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Webster Engine – Gear Cutting

Following are the details for the gears I will use on my webster engine. The ratio of the gears is 2:1. The plans call for the builder to purchase gears from WM Berg. I will attempt to cut my own based on the dimensions of the commercially available gears.

GEAR 1 : BERG Product number: P32S28-48
No. Of Teeth : 48
Bore : 1/4
Outside Diameter : 1.562
Material : 303 STAINLESS STEEL
Type : SPUR GEARS
Style : PIN HUB
Pitch Diameter : 1.5
Face : 3/16
Pitch : 32
Pin Hub Diameter : 1/2
Overall Length : 7/16
Pressure Angle : 20

Gear 2: Berg Product number: P32S28-24
No. Of Teeth : 24
Bore : 1/4
Outside Diameter : 0.812
Material : 303 STAINLESS STEEL
Type : SPUR GEARS
Style : PIN HUB
Pitch Diameter : 0.75
Face : 3/16
Pitch : 32
Pin Hub Diameter : 1/2
Overall Length : 7/16
Pressure Angle : 20

So basically a 48 teeth with OD 1.562″ and a 24 teeth with OD 0.812 to give the 2:1 ratio.

Trying to find out the module or DP cutter used to make these wheels I then used Marv`s excellent Gear program and using trial and error until I got the following details using a 32DP cutter:

FOR BOTH GEARS:
Gear Ratio = 2.000000:1
Diametral Pitch = 32.0000
Pressure Angle = 20.0000 deg
Center Distance = 1.1250 in = 28.5750 mm

FOR GEAR 1:
Number of teeth = 48
Outside Diameter = 1.5625 in = 39.6875 mm
Addendum = 0.0313 in = 0.7938 mm
Dedendum = 0.0375 in = 0.9525 mm
Whole Depth = 0.0688 in = 1.7463 mm
Circular Pitch = 0.0982 in = 2.4936 mm
Tooth Thickness = 0.0471 in = 1.1969 mm
Pitch Diameter = 1.5000 in = 38.1000 mm
Base Circle Radius = 0.7048 in = 17.9011 mm
Tooth Profile Radius = 0.2565 in = 6.5155 mm

FOR GEAR 2:
Number of teeth = 24
Outside Diameter = 0.8125 in = 20.6375 mm
Addendum = 0.0313 in = 0.7938 mm
Dedendum = 0.0375 in = 0.9525 mm
Whole Depth = 0.0688 in = 1.7463 mm
Circular Pitch = 0.0982 in = 2.4936 mm
Tooth Thickness = 0.0471 in = 1.1969 mm
Pitch Diameter = 0.7500 in = 19.0500 mm
Base Circle Radius = 0.3524 in = 8.9506 mm
Tooth Profile Radius = 0.1283 in = 3.2577 mm

So after all that effort, I identified that the wheels were cut with a 32DP involute cutter. Hummmm, think I may have wasted my time there as the “pitch” quoted on the Berg website for each spur gear identified it as 32…I guess pitch is the cutter DP !! Never mind – Marv`s programe has now given me everything I need to cut the gears!

As the diameter of the gear increases, the profile of the tooth also changes and this is why for each DP or metric module cutter, you can buy 8 different cutters depending on the number of teeth required. This does mean I`m going to have to make 2 cutters….nay mind, if it works for one it should work for the other!

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2 responses to “Webster Engine – Gear Cutting”

  1. Roger says:

    Out of my depth Chris !!!!!

  2. admin says:

    I`m certain not Rodger – I`ve probably over complicated the issue!

    By the way, I know I keep meaning to come around as I really want to show you my little 10V running. I`ll call around one day this week if your free. All the best.
    Chris

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