The Bucket Foundry

[Niels Abildgaard]

But is the extra layer (no pun) of complexity really neccessary ?



KISS - and proven technology should be satisfactory IMO.

I asked a danish maker of superkart engines why his crankpins were 22mm instead of 25 and his explanation was more or less that conrod bigend area life was short enough as is.
Some italian makers used 25 mm pins for cranks and had even shorter lives.
Frits, I think, has explained that cages live a very hard life due to the violent angular accelerations and this gets worse with bigger crankpin diameter.
present day technology is not good enough.

[Grumph]

Well - yes and no...I think I've seen somewhere a pin size/bearing load sheet from INA which suggested that crankpins at least in the 80's were unneccessarily large OD for the loads. Cage lfe has been getting better as materials and surface treatments have improved. The INA needle roller bigends are pretty good...
The big tradeoff is crank stiffness vs load capacity. The small pins can handle the loads with a suitable bearing but if case stiffness isn't optimum the crank is going to move - which leads to fretting and what looks like a failure due to a too small pin...

As sims have got better and the virtues of longer rods have been shown, the big end accelerations have at least stayed constant - as revs have been able to rise without exceeding known safe levels...

[Frits Overmars]

I asked a danish maker of superkart engines why his crankpins were 22mm instead of 25 and his explanation was more or less that conrod bigend area life was short enough as is.
Some italian makers used 25 mm pins for cranks and had even shorter lives.
Frits, I think, has explained that cages live a very hard life due to the violent angular accelerations and this gets worse with bigger crankpin diameter.

That's right Niels. Bigger crankpin diameters lead to heavier cages with more polar inertia, and more and/or bigger needles that put up a bigger struggle against those angular accelerations. The rolling velocity of the needles is proportional to the crankpin diameter, and so is their angular acceleration. In short: the needles will tend to skid instead of roll.
But wait, there's more. A big end bearing does not just rotate; it is flung around the crankshaft center and all needles try to crowd towards the outside.
In a cageless bearing all needles push in the same outward direction and the outermost needles are heavily pushed against each other, causing so much friction between them that the lubricant may char. These pushing forces increase with the crankpin diameter and with the total mass of the needles. All in all the crankpin diameter can be too big for its own good.
Niels, note that this centrifugally-induced friction will occur even if your cageless big end bearing would rotate with a uniform velocity without any angular acceleration.

I think I've seen somewhere a pin size/bearing load sheet from INA which suggested that crankpins at least in the 80's were unneccessarily large OD for the loads. The big tradeoff is crank stiffness vs load capacity. The small pins can handle the loads with a suitable bearing but if case stiffness isn't optimum the crank is going to move - which leads to fretting and what looks like a failure due to a too small pin...

That's it Grumph. Bearing load is not a problem. Crankshaft stiffness demands large crankpin diameters while heat generated through needle skidding demands modest diameters, It's a Catch 22-situation. Maybe that is why many engine makers went for a 22 mm pin .

Come to think of it: Fletto, how is that epicycloid crank coming along?

[guyhockley]

Not to detract from the brilliant JBB engine but the sealing ring between the rods is pretty common on V4, V6 and V8 outboards.
Most extreme example is probably Konig 3 and 4 cylinder radial engines for powered paragliders, no idea if that's the same Konig as the Kim Newcombe one, or if they're still going.
I've also seen an outboard crankcase that seemed to have labyrinth seals machined into it.

[dark art]

But is the extra layer (no pun) of complexity really neccessary ?

I do remember reading somewhere, probably Jan writings, the Aprilia 125 RSA big end last an entire season on dyno testing. Frits, can you confirm this?

Being like this, current big end tecnology is quite enough for the level of power being developed. That said, things are in constantly evolution and doesn't hurt to improve what is alreay good

[Frits Overmars]

I do remember reading somewhere, probably Jan writings, the Aprilia 125 RSA big end last an entire season on dyno testing. Frits, can you confirm this?

Yes I can.

[WilDun]

But is the extra layer (no pun) of complexity really neccessary ?

The whole bearing looks too much IMO like the floating bush bigends originated by Henri in the 1920's and perpetuated by Royal Enfield.
These proved to be too heavy and suffered from a lack of lubrication to the inner bearing.

KISS - and proven technology should be satisfactory IMO.

Yes and the RE bushes were a helluva lot heavier (might have been brass with white metal coating) - but in saying that, they were still useful after being worn out in the big end, - I used one as a spacer to fit Matchless front forks to my old Model G! - try doing that with a stuffed needle roller!

[Grumph]

Yes and the RE bushes were a helluva lot heavier (might have been brass with white metal coating) - but in saying that, they were still useful after being worn out in the big end, - I used one as a spacer to fit Matchless front forks to my old Model G! - try doing that with a stuffed needle roller!

Some years back I finished off an Aermacchi race engine build which had been started by a South African who brought it with him when he emigrated here.
He sold it to an Auckland based customer of mine.
It had some nice bits and some dubious ones...I got to know him later and he came out to visit me. When he walked into the workshop I reached up to the shelf and handed him a silver bracelet. Here - a gift for your wife, you've paid for it...
It was the rod insert and needle roller bigend from the macchi rod - all fused into one solid lump which had spun in the rod after about 2 hours use on Pukekohe..An english aftermarket part.

For Husa - A Bladen bros part. they were the go-to people for macchi bits for a while.

[husaberg]

Some years back I finished off an Aermacchi race engine build which had been started by a South African who brought it with him when he emigrated here.
He sold it to an Auckland based customer of mine.
It had some nice bits and some dubious ones...I got to know him later and he came out to visit me. When he walked into the workshop I reached up to the shelf and handed him a silver bracelet. Here - a gift for your wife, you've paid for it...
It was the rod insert and needle roller bigend from the macchi rod - all fused into one solid lump which had spun in the rod after about 2 hours use on Pukekohe..An english aftermarket part.

Alpha?
RE big end was their designers answer because they could not obtain solid plated cadges for the big ends. Like a modern race two stroke has.
As Frits mentioned cycli variations in speed plays havoc on heavy and weak bearings.

[husaberg]

Not to detract from the brilliant JBB engine but the sealing ring between the rods is pretty common on V4, V6 and V8 outboards.
Most extreme example is probably Konig 3 and 4 cylinder radial engines for powered paragliders, no idea if that's the same Konig as the Kim Newcombe one, or if they're still going.
I've also seen an outboard crankcase that seemed to have labyrinth seals machined into it.

They certainly do.


i always liked the rd200 lab seal over bearins for space saving
https://www.kiwibiker.co.nz/forums/a...7&d=1450508329
https://www.kiwibiker.co.nz/forums/a...hmentid=318036

I think the Konig as it was a 180 opposed four only had seals on the outside and maybe the middle but it should have not needed it for the opppsed pairs.
https://www.kiwibiker.co.nz/forums/a...8&d=1426758309

[guyhockley]

Modern version of the Konig 4

http://konny.cz/price_b/2s.htm

There are other manufacturers of hydroplane racing engines making "boxer" engines such as Arens, Vrm and Rossi using similar cranks.

Also the Swissauto/MuZ V4 was a kind of bent flat 4:

[guyhockley]

Interesting Konig variation by yet another clever, Dutch tuner, Dirk de Jager. Modified Hoekle/Konig crank, home made case and TZ250 barrels.

Pictures stolen, with blatant disregard of copyright law, from a 1979 article by some young whipper-snapper called Frits Overmaars...

[Frits Overmars]

Pictures stolen, with blatant disregard of copyright law, from a 1979 article by some young whipper-snapper called Frits Overmars...

You're welcome . Glad to see that at least some of my former work made it to eternity .

[husaberg]

Paging mr Moore
http://www.alloyavenue.com/vb/showth...acing-cylinder

[Michael Moore]

What can I help you with? I think that Alloy Avenue thread has most of the information on Jeff's cylinder project, but there might be something additional on his highwaymanbikes website though if there is I'm not finding it.

My replica Webco head is stalled at the mold boxes/match plate stage right now and likely to stay that way until higher priority things are out of the way.