Sleeving a shaft

I am more a lurker on this forum but active on the sister model flying forum. The Proxxon PD 400 thread has been very interesting because I picked one up second-hand from Lancaster Model and Hobby World about two years ago with a job lot of associated tooling. It is noisy so I may have to look into that before I get stuck into any real project.

​Here is my question:
​I am just completing a 2m motorised glider and the out-runner motor has a 3mm shaft. The only spinner I could get hold of that matches the profile of the nose has a 5mm aluminium taper collet so I have to make an adaptor. The model shop where I bought the items suggested a piece of brass tube that would make up the gap with a longitudinal slit so it would be clamped to the shaft by the action of the collet. The standard sized brass tube that was suggested however was sloppy on the motor shaft and instinctively I don't like this idea. This is happening in Spain but I do speak Spanish and understood the advice.

​I have a suitable piece of Dural that I could make a sleeve from and a 3mm reamer so the adaptor could be a close fit over the shaft. My inclination is to Loctite the sleeve to the shaft so it is a permanent feature converting the shaft to 5mm and then using the collet on the spinner as intended. If I go this route what Loctite should I use.
​The alternative would be to make the adaptor sleeve exactly as before but put a longitudinal slit so it would clamp on the shaft more in line with the model shop advice.

​It is not a big powerful motor being only 280W driving a 7" folding propeller but nonetheless it would be embarrassing if it came off and the rearward shift in cg would probably by fatal to the aircraft.

What is the better option?

Tim

I would not loctite the sleeve in place as you would then be relying on it to secure the prop and the forces are high and motor shafts are notoriously highly polished. A shock (like the prop hitting the ground when rotating) could break the bond without this being obvious.

A snug split sleeve is better as then the full force of the collet will be transferred to the motor shaft.

Neil

If the sleeve is secured to the shaft with adhesive it may also prevent a change of bearings.

Robert Butler

3mm to 5mm shaft connectors for RC applications are available on epay. Not good enough?

Other changes are available.  You might need to buy one which is smaller and bore it out?

Edited By not done it yet on 21/05/2018 13:06:08

If you can make a sleeve you should be able to make a new tapered collect with a 3.0mm bore which would be a lot better than having two parts

Thank you everyone for the quick and useful comments.

​Here are photos of the collet.





This second photo shows the collet in the backplate of the spinner. I should have described the arrangement a bit better. Overall it is a bit more complicated than my ability to make a new one although I like the idea. Perhaps I will have a practice some time but the slits might defeat me.

​For the moment I will avoid the Loctite and split a sleeve for all the good reasons given. I will check out what is available on eBay too.

​Again, many thanks

Tim

Hi Tim,

You could do four slits, with your trusty hacksaw.

Regards, bear..

Hi Bear
Now why didn't I think of that! Doh!
Tim

Or use a cut-off wheel in a toolpost-mounted dremel/rotary tool.

Neil

A Junior hacksaw will give a nice narrow slit.

Ian S C

A piercing saw will give you even narrower slot. Blades are available down to 0.33 mm but you will need a steady hand!

Russell

Very helpful everyone but for the moment I have pushed the problem into the long grass.
Among my projects further down the list is a smaller motor glider with a smaller spinner. The collet was the same OD but drilled for the 3mm shaft. Overall it was a bit shorter needing a longer machine screw to retain the spinner cone but I have tried it and it works.

I am in a hurry to get this one finished but now I have time to set up to make a new one for the later model. Looks like it could become the perfect excuse to buy a few more tools.

Tim