The novice, The "WEBSTER", the mistake!

[Longboy]

What you see here behind the base plate of my 1st I/C engine is the first axle. The counterweight,gear and flywheel are secured with setscrews to the axle. I milled flats to where the scews would seat and when turning engine over to start the flywheel and counterweight were slipping. I drilled and tapped then half way into the axle and continued trying to start engine. Now the set screws are threaded to the hubs and axle.............set screw on flywheel and the counterweight jammed cause they got loose and started to shear. A hex key fianally snaped the flywheel s. scew in removing and the key stripped in the counterweigh s. screw and had to be pressed out of axle completing the shear. "WHAT I LEARNED" 1) Use your threadlocker fluid! " Hey, I was just trying to start it". Compression kickback is enough to loosen setscrews. 2) The set scews were stainless and can shear when tying a heavy flywheel to an axle. This maby would have never been an issue LocTighting them in the firstplace. Not an issue in my Stirlings but with a gas motor fasteners have to be more robust when used in a rotating application. Now I have grade 8 set scews and the LocTight with no further problems!

 

[solver]

Longboy, what size of set screw was in use?

Probably it was too small anyway, compared to flywheel weight ???.

Even smaller engines can give enough kick to loosen the set screw, if the axle material is too soft and/or set screw is too small, to provide enough contact surface between it and the axle.

 

[Longboy]

They are #6 into a 5/16 dia. CRS axle. So they are sized right. These hex keys for these smaller set screws can be a strip problem, such a small contact area, but I have been able to back them out without softening up the Loctight. Dave.

 

[cfellows]

Dave, I don't have much experience with Loctite, so can't comment one way or the other. However, I think a 3/8" crankshaft rod and 10-24 setscrews might have reduced the risk of working loose. That's what I have on my Hit n Miss engine which has a 1 1/16" bore and 1 1/2" stroke.

Chuck

 

[cfellows]

Let me add that I also have a 3/8" crankshaft rod on my Henry Ford engine and it has a .81" bore and 1.875" stroke. For the flywheel, I used a tapered compression collet instead of set screws.

Chuck

 

[Longboy]

Thanks Chuck, I see on my Breich H&M there are #10's securing the flywheels on a 3/8 axle. Since a Webster has a 5/16 axle and I tapped into the axle, a #10 would be too much metal drilled from that diameter axle. In Joe's notes describing his baby, he had one roll pin in the flywheel and it sheared while running. He corrected with 2 pins each side of flywheel and solved that item. He has a heavier iron flywheel where I got an aluminum one and so far one set screw is doing the job. I don't believe going to a #8 or 10 setscrew would have overcome it becoming loose, but that the threadlocker played a bigger part here in keeping tight. Dave.

 

[Longboy]

Today one of the grade 8 set screws got loose (flywheel) and broke. Going to drill a thru hole in axle same size and use a socket head cap screw with nut and Loctite. There's enough room on hub to do a criss cross with 2 thru holes which should end this kickback loosening issue. With the axle then carrying the flywheel load from the hub on both sides I'll try one thru hole 1st. Thm: