How to attach a thin wheel?

XNOR

Greetings,

I am having a problem attaching a wheels to a motor shaft.
(This is not related to Parallax).

I've attached a drawing of the wheel in question.

The wheel is attached by fitting the motor shaft into a hole in the rim (by friction fitting).
The problem is that the wheel "wobbles" because the rim is very thin.
I don't have any tools to make very precise right-angle pieces to balance the wheel.
Does anyone have any ideas what I could do?

Thanks!

Catharsis

Maybe consider attaching two wheels into one.

Robert Kubichek

Get a flanged hub with the same hole size as the motor shaft.
Is the shaft keyed? If not, the hub would need a balanced setscrew.
Here are some sites that might help you;
http://www.pololu.com/
http://www.active-robots.com/

Bob

tech-mech

After attaching the wheel you can try tracking it like they do light aircraft props.

Pick a fixed spot on the bot and use somethng to measure the distance to the wheel, rotate the wheel a little and measure again, bend the wheel until all points are the same distance from the reference point.

Dale

Ken Gracey

How about this:

Use a washer on the motor's side of the shaft, or a collar with set screw. Put another collar and wide flat, round washer on the outside. The collars will provide a square 90-degree surface to which the wheel may attach, preventing the wobbles. A bit of experimentation with washers and collars should do the trick.

- Ken

LoopyByteloose

I suspect collars and set screws will tend to slip and loosen up.

You might try radio-controlled model airplane propeller collets. One side has a nut and thread to accept a propeller [noparse][[/noparse]or your wheel] and the other side has a friction fit that tightens to the shaft of the motor.

For small shafts, these provide better security that a set screw. [noparse][[/noparse]more complete friction grasping the shaft]
You have to measure your shaft and buy one that is designed to fit its diameter.
The come both in metric and standard sizes.

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XNOR

Thank you everyone for the ideas and suggestions.

It sounds like the easiest and cheapest way would be to use collars and washers.
(The motor shafts are about 1/4" diameter, non-keyed, have no set-screw or hole,
and are only about 1" long.)

Thanks again!

LoopyByteloose

This might sound a bit silly, but if the shafts are 1/4" this will work.

Get a couple of potentiometer knobs and glue them to the wheel centers on the outside.
Just put the shaft through the center hole and use the knob's set screw to secure the shaft to the wheel/knob assembly.

The propeller collets can reach down to 2 or 3 mm shafts which are nearly impossible to attach by set screw.

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···················· Tropical regards,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan

XNOR

Kramer said...
This might sound a bit silly, but if the shafts are 1/4" this will work.

Get a couple of potentiometer knobs and glue them to the wheel centers on the outside.
Just put the shaft through the center hole and use the knob's set screw to secure the shaft to the wheel/knob assembly.

The propeller collets can reach down to 2 or 3 mm shafts which are nearly impossible to attach by set screw.

Kramer, thank you for the additional suggestion.

Actually it doesn’t sound silly to me, since I was actually thinking of doing the same thing.
But I didn’t have any large knobs to try it out - actually, the collars I have aren’t big enough either!
( ...and off I go to the hardware store again... )

Alphawookie

If you haven't tried two-part epoxy putty, give it a go. It's easy to work with (knead it like play-dough), cleans up with water and cures fast enough to be handy but slow enough to have a bit of work time. Epoxies come in different strengths, Metal-metal is costly, but holds with 1000+ psi shear.
It makes great parts too. Can be drilled, tapped, sanded etc. if you can get it the shape you want, like a custom servo arm or the like.

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Engineering is the art of doing·something well with one dollar, which any bungler can do with two after a fashion.