A mini rotary engine for a bike?

Discussion in 'Motorized Bicycle General Discussion' started by Tmoney, Jun 22, 2011.

  1. Tmoney

    Tmoney New Member

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    Hey I just thought of getting a mini rotary engine built for a bike like the ones seen in Masada cars. Does anyone perhaps sell parts to build a small bicycle engine scale rotary engine? This Idea would be useful because there would be less parts to replace and using the right parts there would be fewer chances of break downs. If there no parts I might half to have one custom built.
     
  2. 42blue15

    42blue15 New Member

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    Sachs made a few models of small rotary engines back during the 1970's. They were used in motorcycles, go-karts, snowmobiles, chainsaws and other stuff. Google "Sachs 303". The old ones trade on eBay fairly often. I don't know if they have made anything newer than that.

    I am almost certain that in the last ten years or so,,,, some company was selling a rotary snowmobile engine. It made about 40 HP, which was comparable to what a typical piston two-stroke in a big snowmobile would.

    As for "having one built from scratch", that would be very expensive. And I mean, like,,, ten thousand dollars. Having a machine shop make on-off parts is fabulously expensive. How expensive, you ask?

    Recently I had a desire for some custom gears made: these would be made of regular carbon steel, four inches in diameter, a 1.25" keyed bore, 3/4" thick, and needed to have helical-cut teeth. The prices I was quoted for a 30-day delivery, was about $300 each. $600 for a pair of 4-inch-diameter gears. I ended up using steel camshaft gears (which are 2:1 ratio) but only cost about $50 a pair. ​



    If you reeeeaaaalllly insist on doing this, starting with one of the old Sachs is probably the best way--but rotaries are not exactly 'bombproof' in terms of reliability. Read up on the history of Mazda's engines to see plenty of early problems, and note that the Sachs engines never became common even when they were in production.
     
  3. Tmoney

    Tmoney New Member

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    It looks like its possible to install a rotary engine on a bicycle. It looks like the Sachs motors would fit a bicycle with a big enough engine compartment. I have in fact I have seen a motorcycle with a rotary engine installed. So that shows you can do almost anything with two wheels. I little off topic but I have seen a stretch bicycle with an ATV engine. now that's a motor bicycle that's got some power!
     
  4. Allen_Wrench

    Allen_Wrench Resident Mad Scientist

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    Rotaries have an interesting torque curve, but they're so derned problematic. Maybe you'd be better off with a small gas turbine. Or, if you're brave, you could build a small jet engine out of an old turbo charger. There's instructions online.
     
  5. camlifter

    camlifter Active Member

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  6. cannonball2

    cannonball2 Active Member

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    OS made a rotary for larger model aircraft. They show up on ebay but are probably too few ccs. Plus you would have to convert it gas. Still its a cool little engine.
     
  7. ferball

    ferball New Member

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    Didn't rotaries end up in boat motors? Volvo I believe put them on boats, so find a small boat motor and convert it to a bike, much like the HT sales literature says you can use it for a boat.
     
  8. Fulltimer

    Fulltimer New Member

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    The Sachs 303 has 303cc and 19hp. If someone put that on a bike they would have to have a pilots license! It would have a decidedly cool factor though!!

    Terry
     
  9. 42blue15

    42blue15 New Member

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    Well,,,, putting a huge engine on a bicycle isn't a totally idiotic idea, if you use an intake restrictor plate. And you might need a hefty flywheel on there to smooth out the engine, since it's going to spend a lot of time puttering on its lower-end.

    The benefit is that you still get most of the engine's low-end torque.

    The drawback is the bigger engine's weight.
    The 35cc Robin/Subaru 4-stroke I had was about 8.5 lbs.
    A Briggs & Stratton Vanguard v-twin (16 hp normally) weighs about 75 lbs,,, + the flywheel you added....
     
  10. 16v4nrbrgr

    16v4nrbrgr New Member

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  11. rotary guy

    rotary guy New Member

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    Suzuki had a RE5 rotary in I believe 1975- 1977 it didn't gain much popularity.I have a 1987 Mazda RX7 with a brideported rotary, It's a bit radical for the street it likes the rpm's around 4500-10,000. it has a weber 48IDA carb, it's another one of my toys.
     
  12. mabman

    mabman New Member

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  13. 16v4nrbrgr

    16v4nrbrgr New Member

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    I should go talk to them, it's not far from where I live. 2.5 hp in a 4 lb package is incredible power density, and rotary engines are more reliable than high revving piston engines by a long shot due to less cyclic stress reversals. The 13b engines are a favorite in formula car racing because they last 5 times longer than a high strung four banger under hard use.

    Check this out:
    http://www.renntechkarting.com/products_xr50.html

    Putting this engine on a kart gives it F1-level acceleration, some reviews I read left the test drivers speechless. I can't imagine how fun one of those would be on a super pocket bike or a bobber!
     
  14. mabman

    mabman New Member

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    48hp out of a 32lb motor is pretty good power density also! A bit much for a bicycle frame but would make a nice engine to refit in a 125 mc frame.

    Might be worth going to freedom and knocking on their door, if I lived closer I would.
     

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