Al alloy for Cat pony motor bearings

[Harold_V]

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

That would be obvious, as it's a pale yellow color, and tougher than the hinges of hell.

Harold

[ronm]

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

That would be obvious, as it's a pale yellow color, and tougher than the hinges of hell.

Harold

Yeah, it's definitely not that...
Another post came in on the Cat board late last night from a guy who did in fact make bearings with 6061, & they are working...there's no big hurry here, so I don't have to make a decision instantly...
There's another upgrade I'm looking at too, using bronze thrust washers to take up the crank end play, to eliminate the poor design Cat used for that. They basically squeezed the main bushing between the crank cheek & the timing gear, & held the bushing in place w/a dowel pin...on this one, the bushing was moving in the case & rocking the dowel back & forth...it had about 1/8" of end play, that's what got me to snooping inside, & I found all these other issues...

[ronm]

Harold (& others),
I took a cut on the one bushing, .010 cut, 800 RPM, HSS tool-here's the result & the chips it made-short, curly, shiny...
Any ideas?
I took a cut on another piece of "mystery Al" in the scrap box, probably 6061, but I don't know that for sure...chips were long & continuous, not short like the bushing...

Edit: No sign of welding to the tool edge.

[Harold_V]

Sounds and looks a great deal like 2024. It rarely cuts strings, and the surface finish tends to be frosty, even when it's a nice cut, and lube is used. That's the nature of the material. It also can't be welded by normal procedures, although I don't know that that bit of information helps in this case. That being said, if the picture you posted is the bearing in question, 2024 is my bet.

On the outside chance the bearings are cast, it has lousy machining characteristics---typically inclined to chip weld and tear, and rarely machines with a great finish, and often with a distinct cast aluminum surface (after machining).

I hand grind parting tools, so I pay close attention to how metals part, as it's dead easy to break the ones I grind, and they're very labor intensive to create. So then, one of the qualities of almost all aluminum alloys is their need for lubrication when parting, as they're more than capable of breaking a parting tool due to galling or chip welding. The only one I consider parting dry is 2024, and then only when it's artificially aged. I still use lube, but it is forgiving, unlike 6061.

To be clear, 2024 will cut long chips, but not readily and they are generally easy to break.

Harold
Edit: Took a better look at the chips. They appear too shiny for the material to be 2024.
Was the cut taken dry, or did you lube? That could account for the less than shiny finish on the bearing. Frankly, I'm getting mixed signals from what I'm seeing.

[ronm]

Yes, cut was dry-& the tool could have been ground a little better, I of course got in a hurry to get a pic & post it, so I just touched it up on the grinder, so the finish probably isn't what it could be...(that "threaded" look)...& yes, that is the Cat bearing.
There was another poster on the cat board last night that said he made bearings out of 6061 15 years ago, & it's still running...
I left a message w/my friend who ran the auto machine shop here for 40 years, to see if he ever had experience w/doing this, but haven't heard back...he's dealing with some health issues at 85, unfortunately....it will be a huge loss when he's not around any more.

Edit: One other thing to consider-Caterpillar has always been known for pretty much doing their own thing, so this may be some proprietary alloy nobody else ever used...plus, the rod bearings out of this engine were dated 6-60; meaning that was the date the bearings were made, so it was probably overhauled within a year or so of that date...it's safe to assume the mains were about the same age as the rods, so ~54 years ago...who knows what they were using for aluminum?

[Harold_V]

If you harken back to 50 years ago, both 6061 and 2024 would be found--although 2024 would be less likely to be found for general use. It was developed for high strength and used extensively in the aircraft and aero-space industries. You can pretty much exclude 7075, although it, too, was in use.

The threaded finish isn't much of a concern, not so long as the tool had proper geometry and was not dragging anywhere. A sharp tool may define the feed rate, but still yield a bright finish, especially if the cut is lubricated. Dry, you can achieve mixed results. That's not typical of machining 2024, and that's what made me think that may be the alloy in question. However, the shiny chips give me cause to think it's not that alloy, as they, too, should have a frosty finish.

My concern for chip welding as a reason for dismissing 6061 may be totally irrational. If you make that your choice, just ensure that you use a T6 condition, which offers the best machinablilty and greatest tensile strength (for that particular alloy).

Harold

[ronm]

After much research & discussion, & a bit of pure luck, I was able to find that the alloy Cat used for these bearings was 750-T5. That being a cast alloy, it's pretty much Unobtanium from any source I could find...
After much more research & consultation, (Harold), it was decided that 7075-T6 was about as close in formulation as any wrought alloy readily available.
So, after about a month of spare time working around actual paying work, here's what I came up with...Yeah, if I charged my time out at my going rate, I probably have twice as much in them as buying new ones from Cat...but hey, it's a frickin' hobby, OK? It was a challenge, & an interesting one.
A set of .020 undersize cat pony main bushings:

Now to proceed with assembly & get Wilford to run...

[Harold_V]

Pretty work!

Harold

[ronm]

Thanks, Harold. I wasn't super satisfied with the finish, I used Tap Magic Al cutting fluid, & it worked OK, I guess, but not a real mirror finish...anyhow, I suppose good enough for being buried inside an engine.
They did turn out within +- .001 of specs though...

[earlgo]

This may be a cautionary tale for when you get this running.

My cousin had/has a smaller shorter version of Wilbur, and as he was driving cross lots, he stood up to check the gas in the tank, which in your pic is in front of the controls. At the same time, the cat started to traverse a ditch and the front end dipped sharply. It catapulted said cousin over the front and into the path of the tractor. He survived the cleats, because the ground was swampy, but it took many months and several surgeries for him to function again.

--earlgo

[ronm]

OW!!!
Thanks earl, I've heard of such things with little dozers-a friend of mine got launched over the front of a TD6 IH into a muddy pond...fortunately he hit the clutch just as it broke over, so he didn't get squashed...the rough ride was one reason the tailseat tractors weren't real popular, I think.

[Torch]

Thanks, Harold. I wasn't super satisfied with the finish, I used Tap Magic Al cutting fluid, & it worked OK, I guess, but not a real mirror finish...anyhow, I suppose good enough for being buried inside an engine.
They did turn out within +- .001 of specs though...

I don't think you want a mirror finish on an oil film bearing, do you? Slightly frosty or matte means there's some tooth for the oil to stick to. Better for the next start-up.