Rear hub - jack shaft

Discussion in 'General Questions' started by Alaskavan, Sep 17, 2007.

  1. Alaskavan

    Alaskavan Guest

    Okay, the idea here is to get power to the rear cassette from the motor without interferring with pedaling. Use a rear hub for a jack shaft. Cut it in half, install a small gear on the inside of the right hand flange (my feeling is like 16t.) Weld the hub back together using some tubing to achieve the desired width. Attach a big gear (44t?) on the outside of the left hand side of the hub. Attach a freewheel with just one 16t gear on it on the right hand side. Cut a piece of thread stock to length as an axle to mount it.
    Jack shaft_1.jpg

    Sorry about the quality of the picture. It took me longer to uncover the scanner, than I took to draw the picture.

    Oh yeah. I suppose you might want to start with a 5:1 reduction at the motor.

    So cut me to shreds here. What am I forgetting/missing?

    If you want to delve into the gear ratios, please keep in mind I'm looking towards a 20" wheel.
     

  2. 5-7HEAVEN

    5-7HEAVEN Guest

    :cool:Alaska, what kind of bicycle and for what purpose?

    do you intend to make full use of how many gears of your cassette?

    how many teeth on the rear sprockets(cassette)?

    which engine and rpm range are we shooting for?

    you could copy ZOMBY'S jackset. weld another crankset hole in the frame and use that as a jackset housing with 5/8" jackshaft.

    if you want to make good use of the rear cassette, you need gear reduction at the jackshaft.

    that can be calculated when you tell us about the cassette's ratios.

    using the gears you suggested would be too much. it'd be like happy time engine and 106-tooth rear sprocket. besides, that 44t sprocket would be the size of a radial sawblade spinning next to your calf.

    if your useable cassette gears are 32t/27t/22t/18t, you could use a 12-tooth jackshaft sprocket(left-side) and 10-tooth jackshaft sprocket(right side).

    gear ratios with 32t = 19.2:1, similar to happy time engine and 46t sprocket;
    27t = 16.2:1..............................................39t sprocket;
    22t = 13.2:1..............................................32t sprocket;
    18t = 10.8:1..............................................26t sprocket.

    if you MUST use the 16t freewheel gear on the right side of the jackshaft, the left-side sprocket needs to be changed to 18t gear. consequently,

    gear ratios with 32t = 18.00:1, similar to happy time engine and 44t sprocket;
    27t = 15.19:1..............................................37t sprocket;
    22t = 12.38:1..............................................30t sprocket;
    18t = 10.13:1..............................................24t sprocket.

    calculations were verified at http://www.compgoparts.com/TechnicalResources/JackshaftRatioCalculator.asp



    i don't think that rear hub will be strong enough for the task. you need stronger support, welded to the frame.

    Myron
     
    Last edited by a moderator: Sep 18, 2007
  3. Alaskavan

    Alaskavan Guest

    Application

    This is the bike I'm getting.
    1.jpg

    The wheels are 20".
    The rear cassette is 8-speed, 11 - 30t.
    I'd like to use all the gears.
    The basic use is a 26 - 30 mile commute. Each way. Some hills, not bad. I'll want to be able to tow a trailer with groceries.

    I'm pretty happy with the Mitsu TLE 43 I have on my Trek. So I might use one on the trike. Max. RPM=8,300. Probably operate around 6.

    Caveat: I intend to mount the engine behind the seat. I will probably have to cut and extend the frame. I might change to a larger wheel if I do that (I understand the impact on ratios).
     
    Last edited by a moderator: Sep 18, 2007
  4. 5-7HEAVEN

    5-7HEAVEN Guest

    :cool:Okay Alaska, here's more numbers:

    using 16t on the right side of the jackshaft, add a 22t sprocket on the engine-side. using arbitrary numbers on 11t-30t cassette, you'd have:

    30t with 20.63:1, similar to happy time engine and 50t;
    27t with 18.56:1,.............................................45t;
    24t with 16.50:1,.............................................40t;
    21t with 14.44:1..............................................35t;
    18t with 12.38:1..............................................30t;
    15t with 10.31:1..............................................25t;
    11t with 7.56:1..............................................18t.

    try these numbers for size.

    Myron
     
  5. Freewheel crank.

    (Sorry. I threw these pics out at another thread,but it's too cool)

    Um,I don't see how your hub design is any different from a regular spoke mount design except it's connected to the hub. How does that design utilize gears?
     

    Attached Files:

    Last edited by a moderator: Sep 19, 2007
  6. 5-7HEAVEN

    5-7HEAVEN Guest

    :confused:Alaska, it doesn't seem like an easy bike to install an engine, using jackshaft to connect to original chain drive. STATON chain gear or friction drive would all seem more practical.

    exactly where on the frame do you intend to install the jackshaft?

    Myron
     
  7. Alaskavan

    Alaskavan Guest

    Hi 5-7, It might not be easy, but it's one of those things. I got it in my mind to do it, so we'll see how it goes. The idea is to install the engine on the rail behind the seat. I'll probably have to do a bit of a stretch there. A lot of this is just in my head for the moment. The bike arrives in Fairbanks the first week of Oct., and I still have to figure out exactly how to get it here from there.

    I must admit that the more I look at what I drew, the less enamored I am of it. I was just trying to find a way to do this that could be fabricated by an average guy (me)using easily available parts (the ones I have). It was perhaps one of those ideas that sound good, but don't really work. Maybe you know how it is. The idea seemed so good that, in my exuberance, I had to share it. And did so before taking a reasonable amount of time for reflection. I 'll let this idea ferment a bit more. It could turn out to be vinegar rather than wine. But ya never know.

    In the mean time, I'll look at building a more conventional jack shaft.
    Thanks for checking the gear ratios for me.
     
  8. 5-7HEAVEN

    5-7HEAVEN Guest

    :cool:you're welcome, Alaska.

    i share your feelings. i'm torn between buying a SCHWINN AEROSPORT and a SCHWINN SKYLINER. the AERO has balloon tires and retro frame, but doesn't have front suspension fork or front brakes. i don't want to buy the upgrades and spend too much.

    i'll probably buy the SKYLINER, which has steel frame,suspension fork and front/rear brakes. the dealer's not gonna like it if i buy it from WALMART and have him service/repair, but he can't get the model i want.

    all this is for my twin-engine project. now you have me thinking about utilizing the bike's 21-speed drivetrain.
     
  9. Freewheel crank. Engine....Happy time engine behind seat with some kind of fabricated mount. Jackshaft very similar to those pics I posted earlier. Crank is too far away from engine so leave the crank alone. Get two chain tensioners on on top and one below to sit just in front of your jackshaft, Solid sprocket in back,no ratchet.
    The way I picture it,the chain will always be moving. Behind the seat the top chain going to the gears and the bottom chain going away from the gears will be met with the left sprocket of your jackshaft with the same number of teeth as your crank. Engine should turn this okay for the entire assembly is constantly turning.
    I wish I had photoshop skills.

    Wait. That black wheel that's under that seat that's making that chain cross over. Just lace the top chain to your jackshaft sprocket and get another black wheel like that and mount it just behind your jackshaft. Then lace your chain to go under the black wheel and over the top,then under your jackshaft sprocket and over the top to your gears.

    Yes. That set up would most definetly work and still have pedal with little resistance.
     
    Last edited by a moderator: Sep 19, 2007
  10. Dockspa1

    Dockspa1 Guest

    Van, I can apreciate what you are shooting for but, If it were I, I would go with the varidrive units and a belt to the jackshaft. Or the Torq-a-verter.
    A lot less to brake down when you got a mama Kodiak on you butt@.
    May the farce be with you ,either way!
    Doc
     
  11. toxicmammoth

    toxicmammoth Guest

  12. srdavo

    srdavo Active Member

    A-van,
    dare to dream!! look back at this---> http://www.motoredbikes.com/showpost.php?p=78789&postcount=47

    WE used 2 rear hubs as jackshafts...on the same bike!! 3 chains, not counting the pedal side chain. you'll notice one hub was atached bolted to drop-outs...the same way wheels are mounted. the other one, the outer body of the hub is welded solid, and the axle spins freely.
    We had zero "out of pocket" expen$e on this build. Just used parts on hand.
    (the guy we built this bike for, stopped by tonight on his bike. he loves it....mile wide grin. said he was clocked at 40mph....but 35 is more comfortable.)

    dude...share all your ideas.
    I really like wine....... but vinegar has it's place in the world, too!! ;)
     
    Last edited: Oct 7, 2007
  13. Alaskavan

    Alaskavan Guest

    Thanks for the encouragement. I was thinking a bit today about changing my friction drive to chain. Maybe I'll revisit this idea. (Rube Goldberg would be proud of you.:D )
     
  14. srdavo

    srdavo Active Member

    Rube who??

    Deja' vu ?

    :lol::lol::lol::lol::lol:

    thanks, A-van....I'm kinda proud of Rube, too. ;) (now that I know who he is)
    http://www.rube-goldberg.com/
     
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