ESE's works engine tuner

[seattle smitty]

(EDIT) I'm trying to delete this . . . ???

[Grumph]

Wonderful engines and photos, thanks for those! They all look big and heavy for today's outboard racing, but certainly food for thought. I think any triple has to have four main bearings, whereas an opposed-four can do with three and an opposed twin with two. One of the things I wondered about is if that also could be done with 90degree V-twins and fours; could adjacent crankcase sections (for adjacent cylinders) have a wide, flat, full-circle crank throw between them (no main bearing), with a labyrinth seal around the crank-wheel, . . . would a seal like that work at high rpm and effectively seal the two crankcase sections, and if it did would the oil retained by the seal have a lot of drag?

Do you have any personal experience with the OMC V4's ? I have in a book here a couple of pics of the OMC cranks which are pretty much as you describe but with large dia piston ring type seals on the webs. Intake was compromised with small reeds feeding at very poor angles and restricted areas. I may yet scan the pics and send them to husa...unless he finds them on the web first....

[seattle smitty]

I know of them, at least the old cross-flow V-4s of my youth, but never had one apart.

[wobbly]

What you describe is exactly what SA Design did with the flying web V4 - 500, but needed no sealing between the crank pairs.
The Swiss Auto had adjacent cylinders crankpins running at 90* opposite each other off a common web that was sitting inside a common crankcase volume.
This eliminated a seal and bearing between those cylinder pairs.
Gave a very small package, but required very expensive materials, extensive FEA and heat treatment to overcome the stress levels generated in
the unsupported "flying web".

http://www.swissauto.com/d/motor/pro...Display=20000D

[jonny quest]

How did the SA seal between the crankcases?

It also said that motor has numerous wins... what teams did they win with?

[Frits Overmars]

One of the things I wondered about is if that also could be done with 90degree V-twins and fours; could adjacent crankcase sections (for adjacent cylinders) have a wide, flat, full-circle crank throw between them (no main bearing), with a labyrinth seal around the crank-wheel...

What you are exactly describing, is the French JBB 250 V-twin. The pictures below should speak for themselves but I would add that, given your freedom of shape on a boat, a boxer would be simpler, lighter and more vibration-free.

[wobbly]

The SA didnt need to seal adjacent cylinders - they fired together off a common case volume.
ie the crank pins on each side of the flying web were displaced by 90*, as were the cylinder axes - thus both pistons arrived at TDC together.
Put two of these pairs in line and you have a V4 with the minimum seals/bearings.

[jonny quest]

Look at that fancy cylinder head in the pic Frits posted.

Frits' motor pics also show a sealing ring between crankcases. How would the dual carbs work then?

Thanks Wobbly for info

[husaberg]

Look at that fancy cylinder head in the pic Frits posted.

Frits' motor pics also show a sealing ring between crankcases. How would the dual carbs work then?

Thanks Wobbly for info

works like this.....


A few pics of a Rotax homebuild special flying web
http://www.kiwibiker.co.nz/forums/al...p?albumid=4834

JBB
http://www.kiwibiker.co.nz/forums/al...p?albumid=4836

Swisauto
http://www.kiwibiker.co.nz/forums/al...p?albumid=4833

Konig inc crank pics
http://www.kiwibiker.co.nz/forums/al...p?albumid=4851

Boxer 2 strokes
http://www.kiwibiker.co.nz/forums/al...p?albumid=4879

[fatbastd]

Apologies in advance for the thread hijack, but I'll keep it brief..

Question for Frits really-I see you name in connection with a Yamaha 3 cylinder article from some time ago. In Dutch, sadly for me!

I am contemplating buying such a machine-in terms of reliability and usability, assuming properly maintained and prepared, would you suggest avoiding the idea or see it as no worse than anything else similar?

Thanks.

Now, back to the regular programme...

[seattle smitty]

Well . . . as the old traveling, Bible-thumping preachers used to shout at their big-tent revival meetings, "ASK-uh and yew shall RECIEVE-uh!!!!"

What a great website!! My only problem is that my brain gets full, and I have to go away and do other things.

There are several things that jump right out at me from the responses and photos on which I could comment, but they are equally obvious to all, and I've already taken more than my share of space and attention, so I'll resist for a while (have I said that before??).

Many thanks, gentlemen.


(EDIT) AW DANG, okay, here I go again, ONE observation/question: On some of the photographed engines, it appears that the stubs on either end of the crankshaft only have room for a single-row bearing. Given the power, and twisting forces that these engines put out, would it not be better to support the crank with double-row bearings whenever possible, even at the cost of a small increase in overall width??
I once read an account by American auto racing engine-builder Smokey Yunick. Smokey described watching a sort of dyno run in which a dummy engine with some viewing-ports cut into it was spun up to racing rpm with a powerful electric motor. Stroboscopic lighting was used to see the effects of horsepower and rpm on various components (I think this was all done at GM). Smokey said that at 7000 rpm a camshaft twists and wriggles and winds-up and releases like a snake that is desperately trying to tear itself free of the engine. And I had heard a similar description of a dyno run of the first Mercury Mk75 outboard in the mid-1950s, as witnessed by a local racer/tuner, Bill Rankin. Bill said that the Mercury engineers had the base of this 60hp inline six mounted rigidly to a plate of steel . . . and had a measuring device (machinist's scale or dial indicator or ?) set against the top of the tall engine to see how much it might twist along its length. Bill told me when they put full throttle to that motor you didn't have to read the scale . . . the top of that engine visibly twisted waaaayyy out-of-line!!
So I have a hunch that as you add power and rpm, and heat, to any sort of racing engine, it is twisting and ringing and wiggling and oscillating to a degree that would be alarming if you could see it "slowed down" with strobe-lighting or some-such method (AND, different subject, that the lovely round and parallel cylinders that you examined cold with your bore-guage are a good deal less round and parallel when hot). IF this hunch is at least somewhat true, wouldn't it follow that you want REAL GOOD mainbearing support at the ends of a crankshaft?? And maybe the fattest, longest, best-supported crankpins (consistent with their trade-offs)??

Sorry, I can't seem to stop myself.

[Grumph]

Smitty, the answer is yes - and no....from personal experience i've seen big end pins in pressed up cranks get bigger as power has gone up - but there is a limit to this. Pressed up cranks can and do flex to accomodate case movement.

There's a very good - but 4 stroke - example local to me. One of the last survivors of the 1927 Delage straight 8 GP cars was being rebuilt here. The car changed ownership part way through the rebuild. First rebuilder (friend of mine) had copied the original crank - one piece, about 3 feet long, split roller big ends...Second rebuild shop took one look at the crank and said "we can do better" so beefed it up...
When the finished car was run, the stiff crank cracked the block...It's now running with a stitch repaired block and my friend's OE copy crank in it...And flexes quite happily.

[seattle smitty]

Oh sure, it has to be an integrated set of design changes.

[RomeuPT]

I did proper back to back testing of the bent Vs dead straight pipes when building the BSL500.
The top pipes could be dead straight with just a small angle where the slip joint fitted onto the header,and these 2 pipes would deto as soon as you got close to spot on tuning.
Fit a deto button and the effect simply disappeared - we always had egt probes fitted and they made no difference.
On the bottom pipe of the tripple, this had a serious S bend to get the belly forward enough for it to fit nicely into the banana arm.
I found that as long as we had about 100mm of dead straight header fitting onto the slip joint I could get identical Hp within 1/2 in 55 as long as compensation was
made for weld shrink on every joint, as well as every joint being hammered smooth.
And the S bent pipe did not need a deto button at all.
I discussed the straight header effect with the Yamaha R&D chief at the time called "Suzan" and he opined that if you had a bend too close to the slip joint
especially if it was bent in any way than on the vertical plane, this gave rise to an asymmetric plugging pulse flow, and this adversely affected the loop scavenge regime.
Sounds pretty plausible to me.

Good info. Thanks
I usually divide the header into several pieces, starting from cuts of 5 or 6º to 7/8º depending on the needed bend. So the first 100mm of header encouters 2 or 3 hamered cuts of 5º and 6º. Some other pipe builders give the a bit of straight header and then a 90º of sharper bend follow by other straing and other bend to go under the bike

Don't know what's better.

[peewee]

i had a similar thought not long ago for a banshee crankshaft. why not use a cylindrical roller bearing on both ends ( instead of a 6 ball ballbearing) and 8 ball ballbearings in the center ( instead of 6 ball ballbearing). crankworks told me this may cause too much stiffness and create a failure. im not sure i believe it though. didnt some of the yamaha twins have a similar setup with roller bearings on each end and two hefty ballbearings in the center ?