slipping eccentrics?

[Terry Chapman 2Participant @terrychapman2]

Hi,I have a little problem with my 3/4" Holden engine. I can set the timing up and it runs fine but after a while it goes out because eccentrics slip.

They have tiny little screws holding/for adjustment but dont seem man enough for the job? I dont want to over tighten them for fear of breaking the slot? Would loctite be the answer or go to allen screws?

Many thanks.

[Terry Chapman 2Participant @terrychapman2]

[Howard LewisParticipant @howardlewis46836]

Can you drill a small dimple into the shaft for the grubscrew to enter, so that the eccentric cannot slip without shearing the grubscrew (Which seems unlikely )?

This cured a problem of the lever slipping with the over centre belt tensioning on my lathe which uses B section belts.

Howard

[Brian WoodParticipant @brianwood45127]

Hello Terry,

Better still, pin them together.

Brian

[Mick B1Participant @mickb1]

Posted by Howard Lewis on 04/04/2021 10:13:30:

Can you drill a small dimple into the shaft for the grubscrew to enter, so that the eccentric cannot slip without shearing the grubscrew (Which seems unlikely )?

This cured a problem of the lever slipping with the over centre belt tensioning on my lathe which uses B section belts.

Howard

That, and/or drill and tap more and bigger grubscrew holes?

[Jim NicParticipant @jimnic]

I've never experienced this problem on any of the dozen or so stationary engines I've built, most of which have eccentrics secured as yours is. I would look at the valve linkage to ensure it is free moving. The eccentric only has to operate the slide valve which itself should be fairly easy moving. Perhaps the gland nut is a little on the tight side?

Jim

[Dave HalfordParticipant @davehalford22513]

Posted by Terry Chapman on 04/04/2021 09:36:14:

Hi,I have a little problem with my 3/4" Holden engine. I can set the timing up and it runs fine but after a while it goes out because eccentrics slip.

They have tiny little screws holding/for adjustment but dont seem man enough for the job? I dont want to over tighten them for fear of breaking the slot? Would loctite be the answer or go to allen screws?

Many thanks.

Allen screws assuming they aren't tiny. Some are pointed and some have a cup end.

[Terry Chapman 2Participant @terrychapman2]

Posted by Brian Wood on 04/04/2021 10:16:18:

Hello Terry,

Better still, pin them together.

Brian

How?

[Howard LewisParticipant @howardlewis46836]

Taper pins, if grubscrews in dimples fail to cure the problem.

But first find out what is so stiff that the eccentrics slip.

Howard

[Brian WoodParticipant @brianwood45127]

Terry,

I don't know the design in this case but is it not possible to drill radially down the eccentric and shaft and pin them together with a silver steel pin? That's what I had in mind.

Regards

Brian

[Author]

Posts