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Best method of retaining bond between collars/plates on motor shaft

Best method of retaining bond between collars/plates on motor shaft

(OP)
Hello,

I hope I can state this concisely and clearly for you all.

I have a small 12v motor (automotive heater blower motor to be exact). It has a 5/16 "D"-shaft.
Mounted on the shaft is a "propeller" (for lack of a better term) sandwiched between two shaft collars.
The motor does not produce tremendous RPM (maybe 1000) nor torque, and unfortunately, i can tell you neither...it is the size of your fist.

The propeller has a 5/16 hole thru it, with no "D"..just a full hole.
This leaves the only method of preventing the prop from unwanted spinning..is the compression between the two shaft collars. I prefer NOT to use glues/welding, as that makes disasassembly impossible.
Granted...a single hole drilled thru all 3 with a pin or screw would prevent spin...but that is not an option labor/effort/tooling wise.


To date, I have used:

1.) Star washers between the collars and the prop - This required a difficult clamping process of the collars to create friction on star washer before tightening collars. And it also applies a side load to shaft collar. Not sure if that matters.I drizzled a little epoxy over the assembly before final tightening.
I dislike this assembly because it requires extreme clamping of collars to affect any real friction on star washers. Wrong solution.

2.)By the time this pic was taken, I had upgraded the components, and switched to faucet washers which required much less force to retain friction with the propeller.
This was a far, far easier assembly with regards to the clamping and tightening of collars, and utilizes no epoxy...which allows for repair/disassembly.
My concern is this: All my life I have seen rotten, decomposing hose-washers, faucet washers, gaskets, o=rings, etc.
I have no idea whether these washers are rubber, HDPE, or what. I do not know their performance under the rather extreme pressure they are under, nor their lifespan. It worries me that they could decompose and compromise the device. They still don't seem like the right fit. I do not feel that the faucet washers are a proper solution.


Which brings me to my questions.

1.) I have considered that perhaps there is some sort of coating that one could paint on the two surfaces to increase their friction...perhaps some sort of Loctite offering like this: https://www.mcmaster.com/#91458A520
2.) I am really leaning towards rubber coated zinc washers..I presume they would have at least a 10 year lifespan?
https://www.mcmaster.com/#90130A030
3.) But there are also just EDPM rubber washers, Buna-rubber washers, etc.

And these look cool too, but don't provide near the surface contact of zinc rubber-coated or a rubber washer.
https://www.mcmaster.com/#93783A030
So, in closing...do the rubberized washers seem like the way to go? Or should I go with a coating, or some sort of other mechanical solution?

Thanks so much for any comments or advice.

RE: Best method of retaining bond between collars/plates on motor shaft

What's the production volume? Do you know if the coupling needs to transmit significant torque in both directions, or just one?

You've already got an anti-rotation feature on the motor shaft (the D profile), so one of your options must surely be to use it. If the production volumes are very low, I'd be thinking in terms of modifying the shape of the hole in the propeller with a hand file, then filling the resulting gap with a key.

A.

RE: Best method of retaining bond between collars/plates on motor shaft

(OP)
Zeusfaber:

I never even thought of a key! Don't work with motors/shafts/collars much.
The torque is fairly low, and it only spins one direction.

The propeller is only 1/2" wide...with 5/16 of that occupied by the hole thru it, so I have very little room on the short sides of the hole, but could put it on the long side of the hole.
Production is in the dozens right now. Apart from filing, is there any quicker way to notch the propeller?

Great idea.

RE: Best method of retaining bond between collars/plates on motor shaft

What's the propeller made of?

How does it get to be the shape it is?

A.

RE: Best method of retaining bond between collars/plates on motor shaft

(OP)
The propeller is 6 of these stacked.
The hole in the center that goes thru all of them is enlarged by me to 5/16.
These are being made in a garage with little if any machining capability. We have a hand drill, Dremel, etc.
Would happily swap it out for some other platter, but have not thought of anything yet.
https://www.lowes.com/pd/The-Hillman-Group-1-2-in-...

RE: Best method of retaining bond between collars/plates on motor shaft

If you're not going to be transmitting a lot of torque, it might be possible to elongate the hole in just one of the plates (making it a job you could do by hand or with a Dremel) and build a flat key into the middle of the stack.

A.

RE: Best method of retaining bond between collars/plates on motor shaft

(OP)
I'm not following you on this idea.
Build a flat key into the middle of the stack? How would a key make it thru all the others in the stack?
Thx

RE: Best method of retaining bond between collars/plates on motor shaft

Get yourself a 'D' punch to enlarge the holes.

OR have a local sheet metal shop make the laminae for you with a central D hole, and other holes as appropriate. They can probably beat the price you are paying, for lots of ~500 parts or so.

The full radius on the ends can be expensive; consider a truncated radius or two chamfers.

Mike Halloran
Pembroke Pines, FL, USA

RE: Best method of retaining bond between collars/plates on motor shaft

(OP)
Geat ideas.
I think I will look into having a shop do them. I only utilized those because they worked well in a prototype capacity.
The ends could be square..I don't think it would matter.
I like the idea of getting a shop to do them because then they could just be plate stock instead of the unwanted flex that occurs with the current configuration.
Thx for the ideas.

RE: Best method of retaining bond between collars/plates on motor shaft

Buy the cheaper zinc/aluminum collars and drill an axial hole for a pin or bolt through them, mating to a hole in your propellor.

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