength
—0.50
0.380.54
0.420.56
0.470.59
0.550.64
0.620.68
0.680.72
0.780.79
0.870.87
0.940.94
1.151.15
1.241.24
Xc and Xb to be divided by factors below for different hrs/day
efw = 2 x Addendum” (Worm O/D” – Addendum”)
RUNNING TIME (hours per day)
Note : The lowest of the fourvalues for Worm and Wheelgives the gear rating.Cosθ =
Lr = 2 x θ° x Worm O/D2
x 0.01745
Angle θ° = Cos -1 θ
efw
Lr
Technical Section
Telephone+44(0)1246268080 Fax +44(0)1246260003Unit 14, Foxwood Ind. Park, Foxwood Rd. Chesterfield, Derbyshire S41 9RN
27. 58
SPEED FACTORS WORMS & WHEELS
Xb FOR STRENGTH
RPMSpeedFactor RPM
SpeedFactor RPM
SpeedFactor RPM
SpeedFactor
10
15
20
30
40
50
60
70
80
0.560
0.540
0.520
0.500
0.480
0.460
0.450
0.440
0.430
90
100
150
200
250
300
350
400
450
0.420
0.415
0.384
0.365
0.350
0.340
0.335
0.330
0.320
500
600
700
800
900
1000
1500
2000
2500
0.310
0.300
0.290
0.280
0.270
0.260
0.240
0.225
0.210
3000
3500
4000
4500
5000
6000
7000
8000
9000
0.200
0.190
0.180
0.175
0.170
0.160
0.150
0.140
0.135
Technical Section
Xc FOR WEARRPM ofWorm &Wheel 1 4 10 40 100 200 600 1000 20002500
2000
1000
800
500
200
100
40
20
10
2
.19
.21
.26
.27
.32
.42
.48
.58
.65
.71
.82
.17
.185
.24
.25
.3
.38
.46
.55
.6
.7
.8
.165
.18
.23
.24
.28
.36
.43
.51
.56
.61
.71
.145
.155
.195
.21
.245
.32
.37
.45
.50
.54
.65
.13
.140
.175
.19
.23
.28
.34
.40
.45
.48
.57
.118
.13
.16
.175
.20
.260
.31
.36
.41
.44
.54
.099
.107
.135
.15
.17
.220
.26
.31
.34
.37
.45
.090
.097
.125
.135
.155
.20
.23
.28
.32
.34
.42
.078
.085
.106
.115
.135
.17
.20
.24
.27
.29
.36
RUBBING SPEED (ft/min)
27. 59Telephone+44(0)1246268080 Fax +44(0)1246260003Unit 14, Foxwood Ind. Park, Foxwood Rd. Chesterfield, Derbyshire S41 9RN
A B C D E
7,000
8,500
10,000
6,000
Phosphor BronzeSand CastPhosphor BronzeChill CastPhosphor BronzeCentrifugally Cast
Cast Iron (Gray)
A
B
—
—
—
900*
600*
800*
1000*
600*
600
800
1000
600
700
900
1100
600
1400*
1600
2000
750
Find surface stress factor Sc forwheel, under worm material
classification letterBending Stress
Factor SbPounds per
Sq. In.
WHEEL Materials
HPC ‘standard’ wheels use sand cast PB2*For ’standard’ hardened worms use 1400 Sc value for wheels
NOTE: Section E - hardened, ground and polished.HPC Standard Worms Unhardened - Sc = 1400 Sb = 17,000
Hardened - Sc = 6000 Sb= 27,000
Wheel
A B C D E
20,000
22,000
27,000
40,000
47,000
47,000
47,000
0.4% Carbon SteelNormalised0.55% Carbon SteelNormalisedLow-carbon CasehardeningSteel3.5% NickelCasehardening Steel5% Nickel Casehardening Steel3.5% Nickel ChromiumCasehardening SteelHigh Nickel-chromCasehardening Steel
1400
2000
6000
6500
7000
7000
8000
900✝
1100✝
4000✝
4000✝
4000✝
4000✝
4000✝
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
2000✝
2000✝
2000✝
2000✝
* Maximum permissible rubbing speeds, 500 feet per minute.✝ Should not be used except for hand operated gearing.
Bending StressFactor Sb
Pounds per Sq. In.
WORM Materials
Worm
BENDING AND SURFACESTRESS FACTORS WORMS & WHEELS
D
E
C
Find surface stress factor Sc forwheel, under worm material
classification letter
Technical Section
Telephone+44(0)1246268080 Fax +44(0)1246260003Unit 14, Foxwood Ind. Park, Foxwood Rd. Chesterfield, Derbyshire S41 9RN
27. 60
RubbingSpeedFt. permin.
Coeffi-cients ofFriction
RubbingSpeedFt. permin.
Coeffi-cients ofFriction
RubbingSpeedFt. permin.
Coeffi-cients ofFriction
RubbingSpeedFt. permin.
Coeffi-cients ofFriction
30405060708090
100110120130140150160170
0.0730.0700.0660.0620.0600.0580.0560.0540.0520.0510.0500.0490.0480.0470.046
180190200225250275300325350375400425450475500
0.0450.0440.0430.0410.0400.0380.0360.0350.0340.0330.0330.0320.0310.0300.030
550600650700750800850900950
100011001200130014001500
0.0280.0270.0260.0260.0250.0240.0230.0230.0220.0220.0210.0200.0190.0190.018
160017001800190020002100220023002400250026002700280029003000
0.01750.01700.01650.0165 0.01600.01600.01550.01500.01500.01500.01450.01450.01400.01400.0140
Coefficients of Friction for Worm Gearing
Excluding bearing and oil churning losses. Values are based on PB2 Wheels and casehardened and ground and polished worms lubricated by mineral oil. The efficiency maybe improved after the “running in” period. NOTE: As HPC standard worms are nothardened ground and polished lower efficiency values can be expected.
Output Torque 100INPUT TORQUE = x
Ratio Efficiency
OUTPUT TORQUE = Input Torque x Ratio x Efficiency 100
EFFICIENCY WORMS & WHEELS
TAN )<°Efficiency (%) =
TAN (θ°+ )<°)
θ° = TAN-1 f)<° = Lead Anglef = Coefficient of friction
[ ] X 100
Technical Section