Pull start re-design.

[Frankenstein]

Have some extra parts to play with, a centrifugal clutch one way bearing and related parts. A couple of pull starts one in plastic the other in metal. Going to rebuild and use bearings to support the pull start and keep it lined up and moving SMOOTHLY!

So there's the center of attraction, an aluminum hub roller skate wheel. On the right is the centrifugal clutch gear and one way bearing assembly.

The skate wheel has a large groove in it, and I'm deciding if I'm cutting it in half or not to reassemble with bolts.

A housing for the pull start, will likely cut the post out and replace with a quarter 20 bolt or an 8mm bolt, both of which fit the skate/skateboard bearings inner race well.

I had to literally chisel the urethane rubber tire off the aluminum hub, and I still have more to remove. I then did a rough finish to remove the most of the surface residue of tire rubber. I will figure out the surface finish or machining after I determine the style of rope reel I'm using.

If I can make the bearing even more compact in the hub that would be great. I'm dealing with the issue of making the shaft that gets gripped by the bearing be full on center with a nut pressed to the inside of it. I may have to machine one down to make a centered part and then weld it in place in the shaft.

My only worry is the nut might strip the threads. If it does then the pull start will fail to operate and may even cause a self destruct on the mag side of the engine. But I revived Frankenstein from that death a few times now so if you don't fail you're not challenging yourself enough, I'll survive.

 

[Frankenstein]

I hate the fact that a one way bearing is indeed only 1 way. The orientation needed by the bearing is kinda awkward in this set up.

 

[Frankenstein]

Course turns out that I can just hammer the rivets straight out after taking the end off with a dremel, I was going to need a way to secure the bearing to the wheel so I figured I would punch them, flip the bearing ramp, and redrill to a slightly larger size hole which lets me put 5 #6 machine screws through to hold it all together.

Also the bearing ramp material is some really hard stuff, I'd almost say too hard as it was chipping on the edge from being held in a vice, course this was also the part of the centrifugal clutch that engaged the motor to the rest of the drivetrain, being its supporting that force on just a few square mm of surface area it should be hard as to not indent and become faulty by locking up.

 

[Frankenstein]

Not sure why that photo is showing oddly but I cropped it so maybe it's a bit nicer here since I can't even embed the other in the post.

A few more shots with the bolts inserted, the third image is with the bearing ramp moved out from the main holder, and it's flipped over to accommodate the design as the one way bearing of course only works in one direction as mentioned before.

This is what the bearing shaft (technically the inner race) looks like with and without a bolt inserted, the thread is from a crankshaft arm I cut off and pressed into the bearing shaft using a bench vice. It would seem that the thread (8mm fine) is pretty standard on these motors, and the magneto shaft threads are the same type as the bevel gear side's threading for the bolt, by pressing the gear side arm into the shaft I have a shaft that is relatively centered and can be screwed onto the magneto side arm. It's slightly off from perfectly vertical (inner threads compared to the rest of the shaft) but that is an issue that will be easily resolved later. Anyway, pics.

More to come!

 

[Frankenstein]

A few shots with the hub drilled to accept the bolts and assembled to the bearing parts, a tube of some sort will be fitted in under the outer race (bearing ramp) inside the hub which will suspend it up from going inwards and disrupting the mechanism.

The nuts will be cut down to fit inside that empty space in the hub, and locktighted to keep them there while the bolts will be trimmed as well to make for a desirable fit.

 

[Frankenstein]

Ramp inside as well, getting measurements for the small retaining tube that will be placed inside. Starting to look even cooler and getting heavier too, it's overbuilt but it's a good thing, thinking of some pull cord used on snowmobiles, the Temps won't be all that higher so the cord should be just fine.

 

[Frankenstein]

In an earlier post I mentioned a quarter inch bolt, I was thinking of something else and meant a 5/16, which is about the same as 8mm, the bolt will come out the back of the pull start case/cover and be helped to alignment with washers and careful adjustment.