Hi Team,
the issue I see with this system is that on the surface what appears to be a great idea is that the thrust loads are being transmitted via the known weak centre web of the crank.

It could be that these loadings are no different to the standard set up but I do not have the engineering design experience or formulae to work it out ??

Cheers,
Eddie B.

I’ll defer to the experts on this, but I’m thinking is as long as the end play on the crankshaft is within spec, there’s little chance of breaking a crank short of an overspeed accident or bearing failure. So HOWEVER the end play is controlled, as long as it’s controlled, you’re good.

I’ve had one break but it was a long time ago and I wasn’t as interested in that sort of stuff at the time. Just got another pony and slapped it on there. I don’t even know if it had excessive end play before it broke but it almost certainly did.

Most commonly the thrust bearing in an engine is controlled by the center main. The pony hasn’t got one so that’s out. So either it’s controlled by one main and there’s plenty of room for thermal growth/contraction or you controlled it from both mains but you have to allow for thermal growth. I would be interested to know how the clearance of one of the conversions changes with a hot engine.

Hi Neil,
with the modified thrust washer set up the end thrust loads are taken thru the centre web when using the thrust washers either end of the crank--as long as the washers contact the machined trued up crank journal end faces fully there should be no problem if this is what you mean--standard engineering practices followed.

With the standard set up, the thrust is all done at one journal, at one end of the crank and has worked well--- except for the doweling system that fails when people flog the flywheel off and on the crank.

There will always be excessive loading on the web if people do not support under the flywheel when undoing or doing up the flywheel retaining nut. OM designed a flywheel support to overcome the issue. I usually use a slow ramped wedge of hard wood or suitable metal packer to take up any clearance between the flywheel and the housing below it.

At the end of the day it is likely there is not much difference in web loading between either thrust system during operation.
Cat likely went with their system due to ease of manufacture in regard of tolerance stack ups and the need for shimming the flywheel side end cover to achieve specified end float and if too tight would cause excess loading on the centre web during operating flexing and likely from thermal changes as well.
Cheers,
Eddie B

Update...
I finally got around to taking the pony back apart to see what was causing the end play. Turns out the dowel in the front (near crankshaft gear) was loose. I pulled the dowel out and the hole doesn't appear to be enlarged or rounded like I originally thought. Reset the dowel and checked the clearance and it is about .015. I was able to push the dowel in and it seems to be snug. Was thinking about using red loctite and tapping the dowel in to seat it. Photos below show the dowel hole, and the other two show the amount of end play clearance. Anyone have concerns about my plan? Neil and I discussed this yesterday (thanks Neil), but that was before I reset the dowel and checked the clearance.

I decided to pull the front bearing to double check it. Turns out the dowel hole is oblong. The dowel fits snugly into it but I’m afraid that the bearing will work its way out of alignment. I’ve heard a few say just turn it around and drill a new hole. If I do that, I need to drill the other two oil holes, correct? If I do this then I lose the slot under the holes where the oil can lubricate the entire width of the journal. Wouldn’t this be a problem?

Sounds like a plan. Thanks Neil.