Tumbler Gear reduction pulley setup

[tomjt182]

Hi, I've built a 8'X4' fur tumbler, I need it to turn 18 to 26 RPM. the sides are made from 3/4" plywood and center circumference is made from 1"X4"X4' pine boards and Axles are 1 1/8" steel shaft, with 1 1/8" pillow block bearings. I'm guessing it weighs 800 pounds. I have a 1 hp TECO VFD phase converter connected to a Dayton 1hp 3 phase 1200 RPM motor, it's connected to a aurora gear reducer right angle 1.72 hp 44 rpm- gear ratio 40:1. The gear reducer has 3" diameter 40 tooth sprocket and the axle has a 6" diameter 40 tooth sprocket, gear reducer is connected directly under the axle. My problem is the tumblers rotational inertia with hides in tumbler is causing the gear reducer to strain at 7 rpm and I need 18rpm & the weight of tumbler & hides tries to speed up the gear reducer causing it to skip teeth, so I've turned it off until I can figure out what pulley system is needed, or a new motor setup. I hope it's detailed enough. I have video & pictures if that would help. Thank you all in advance.

 

[tomjt182]

These are some more photos of Tumbler. Thanks

 

[MikeHalloran]

I assume you mean the _chain_ is skipping teeth, probably because the motor mount is not real stiff, and the driven sprocket is mounted a bit far out on the tumbler axle, which looks a little spindly for what you are doing. If the reducer is skipping teeth internally, it's already scrap.

You could just upsize everything until it starts working, but it would be cheaper to get a Browning or Martin catalog and study the engineering section, and start running the numbers.

For load torque, assume that the entire payload of hides is being lifted at a 4 foot radius, which is pretty close to what actually happens in a tumbler.

Separately, calculate the shaft as a beam, with two simple supports at the pillow blocks, the hide weight plus the tumbler weight applied as two equal forces at the tumbler end planes, and the chain pull (which you get from the torque calculation) applied at the sprocket location.

OR, hire a local engineer to work it out for you.


Mike Halloran
Pembroke Pines, FL, USA

 

[tbuelna]

Way to much polar inertia for the motor/gearbox/chain drive. The load of furs tumbling inside the drum is likely producing a cyclic impulse load on the drivetrain. Your motor/gearbox/chain drive all likely need to be significantly larger, or your drum speed needs to be much lower.

It looks like your chain drive would benefit from a tensioner on the slack side. It would also help to move the two chain sprockets as close together as practical to minimize stretching in the chain. And it would also be a good idea to add another bearing outboard of the driven sprocket so that the sprocket is supported at both ends and is not cantilevered.

Good luck to you.
Terry

 

[tomjt182]

I see what your saying now, I'm gonna upgrade my motor setup. Thank you for replying.

 

[Jboggs]

I would get a much larger driven sprocket. Two or three times bigger. You would get much better speed control.