Homebuilt "Primary" Belt-Drive

Discussion in 'Performance Mods' started by gone_fishin, Jun 15, 2007.

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  1. gone_fishin

    gone_fishin Guest

    gonna start this with nothing but...

    i want to build the manual belt/pulley system MotorbikeMike mentioned elsewhere & we thought it would be a good idea to do a project style thread about it...

    it looks like there will be some serious interest in this, so let's keep the OT to a minimum please, and try to not get too mad-scientist on us...the goal is to develop a primary drive that can be bought off-the-shelf and built at home using standard hardware, as much as possible anyway.

    i'm gonna start searching for pics of existing systems...

  2. SlicerDicer

    SlicerDicer Guest


    Maybe that would be good for the clutch? then you can run a single belt to the back? Not saying you have to get it from there just the ball rolling idea :)

    Edited: It was while you replied here is the chain/belt :shock: :shock: great minds think alike :D


    Combo chain/belt drive?


    I know your not using a fork to do it but can give some good ideas from off the shelf stuff :)
  3. gone_fishin

    gone_fishin Guest

    neat! i could see that in there on some systems, maybe even mine...never having had a need before i'm just now learning about these components.

    my personal plan, right now: belt primary (manual) / jackshaft to adjust ratio & offset in /chain secondary to rear wheel.
  4. SlicerDicer

    SlicerDicer Guest

  5. First system to study: Whizzer

    HI All! I'm getting ready to go to Antique Motorcycle Club of America
    event this weekend and am rushing to do errands now so I'll write more later.
    Look at how, in my 08 prototype that the belt-pulley clutch assembly effectively
    offsets the drive system, yet is still inline, Mike
  6. gone_fishin

    gone_fishin Guest

    still too new for me to decipher what i'm looking at...i'm sure you'll 'splain when you have time

    this rough mock-up shows how far i need to offset back in to line up with the rear sprocket, the zip-tie is the balance point of the engine/centerline of bicycle, the end of the chain is roughly at the centerline of the jackshaft, which should fit directly behind the seattube:
  7. SlicerDicer

    SlicerDicer Guest

    Augi, I am curious what you are planning on putting over the motor shaft/pulley. I am only curious as if your leg gets in the way get ready for some grinding. So what kinda shield are you going to do? Custom fabricated?

    I did not realize that motor was so wide...
  8. gone_fishin

    gone_fishin Guest

    i'm imagining a mesh/perforated cover over the primary & i'll be installing a pull-start.
  9. Engine/Drive offset

    Hi well I got to tell you Augi, that I think that the most important starting point is to have the engine centered in the frame (plumb) BUT, the centerline would best be determined by it's "balance" or Weight distrubition". This may not be as hard to figure as one might think. Get a friend (ok if he is likkered up, but only a little) and put the engine on a piviot.
    If yer friend is too likkered up, use a piece of pipe lying lenghtwise under the engine, and play till you have the balance. NOW..........
    Now you can figure out how to do the frame mount, as balance is critical unless you rever in Razzberrys, or roadrash.
    More to come Mike
  10. srdavo

    srdavo Active Member

    I volunteer to be the 'likkered" up friend :lol: :lol:
    okay...that''s my mini OT.

  11. gone_fishin

    gone_fishin Guest

    yep, mike...the black zip-tie is my centerline as determined by balancing it on a broom handle...that must be another one of those "great minds..." moments 8)

    i know the center of balance will change as i add components, but this is close enuff for now.

    i did it by myself because i just knew srdavo'd be too wasted to help with a balancing act :p :p
  12. Step 2 Already done?

    Hi well, ok, now what you got to do is figure out how low you can mount your engine, and yes I said low. Now what you are instantly gonna find out is a large engine is going to be much happier in a cruiser bike, than in a v-frame (easy to figure out how the drop-loop came about, ain't it?). You may wish to consider to modify a frame or do some building but lets get on with it.
    Now, with engine mounted, to use the Whizzer style of drive, you want to look into your ratios if you are doing a dual belt, the cool thing is the center pully is above center, spring loaded into drive, pulled down by the clutch lever to make a "Nuetral"(non-moving) position. The only thing I think you'd need for this real special would be a Whizzer drive sheave and clips. The center pulley section could be made from 2 pulleys fastened together, on an axle (even an old bicycle front hub could work) swinging down from a piviot, a large extension spring hanging down from a point on the frame. I suppose I could make a crude drawing if I've not spoken clearly. If there are no real questions:

    Next, the concept of Single belt, cam-over pulley

  13. gone_fishin

    gone_fishin Guest

    mike, is it ok if we assume, for now, that the engine's mounted? in sabrina, it WILL sit very high (but it's a surprisingly nice fit)...the only reason i can get away with this is because i also sit quite high, plus i want my project to be truly "engine" on "bicycle". this is a project that must be done in a fell swoop, with everything rocked out ahead of time.

    so, do tell more, please, about the whizzer method of clutching (and shifting?) and how it can be homebuilt. as the king of crude drawings ( :lol: ) i would love to see some sort of diagram, if you have time...thanks very much for helping with this :)
  14. High mount

    Hi Augidog, yes It's ok, you just have to know that the bike will need a VERY good stand to help overcome the High Center of Gravity (we will now out call COG).
    The other thing to know, is that for the "Falling Pulley" clutch to work properly, the "clutch" or center pulley MUST be signifacantly above the centerline of BOTH the front and rear pulleys or you will not get adequate slacking in the belts, and you'll never be in "nuetral".
    What we are seeing here can work very well. I will sharpen a pencil, and give some thought to stick-figure quality drawings, if indeed we get to the point where I'm not able to paint adequate "Word Pictures"
    This whole concept is a wonderful drive system, cheap, effective, andique, and do-able.
    I need to go to the store, and get a card-reader for a treat for all who will see, Mike
  15. Today's Treat- Single Belt 1910 Excelsior

    Hi well we had quite a day, and there was so much to see. Here is a perfect example of a single flat belt drive, with a spring loaded cam over style engagement.
    Notice that the lever actuates a curved bar, which loads a pulley into the bottom of the belt, loading it into the small primary pulley, which of course is much more likely to slip, than the larger pulley with the larger contact area. The lever runs in a series of notches (Ratchet type) to hold it in the position you want (locked).[​IMG]
    I think this is a 31cu in making a small HP that I will look up, as the owner did not know.
  16. gone_fishin

    gone_fishin Guest

    8) standing by...and getting psyched!
  17. Indian Belt drive

    Indian built a lot of chain drive bikes, even some of the earliest ones, this is a pic of a rare belt-drive indian, see the same concept for the belt clutch. Mike[​IMG]
  18. gone_fishin

    gone_fishin Guest

    i'm getting this in my head and this is my best effort to express it...2-speed?

    i'm not sure how loose and tight the belts need to be so this is very rough...it's based on off-the-shelf hardware-store stuff...how'd i do so far?

    someone have close-ups of similar systems?
    do i have to use mini-bike grade belts and pulleys or can i go a tad lighter?
  19. SlicerDicer

    SlicerDicer Guest

    Augi would you mind telling me what hardware you were planning on using for this? I am getting my tecumseh this month it looks like. I am debating about using a chain drive and modifiy the clutch to where it can engage at lower rpm to give me better control but I would love to hear what you are planning and aprox cost :)
  20. gone_fishin

    gone_fishin Guest

    sorry for the delay...just saw this.

    i didn't really get into specific parts or costs. basic shafts, pulleys, bearings, collars, strapping, etc...

    it's really as simple as building one drive twice with different ratios, all you have to do is figure out the geometry needed for your desired range & performance 8)