'The Garage' Quest TV. - Page 2

I think you are confused. What is 'the babbit'?  Actually spelled with two
t's BTW.
There's no such thing as 'the babbit' or Babbitt.

OTOH 'Babbitt bearing' is the general term used for a bearing that uses a
'Babbitt alloy' as it's bearing surface. Commonly a tin based alloy with as
high as 90% tin, possibly with the rest made up of copper or copper and
antimony.

That makes automotive shell bearings, Babbitt bearings. The 'tin flash' you
mention is actually the thin layer of Babbitt alloy bearing material. It is
certainly NOT a sacrificial layer, there to protect the journal in case of
oil starvation for whatever reason. To suggest that it is, is totally wrong.
Basically the alloy layer IS the bearing.
Mike.

On Tue, 17 Aug 2010 19:05:38 +0100, Mike G  


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.

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.

On Tue, 17 Aug 2010 21:22:01 +0100, Mike G  


Clevites information pack.

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 Wed, 18 Aug 2010 01:33:01 +0100, Mike G  


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.

..

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.

Gio wrote:

The 1965 Honda S600
http://www.hondas600.com/specs.php
http://www.hondasportsregistry.com/images/posters/s800poster_engine1.jpg


Slatts

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

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.
http://www.cooperbearings.com /
Others are built up either press fit or by bolted clamps. All the Auto
Union / Mercs of the pre WWII era had roller bearing cranks. It was
the "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.
http://slcelectronics.com/GS1000_Build/Yoshimura-specs.pdf
http://en.wikipedia.org/wiki/Yamaha_XS_650
A key reason for use of roller bearing on 4 strokes was the low oil
requirement for high speed and load. A roller bearing can live at
9000rpm on oil mist, so if it's been whipped to froth, taken a jump
and the oil is everywhere around the engine except the sump so it's
pumping air, it doesn't matter. Cams only run 1/2 engine speed, most
bikes and cars run cam direct on head alloy. Lube to the roller big
ends was by circumferential grooves in flywheel that caught oil as it
spilled 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 forged
conrod, the lack of split means no bolts to fail or accommodate making
the big end of the rod wide (not such an issue with modern square or
undersquare engines). Same at mains the roller will be quite narrow
compared to shells giving more space for a wide crank web and good
length 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.
http://images.cmsnl.com/img/partslists/crankshaft-cb250ndc-1983-superdream-england_big00026149e14_8992.gif
It was 360° parallel twin, with engine time balance shaft (= heavy).
The preceding CB72/CB250K4/G5/CJ250 and 360s had 180° roller bearing
cranks, 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.
--
Peter Hill
Spamtrap reply domain as per NNTP-Posting-Host in header
Can of worms - what every fisherman wants.
Can of worms - what every PC owner gets!

We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember "Mike G"


It's true to a certain extent - I've seen some cranks that only needed a
clean up and new shells after a low oil episode, and on some engines the
shells are a service item - think bus diesels, for example. Ime, the old
Essex benefitted from new shells around 100K.
So yes, the presenter wasn't talking complete bollocks, as is usual for
one of them.