Understanding OM's taper-hobbed (TH) gearbox

[Gerald_D]

Copied from another thread:

That "tapered hob" issue: A hob is a tool for cutting a gear, why is Oriental practically the only company in the world that makes an issue of the tool with which the gear is cut? Its like saying my house was built with a 2lb claw hammer - why is that supposed to make a difference?

[Dirk Hazeleger]

I have no idea as far as the tapered hob issue. They don't publish the spur gear spec, and I think the rep was guessing when I asked him. It would be interesting to break down both reducers and see what the real difference is.

[Gerald_D]

The "tapered hob gear" is actually a "taper gear". From a newsletter:


http://www.mechmate.com/Forum/messages/15/2039.gif


I suppose the pitch diameter is an average across the width of the gear.


http://www.mechmate.com/Forum/messages/15/2041.gif

[Gerald D]

The above posts bumped for Mike :)

From the picture, the tapered gear is only on the final meshing pairs of teeth - there are one or two pairs before that without wear compensation (no. of pairs depend on overall ratio).

Unless the tapered adjustment is spring-loaded, the gears will not self-compensate for wear. There is probably a wave washer (http://images.google.co.za/images?hl=en&rlz=1T4IRFA_enZA279ZA280&um=1&sa=1&q=wave+washer&aq=f&oq=&start=0) behind the tapered layshaft.

The wear rate could be higher because the tapered gear has a sliding action between parts of the gear teeth (the small side of the gear has a different "ratio" to the big side) My guess is that the actual amount of taper is very little, otherwise the wear would be high.

Range of gearboxes: http://www.orientalmotor.com/products/ac-dc-step-motors/geared-step-motors.html

The output shaft may be the one that is spring loaded. You might be able to feel this if you pull on a TH's shaft vs a SG shaft.