trunnion support bracket

[mikegt4]

Like most HG & OC3s my track frames are a little toed in and angled over. Today I decided to take a look at the trunnions as the were obviously very loose. I found about 1/4" slop between the support brackets and the trunnions. The inside brackets had a thin bushing pressed into the casting, the outside brackets had none and looked as if they never did. I checked the brackets on my parts undercarriage and found the outers to be the same casting # as the inner brackets on my running machine but with a different diameter trunnion. A quick check in my parts manual shows that my outer brackets are correct but my inners are not.
Not a surprise on an old crawler.

Here is what I have:

early OC3-42, pre-full frame
outer brackets 117620, 2-7/16" ID bore in casting (no bushing)
inner brackets 112943, 2-13/16 to 2-7/8" ID in bushing, casting bore 3"
trunnion dia., outside 2-5/16", inside 2-5/8"
axle nut against trunnion

parts machine, judging by componets, 1950 HG-42 (no number plate)
outer brackets 112943, 2-25/32" ID in bushing, casting bore 2-7/8"
inner brackets 112940, 2-25/32" ID in bushing, casting bore 2-7/8"
trunnion dia., outside 2-23/32",  inside 2-9/16"
axle nut in counterbore in trunnion

I can make up bushings to fit and bore out the brackets if needed. I would like to know what I am suppose to have as a good place to start. What is the normal trunnion to bushing clearance?

Mike

[Jack in NB]

They are a loose fit. Mike.

The problem is that the trunnions on the casting are usually worn oval, and unless you can true them up, making bushings to tighten them up will just cant the track hangars, keeping the knock-kneed appearance, wear, and possibly sprocket interference on the lower rear track roller.

The outer blocks can be built up with braze and chucked in a lathe to true them up. I actually bored out the outer hangars to true them up (fly cutter in a drill press, with everything clamped solidly), then turned the blocks oversize to fit the bored hangars.

I did the inner ones (part of the final drive castings) by driving the stub axle out, building them up with brazing, then put an arbour into the axle hole and used a belt driven fly cutter - sort of improvised lathe - to turn them down to fit the bored out hangars.

End result probably 10 thou clearance, but light years ahead of the previous situation.

Discarded the steel bushings - some engineer's BRIGHT idea! - and put grease fittings on both sides of each track hangar. Originals had holes only on one side, and 2 of the 4 got no lubrication on the front (pressure) sides.

Fitted them with rubber shields on top to keep dirt out, but that didn't last long. Now I just grease every couple of hours, to blow the dirt out.

[mikegt4]

thanks Jack,
that is just about what I was expecting to do. Machining parts or making bushings is not a problem. My trunnions seem to be in fairly good shape, the mismatch and wear are fortunetly in the removable parts.

[Eric Carlson]

You guys make/making the bushings out of brass? I have one side of my OC-46 apart and would like to tighten it up a bit. Trunnions are good.
Eric