Eccentric Straps

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my2cents
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Joined: Thu Mar 25, 2021 8:56 am

Eccentric Straps

Post by my2cents »

All,

I am having to make new eccentric straps for my locomotive. I have machined them and re bored them in the past so its time for new ones. The ones on the locomotive are brass and I want to make the new ones out of bronze. I have some silicon bronze left over from a different project and wanted to know how silicon bronze would work in this application. I am no expert when it comes to metallurgy, but I looked it up and seen that Silicon bronze does not have any lead in it. My understanding is that lead in the composition makes a better alloy for bearing purposes. What is everyones thoughts? I know there is a lot of experience here.

Thank You!
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Rick
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Re: Eccentric Straps

Post by Rick »

Silicon Bronze should be fine. The silicon in the bronze is a lubricant.
Rick

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cbrew
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Re: Eccentric Straps

Post by cbrew »

what are the eccentrics machined from? Silicon Bronze is pretty hard isnt it? I would prefer to replace straps vs eccentrics :)
If it is not live steam. its not worth it.
Berkman
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Re: Eccentric Straps

Post by Berkman »

wouldn't the best long term wear strategy for Stephenson be to have hardened eccentrics with some sort of replaceable bushing between it and the eccentric strap? then of course a grease fitting or oil hole
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cbrew
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Re: Eccentric Straps

Post by cbrew »

Berkman wrote: Wed Sep 14, 2022 1:38 pm wouldn't the best long term wear strategy for Stephenson be to have hardened eccentrics with some sort of replaceable bushing between it and the eccentric strap? then of course a grease fitting or oil hole
I always wanted to machine up hardened eccentric and straps to run loose ball bearings, but that phase past by :)
If it is not live steam. its not worth it.
Berkman
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Re: Eccentric Straps

Post by Berkman »

ya, that'd be a PIA. But still think a easily lubricated bushing setup allows at least for pretty easy replacement
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cbrew
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Re: Eccentric Straps

Post by cbrew »

yup,,, the existing eccentrics on the Allen American are 22 years old and still have minimal play..
If it is not live steam. its not worth it.
my2cents
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Re: Eccentric Straps

Post by my2cents »

The eccentrics are cast iron. I have always heard the bronze running on cast iron lasts forever (at least the old timers always said that). Like CBREW was saying i would rather have to make new straps instead of new eccentrics. There is currently no where on the eccentrics. I measure them at a few different points of each eccentric and they are still round and the dimensions are according to the print.
Pontiacguy1
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Re: Eccentric Straps

Post by Pontiacguy1 »

Trick I learned from Gene Allen himself... When he built the locomotive that I later was re-building, he put a 0.010" piece of shim stock between the faces of the two halves of the eccentric strap, and then he machined the center of it round. It was installed on the locomotive with the 0.010" shims in place and ran that way for years. To my delight, I found that tightening up the eccentric straps only required removing the 0.010" shims and bolting them back together. I am not 100% sure about the thickness of those shims, but that is what was sticking in my mind. It might have been a little bit more.
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Bill Shields
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Re: Eccentric Straps

Post by Bill Shields »

AMEN on the shim trick....

I have almost 20 years on cast iron on bronze straps with the shims.

doubt i will live long enough to have to take them out
Too many things going on to bother listing them.
my2cents
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Re: Eccentric Straps

Post by my2cents »

Bill, what material is your straps made of? The is the longevity that I am looking for. I learned the shim trick years ago with traction engines.
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Bill Shields
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Re: Eccentric Straps

Post by Bill Shields »

some sort of bronze that I had laying around 25 years ago when I built the valve gear.

know it is NOT brass -> not phosphor bronze (wrong color)...not from a casting (which could be what the brits call 'red brass')

beyond that -> totally unaware, which describes most of my cranial activity these days (giggle).

Came out of my 'bits and pieces drawer', like many of my loco parts.
Too many things going on to bother listing them.
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