Can an axle connected to a wheel transmit momentum to the plate to which it is attached?

[cahewstone]

Basically I am calculating how many bolts to use for an aluminum plate that connects to the shaft of a motor that drives a wheel. The shaft is connected by bearings to the plate, so it should transmit very little moment to the chassis through the plate, but I don't know if I'm thinking about it right, especially when the wheels connected to the motor start running (should I maybe push the bolts with the maximum torque of the motor at that instant?).

 

[DaveC426913]

Diagram? Not sure of the arrangement of plate to shaft.

 

[cahewstone]

Ok, sorry for the simple drawing. I hope it helps. First, the plate that conect the shaft with the robot.

So, the big hole is where the shaft pass, the three little holes araund are part of the shaft holder. The other holes are for attaching the plat to the robot. The robot has a motor that conect with a wheel

 

[Baluncore]

If the shaft passes through an efficient bearing, then torque will not be transmitted to the plate. Only translation forces will act in the plane of the plate.

There will be vertical forces on the bearing, due to the weight of the robot and its load. There will be a horizontal force on the bearing, due to the drive or braking torque applied to that wheel through that axle.

 

[Tom.G]

You might consider what happens if the bearing seizes, common with sleeve bearings, almost unheard of with ball or roller bearings.

Oh, and don't forget the motor mounting bolts.

Cheers,
Tom[/i]

 

[cahewstone]

Thanks for your answer! I'ts clear to me now, that the torque should be insignificant. Taking advantage of the previous question, I think it could be useful to consider the maximum force generated by an impact (such as a fall for example). Do you have any idea how I could estimate it well?

 

[Baluncore]

Do you have any idea how I could estimate it well?

What could it fall onto?
How much time falling, then how much time stopping?

It is hard to predict accidental damage, so often better to build it and test it under harsh conditions. Parts that never break should be reduced in weight, until they do break. Parts that break should be strengthened locally, or reengineered only where the part broke.

 

[Juanda]

You might consider what happens if the bearing seizes, common with sleeve bearings, almost unheard of with ball or roller bearings.

Oh, and don't forget the motor mounting bolts.

Cheers,
Tom[/i]

I had no idea sleeve bearings commonly seize. I'm assuming you're referring to metallic sleeves, maybe welding themselves to the shaft due to the generated heat? Is that the case?
Have you heard of plastic-made sleeves seizing as well for whatever reason?

 

[Tom.G]

I'm assuming you're referring to metallic sleeves, maybe welding themselves to the shaft due to the generated heat?

When the lubrication fails and under high loads or high speeds, the bare metal shaft scrapes against the bare bearing material. With no protective oxide or lubricant film between them, the two metals then cold-weld¹ together. This usually starts on the microscopic level and rapidly increases with continued usage.

Have you heard of plastic-made sleeves seizing as well for whatever reason?

I have not but I have little experience with plastic bearings. That said, plastic bearings can, depending on the situation, cold-flow, thus allowing misalignment.
Another consideration is due to their softness, plastic bearings need a clean environment. Particles in the air can be small and hard enough to get into them and grind them down.

(1) Cold-flow: Under a compressive load plastics can deform, much like putty deforms when you stick your finger in it. However the plastic won't return to its previous shape.

Cheers,
Tom

 

[Baluncore]

Plastic sleeve bearings are able to absorb water, and so if machined dry, and then used in a wet environment, will expand by a few percent. That can lock a shaft solid, in a plastic bearing. A plastic sleeve bearing therefore needs more initial clearance than does a bronze sleeve.

Plastics are more durable when operated wet. For example, PE is protected from UV and ozone damage if it is kept wet. That is good for bearings, but distressing for sea life. Water is a natural lubricant of rubber, which makes braking on a wet road more difficult.

Dirt from the environment may enter the clearance of a plastic sleeve bearing. Fine grit then becomes embedded in the soft plastic, which protects the plastic, but scours the metal shaft. That is similar to mills, where steel shafts ran in wooden blocks, lubricated by tallow. The steel shafts rapidly wore, due to grit becoming embedded in the softer wood blocks.

 

[Lnewqban]

We

Thanks for your answer! I'ts clear to me now, that the torque should be insignificant. Taking advantage of the previous question, I think it could be useful to consider the maximum force generated by an impact (such as a fall for example). Do you have any idea how I could estimate it well?

Welcome!

How is power transferred from the motor shaft to the wheel?
Is the bearing self-aligning?
Any flexible coupling between shafts?

I am asking those questions based on a concern of mine about moment and thrust forces induced by weight and impacts on the single pivot of the bearing and the motor or coupling.

If that happens, you may see potential misalignment and overload of bearing, coupling and motor guts.

 

[cahewstone]

We

Welcome!

How is power transferred from the motor shaft to the wheel?
Is the bearing self-aligning?
Any flexible coupling between shafts?

I am asking those questions based on a concern of mine about moment and thrust forces induced by weight and impacts on the single pivot of the bearing and the motor or coupling.

If that happens, you may see potential misalignment and overload of bearing, coupling and motor guts.

Hi! Thanks for your answer.

The power is transfered through a pulley, so i think thats going to prevent damage and impacts. The bearing, i believe is self-aligning, cause is the same bearing used in a car (nisssan tiida), so i thinks its probably ok!