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Post some unusual engines

19K views 83 replies 17 participants last post by  ROBBO 
#1 ·
Thread for those alternate engine designs you'll probably never see in a bike, but might like to. Or just for unusually cool engines in general.

Inspired by this thread. Gonna start by shamelessly ripping off Eatabullet's great links.





 
#56 ·
There was someone on this forum that did the conversion. I am sure there are more. If I remember right, the inefficiencies were greater than the gains and he would have been better off leaving it a parallel twin.

(Something is telling me it was a Ninja 500 or 650R? It was years ago.)
 
#57 ·
Yeah, for the twin-to-supercharged-single conversion, you'd expect to loose some power vs just running both cylinders. It only seems worth doing to fit in a specific engine class for racing, or as an learning project / oddity. You might gain some efficiency from the effectively higher compression, but then you have all those tuning and fuel issues. Which again, lends itself to racing use (super high octane fuel).
 
#60 ·
Right, that's exactly what I was saying. With only one expansion piston its gonna sound like a parallel twin. The exhaust note depends entirely on the exhaust valve timing for the expansion chamber. There might be some interesting overtones from the intake synching up differently, but usually only the rider can hear that, if at all.
 
#66 ·


Pretty old engine, from the 80's. What's interesting? All the yellow bits are plastic, making it much lighter. As in 168 pounds for a DOHC 4-cylinder configuration that pumped out 290 naturally aspirated horsepower at 8,500 rpm. Never made it to market because it was to expensive (guess the high end plastic cost more than metal, plus new tooling costs etc.)

I imagine they could do a sub-80-lb motor making 100 HP, sounds like a good route to go to make a 300 lb / 100 hp bike.

Is back in the news because the company that built that one is making one for a demonstration race car, using modern carbon reinforced thermoplastic. Will be 2 liter engine under 150 lbs. With turbocharger, it will make over 400 hp.

http://www.enginelabs.com/news/plastic-race-engine-returns-as-polimotor-2-project-underway/
 
#71 ·
I think to match VFR timing / exaust note, you would have to offset the middle two cranks by 90 degrees in the same direction. That's not a crossplane, it's a ..... well, something else. Would need some extra balancing, though i guess no worse for each pair than a parallel twin.

Sent from my SCH-I605 using Tapatalk
 
#72 ·
Here's a one I'd never heard of, that seems surprisngly simple and practical. In fact, it seems they are in actual production! Has the advantages of a two stroke, but with a fully sealed crank (uses stepped pistons instead of crankcase pumping).

http://users.breathe.com/prhooper/opads.htm

 
#73 ·
Can't remember if I got this one yet. Is a 2 stroke, but without a crankshaft, and has 12 cylinders (and 12 sparkplugs). Claimed 75LBS / 300HP. First video shows the "elbow engine" configuration, second shows it running. Sounds angry!



 
#76 ·
Yeah, 28K rpm is pretty crazy. It also reportedly has great torque, even as low as 100rpm. Transmission would be more or less optional. The exhaust... in that video, its running wide open. Don't see why it couldn't have a conventional muffler though. It doesn't need (or benefit from) an expansion chamber, as it is forced induction and the port timing can be set however you like (is asymetric). The design effectively builds a positive displacement super charger into the case (which uses the joined V sections to push air) but it looks like it would do well with (additional) turbocharging.

I don't know how the ignition is handled, might be explained in the patent I found. My guess is the entire engine case would act as a distributor, so the wires (if any, you could probably work it so the plugs themselves are the pickups) would spin around with the cylinders.

http://www.google.com/patents/US5029558

I found an article that explains how in one example, there were ports that allowed burning gas from one cylinder to cross into the next and ignite the charge as it came over TDC, resulting in "continuous combustion" much like a turbine would have. Spark would still be needed to start the engine, and that was only for one of the three examples built. But once it was running, you could (in theory) shut the spark off!

The article (from Aug 1974 popular science) is a good read!

https://books.google.ca/books?id=uR...X&oi=book_result&ct=result#v=onepage&q&f=true
 
#79 ·
wouldnt the "exhaust manifold" be spinning with the "head" unit?
Yep, it is. But there's a case around the entire thing (its what holds the bearings) that collects and directs the exhaust (and also acts as the 'supercharger' manifold). Your concern is certainly legit though - the article I linked to actually quotes the builder describing the challenges of dealing with gas flow in a spinning system. Apparently the spin related forces made it so that normal rules regarding 2 stroke piston crown shape etc didn't cut it.

Also its apparently not to difficult to build one, or at least a version powered by compressed air. Manual mill and lathe (and a bandsaw) is all you need, as there's no cams.

@Shinyribs - about the highest compliment I could ask for. :)
 
#81 ·
Hell no. I want to ride that bike sometime before I die (actually hoping for July).

I might look at building a little air powered demo model, does seem like fun project. The one this guy did is very pretty.

 
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