after a rear mounted motor that drives wheel by belt and large pulley o the wheel?

Discussion in 'General Questions' started by joshua97, Jan 2, 2014.

  1. joshua97

    joshua97 Member

    hey iv seen a few people here with a rear mounted motor -around 30cc that drive the rear wheel by what almost looks like a smaller rim mounted onto there wheel and a belt driving them. just wondering if anyone can shed some light to where i can get one and what thy cost or if i can get a kit without an engine? i have seen a few kits but they are around 700$ thanks
     

  2. rawly old

    rawly old Member

    What you saw was probably a Golden Eagle Bicycle Engines kit,G.E.B.E.
    They're kinda pricey, but have a strong following. I thought about getting
    one, but after studying their specs. I found it wouldn't fit my bikes. I've
    since been thru several configurations of a DIY belt drive. So far this is the one
    that works best for me. The sheave(large pulley) is the rim of a 20" bike wheel
    The small pulley is 2 spring washers with a spacer between on a 5/8" bolt
    tooled to thread into the clutch bell. The engine(here covered) is mounted
    to the channel of an old friction drive kit.
    I've got a 40cc Tanaka on it. It'll do 30+, but I don't like to go that fast.
    it cruises nicely at at 17 to 20 mph, gets around 120 mpg.(that's US gallons)
     

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    Last edited: Jan 4, 2014
  3. joshua97

    joshua97 Member

    thanks a lot mate, appreciate the pics :) yeah thats the one :) how did u mount the rim pullet to your wheel as i couldn't quite see? and i now have to work out a mounting plate to fit a 49cc pocket bike motor and work out gearing haha- me weak point :) and nice job on the small pulley thats sweet
     
  4. rawly old

    rawly old Member

    It is a lot of work, and has to be very precisely done to work
    properly. If the rim isn't precisely centered you get a nasty wobble
    that can damage the clutch and rattle your teeth out.
    If you send the pic to your pictures you can blow it up for
    a better view.
    What I did there is notch the rim to an exact depth matching the notches
    to the spokes,(again I can't over emphasize the importance of being
    centered) the depth of the notches is such that when placed on the
    wheel there was just enough room to wedge a strip of alu 1/16" between
    the spoke and the inside of the rim. these were then secured with
    self tapping screws. You've no idea how many arrangements I went through
    to arrive at a system that works as well as this one. Success at last!
    Oh yes, It is the rim of a 20" bike wheel. This setup can handle a bit more
    power than the cogged belt kits. I'm running a 2,2 hp Tanaka 40cc,
    very reliable but costly Japanese engine.

    Mounting a pullet is not as difficult as catching one:)
     
    Last edited: Jan 6, 2014
  5. grinningremlin

    grinningremlin Active Member

    Rawly is correct, GEBE is the best belt driven kit, I'm biased, I own three.It's expensive if you buy the whole thing, but you can buy it in parts if you have an engine and save bunches of $$.If you notice they RARELY come up for sale used, that's because once you have it you realize it's worth.I would suggest buying the sheave (pulley) and using it's notches as a guide for a 20"BMX wheel modification.Whizzers are roughly the same thing.What GEBE has over others is the notched-geardriven no slip belt.There was an Aussie ripoff called "Blackstar" though I don't know if they're still in business.Here's a decent pic of a whizzer-like belt-driven bike.
     

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  6. rawly old

    rawly old Member

    I don't know what sort of engine that is, but it looks to be
    geared about 8 to 1. That's way too high for most small engines.
    I checked out the GEBE, but my stays being to narrow, I couldn't
    use it. I found that a regular wedge pulley slipped if the pulley small enough
    to give a good raitio. I solved that with the convex Belleville washers
    that compress against the belt as it passes. It's still necessary for
    the belt to be in contact with 50% of the pulley's circumference.
     
  7. grinningremlin

    grinningremlin Active Member

    I was just showing other builds.My stays were too narrow as well on my Bridgestone MB5, soooo I got out a 2X4 and a framing hammer and "adjusted" (didn't spread, just slightly flattened the sheave side stay) the side the pulley was on.If you ever think about GEBE, you can always redo the spacing on your axle washers and make it fit.
     
    Last edited: Jan 6, 2014
  8. rawly old

    rawly old Member

    I considered that & forcibly widening the stays. I even
    replaced the quick release axle with a longer solid one.
    I probably could have made a GEBE work, but where's
    the challenge in that? Oh no, I had to go through a half
    dozen builds to finally devise something that worked as well
    or better spending half again more than a GEBE kit would
    have cost. But, dammit, I did it my way, and it works!
     
  9. grinningremlin

    grinningremlin Active Member

    Can't fault you one bit there, I must admit I've downed every pic you've put up including the handwritten diagram with the "bellville washers", as it's a great idea.The benefits of the actual GEBE is it takes out the guesswork, and it's LIGHTER than any other drive system I know of.Now if I could find someone to make me the engine bracket and the lower strap out of titanium I would have a drive system that weighed in at around 12-14 lbs total!!
     
  10. darwin

    darwin Well-Known Member

    OP very functional MAB, cool bike.
     
  11. rawly old

    rawly old Member

    Well, obviously it's winter & no one seems to be out
    riding much. Bitter cold here, but not as bad as the mid-west.
    However, I am busy fashioning a new shaft with a file. Though
    the above set up works fine, I'm planning to swap out the old
    friction channel & replace it with my Staton. It will basically be
    the same. I just want a more precise shaft & bearing platform.
    I also intend to change the plastic tensioner to something with
    a better bearing, a skate wheel perhaps. I have boocoo clip ring
    bearings. so I may as well put them to use. The result will be only
    slightly lighter. What I'm aiming at is long distance durability. This
    set up is, if nothing else, very tough. My carpal tunnel's eased up
    so back to the file.

    P.S. I"ve got a 2" x 36" x 1/8" strap of titanium I thought to split
    & use, but the dam stuff is so hard to cut.
     
  12. darwin

    darwin Well-Known Member

    Hmm what's the scrap value of titanium?
     
  13. joshua97

    joshua97 Member

    thanks a heap guys :) but i have decided (at the moment) to try and weld a 44tooth or similar sprocket to a cheap biles steel rim ? hopefully if centered it should be enough to run a chain to the pocket bike motor (mounted on a basic plate 4mm thick bolted to frame and welded to the lower frame where the wheel hub is) then weld a sprocket of some size (i don't know what size atm ) to the pocket bike motor output sprocket (not using a gearbox-using a race bikes direct clutch bell to sprocket for simplicity. as long as i can have the motor adjustable (sideways) and get good chai lineup it should be simple isn - ohh and welding the sprocket to the hub hmm thoughts? thanks again :)
     
  14. Loose Nut

    Loose Nut Member

    I hope I understand your plan right. I respectfully recommend against welding to the rear hub. With a motor of that power, you need a strong connection, and enough welding to get it done will warp the hub. Also, I just don't think there is enough steel there on most hubs to weld to. If you are sure you need to do it anyway, do you have access to a lathe that you can use as a fixture to make sure the hub is lined up? Very useful for stuff like this.

    In you shoes, I would buy rear hub from a Puch Maxi, or Motobecane Moped. Wheels with rusty rims/spokes are available for reasonable prices. Make sure it's one with 36 spokes, most are. Use an online spoke length calculator tool and order 12 gauge or 10 gauge spokes from that online auction site to lace the moped hub to your wheel. These hubs have a bicycle freewheels on the right side, and a big sprocket on the left. They can be swaped out for different tooth counts. Also the hubs have good brakes. Of course going to all that effort, I would make sure I was using a strong rim.

    It's your project though, I would like to see pics of how it's going.
     
  15. joshua97

    joshua97 Member

    hmm i threw out a motobecane wheel :( shame haha. yea thanks i welded it today and lined up sweet, and got a hot strong weld so i suppose ill just see how it goes ( ill test it on my 70cc pit bike motorised bike first to see how strong it is) cheers, and ill upload pics asap :)
     
  16. Loose Nut

    Loose Nut Member

    Glad it went well.
     
  17. joshua97

    joshua97 Member

  18. butterbean

    butterbean Well-Known Member

    Unless the pocket bike has internal reduction, direct drive from clutch to rear wheel may not work out as well as you think. This is not meant as disrespect, so please don't take it that way. Race bikes go clutch to rear wheel because they have modifications that allow theengine to hit peak rpm's in a very short amount of time. Unless you have experience with these modifications and are an expert tuner, the engine most likely will not reach optimum rpm's for direct drive most of the time. When (if) it does reach peak rpm's, it's either going to climb walls or take off like a raped ape, but you won't get both i.e if it climbs hills well it will have no balls on the flats at all, or it goes like a demon on the flats and you spend a lot of time pedaling whilst staring up at the tops of hills. Unless this engine is already modified to run as direct drive, in which case you will still need expert tuning knowledge to keep it alive. A pocketbike engine running 24 or 26 inch wheels direct drive, I just don't see it working out well. You have to remember that wheel diameter plays a part in gear ratio as well. Not everyone realizes that the wheel is the final pulley/gear and the larger the wheel, the more speed but the less torque. From what I know, pocketbike engines are high revving, so the larger the wheel you're driving, the more reduction is needed to achieve a usable gear ratio. You may end up with a bike that takes a kilometer of pedaling just to get out of its own way. At the very least, find out the max rpm's of your engine and use a gear ratio calculator to plug in different numbers until you come up with the top speed you want and then you will know if direct drive is a possibility or not. There is a sticky somewhere with a link to a good executable ratio calculator, I will find it.
     
  19. butterbean

    butterbean Well-Known Member

  20. butterbean

    butterbean Well-Known Member

    Download the gearratio.exe file
     
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