Saturday, 10 July 2021

Many, Many Years Ago,

I was chatting with some friends,

and mentioned a fantastical motorcycle that Honda had produced, it had an oval cylinder and two connecting rods per cylinder, it could also rev to an amazing 23,000 RPM! which is amazing for any engine, never mind a V4, I was meet with more than a little disbelief, I thought no more about, until saw this, all photographs Honda, here it is, the engine was fitted to one of Honda’s most unsuccessful race bikes ever, the NR500, a bike that represented Honda’s ambition to displace two-stroke bikes as the darlings of Motorcycle GP with a four-stroke bike,

Honda has detailed articles about the development of this engine in its archives, which are worth a read, one quote there is from Toshimitsu Yoshimura, who designed the engine. The engineer said,

 “When I look back at it, I’m not sure if we were experimenting with cutting-edge technologies or obsessed with foolish ideas.”

it is fair to say that Yoshimura was right on both counts. The engine was both cutting-edge and foolish, but it’s still fascinating and the engineers had wildly ambitious hopes for the oval piston engine’s output. Maybe a little too ambitious, if the figures from Honda below are any indication,

with eight valves lined up atop the pistons, each supported by two connecting rods, the team’s new 4-cylinder engine looked like an 8-cylinder. According to Fukui’s calculation, the engine could potentially reach a maximum speed of 23,000 rpm and output of 130 horsepower. Therefore, the target output was set accordingly, at 130 horsepower, above perhaps one of the strangest pistons ever to grace a petrol engine,

and here is a road going motorcycle if you want to hear what a oval pistoned motorcycle sounds like, the oval piston design might have failed to beat its two-stroke rivals decades ago, but its one of the most memorable chapters in the company’s history, and it went on to produced one of Honda’s best bikes, for the full story have a look here, oval pistons, who would have thought it!


Jil Wrinkle said...

I was just watching this video a few months ago: Why it is almost impossible for an engine to rev over 20,000 RPM

PattayaStan said...

Dear Jil, just watched the video, interesting to say the least, but I have to say if Honda engineers can make a engine rev to 23,000, imagine if it had been a success and they threw more money at the project, what RPM could they ultimately archive? in any event the V4 Honda in my book has got to be an engineering marvel, best regards, Stan and Diana.