Gear Wear Rig Design: Calculating Load for Maximum Durability

[Aciek]

Below I've attached a sketch of the rig designed to wear down the gears.f
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 want to 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.

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 will really appreciate the help with what kind of equations I should use for determining these.

Apologies in the sketch the pulley should be going clockwise.

 

[anorlunda]

Welcome to PF. I hope we can help.

I would describe your project as two parts.

1. You have some gears that must meet requirements, including wear.
2. You want to design a gear testing rig. The rig should handle a range of gears. It should also be adjustable so that it duplicates the required conditions on the gears being tested.

Perhaps a third part might be added; how to instrument the rig to record the results.

Is that a good explanation of your goals?

 

[Aciek]

Hi, thank you for the quick reply.
Mostly I can select any gears that I want as I will be 3D printing duplicates, just need to select them and I've decided for now I will only work with nylon spur gears, that's why the design is very simple.

 

[jrmichler]

Your rig will work at low speeds and loads. Be aware that you show no way to measure the tension on the slack side of the friction belt, so your only knowledge of the gear torque will be the motor current. The accuracy will be low, although it may be good enough for your purposes.

For higher loads and speeds, plus better accuracy, search four square gear test rig. Most of the hits discuss precision tachometers and strain gages. If your accuracy requirements are not too stringent, none of that stuff is necessary.

 

[Baluncore]

Gears are usually tested in pairs on parallel shafts. A motor drives one shaft with two fixed gears on that shaft. The lay-shaft has one meshed gear fixed, the other is spring loaded to set the contact force. When the motor runs it only has to turn the gears, it does not need to overcome or set the gear face contact pressure which is set only by the spring coupling.

 

[Aciek]

I've the gears now selected and will be sourcing the pulley and belt now. After having a look at an appropriate motor so I've made progress. Still open for any suggestions and discussion. Thank you all.

 

[Baluncore]

search four square gear test rig.

That is good advice.

I've the gears now selected and will be sourcing the pulley and belt now. After having a look at an appropriate motor so I've made progress. Still open for any suggestions and discussion.

Do you understand that you only need to apply a closed loop of forces between the faces of four gears that remain meshed. Force is not work until a distance is travelled. In your design, all the energy sourced by the motor will go into heating and burning the brake belt.