'The Garage' Quest TV.

Any modern bearing has several layers, on a modern tri metal bearing on the steel backer there's a layer of copper/lead alloy, a layer of nickel plate , then an extremely thin layer of babbitt alloy & a flash of tin or tin/lead on top. It's not the primary purpose to let it run with no oil, as evidenced by the entire discussion existing it won't run without oil.

Thanks for that Slatts, My own 4 cylinder m/c engines always had white metal bearings so seeing a 4 cylinder roller raced crank is interesting. I was expecting such an engine to have developed more HP given the less resistance or at least had a far higher rev limit. The HP comes out more or less equates to my Honda 500 twin m/c with the usual white-metal bearings. Gio

What is under the babbitt alloy bearing surface is irrelevant as far as this argument is concerned. As for babbitt alloy surface having a flash coating of tin or tin lead on it, maybe you'd like to show me where that information may be found.

To me there seems little point in putting such a coating on a surface which is probably 90% tin anyway. Plus the fact that it would interfere with the design concept of a babbitt alloy bearing. Mike.

Clevites information pack.

Not always, I got away with it, once, on an old Ford Onion I had. It only had to last a few months, and the bottom end had a light rattle. New shells cured it for a few months at least....

I suspect I may have just been very lucky.

Try again. First of all your reference is to a specific manufacturer, but looking through the information they provide, I found the following passage:-

"TriMetalT design first developed by Clevite 50 years ago and perfected over time. This design incorporates the strength of a copper-lead alloy layer on a precision steel back and finally, a precision electroplated white metal "babbitt" surface layer"

Notice that it says the 'final' surface layer is babbitt metal which is what I've been saying all along.

So, to repeat my question. Where do I find information about a 'flash tin coating' on the babbitt alloy bearing surface you are so insistant about? Mike.

On Tue, 17 Aug 2010 20:56:50 +0100, "Gio" wrote:

The reason for the soft layer is it's ability to embed very fine hard particles that can't be filtered. In a long life well maintained engine the soft bearing shell will be unworn but the hard journal will be worn by the embedded particles acting as a grindstone. Engines that run higher loading use harder alloy mix for shell surfaces to take the pressure but run shorter engine life as the bits don't embed so well and wear the journal faster. Without the soft layer the dirt would simply grind both surfaces away very quickly.

Modern better finished bores, journals and other metal to metal contact don't produce as much fine hard particles as of old. Engines have full flow filtration and pressure fed. The days of splash fed big ends or mains fed from catching what runs down the crankcase wall and hand pumped one shot at every 10 lamp posts, are long gone. All goes to reducing the amount of material that gets embedded and likelihood of running dry.

Against the requirement to be soft the bearings need to resist fatigue, each revolution of the crank a pressure wave sweeps round the whole bearing compressing the surface which after the wave has passed springs back. This cyclic compression can cause cracks in the bearing surface, the cracks join up and then the bits fall out to be carried round the bearing doing damage before being washed out.

Newton & Steeds used to say that mild steel on mild steel or phosphor bronze on mild steel are very bad bearing surfaces while white metal on mild steel or phosphor bronze on hardened steel are good. Journal bearings are always soft with hard, while roller/ball bearings are hard on hard.

While running shell and journal don't contact. A motorbike tuner has photos of shells before and after a seasons running. The bearings are supplied with a very soft protective film that can be wiped off with a kitchen towel. He leaves it on and it's still there after a seasons racing.

There are lots of cars, mainly pre WWII. Some have one piece crank and split roller bearings bolted by caps to plates that bolted in as crankcase webs.

are built up either press fit or by bolted clamps. All the AutoUnion / Mercs of the pre WWII era had roller bearing cranks. It wasthe "cheap" touring car derived "losers" that had shell bearings. All early Suzuki and Kawasaki 4 strokes had roller bearing cranks. GS1000, Z1000 etc. Yamaha 650 twins had roller bearing cranks, I'm not sure about 4 pots. key reason for use of roller bearing on 4 strokes was the low oilrequirement for high speed and load. A roller bearing can live at9000rpm on oil mist, so if it's been whipped to froth, taken a jumpand the oil is everywhere around the engine except the sump so it'spumping air, it doesn't matter. Cams only run 1/2 engine speed, mostbikes and cars run cam direct on head alloy. Lube to the roller bigends was by circumferential grooves in flywheel that caught oil as itspilled from mains with a hole that fed oil by CF into the big ends.Aother reason is a narrow full circle big end is used on forgedconrod, the lack of split means no bolts to fail or accommodate makingthe big end of the rod wide (not such an issue with modern square orundersquare engines). Same at mains the roller will be quite narrowcompared to shells giving more space for a wide crank web and goodlength to make the crank pin pressed fit rigid. All Honda 4 pot motorbikes starting with 1969 CB750 had shell bearing cranks. Yet first Honda twin with shells was the 1978 Superdream. was 360° parallel twin, with engine time balance shaft (= heavy).The preceding CB72/CB250K4/G5/CJ250 and 360s had 180° roller bearingcranks, pressed up with 4 main bearings For drag racing the built up cranks of Zeds and GS had to be welded to stop the pressed together parts moving resulting in a twisted crank.

Twin cyclinder Brit bikes had gone to shell bearing big ends in the

40's but except for AJS/Matchless not the mains. By using shell big ends they could make twins with the outer flywheels having integral big end pins that bolted up on big flanges to the cast centre flywheel, they couldn't get a roller on over a flange. The crank ran in a ball and roller or 2 ball main bearing. The crank was made in one piece, machined, then split at the middle flange. I've been told that Norton just put the left hand bits in one basket and the right hand bits in another basket so they would never meet again - part of the reason Norton had to use special self aligning "wobbly" main bearings.

Royal Enfield had lead the way pre WWII with a big end floating bush, overlayed with white metal on inside and outside that replaced the rollers and cage. As the oil couldn't be passed though the main roller bearing to the big end it needed a better pump, a filter and end fed crank to get the lube to it. They used this floating bush on singles. The RE filter is still used on industrial engines to this day.

AJS/Matchless twin had shell centre main bearing crank by putting a horseshoe plate in with a cap to hold middle bearing on a one piece cast crank. The plate was lightly bolted to timing side of the vertically split crankcase, the crank lined up by dial gauge and a bit of tapping on the plate, then the bolts were done up, final check with dial and the other crankcase half was bolted on. As outer mains were still rollers, oil was fed into the crank for big ends from this centre bearing which was fed though a drilling in the horseshoe plate. This was the only high pressure feed on the engine all other bearings being fed by splash or from overflow from head down pushrod tube to cam trough. If the crank wasn't clocked correctly it wore the centre main shell barrelled and pissed the oil out starving the big ends with the usual outcome.

Fine, go & read their technical manual, that's ignored the fact you need a nickel barrier layer between the copper lead layer & the tin or tin/lead flash they put on the top, tri-metal's a marketing term, not a description.

Yes. It may well last for a few hundred miles of gentle driving. Certainly long enough for a TV prog to say it's cured. ;-)

How many more times? It's the bearing surface layer that makes a babbitt bearing. If that final surface is babbitt alloy, it's a babbitt bearing. What surface the bsbbitt alloy is applied to is irrelevant to the argument.

I'm not referring to any specific manufacturer. You, OTOH, seem to be using information from Clevite to support your argument.

You also seem unwilling to provide a URL so I may read it for myself, but I have a sneaking suspicion since you now refer to a tin/lead flash that that is just the final layer of babbitt metal, since babbitt metal can be an alloy of tin and lead. Mike.