2008 World Championships: Have you ever seen this? (pics)

Hello,
A friend of mine in Landres sent me a couple of pictures of a really weird engine (Russian). Have you EVER seen one with an OVAL cilinder??
(not me, for sure...)
And look at the muffler also. A very unique piece indeed!

Well, check this out!



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...More Cold War secrets revealed!

Looks like it's very well made.

Wait a minute! Whilst the fins are oval, the bolt pattern indicates a normal round bore.

Floyd in OR

Got to love the NVA . Now that is a real machinist putting a nice finishing touch on the attention to details. Pretty !

I don't know about model engines, but back in 1992 Honda built some motorcycle (and perhaps F1) engines with elliptical pistons. I believe their motivation was to enlarge the amount of space in the cylinder heads for valves.I can't imagine having rings on such pistons, perhaps they were ABC or similar..

Not sure where that all went.

Edit: here's a link to a document about it (which costs $14): http://www.sae.org/technical/papers/930224

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"That which seems the height of absurdity in one generation often becomes the height of wisdom in another." -Adlai Stevenson

>I don't know about model engines, but back in 1992 Honda
>built some motorcycle (and perhaps F1) engines with elliptical
>pistons. I believe their motivation was to enlarge the amount
>of space in the cylinder heads for valves.I can't imagine
>having rings on such pistons, perhaps they were ABC or
>similar..

Nope - conventional ring types. The pistons were actually ovals. The idea was to get around a rules limitation of only 4 "cylinders". They had previously gotten around the limitations of a 4-stroke by having many tiny cylinders - a 5-cylinder 125 and a 6-cylinder 250 that both could safely rev to around 20,000 rpm.

Effectively, it was like they had built a V-8 where the pistons just happened to intersect - two connecting rods per piston, 8 valves/cylinder, etc. They got it to more-or-less work, eventually, but it wasn't competitive. Then they built a very conventional 2-stroke that blew everybody away.

http://world.honda.com/history/challenge/1979pistonengine/photo/02.html

Brett

If you like tiny screamers, Suzuki built a 3-cylinder 50cc 2-stroke with two cylinders parallel and one at an angle to the others in the 1970s. Did some ungodly rpm like 25,000. It was soon banned as too powerful and unfair to the others, at least that was the official reason. The Honda oval-piston machines had IIRC eight valves per "cylinder" in the attempt to beat the 4-cylinder rule. Talk about brilliant engineering and out of the box thinking! Practical considerations brought down these flights of engineering fancy rather than any defect in the thinking or execution.

Then there were the German diesel seaplane engines with pistons that opposed each other with the "compression chamber" where the piston crowns met in the center of the cylinder... (there, an airplane reference)

>>I don't know about model engines, but back in 1992 Honda
>>built some motorcycle (and perhaps F1) engines with
>elliptical
>>pistons. I believe their motivation was to enlarge the
>amount
>>of space in the cylinder heads for valves.I can't imagine
>>having rings on such pistons, perhaps they were ABC or
>>similar..
>
> Nope - conventional ring types. The pistons were actually
>ovals. The idea was to get around a rules limitation of only 4
>"cylinders". They had previously gotten around the
>limitations of a 4-stroke by having many tiny cylinders - a
>5-cylinder 125 and a 6-cylinder 250 that both could safely rev
>to around 20,000 rpm.
>
> Effectively, it was like they had built a V-8 where the
>pistons just happened to intersect - two connecting rods per
>piston, 8 valves/cylinder, etc. They got it to more-or-less
>work, eventually, but it wasn't competitive. Then they built a
>very conventional 2-stroke that blew everybody away.
>
>http://world.honda.com/history/challenge/1979pistonengine/photo/02.html
>
> Brett


What Brett says is true, but Honda did want very badly to beat the two-strokes with a four-stroke. Back then Honda was known almost exclusively for four-stroke engines.

While it is literally true that the oval-piston engines were not competitive in GP racing, they came very close. Scary close, actually...

Dan

>What Brett says is true, but Honda did want very badly to beat
>the two-strokes with a four-stroke. Back then Honda was known
>almost exclusively for four-stroke engines.

Of course, that was the entire motivation for the effort. But they knew it would take extraordinary steps to do it. Eventually, even the mega-Yen available to Honda proved insufficient, and they found out why the "box" existed in the first place.

Brett

>I don't know about model engines, but back in 1992 Honda
>built some motorcycle (and perhaps F1) engines with elliptical
>pistons. I believe their motivation was to enlarge the amount
>of space in the cylinder heads for valves.I can't imagine
>having rings on such pistons, perhaps they were ABC or
>similar..
>
>Not sure where that all went.
>
>Edit: here's a link to a document about it (which costs $14):
>http://www.sae.org/technical/papers/930224
>
>[photo not recovered: 29334.gif]
>
>"That which seems the height of absurdity in one
>generation often becomes the height of wisdom in
>another." -Adlai Stevenson


Ron B.
F4Fguy

It goes back a lot farther than that. MG did it in the thirties. the purpose being to get more displacement in the existing block, which was already "stroked out".

In any case this has little to do with the present case. Floyd got it in one. The fins are oval, the cylinder bolts are in a circle! The cylinder is almost undoubtably round.

Ron B.

Ya, I am sure this is a round cylinder by the head bolts but staying off topic I sure would like an old Honda 50 trail bike right now! Those things were bullet proof! Honda sure did show us what reliability was back then. Remember the Harley AMF days Argh! Kind of like OS and a Fox motor. Please no torchs with that comment. [photo not recovered: sipcof.gif]


Have fun, Bruce

Someplace, I saw a picture of one of Honda's "eliptical" pistons, with rods. To my thinking, they were oblong...two straight sides, with a 'full radius' at each end. To me, "eliptical" means no straight lines, and Dictionary.com agrees. http://dictionary.reference.com/browse/ellipse

Machining oblong pistons, rings and cylinder bores would be a challenge, but with the right equipment, almost anything is possible. The programmer has to leave his tinfoil hat home, tho.
Yes, I got a bad program today! I programed one side of the part, and he did the second side. Mine was fine, at least. Steve

Steve Helmick
Renton, Washington
USA

>Someplace, I saw a picture of one of Honda's
>"eliptical" pistons, with rods.

The link in my post above is a picture of the piston on it's two conrods, and yes, it's an oval not an ellipse.

Brett

>>Someplace, I saw a picture of one of Honda's
>>"eliptical" pistons, with rods.
>
> The link in my post above is a picture of the piston on
>it's two conrods, and yes, it's an oval not an ellipse.
>
> Brett


I saw Freddie Spencer (I think), ride one of these things at Laguna Seca in (I think) 1981 or so. It was fast and had an incredible sound but didn't finish. Rumor was electrical problems. The Honda team was very secretive in those days (actually they still are), and it was impossible to get close enough to the bikes in the pits to see anything of real interest.
About halfway through the race it would intermittantly miss especially coming out of corners. That must have been a real thrill for Freddie in the "corkscrew".

Randy C

>
> Ya, I am sure this is a round cylinder by the head bolts
>but staying off topic I sure would like an old Honda 50 trail
>bike right now! Those things were bullet proof!



I still have my XR-75. I haven't run it in a few years, though. (Like 20 years...)


Steve

XR 75s rule! I have heard the value of those and the z-50 and the trail 70 has gone through the roof!

Never sell it! It is too cool and they will never come back!

Ha, you mean to tell me that my ST .51 with the square head actually has a round cylinder and piston? [photo not recovered: sipcof.gif]

>
>Ha, you mean to tell me that my ST .51 with the square head
>actually has a round cylinder and piston? [photo not recovered: sipcof.gif]

No! The piston and liner in the ST.51 (at least in yours and mine) both ARE square! How can it be otherwise???

I just love that muffler set up. I wonder if "they" would be willing to sell them in the USA for Euros. Or even Monopoly money like we have here in the US A little humor there, darn little

>Or even Monopoly money like we have here in the US A little
>humor there, darn little


mmmmm...Not a bad idea at all. Just place your bid, wait for the answer and tell me what happens!
(I have some "alternative currency" the can be very useful...)

Have a close look of unusual cylinder head shape on new Evo .36. It is not circular shape- it has somewhat elongated shape facing rear- could it be an attempt to manipulate the cooling air flow pattern around the head to improve the heat removal? Maybe its to serve as streamlining to reduce the drag from the engine cylinder?
Lyle

>Have a close look of unusual cylinder head shape on new Evo
>.36. It is not circular shape- it has somewhat elongated shape
>facing rear- could it be an attempt to manipulate the cooling
>air flow pattern around the head to improve the heat removal?
>Maybe its to serve as streamlining to reduce the drag from the
>engine cylinder?
>Lyle

Exactly what OS is doing to their new crop of AX engines.



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The OS has extended the forward side of the cylinder head ( facing into the air stream)- thats opposite from EVO.
Lyle

In the 1930s, Lancia built a straight 4 engine, then bored it out by angling the bores into a 4 or 5 degree vee to make room for the enlarged pistons, does this count as a straight or vee engine??

As for the opposed pistons, that was known as the "Commer Knocker" used in many heavy vehicles in the 50's & 60's including the Greyhound bus that I am sure a lot of you have had the (dis)pleasure of riding in.

A small note on a similar subject, tuned pipes were developed for 2 stroke supercharged diesels (again heavy earth moving rigs) in the 1950's I think, I did the sums in 1971 for a .29 tuned pipe, and although I never got around to building it, the numbers were similar to todays pipes.

So, in the words of the classics, what goes around comes around (which, being a control line forum seems appropriate)