MM Tokyo Motorshow Coverage

[.RJ]

edit...I remember reading about theoval piston when they first came out with it...what was the problem with it?

Internal friction and HP. They built the oval piston concept to compete with 2-strokes, as honda thought they could compete with a 4-stroke in GP racing. The max engine size at the time was 500cc (no more than 4 cylinders or 6 gears in the trans) and all the other manufacturers were using 2-stroke engines. The bike had a few new concepts on it besides the oval pistons and they never fully sorted it out.

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[Kaan]

I spy a mugen B series... the ricer inside of me is now satisfied.

[PGK]

The problems with oval pistons are myriad....and they all stem from oval pistons being a dumb idea, and the entire affair was undertaken because of foolish pride and hubris.

If you look closely you'll notice that the connecting rods on the oval-piston motor are one-piece....meaning that the crank is made up of 5 pressed together pieces. all of the internal parts on that motor have to be extremely precisely machined...since each piston has two wrist pins with two rods and two journals, anything even slightly off-kilter means death. Honda also had a lot of problems getting rings to seal properly, problems they never completely solved. It won't hold the same leakdown test numbers as a conventional cylinder. The rings are all made of several interlocking pieces. I would have loved to see a pic....but I don't think any NR750 owners are lining up for engine rebuilds. Overall it was a quixotic endeavor, no point really. taking on an impossible task out of fear of change.

Elf was not the first single sided swingarm, nor were they the first to use hub-centric steering. Both of those ideas go back to the 1930's. Imme used single-sided front and rear suspension in 1949, but it appeared before then. There is nothing new under the sun. For that matter, I've heard rumors and seen in print, though you can't believe everything you hear or read, that triumph had experimented with oval pistons, and even constructed a prototype motor in the 1950's, when they were being battered in GP's by the onslaught of multi-cylinder machines from the continent and the orient. Like Honda, through their own hubris they didn't want to abandon the tried-and-true single-cylinder British motor, so they turned their attention towards witch doctors preaching false hopes. The metallurgy of the time could not support the oval piston, nor it's rings, and they gave up. Like Honda, they tried to skirt a rule in the upper-echelon of prototype racing. They gave up and made a twin. And still lost. At least Honda switched to two-strokes and won.

[G.Irish]

It was a hell of a ride with me getting lost in the Japanese countryside, pulled over for speeding, having to bump start the VFR, and getting buzzed on both sides by crazy Japanese dudes on scooters.

Did you have to get an International Driver's Permit thingie to drive there?

Yep, about 10 minutes and $15. If you do get one make sure you check the endorsements on it before you leave. The lady forgot to put my motorcycle endorsement on mine when I had clearly marked it on my application.

[G.Irish]

The problems with oval pistons are myriad....and they all stem from oval pistons being a dumb idea, and the entire affair was undertaken because of foolish pride and hubris.

If you look closely you'll notice that the connecting rods on the oval-piston motor are one-piece....meaning that the crank is made up of 5 pressed together pieces. all of the internal parts on that motor have to be extremely precisely machined...since each piston has two wrist pins with two rods and two journals, anything even slightly off-kilter means death. Honda also had a lot of problems getting rings to seal properly, problems they never completely solved. It won't hold the same leakdown test numbers as a conventional cylinder. The rings are all made of several interlocking pieces. I would have loved to see a pic....but I don't think any NR750 owners are lining up for engine rebuilds. Overall it was a quixotic endeavor, no point really. taking on an impossible task out of fear of change.

Well with Honda part of their philosophy is to take on big engineering challenges in racing and to do things different. They had beaten 2-stroke engines with 4 strokes before so they figured they could do it again. Furthermore, Mr. Honda had a particular disdain for 2-strokes ('stinkwheels' as he called them).

In the end it was an expensive and very unsuccessful venture in racing but they ended up learning a lot. When you think about, the fact that they made anywhere close to the power of a 2 stroke with a 4 stroke of the same displacement was a decent accomplishment. Enough so that Formula 1 banned oval pistons before Honda (or anyone else) had a chance to use them. The current Moto GP rules banned oval pistons too so Honda wouldn't have an unfair advantage (they hold over 200 patents related to said engine).

Even to this day people at Honda that worked on the project don't see it as a total failure. One of the lead engineers at the time is now Honda's president actually.

Elf was not the first single sided swingarm, nor were they the first to use hub-centric steering. Both of those ideas go back to the 1930's. Imme used single-sided front and rear suspension in 1949, but it appeared before then. There is nothing new under the sun. For that matter, I've heard rumors and seen in print, though you can't believe everything you hear or read, that triumph had experimented with oval pistons, and even constructed a prototype motor in the 1950's, when they were being battered in GP's by the onslaught of multi-cylinder machines from the continent and the orient. Like Honda, through their own hubris they didn't want to abandon the tried-and-true single-cylinder British motor, so they turned their attention towards witch doctors preaching false hopes. The metallurgy of the time could not support the oval piston, nor it's rings, and they gave up. Like Honda, they tried to skirt a rule in the upper-echelon of prototype racing. They gave up and made a twin. And still lost. At least Honda switched to two-strokes and won.

I think I heard that an aircraft engine manufacturer tried oval pistons unsuccessfully back in the day. I didn't know about the single-sided swingarm but Elf's implementation was an idea from Guy Coulomb (who works on Tech3 Yamaha now) for endurance racing. Like you said, a lot of ideas are old but a lot of the time the people who tried it back in the day didn't get it to work very well.

[PGK]

IMME used the single-sided swingarm pretty successfully for a 250cc two-stroke single....it also had a single-sided front fork. The endurance racing advantages of the design comes from the quick tire changes you can do with a single-sided swingarm. You compromise the chassis, but if you're talking about losing less than a tenth second a lap because of a flexier swingarm vs. 5 seconds on a pit stop, it can make sense.

Racing, either through rules or a desire to shave seconds off times, provides an endless supply of clever ideas and genuine innovation. At the same time, it provides an endless supply of pointless innovations that are impractical for anything but racing.

the ELF racers were some of the neatest and most exciting race bikes of their era. It baffles me that with so many functional, and in many ways superior, alternative suspension systems out there manufacturers refuse to deviate from the telescopic fork.