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Build yer' own.

Discussion in 'General Motorcycling Discussion' started by N2O, Jul 23, 2006.

  1. Okey Dokey.
    So i'm a poor uni bum who needs to get to and fro'.
    I went out today and picked up myself an old mountain bike from teh tip shop for $4 and a new ducar 50cc 2-stroke motor (1 gear centrifigul clutch) off ebay for $60. I got myself an old chain that will fit the sprocket on the crank.
    Blew the dust off the gasless mig and started some planning.

    I have 2 ways of approaching this:

    1) Rip off the old push bike pedals, rig the motor to the forward crank of the bike then let the original pushbike chain run to the back, giving me 7 gears albeit on a flimsy little bike chain.

    2) mount the motor up in the middle and run the chain straight back to another sprocket welded to the rear axle.

    What do you guys think?
    Option number 2 is more viable of course, but I'm sort of just after opinion and thoughts, rather than technical advice.
  2. is it legal to ride that on the road??
  3. Highly doubtful.
    Hence why it will be ridden on bike tracks, etc.

    There's no need to hear about dangers, etc as they have all been contemplated and covered.
  4. There's also another method of mounting the motor on the back and i think (correct me if i am wrong) drives the rear wheel with a smaller wheel on top
  5. yeah i ave seen it done that way aswell. put i think you would get more power and less tyre waer mounting the engine so it was chain driven.

    wasnt going to go into dangers/consquences N2O, just wondering if they are legal. i think under a certain amount of CC's isnt but not sure.
  6. Hahaha, this sounds so damn illegal. I love it.
  7. Yeah I checked out a place in chadstone that does that with the smaller wheel on the back. I think making up the mounting brackets would be harder that way, and the chain to the back would just look cooler too.

    I just really think that having 2 chains is asking for trouble especially when one of them is just a thin push bike chain.

    Sorry for sounding like that Breno, I was just getting in before I get the flood of those messages.
  8. hey man its cool. i knew what you meant, just explaining myself. its funny some of the topics one question is asked and it goes into a totally different direction :p
  9. It's only illegal if I get caught.
    And i'll only be on biek tracks because there is one path straight from my house to clayton and I only have to cross warrigal road near the corner of waverly rd (in which case the motor can be turned off and walked along the road)
  10. well, there's plenty of small-motored pushies around my area of Wollongong, they travel on the bike path that runs nearly right round the lake...

    They are all, however, professionally maunfactured, and I don't know what legal requirements govern their sale, riding, etc....
  11. if your going to do it definately go chain drive. probably best to go midmount in the frame and just have the chain run straight back from front sprocket on engine to rear on the wheel.
  12. Yeah. I drew a picture.
    I draw a lot of pictures.
    I'm lonely.

  13. Oooooookay!.

  14. It needs a front wheel as well, that'll drive up the costs significantly :p
  15. Nah.
    It's like a sled.
    A pavement grinding sled.
  16. Anyway,
    Back to the real discussion...
  17. Well if your heart is set on this the best place to go to is http://scooters.tziworld.com/
    It has a ratio calculator for gearing down engines aswell. The actual site is pretty dead but if you trawl the archives there use to be some good tips for this kind of thing. Im working on similar but larger engined project. As long as it looks more bicycle than motorbike and I be respectful and not hoon around like an idiot I don't expect any negative attention from the authorities. Wouldn't want to ruin it for other tinkerers such as yourself.
  18. I was quite interested in these motorised pushbikes at one stage. I believe the rules are that as long as the engine is below 50cc and its power below ... something... it is still classified as a pushbike. So it doesn't have to be registered or anything. You just have to check exactly what these figures are.

    Now, the mounting: The easiest thing is to mount the engine above the wheel, and deliver the power through a roller that rubs against the outside of the tyre. It is the easiest, because it requires the least modifications to the bike itself, but it is also a really crappy and inefficient way of delivering power. It becomes even less efficient in the wet (because rubber gets slippery), also it wears out the tyre very quickly. But one good thing about this setup is that when things go wrong you can just lift up the roller off the tyre, and pedal away.
    (BTW, whatever you do, don't remove the pedals and chain! You want them as the backup.... in fact, it might also be a requirement for it being still classified as a pushbike, but I'm not sure about that one)

    The better ones I've seen were powered by Sachs engines. This was a kit that consisted of heavily modified back wheel with the engine driving the hub directly (ie, not using the chain). Again, all the pushie bits were still there and useable; in fact the most efficient way of using one of these was to pedal away using the engine to help you along, rather than replace the pedal power completely.
  19. 200 watts of power is the maximum! i have made a few of these in my younger days, mouting a whipper snipper motor to my scooter and ran a friction drive staright onto the back wheel, nearly no trouble with tyre wear! and this thing would rip along at about 50 ks!

    If you can find a cop who can tell if a whipper snipper is putting out more or less than 200 watts id like to meet him. You will not be able to be fined! this is and always will be a a grey area until they make a dyno for whipper snippers that they carry with them:p

    you will derive a great deal of satisfaction from such a project:D