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Author Topic: Mind the gap - lower end con rod side slop  (Read 191 times)

CBWho

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Mind the gap - lower end con rod side slop
« on: February 04, 2020, 09:17:18 am »
Another post made me think of an issue with an engine I am working on...

There is a gap to the left and right of the lower end of the connecting rod.
It will run in the center, so no thrust left or right but if it starts to rub the left or right, it knocks. Thinking of tying plumber pipe tape there but perhaps cotton wick is better? It will hold the oil? I could do a drip oiler above it?

There is no wear in that lower end, so what did they have there 100 years ago?

https://www.deboltmachine.com/search?q=oil+cup&type=product

crazydoug

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Re: Mind the gap - lower end con rod side slop
« Reply #1 on: February 04, 2020, 10:16:45 am »
I have eliminated that side slop with teflon bushings. You can cut a slot in the bushing with a slight V opening towards the outside of the bushing. It will then allow you to push it onto the journal until it snaps into place, leaving no gap in the spacer. I make the spacers out of black delrin, but you can byr white teflon ones with different i.d.'s and thicknesses as well.
crazydoug

RedRyder

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Re: Mind the gap - lower end con rod side slop
« Reply #2 on: February 06, 2020, 02:42:45 pm »
I moved this thread from "Meet the Members" to the correct General Discussion category.
Hopefully gets it the attention it deserves.

CBWho

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Re: Mind the gap - lower end con rod side slop
« Reply #3 on: February 06, 2020, 11:20:15 pm »
Thank you Doug,
At the hardware store, I found thin nylon washers. I sliced them and popped them in place. Still a wee bit of slop but it's much quieter. (Seems cured.) I suppose Teflon is better And I will keep on the lookout for those.

Belugawhaleman

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Re: Mind the gap - lower end con rod side slop
« Reply #4 on: February 19, 2020, 02:18:58 pm »
I  had the same problem on my D20 wilesco. A tiny silicone o-ring used as a spacer worked for me.
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Stoker

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Re: Mind the gap - lower end con rod side slop
« Reply #5 on: February 19, 2020, 04:44:29 pm »
I have eliminated that side slop with teflon bushings. You can cut a slot in the bushing with a slight V opening towards the outside of the bushing. It will then allow you to push it onto the journal until it snaps into place, leaving no gap in the spacer. I make the spacers out of black delrin, but you can byr white teflon ones with different i.d.'s and thicknesses as well.
crazydoug

I have done the exact same thing on gear shafts in large scale electric locomotives that are driven by a worm. In one direction the worms rotation pulls the worm gear into a nice central position providing full gear tooth surface area of contact. But in the opposite direction there is enough slop on the worm gear's shaft to allow the worm gear to be forced to the side so the worm is only engaged on the very edge of the worm gear and only getting about 1/3 of the proper tooth face surface area actually engaged, so very likely to rapidly wear out / strip out when under load. I have several thicknesses of sheet Teflon that I punch my own washers / gaskets from, and slitting the circumference as Doug has suggested works well for me in this application.

To add to the concept, I like to cut the washer / spacer on as hard a diagonal as I can manage using a pair of wire cutting dikes. This produces a chamfer on the slot, instead of square corners that are created by cutting with a knife. The chamfer allows the rotating gear hub to slide past without snagging on the slot trying to open it up, as might happen with a square shouldered cut. Making the cut on a diagonal like starting on the outside rim at 6 o'clock and cutting to the inside rim at about 8 o'clock, or as near tangent to the rim of the I.D. as you can make it, increases the length of the slot, thus helping it to lay flatter and only present a "tapered" line for the rotating adjacent parts to slide past, instead of a line that is fully square to the angular motion.

If the concept is not quite clear, I can post photos to provide a more graphic example.
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