Torque Converter Thoughts

[yawstick]

I guess I should preface this by saying that for the time being I'm pretty much sticking with the RC outrunner RC ESC route for the dirt bike conversion and there there will be no pedals to assist in starting. I have a beefy 300 amp 20 s ESC with sensor capability.... and the 12080 and 8085 and 6374 motors in transit. I didn't see the posts about the 12080 variants being prone to overheating due to what I think was described as induction heating of the magnets in the outrunner part.until after I had ordered them. So I may end up with two 8085 motors on the dirt bike and should have plenty to do soon.

Long ago I had an ultralight that had a torque converter of sorts on it and with luck hopefully I can round these up as I actually had two of them. This plane had a snow mobile type engine on it with a HTD type belt reduction to drive a relatively large prop at low speed. The device was in the hub of the large pulley. I think the hub was an off the shelf device bolted to the pulley. Inside the hub which had bearings on each side and was hollow inside. There was a wavy plate inside that was attached to the output shaft which passed through the bearings and the hub. Inside the hub there was lead shot which was slung to the perimeter and would lock up the wavy plate at some designed speed. This could be adjusted to some degree by the amount of shot inside. The shot was fairly fine... about the consistency of sand.

It just came to me after reading some of the posts concerning the effectiveness of sensored ESC type drive low speed starting on outrunner type motors that I may need more than a sensored drive to start a pedal less bike effectively. In the meantime I'll see if I can round those things up.

 

[gogo]

Here's member gwhy! doing something for a trials bike that is similar:
Subject: its now a e-motorcycle

 

[Hillhater]

What you are describing is a form of "centrifugal clutch" .
They allow the motor to start and run up to a predetermined rpm before the drive is engaged .
These are common on many ICE motored devices,..chain saws, pit bikes, go karts, moped scooters, etc etc
If you search "pit bike clutch" in eBay you will find lots.
Specialist manufacturers (Horstman, Noram, SMC, etc) make a huge range many with adjustable lock up speeds.

 

[yawstick]

Yes I'm familiar with those type clutches. This was a bit unique in that there was very little initial slip. Due largely that is was nearly full of the shot and friction alone would provide a fair amount of drive and it would lock up at a fairly low speed. It was also unique in that the that the part driven by the motor was the outer part as opposed to most of the centrifugal type clutches drive the inner part. I really do need to see if I can find these. It may be the weekend though for I think they were left in a barn on a farm property where I lived and flew that ultralight almost daily in good weather. Quite few years ago though. Finding them may be a long shot.

 

[yawstick]

Well just to convince myself that they were not out in my shop. There is stuff out there that has not moved in years I made a search... and low and behold in relatively plain view there one of them was. Beefier than I remember and more free initial motion as well but I think I removed some of the shot long ago. This thing had a piece of 1 inch chrome moly tubing as the prop shaft and I think part of its purpose was a bit of vibration damper between the engine and the prop. There was a aircraft bolt through the prop hub and this shaft and there was a lot of force on the bolt and had a tendency to wallow the hole out on the shaft.

At any rate here is the proof... I probably would not try such a thing if I did not already have one but will have to tear into it and consider the possibilities.