Posted by Sherman in Idaho [108.162.245.23] on Wednesday, July 13, 2016 at 13:11:14 :
In Reply to: Is this for that "tight" bearing? Cat Donkey? posted by Chris Case [108.162.215.235] on Wednesday, July 13, 2016 at 12:53:31 :
This is for my chicom go-kart motor adapter. I'm not ready to deal with a proper overhaul of the pony motor. I found a junk D4 pony motor block. I need that to mount the drive gear that transfers power to the pinion mechanism. The pony motor crankshaft mounts a small gear that drives a large gear that reaches down into the flywheel housing and engages the drive gear on the pinion clutch, which in turn (when the clutch is engaged) drives the starter pinion which is engaged with the flywheel ring gear.
I can't mount the big "transfer" gear directly to the go-kart motor shaft because it would be too high and it would be turning the wrong direction. Therefore I need to essentially make the go-kart motor turn a simulated pony motor crankshaft. I can't use a real pony motor crank in the junk block for several reasons. First, I'd have to grind the crank main journals build under-sized main bearings and figure out how to lubricate it in a gutted out junk block. Instead my plan is to take the gear end (3" or so) of a junk crank, attach it to a length of 1" keyed shafting, mount that in the junk block concentric with where the crank would be, and attach a belt pulley to the outboard end of that shaft, with belts run to the chicom motor bolted to the fender.
To mount the 1" shaft in the junk block, I can make a flat plate to replace the front pony motor bearing flange, and attach a flanged sealed bearing to it. That part is easy. The rear end is the hard one. I can't mess with it much because I need to mount the "crankshaft" gear exactly in its original location. The original bored hole is sized to accept a proprietary soft aluminum cylindrical (not split) main bearing insert with a tight press fit. I need to press a sealed ball bearing assembly into that hole. The ~.005 undersize that the excellent Cat engineers specified for holding the aluminum sleeve in place is too tight to press a ~+/-.000X hard steel ball bearing assembly into. As a rule, ball bearings should ideally be a modest press fit on the shaft and an easy hand fit in the housing.
Or the short answer is, I'm changing it all around and redesigning it for a different purpose. Maybe I'll post a picture when I get it done, if it's not too shameful. Or I'll just be glad to be back to pushing dirt for a while.
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