Side rod bushing clearance

[NP317]

Watching vids of UP's 4014 clanking down the tracks verifies that thought.
~RN

[amadlinger]

Hi folks,

Excellent information, as always. I have adjustable reamers so should be able to dial in the ID of the bushings nicely.

A follow-up question: when I built my 0-6-0 many moons ago, I recall the Little Engines prints suggesting to use a triangular scraper and Dykem layout fluid to scrape the bushings to size. Any thoughts on the application and/or efficacy of this method?

Many thanks, all!

Sincerely,
Adam

[NP317]

There are much easier tools available to us now. Like your adjustable reamers.
~RN

[cbrew]

i have this hate hate relationship with reamers
i just bore the bearing in the lathe before they are pressed in or on the mill if i miss the mark and end up too tight during the press.

[Harold_V]

I recall the Little Engines prints suggesting to use a triangular scraper and Dykem layout fluid to scrape the bushings to size. Any thoughts on the application and/or efficacy of this method?

Yes, One thought. DON'T USE LAYOUT FLUID.
If that is what was recommended, it's bad advice. Dykem also markets Prussian Blue, which is what SHOULD be used. It can be applied in a very thin layer and does not flake off, unlike layout fluid. It comes in a tube, much like a small tube of tooth paste, and does not dry.

Layout fluid and Prussian blue share only one quality in common----their colors. They are not interchangeable.

H

[Greg_Lewis]

I don't think I'd use a scraper to size a bearing. We scraped in the crank and rod bearings in our Model A engines only to remove the minute high spots (an extremely tedious process), not to size a round bearing. The roundness would be best created with a reamer or boring bar. Scraping would be only for the smallest imperfections and probably not needed for side rods. My first choice would be to bore it to the right size, second choice would be a spiral-flute reamer.

[Builder01]

I used an adjustable reamer. I kept opening the rod bushings until there was no binding with the axles in any position. When I started with the axles shimmed in the 'normal" running position, there was no binding until I started to push an axle up, thus changing center distances. An adjustable reamer to the rescue! It worked quite well. - David

[amadlinger]

Hi all,

Once again, many thanks for the insightful comments!

Below are a few quick photos of the rods in question - prior to installing the bushings, of course.

Sincerely,
Adam

[Builder01]

Looks great!

David

[Bill Shields]

I have always drilled the pressed in bearings to size...except for the bearing on the main crankpin which gets a little more attention.

Trying to be too exact at this time can be counter-productive.

remember, if you are working with film-lubricated bearings, there is a minimum film thickness that must be attained..or you are going to get full-time metal to metal contact..and things will open up in a hurry.

Add up all the tolerances and assume that one wheel can be 'all the way up' and the adjacent wheel 'all the way down' (on our tracks), and before long 0.010" clearance starts to sound like maybe not enough.

don't like the sound of a clank...well...use heavier oil....

[NP317]

Bill S said:
"remember, if you are working with film-lubricated bearings, there is a minimum film thickness that must be attained..or you are going to get full-time metal to metal contact..and things will open up in a hurry."

That is one of the nice aspects of sintered bearing materials. They soon self-establish their required clearances, and then produce the needed lubrication films.
After the initial adjustment wear seems to cease, or at least slow significantly. At least that has been my experience.
~RN

[Bill Shields]

i have not had good luck with sintered materials...as you say, they 'self-establish clearances; (they seem to beat out) because they don't like reciprocating loads...but if your experience is different that is great.

I would not recommend them on the crosshead bearing(s). There I like delrin or nylatron...like timex watches.