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# Gear wear rig design

## Gear wear rig design

(OP)
Hi All,
Below I've attached a sketch of the rig designed to wear down the gears.
Firstly my project idea is to test the durability and overall wear of plastic & 3D printed gears however the 3D prints will be electroplated to see what difference it potentially makes.

The idea of the rig is to have a motor attached to the two gears which I wanna see being worn down. In order to do so however I need to determine the load that they'll be working on and I am not sure how to approach it so it's most efficient.
The pulley would have a belt which would be sliding on top with a mass attached on one side this way I can add on more weight to increase the friction and therefore the load if needed, and the other side is would have the belt fixed.

My question is as I feel a bit stuck now for calculations and general of where to start off with the calculations as I will need to work a little backwards form my understanding

Should I select the gears first, and find out what the teeth maximum load is? From there determine the friction torque of the pulley and then determine the required motor?

I am fairly stuck for what calculations to use to get me started, and I need this to work on my actual concept now and start my tests.

I'll really appreciate help, it'll cure my curiosity.

Thank you

Edit Apologies, in the sketch the pulley should be going clockwise.

### RE: Gear wear rig design

Depends on what power range you are in. If tens or hundreds of kW, which I do not believe it is, I would use a brake motor to conserve energy.
If you use the arrangement shown, I recommend that mass and fixed change places. Otherwise you will have an uneven and not so easy to control torque in the brake.
For brake torque as such, look up the Capstan equation. You can vary the torque by changing the contact angle using a guide roll. That is often more convenient than using different masses.

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

### RE: Gear wear rig design

maybe you should take a look at the design of the FZG gear test rig. i suppose many of its features regarding load control could be replicated in a low power rig for plastic gears.

see: https://www.strama-mps.de/en/products/test-rigs/fz...

### RE: Gear wear rig design

How long do you expect to run test before the belt catches fire from the friction heat?

Walt

### RE: Gear wear rig design

(OP)
Thanks for the info, I'm looking at all the options, calculating the torque of the pulley at the moment and selecting my plastic gears so I'll have their spec to use for a further selection.
I am not sure how soon I'll need to put out a fire but trial and error should do the trick right?

### RE: Gear wear rig design

The trick is to have the pulley hollow and add water to it. The loss energy turns water to steam and cools everything so you do not get any higher than around 100 C. Used in many high-powered dynos only twenty years ago. But mostly brake motors now, not much heat there.

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

### RE: Gear wear rig design

A brush type DC motor can be used as a torque load. Maximum torque is created with the motor leads shorted but a variable power resistor can be used to control the torque.

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