How much wrap should one aim for with a 15 tooth sprocket with #35 chain? A search on CD yielded a few thread that said one should aim for 180 degrees with #25 chain.
We are looking at using a 60T sprocket attached directly to our arm. There would be two CIM motors with Sport gearboxes and 15T sprockets on their output shafts. We are intending to use a fourth sprocket on a shaft to increase the wrap around the sprockets on the Sport gearbox shafts.
I assume you’re arranging the sprockets (not including the idler) in a sort of triangle configuration?
180 degrees is certainly good practice whether you’re dealing with chains (#25 or #35) or even belts, that said, it is possible to get away with less than 180 depending on the application. The biggest concern is really tooth engagement, in the case of the larger 60t sprocket, you’re probably ok anywhere between like 180 and 120 degrees or so, but you’ll definitely want to maximize the contact on your smaller sprockets (which the 4th sprocket would, theoretically, do).
Without knowing the specifics of your application (load on the arm, sprocket spacing and layout, etc.) it’s hard to give a definitive answer. Is there any more detail you could provide (drawings, CAD, pictures, etc) that might help us see exactly what you’re trying to do? Short of that, all we can really do is speak in generalities, which may not give you a good answer for your specific mechanism.
If you set up the sprockets like shown in this quick SW sketch, you’ll get about 180° of wrap on all your sprockets. That should be enough to transfer the required torque and keep them from slipping.
(The sprockets are to scale, but the distances between them can be changed to fit your needs)
Thanks again, Ari
That sketch is exactly the arrangement we are considering. Even the scale is about right. We were aiming for something near 180 degrees of wrap.
Is there a number of teeth that one should aim for on each sprocket?
As many as possible, but never less than about 1/5 of them. Rule of thumb
