Bearingz

Matt · 07-04-2005, 10:53 AM

OK, so outboards use needle roller bearings on the big & little ends, why don't 4 stroke motors use roller bearings on the crank & cams? I would have thought they'd have less friction. I did think that perhaps the combustion loads might disintegrate the roller bearings - but outboards survive without too much trouble?
Didn't bugatti try it on a race motor many many years ago?

CB1 · 07-04-2005, 12:27 PM

Honda used them on the S600 in the 70/80's dont know if they still do.

JamesM · 07-04-2005, 12:56 PM

Lubrication I guess. Two stroke outboards are only lubricated by the fuel/oil mist flowing through the crank case. The con rod big end caps have slots cut in them that are in the air flow thus allowing fuel/oil to directly lubricate the rollers.

As for why they're not used on a four stroke I dont really know other than cost and when the bearing wears your more likely to get a catastrophic failure with a roller bearing.

Jon · 07-04-2005, 01:34 PM

Its more of a question of, "why dont they use shell bearings on two strokes"?

Cos their is no Cheap way of lubricating the fine tolerances of the bearing surfaces on a two stroke.

Needle rollers are cheap to produce and were the solution for two strokes.

Needle Roller bearings have a very short life span compared to shell bearings.

Needle Rollers are for Needle Dicks!

Jon Fuller · 07-04-2005, 05:21 PM

All the big Bikes of a few years back had roller cranks.

But I would imagine they're noisier, and more expensive to produce.

The bike cranks were multi part pressed, with one piece rods, and if a bike were tuned in a big way, the usual practice was to weld the big end pins at each end to stop them twisting.

As we know, the OB cranks are usually one piece, with split big ends, which must make for a stiffer crank.

so I reckon that's it, shell bearings are cheap, and quiet.

Jon, I dissagree, shell bearing require a definite oil feed to the engineered clearance of a few thou, which then generates it's own ultra high pressure within the bearing with the 'wedge effect', to support the massive loads exerted under combustion. So you couldn't use em in a two stroke.

Jon · 07-04-2005, 07:15 PM

Jon, if you read my post again you might understand what im saying:

Why dont they use shell bearings on two strokes? Because there is no cheap way of providing a constant pressureised supply of oil to the surface of the bearings.

Which if i understand your comment correctly is the same thing!

So therefor we are in agreement on this, yes?

Jon Fuller · 08-04-2005, 12:33 AM

Well, ......maybe, but 'no cheap way' isn't really how I see it, i'd say 'no practical way' , or indeed 'no way', at least you could easily supply the oil, but collecting the spill may be a tad difficult.

Next time I'll 'try to understand'.

anyway, nowt wrong wiv rollers.

Jon · 08-04-2005, 08:26 AM

I admit i could of explained myself a little better on that one.

:o

Jon Fuller · 08-04-2005, 08:53 AM

OK, I accept your unreserved appology

You cummin along on the 16th?

Jon · 08-04-2005, 01:44 PM

Quote:

Originally posted by Jonny
You cummin along on the 16th?

Maybe John,

Id like to if i can juggle things about.

Jon Fuller · 08-04-2005, 01:57 PM

It's unusual for a guy who spells his name 'Jon', to spell another guys name wrong who also spells his name 'Jon', so I guess it's deliberate!

You must be able to make the 16th, it's local innit!

I might even do a bit of bote-in if d wevvers ok.

Captain Chaos · 08-04-2005, 02:53 PM

jonny the wax

Jon Fuller · 08-04-2005, 03:07 PM

That nutter Mainwaring named me it over on RIBnit

Jon · 08-04-2005, 04:16 PM

Quote:

Originally posted by Jonny
It's unusual for a guy who spells his name 'Jon', to spell another guys name wrong who also spells his name 'Jon', so I guess it's deliberate!

My appologies Jon, i had assumed your name was spelt JOHN. In the early days as a member im sure i recall it being spelt with an H.

As you must be aware, there are not many Wankers that spell it J-O-N!

Well thats me put straight then.

I will do my best to make it on the 16th as i think im due some rib tickling.

PS. Jon is Chaos, "Behind with the Rent"?

rama · 10-04-2005, 04:24 AM

Damn this site is confusing,
If you want, I will post a version of shell's description of 2 vs 4 stroke lubrication tomorrow (if i get ten minuets to scratch my proverbial) But that's just shell techs, Im sure i will get told they are wrong by one or two "experts"