four stroke engine gearing

[brickyParticipant @bricky]

I have tried to work this small gear train out but I have got it wrong.Can somebody calculate the size of the gear blanks please as the blanks I have made don’t all engage.

The module is 0.5 the centres of the gears from crankshaft to camshaft is28.31mm the gears are 32 to 48 then18 to24

the crank is 32 and the cam is 24 the middle two 48 and 18 on the same arbour. If I have to drive the cam direct the gears will be too big as they will stick out to far and would make the model ugly.I would appreciate any assistance given.

Frank

[JasonBModerator @jasonb]

For MOD gears the formula is (No of Teeth +2) x Mod

48T = 25mm dia

32T = 17mm dia

24T = 13mm dia

18T = 10mm dia

The other way to do it is have a single idler gear, off to one side then you could use say 36/18 and whatever you want on the idler. Probably another 18T to keep it simple.

 

[JAParticipant @ja]

Jason’s suggestion is the way forward. As said, in a simple train the number of teeth on the idler is not relevant. However if it is one tooth different from either of the other wheels you have a “hunting tooth” which helps to spread oil over the gear wheels. This is of little importance on a model but is nice to have.

JA

[brickyParticipant @bricky]

Thank you for your replies ,I will start again and remake the blanks,I might try the three gear suggestion.much appreciated .

Frank

 

[Howard LewisParticipant @howardlewis46836]

The camshaft and circuit breaker need to run at half engine speed, but in the correct direction.

With a simple Idler or even a compound one (Although why introduce another complication?) the cam will have the same direction of rotation as the crankshaft)

With a 32T on the crank, the canshaft would need a 64T, which will be too big to fit in

A 24 on the cam will call for a 12T on the crank, which is about as small as you want to get

I would go for a 18T driver, with a 36T on the camshaft, with an idler, suitably sized, and placed at the correct centres, to keep things as simple as possible.

Crank / Idler / Cam centre distances can be used as a help in calculating the sizes of the driver, driven and idler, if you want to keep the idler position the same.

 

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