Why round pistons not oval????

[BNZ]

Something to do with seals/gaskets stretching un-evenly?

[dawnrazor]

Do some research on the NR500 race bike and NR750 road bike, both were oval pistoned. I believe increased friction was one of the downfalls of an efficient oval-piston engine.

Well as Satoru Horiike (the engineer behind the NR500 and NR750) says, "the oval piston design has a very high potential, but has had a troubled life. I think the idea is very good but ahead of its time, at the time of its introduction (1979) machining technology was not so percise, but now we can make anything, any shape. Technically we could do it now, but it would still be very difficult."

From the horses mouth so to speak, Quotes taken from an interview in BIKE

[avgas]

Be careful now - we're heading into Bimota territory....look where that got them

[Pwalo]

If I recall correctly round pistons also tend to dissipate heat evenly, which is a rather critical factor in engine design.

But as everyone else has said Honda tried, and failed. I'm pretty sure that we'd have seen an oval pistoned RCV by now if the technology was viable.

[vifferman]

The NR had oval pistons not because it was a good idea, but so they could make what was effectively a V8, with only 4 pistons, so it kept to the letter of the law, if not the spirit of the law. Unfortunately, for all the engineering expense and complexity, it didn't produce markedly more power than a V4 could, and in fact a lot less than subsequent V4s, like the RC45, and current MotoGP bikes.

But never mind; it was kewl all the same, and many of the design features of the road-going version (indicators in mirrors, underseat zorsts, single-sided swingarm, etc.) filtered down to subsequent models.

[Lou Girardin]

The Honda had serious ring sealing problems. It was another Honda answer to a question that wasn't asked.

[Motu]

It was just because Honda didn't want to build a dirty stinking 2 stroke.After the failure of the V4/8 they were frog marched down to hall to the 2 stroke room where they finally settled down to play nicely with the rest of the boys.

[steved]

The Honda had serious ring sealing problems. It was another Honda answer to a question that wasn't asked.

Gotta love the 'can-do' attitude. Even though they didn't do it.

[Coyote]

Very interesting concept.. Wish there were more KIWI's like McLaughlin and Britten...

Just give me a few more years

[Flyingpony]

Over the years I have thought about it a lot and still cant work out how you can get a square piston to seal in the corners, its just doesnt seem possible but he has done it. The mans a genius

They may have gotten an idea from the Mazda Wankel (Rotary) engine.

[Forest]

If you take a circle shape andturn it into an oval without changing the outside circumference, does the internal area change? Why would increased friction have been an issue? - I presume something to do with the straight sections of the sides?

Absolutely - if the perimeter is fixed, then an oval/ellipse will always enclose less area than a circle.

To put it another way. For a given perimeter, a circle always encloses the greatest possible area.

[imdying]

Absolutely - if the perimeter is fixed, then an oval/ellipse will always enclose less area than a circle.

To put it another way. For a given perimeter, a circle always encloses the greatest possible area.

The NR750 is neither oval or ellipse iirc... it's two circles, joined by a rectangle (parallel sides).. or a rectangle with two round ends if you will. Best of both worlds?

[McJim]

Very interesting concept.. Wish there were more KIWI's like McLaughlin and Britten...

It's very difficult for them here - every time someone comes up with a new idea all the other kiwis jump on them and tell them it can't be done - tall poppy syndrome I think it's called - never seen it demonstrated more visibly than here in NZ. Shame coz you're really quite a creative and ingenious bunch.

[slowpoke]

Using the KISS principle it's called Keep It Simple Stupid........hence the round pegs in round holes

[degrom]

It's very difficult for them here - every time someone comes up with a new idea all the other kiwis jump on them and tell them it can't be done - tall poppy syndrome I think it's called - never seen it demonstrated more visibly than here in NZ. Shame coz you're really quite a creative and ingenious bunch.

Is that way, when I built my own pressure pot sand blaster and was looking for nozzles nobody wanted to help me find them.

The one place I asked didn't even want to talk to me about it. They thought I wanted to take over.

Luckily I know places like that won't last... The don't they know the first Zen business rule is that when you share with other they will share with you.