Re: Gear Oil and bearing

[Eric Worpe]

Hi Mark, A good point you made about the "cost", of a cheap "bush" deteriorating. Any idea why the bronze cage in the pinion's thrust bearing breaks up ? I've tested some of the bronze thrust washers from the gearbox and not found any lack of "toughness" despite being in the same EP140 type oil. Dezincification should not be a problem as far as bronze is concerned. What could put tension on the cage ? If the balls were of slightly different dia. then some might tend to migrate away from each other as the bearing rotates, and thus put tension on the bronze cage. This might eventually cause the cage to fracture, however it's not easy to see how the cage could be so comprehensively broken up. As Roger Furneaux has mentioned, sometimes the diff. "spits" out the little T sections from the broken cage whilst draining the oil. It's probably impossible to predict the life of the pinion's thrust bearing as any simple inspection is unlikely to reveal potential stress fractures in the bearing's cage. Regards, Eric.

[joecurto@aol.com]

I had remembered years ago in a conversation with my bearing supplier that he said that in actuality a bronze caged bearing was a stronger bearing than a steel one, I have always admired the look of an old R&M bronze caged bearing and was slow to replace one with a new stamped steel one, maybe the trick to longevity was in the oil, but than again the same supplier said that the speed rating of the original TC front pinion bearing was not up to the job and that to run it at 4500 exceeded the rating by quite a lot. Joe Curto

[Robert Grunau]

A better solution is to fit modern tapered roller bearings to the pinion and differential carrier. Much stronger and less expensive. The tapered roller bearings also locate the pinion more accurately if properly preloaded.

And BTW, page 24 of the TC Instruction Manual ( brown book ) says Where adjustment as described is not satisfactory, before the gears are condemned, all bearings should be carefully inspected for slackness, partricularily the rear roller race , which must be renewed if a feeler of .015 ( .381 mm ) thick can be inserted between the roller and outer track . Obviously a typo error and this no doubt should have read 0.0015 ( 0.0381 mm ), 15 thou. slack as indicated will quickly wreck the pinion/crown wheel.

Bob Grunau

I had remembered years ago in a conversation with my bearing supplier that he said that in actuality a bronze caged bearing was a stronger bearing than a steel one, I have always admired the look of an old R&M bronze caged bearing and was slow to replace one with a new stamped steel one, maybe the trick to longevity was in the oil, but than again the same supplier said that the speed rating of the original TC front pinion bearing was not up to the job and that to run it at 4500 exceeded the rating by quite a lot. Joe Curto

[tonygoodall]

Re: [mg-tabc] Re: Gear Oil and bearing Bob You picked up on this one just as I was going to make the same point. Surely .0015 is the correct dim. Tony TC9825

[quote] [b]From: [/b]"Robert Grunau" cgrunau@pathcom.com> [b]Reply-To: [/b]cgrunau@pathcom.com> [b]Date: [/b]Tue, 4 Dec 2001 09:57:39 -0400 [b]To: [/b]joecurto@aol.com>, E.Worpe@surrey.ac.uk>, m.jablonski@mei.unimelb.edu.au>, mg-tabc@yahoogroups.com> [b]Subject: [/b]RE: [mg-tabc] Re: Gear Oil and bearing

A better solution is to fit modern tapered roller bearings to the pinion and differential carrier. Much stronger and less expensive. The tapered roller bearings also locate the pinion more accurately if properly preloaded. And BTW, page 24 of the TC Instruction Manual ( brown book ) says Where adjustment as described is not satisfactory, before the gears are condemned, all bearings should be carefully inspected for slackness, partricularily the rear roller race , which must be renewed if a feeler of .015 ( .381 mm ) thick can be inserted between the roller and outer track . Obviously a typo error and this no doubt should have read 0.0015 ( 0.0381 mm ), 15 thou. slack as indicated will quickly wreck the pinion/crown wheel. Bob Grunau I had remembered years ago in a conversation with my bearing supplier that he said that in actuality a bronze caged bearing was a stronger bearing than a steel one, I have always admired the look of an old R&M bronze caged bearing and was slow to replace one with a new stamped steel one, maybe the trick to longevity was in the oil, but than again the same supplier said that the speed rating of the original TC front pinion bearing was not up to the job and that to run it at 4500 exceeded the rating by quite a lot. Joe Curto Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service http://docs.yahoo.com/info/terms/> .

[/quote]

[Roger Furneaux]

Re: [mg-tabc] Re: Gear Oil and bearing All the more reason then, to replace the two R&Ms with taper rollers. A quick calculation using Timken data gives a limiting speed of over 13,000rpm! A little bit of machining is required to fit the tapers, and I promised Walter my write-up on this and setting-up the CW&P for the tech files on the website. It just needs a bit of rewriting. For the purists, I have a small number of the original R&M type bearings, but they are NOS (40 year old!) and no more will ever be made -: ( oc[b]T[/b]agonally Roger

[quote]I had remembered years ago in a conversation with my bearing supplier that he said that in actuality a bronze caged bearing was a stronger bearing than a steel one, I have always admired the look of an old R&M bronze caged bearing and was slow to replace one with a new stamped steel one, maybe the trick to longevity was in the oil, but than again the same supplier said that the speed rating of the original TC front pinion bearing was not up to the job and that to run it at 4500 exceeded the rating by quite a lot. Joe Curto

[/quote]

[Neil Nelson]

Just a thought on this bearing failure..... On most TC's I have seen the right rear transmission mount usually is broken. Could this cause excessive movement of the drive shaft and place more strain on the bearing? Neil TC 0526 -----Original Message----- From: Eric Worpe [mailto:E.Worpe@surrey.ac.uk] Sent: Tuesday, December 04, 2001 6:46 AM To: m.jablonski@mei.unimelb.edu.au; mg-tabc@yahoogroups.com Subject: Re: [mg-tabc] Re: Gear Oil and bearing Hi Mark, A good point you made about the "cost", of a cheap "bush" deteriorating. Any idea why the bronze cage in the pinion's thrust bearing breaks up ? I've tested some of the bronze thrust washers from the gearbox and not found any lack of "toughness" despite being in the same EP140 type oil. Dezincification should not be a problem as far as bronze is concerned. What could put tension on the cage ? If the balls were of slightly different dia. then some might tend to migrate away from each other as the bearing rotates, and thus put tension on the bronze cage. This might eventually cause the cage to fracture, however it's not easy to see how the cage could be so comprehensively broken up. As Roger Furneaux has mentioned, sometimes the diff. "spits" out the little T sections from the broken cage whilst draining the oil. It's probably impossible to predict the life of the pinion's thrust bearing as any simple inspection is unlikely to reveal potential stress fractures in the bearing's cage. Regards, Eric. Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/

[m_e_jablonski]

--- In mg-tabc@y..., Eric Worpe wrote:

> Any idea why the bronze cage in the pinion's thrust bearing

breaks up ? Hi Eric Could it be stress corrosion? At 4500 rpm the cage would be whizzing around at a not much below this speed and its section is greatly reduced over the tops of the balls. So there would be some tensile stress in the cage induced by centripetal force with a stress-raiser just over the balls. As I understand it, stress corrosion can occur at low levels of stress and low levels of corrosive materials, the presence of stress greatly increasing the corrosiveness of the corrosive material. EP oil is known to corrode "yellow metals". In the case of brass it would be attacking the zinc (dezincification). This could also be the case with some bronzes (eg.Manganese Bronze SAE No 43 has a similar zinc content to most brasses). Do you know what the cage material would be? Could the sulphur in the EP oil attack the copper as well or would it only affect the zinc content? Mark Jablonski Melbourne Australia