Is aluminium ok for this project?

[boscawen46]

Hi,
I am converting a small petrol motorbike to electric for my young son. It will be powered by a hub motor ( the motor is actually the hub of the rear wheel.) The hub spins around but the axle cannot itself spin, it is static. The ends of the axles are flattened as in one of the attached photos and the plates that go over the ends of the axle have the same shape "female" hole and these plates are fixed to the motorbike itself. I want to make some 20mm thick plates and machine the same shaped hole as in photo and ideally want to make them out of aluminium or aluminium alloy. Can someone tell me if aluminium at that thickness should have the strength to stop the axle twisting/turning in that hole and if not which aluminium alloy (there seem to be various ones ) would be most suited. I have thought of steel but am trying to keep the weight down. Thanks

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[Someone-Else]

[Thinking out loud] Would that not depend on the properties of the aluminium you intend to use, of which we have no idea? and also the amount of torque this motor can achieve, would it not be best to ask the supplier of the aluminium? or use steel since it will be stronger and the amount used will not add that much in weight [/thinking out loud]

[boscawen46]

Thanks for your reply. The reason I posted my question here is that I thought that being a metalwork forum someone( not everyone) might have worked with aluminium and know something about the best aluminium alloy for a job like this. As mentioned I have thought about steel but two blocks of the size I am thinking would weigh a fair amount and be more difficult to machine etc than aluminium alloy. If anyone has any experience in aluminium alloy that would be great. Thanks

[dewaltdisney]

Hopefully Hitch will pick this up as he is very experienced in metal.

My laymans thoughts are that Aluminium will fatigue out with use and I wondered if you could let in a steel bush to act as the housing rather than just the alloy?

DWD

[ayjay]

I'm not a metalworker or a metallurgist, but I like to tinker and make "stuff". I'd use mild steel for this, yes it's harder to work than aluminium, but doesn't that say something about the suitability of aluminium for this project?

Why does it need to be 20mm thick? If it's a question of filling the available space I'd still use mild steel, probably 6mm thick and then plain washers to make up the extra 14mm.

[Hitch]

Steel for that without a doubt.
The constant taking up any slight movement will eventually wear the aluminium I'd think, eventually ending up with a rounded hole and spinning axle.

[Bob225]

I would not make them out of alloy, they look to be standard bicycle wheel locking tabs or solid axel tabs they stop the wheel dropping out or in the case of a hub motor or drum brake they stop it twisting

edit. if just want to space the hub out, a bit of round tube will do the trick (to centre the hub in the frame) failing that flat washers will do the job

[Dave54]

If you have the standard plate, then can't you arrange it so that engages on the frame to stop it turning, and just use a plain bush type spaces for the rest?
As ayjay has already said, I've just seen!
Agree with the others. It needs to be steel.

[Bob225]

If you want something to cover the end of the axle, crash bobbins, skate board wheels or even a set of bmx stunt pegs

The world is your lobster http://www.chainreactioncycles.com/

edit. Just remembered the correct name.................... Safety Washer

[boscawen46]

All brilliant answers and appreciated. Many thanks

[Bob225]

iirc all bicycle type solid axels are 3/4" thread, back in my youth we used a few nuts, and a domed nut to finish

[Dave54]

iirc all bicycle type solid axels are 3/4" thread. . .

They must be some big bikes you worked on!
Typo?

[Bob225]

I meant 3/8" thread, front hubs and cheaper Chinese rear hubs are 5/8

Its been a long while since I messed with solid axels