Sprocket Teeth engagement

[CavemanJones]

Hello all,
Does anyone know if there is a formula for calculating chain wrap on a sprocket based off of speed/force? I am certain there is, but I have looked and couldn't find a sure shot answer. Can anyone help with this?

Thanks,
Josh

 

[hydtools]

Is this any help?

http://www.emerson-ept.com/eptroot/public/schools/beltchan.pdf

Ted

 

[JJPellin]

In your question, you did not specify if you are referring to a chain drive or a cog belt drive. But, in either case, I have never seen a relationship between wrap angle and speed or power. In both cases, the wrap angle is only dependant on the geometry (center distance and sprocket diameters). Are you referring to something other that wrap angle? If not, then the attachment from hydtools has the proper formula for calculating wrap angle.

Johnny Pellin

 

[CavemanJones]

Yes, sorry I was looking in a Tsubaki book and they were talking about back tension required on belt and chain, and in the equation it had variables for wrap degrees. In the same section there was a discussion about force related to back tension.. I just thought possibly the RPM might have some to do with the requirements.

The document that he provided is very helpful. Its saying a MIN of 120°. That was what I was looking for. Sounds like there isn't a correlation between wrap required and force or speed. I was wondering if there was.

Example - If I had a conveyor and I was pulling a light load, I was thinking it might only need a few teeth engaged.

 

[JJPellin]

I do not generally work with chain drives, only with cog belts. But, for cog belts, the limitation is generally the minimum diameter of the smaller sprocket. This has the same affect, since the smaller the sprocket, the greater the running tension in order to transmit a given horsepower. I have never seen the limitation called out as minimum wrap angle. The minimum sprocket diameter is often related to the bearing load capability of a standard NEMA frame motor as the driver. I have run into a problem where the resulting belt tension caused a high cycle fatigue failure of the shaft end on the driven machine. In this case it was a ductile iron shaft in a lobe blower.

Johnny Pellin