Author Topic: re-sleeve T/S bushing  (Read 2419 times)

Offline coater87

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Re: re-sleeve T/S bushing
« Reply #15 on: 25.09. 2009 01:12 »
Guys,

 Here is my own understanding of the bronze choices. P/B is harder, as tiny bits of metal begin to circulate through the oil system, these will eventually meet the T/S bush. They will become embedded in both leaded, and Phosphorous bronze. The difference comes in how hard the bronze is- these tiny particles will "mush" into the leaded bronze much quicker, minimizing the nasty lapping effect.

 The P/B being harder, these little metal pieces stand proud of the bush surface much longer, increasing wear to the crank.

 As far as I know about white metal (I would call this babbitt), its "mush" effect is even greater- probably the very best available. Its problem is "dry wear", as mentioned this material gives itself up very easily- meaning at start up every day- and with no way to adjust the bearings (like on a model T Ford) to take up the slack, you need to change these much more often. The up-side to this material is longevity to the crank, there would me very minimum lapping effect.


 Very technical term there- "mush factor"! ;) Anyway, that is how I have come to understand this.

 Lee
Central Wisconsin in the U.S.

Online BSA_54A10

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Re: re-sleeve T/S bushing
« Reply #16 on: 25.09. 2009 01:22 »
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A question. If the oil pressure was to drop to the point of no film on the T/S bush, wouldn't the left-side big end have left the building long since?

Nope, the white metal will retain a lot of oil and take a lot longer than you think to run dry.
Once dry a thin film will melt and allow the journal to run for a lot longer than you think.
The big damage to the steel journal occurs once the white metal has been rubbed through and the journal starts hammering ( there will be a lot of space in there by this time) against the steel back of the slipper.
 
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Have you any calculations on this or is this just opinion?

No numbers, more observations than opinions, leaded bronze bushes need either to be fairly thick or supported by a more rigid material such as steel. You need to understand the metallurgy ( or rather crystalography ) of these materials. The lead sits in the grain boundary region of the material as it is the last bit to solidify and forms a continious marix.
Think of the material as a sponge with really big holes. The hole space is where the copper resides and the cellulose bit is the lead. You would have great difficulty in bending a 2" thick rod of even pure lead where as a 1" thick rod will slump under its own weight.

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I just don't like the idea of inserts even if they are glued and screwed. You hear horror stories of them turning and cutting the oil supply
But that is exactly what was in there in the first place and exactly how the steel backed bushes are made.
If the sleeve can come out & rotate then there are a lot more problems than the bush materials and it is usually caused by not enough clearence between the bush & journal which would have killed a solid bush as well.
Do not confuse the sleeve turning which is extreamly rare with the entire bush turning which is quite (unfortuneatly) common
 
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Trevor

Offline A10Boy

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Re: re-sleeve T/S bushing
« Reply #17 on: 25.09. 2009 13:06 »
As with all these things its a matter of choice. I'm quite happy with my solid bush, it has a nice solid weighty feel to it and I don't believe there's any risk of structural failure.
I will use one on my next bike / rebuild.

Regards

Andy

1958 Super Rocket
Plus
1974 Kawasaki Z1a
Yam XJR 1300