MTFCA Forum

As I was changing the oil, brass pieces fell out of the drain.
After calling an mechanic, it turns out I had a loose triple gear. Pulled the engine out, to find and fix the damages.
However it seems all 3 of the triple bushing failed in a similar fashion
Why the bushings failed in such a way?

Those bushes look to be bronze, no give in that stuff, it's as brittle as cast iron.

PS, just went out to the work shop and grabbed a original Ford triple gear bush out of the scrap bin, beat the crap out of it and bent it every which way, no way it shattered like a biscuit.

Could be material, but triple gear bushes are made of z-bronze, get mine from Bob's.

Maybe the clearance was too tight, the bush on the right is stuck and top flange busted off.

Or the face of the bush wasn't fitted, sure looks like full thickness (see arrow) as made, the flange of the bush should project only 006" - .010" over the side of the triple gear, they need to be machined to that fit.



Might just be the angle of the photo of those twisted off bushings, but seems to me they are missing the very important oil grooves to allow oil to the bearing surface.

Appear to be Oilite - sintered bronze

sintered bronze, an engineered material, is not ductile and will fracture easily under the right conditions and is not engineered to take a severe load

cast bronze is ductile and will not fracture easily and is well suited to a pounding or severe load duty

By the way the broken pieces look, and the way they apparently failed... Something really doesn’t add up here. I’m thinking there may have been some sort of an installation error. But it is really impossible to tell from pictures. Anyone would really need to see the whole assembly in person to make a diagnosis.

Scott

Would agree, and that's why likely the oil groove wasn't placed when these non-Ford type bushings were made.


Those bushings have to run on a surface of oil.

Scott_Conger wrote: ↑

Sat Dec 12, 2020 10:03 am

Appear to be Oilite - sintered bronze

sintered bronze, an engineered material, is not ductile and will fracture easily under the right conditions and is not engineered to take a severe load

cast bronze is ductile and will not fracture easily and is well suited to a pounding or severe load duty

Agreed. They may also have been pressed in, in a manner that further exacerbated a poor choice of material. If the bushings were pressed in using a tool with a fairly small step with which to engage the face of the flange, after the bushing was seated against the gear face, any additional "push" would have had the effect of trying to push the flange off of the bushing. At the very least, there would have been residual tension between the flange and the bushing body that, over time & use, caused the flange to separate from a brittle Oilite bushing. The proper way to press the bushing in would have been to use a tool that covers the whole face of the bushing flange. Naturally, all of this is speculation, but it seems to support the situation now at hand.

Like I said, it’s hard to judge from pictures... But it does appear there are no oil grooves in the bushings which may support some of your theories that these bushings may be oillite. Looking at the pictures, the fractures could be crystalized (work hardened) normal bronze bushing material and just look like fractured oillite, or they may indeed be oillite. The major reason that would make me think these “couldn’t possibly be” oillite, is that it would just be downright STUPID to make this particular bushing from oillite (or sintered bronze). This particular bushing would have to be made in a large quantity, which means that it would have very likely had to originally been made and wholesaled by one of the handful of vendors that makes T parts... And they certainly all know better! If it is indeed an oillite bushing, it would be a good thing to know where it originally came from and notify that vendor of their error because the failure rate of oillite triple gear bushings WILL VERY LIKELY be near 100%.

If these are sintered bronze, they would not be the first that I've seen used in triple gears. And, if I am not mistaken, these were sold as the correct bushing by at least one supplier in the past.

They would be a poor choice indeed.

About 15-20 years ago I received drum bushings that were sintered (oilite). Only makes sense someone made triple gear bushings the same way. By the way I did not use them.

I have a bag of them that I picked up at an auction, never have used them, no oil groove and they where brittle when I beat on one. I know a few years back there where some that hit the market that where to soft and they wear out quick.

Sintered bronze is a fickle mistress... it's a wonderful material until it work hardens, then it's an "if and when" proposition - I have some machinery that dates back to the late 1800s that is as amazing as when it was machined, running bronze castings and bushings... I also have some WW2 era stuff that, similarly, you would think is 21st century. Unfortunately, however, I have seen others do what yours has done, with no apparent rhyme or reason.

I would chalk it up to the nature of the beast. Amazing stuff, but after a century of service you really are rolling the dice.