Al alloy for Cat pony motor bearings

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ronm
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Al alloy for Cat pony motor bearings

Post by ronm » Thu Jul 31, 2014 11:55 am

I am in the process of rebuilding a pony (starting) motor for a Cat D2, 1940 model. The main bearings are an aluminum bushing, & Cat amazingly enough, still supplies them, but at ~ $100 ea. for .020 undersize...I'm considering making them, but need some info on the right alloy to use. I started a thread on the ACMOC board, so I will probably get some info there, but there being such a wealth of knowledge here, I'll throw the subject out here too.
The crank is at the machine shop, looks like it will clean up at .020. It had been built up to standard before, but the build-up metal flaked off of one main & really hammered the bearing...
This is a 2-cyl. opposed, 2-3/4" bore engine, runs at 3000 RPM.
thanks-
Here's the patient-his name is Wilford... :)
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wilford.jpg

Les_S
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Re: Al alloy for Cat pony motor bearings

Post by Les_S » Thu Jul 31, 2014 1:00 pm

Hey Ron,
I don't no nothin' about bearings but what a cool project! Where did you come by Wilford?
Les

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RCW
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Re: Al alloy for Cat pony motor bearings

Post by RCW » Thu Jul 31, 2014 2:04 pm

It is a cool project! Keep us posted on Wilford's recovery.

Bob

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ronm
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Re: Al alloy for Cat pony motor bearings

Post by ronm » Thu Jul 31, 2014 3:00 pm

Les,
Craigslist, of course! The guy advertised it several times, & the price kept going down, until it was just about where a scrapper was gonna take it & cut it up, so I had to rescue him...he was up in the mountains above Silt CO, the pic I posted is from the CL ad. Wilford is a tailseat orchard D2, which is relatively rare...
The owner said the pony motor was blown up, & he wasn't fibbing...

hammermill
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Re: Al alloy for Cat pony motor bearings

Post by hammermill » Thu Jul 31, 2014 3:25 pm

al bearings, I would of suspected Babbitt.alloy bearings.

Harold_V
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Re: Al alloy for Cat pony motor bearings

Post by Harold_V » Thu Jul 31, 2014 3:47 pm

I'd be inclined to explore 2024 aluminum, which has impressive tensile strength (contains some copper). Alternately, perhaps 7075 (high in zinc, and even greater tensile strength). Both of these alloys machine very well, especially in the artificially aged conditions.

Harold
Wise people talk because they have something to say. Fools talk because they have to say something.

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ronm
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Re: Al alloy for Cat pony motor bearings

Post by ronm » Thu Jul 31, 2014 6:13 pm

hammermill,
I think the original bearing were babbit-lined bronze, but the replacements are solid Al. the manual gives different clearances for the 2 types.

Harold,
How about 6061-T6? That has been suggested by someone on the Antique Cat board. Didn't say if he has had actual experience w/it in that application or not. The bearings I took out are not a real hard alloy, a knife blade scratches it easily, not that that's a valid test...they are 2.250" OD, 1.812" ID, so fairly thick wall.
I can get 2.5X1.75" tube from Online Metals...

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Richard_W
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Re: Al alloy for Cat pony motor bearings

Post by Richard_W » Thu Jul 31, 2014 7:17 pm

have you considered converting to direct electric start?

Richard W.

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ronm
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Re: Al alloy for Cat pony motor bearings

Post by ronm » Thu Jul 31, 2014 7:51 pm

Not for this one, Richard-if it was a working tractor maybe, but this one I want to keep as original as possible, plus I just like the sound of a pony motor in the morning... :wink:

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Lew Hartswick
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Re: Al alloy for Cat pony motor bearings

Post by Lew Hartswick » Thu Jul 31, 2014 9:33 pm

I suspect it's Aluminum-Bronz (Sp?)

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warmstrong1955
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Re: Al alloy for Cat pony motor bearings

Post by warmstrong1955 » Thu Jul 31, 2014 10:05 pm

I rebuilt a couple of Cat pony motors. One from a 2U and another from a 631. Been a year or 37 ago though...and the memory is the second thing to go, and I don't remember what they were made of.

If I was gonna make some.....I'm with Lew. 954 Aluminum Bronze would be a good choice.

Bill
Today's solutions are tomorrow's problems.

Harold_V
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Re: Al alloy for Cat pony motor bearings

Post by Harold_V » Fri Aug 01, 2014 4:17 am

ronm wrote:How about 6061-T6? That has been suggested by someone on the Antique Cat board. Didn't say if he has had actual experience w/it in that application or not.
That wouldn't be my first choice, although I'm not suggesting it wouldn't be a good one. I don't like the way it tends to weld to a cutter, which is the reason I suggested 2024 or 7075, thinking either of them might be a better choice. Don't know that they would be, though.
The bearings I took out are not a real hard alloy, a knife blade scratches it easily, not that that's a valid test..
Yep, it's not. Aluminum, any aluminum, is not hard. Mild steel will scratch it easily, so a knife isn't going to be much of a test.
If you can take a cut on the old bearing, you may be able to determine the alloy. That's assuming you're familiar with how each one machines, of course. 2024 and 7075 should be real easy to identify, as each has peculiar machining qualities. 2024 machines very freely, and yields a rather frosty surface, while 7075 cuts very cleanly, leaving a bright surface, and is rather "crunchy", for lack of better description. 6061? Cut the bearing, then cut a known piece of 6061 to see how they compare. It's likely the most common aluminum alloy you'll experience, so it's readily available.

Harold
Wise people talk because they have something to say. Fools talk because they have to say something.

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