Dare I say a plausable multiple roller drive for friction mount...

Discussion in 'Friction Drive' started by bigkat650, Oct 15, 2008.

  1. bigkat650

    bigkat650 Member

    We all know how a typical friction drive works... What if by using a simple air piston- activated by pulling a small convenient lever, the typical friction drive could be transformed into a dual- roller drive, high and low gear system... Perhaps this is a solution to the idea...

    Below I have several pictures illustrating how this system could work.

    Use a C02 container (like one's found on a paintball gun). Attached to the C02 container is a regulator which decreases the PSI down to aprox. 100psi. Next, the constant 100psi pressure is fed into a 3-way valve, splitting the pressure into an 'A' or 'B' line. These lines each are attached to a simple 1-way exhaust valve (to prevent back pressure). Finnally, these lines feed into a small air piston called a Pancake piston, which is attached to the frame of the bike and the frame of the friction drive unit.

    When the valve is opened to line 'A', the piston opens up to either 1, 2, or 4 inches (whichever fits the application best), and the back roller contacts the tire. When valve 'A' is closed, and valve 'B' opens, the piston retracts, contacting the front roller with the tire.

    There are only two potential problems I see with this set-up:

    The chain that would be used to turn both rollers would have to spin at a high RPM. I feel the best chain to do this would be a timing chain, since they are designed for hard usage.

    The addition of a chain and second drive roller would add a small amount of resistance to the motor.

    Ultimately, I don't know if this system would work. I was thinking it was plausible though. I have never built any kind of motorized bike, but am very intregued by the thought. And since I am a larger guy, I thought this system might provide both a high torque and higher speed options. Please leave some comments guys, and sorry about the vagueness of the pictures, I hope they are self-explanatory.

    Attached Files:

  2. bigkat650

    bigkat650 Member

    PS, the price of the valves, regulator, tubing, piston, ect. I have calculated around $150 American dollars.
  3. JemmaUK

    JemmaUK Guest

    This was done back in the 50s/60s with a spring mechanism... but I dont know how effective it was..

    there was someone looking for something like this who eventually went with a twin engine set up...

    Jemma xx
  4. Happy Valley

    Happy Valley Active Member

    Why not?

    Not sure about the technical needs for the pneumatics....something simply mechanical (and cheaper) might suffice.

    Keep at it though, just a matter of time before someone comes up with changeable, on the fly gearing for FD. I'll be first in line.:grin:
  5. bigkat650

    bigkat650 Member

    i looked for a 3-way valve system that would run off a small electrical toggle switch (perhaps small battery powered) rather then a manual lever. However I couldn't find one, that's not to be said one doesn't exist. If someone has the means/time to try this out, i'll let ya know where i found all the component. The air piston with 100psi should hold down with over 100lbs of pressure-which should keep good pressure on the tire. The tricky part would be figuring out how long of a stroke needed to push the motor mount down to the precise point, and making sure that when it was retracted- it put the correct pressure on the tire with the other friction roller. I think it would take a little bit of tinkering, but I think it is very plausible it would work rather well. With that being said, I don't think a 'kit' could be fabricated only because it has to be rather precise... But once its in the correct place, it should be something that will last for the long haul.

    I don't know how long a typical c02 cartridge would last, but I would think it would be at least 100+ switches, could be several hundred or more before it requires recharge... aaand that cost what, 5 bucks at a typical sporting goods store. Basically, it would require almost zero cost once the initial price for the components was spent.

    I don't know... it was just a thought I had and figured I would share with you great people
  6. Mountainman

    Mountainman Active Member

    that's what I was thinking also

    yes -- I think that you are on to something here

    but remember there should be a way to keep it very simple

    and also please note
    just in case you truly come up with something new
    if you post these thoughts in those (as above) fine pictures of project
    some one will be sure to steal you idea
    it's not the mountain way -- but just the way that some are these days

    ride that thing
  7. bigkat650

    bigkat650 Member

    true... i would just hope if it was a successful idea- and even if someone did steal it, they would at least send me working version of it lol. or cut me in on a little of those profits :p
  8. Mountainman

    Mountainman Active Member

    I shouldn't laugh

    guess what -- THIS IS A TRUE STORY

    the Sting-Ray bicycle was (very first one built)
    right here in Hillcrest Calif -- part of San Diego
    built by a father and son team ---- late 50s or early 60s
    many pictures in that bicycle shop telling the whole story
    Hillcrest Bicycle Shop
    Scwhinn stole the idea
    and guess what they gave the inventor

    one new Sting-Ray bicycle ------- THAT'S ALL

    watch out what we pray for -- we just might get it !!!!!!

    ride that thing
    Last edited: Oct 16, 2008
  9. bigkat650

    bigkat650 Member

    lol well i'm not looking to invent something... i really was just looking to put the idea out there. If someone does invent it, that's fine. I'm not a material guy... i'm more of a sharing of information guy. If people are happy from something i've thought of, thats awesome and really reward enough... but a free working version of my model wouldn't hurt!!
  10. Mountainman

    Mountainman Active Member

    that's very cool bigkat

    well - that's the least that they could do for you

    not to get lost here and forget
    can you simplify it any ?

    maybe instead of hoses and valves ect
    cables and springs ?

    I don't know -- it's your thing -- got to love the idea !!!!
    maybe low gear 10mph up ANY HILL
    high gear 35 to 40 mph no strain on the level ???

    ride that thing
  11. bigkat650

    bigkat650 Member

    I think a spring has the potential to work-- and the great thing about a spring is that it really doesn't get much simpler or easier... or cheaper. I can consult with one of my good friends who is a marketing manager for a regional spring supplier to see what he thought would work well for the situation.

    As far as roller size, I was thinking like 5/8 to 7/8inch for the low gear... and something like 1.5 to 2.0 for the high gear... Which should get just about anyone up any hill... pending on motor size... and still allow for high top-end, with the bonus of lower RPM at a moderate cruising speed. And you could use different roller sizes as well, just a suggestion on sizes.

    Ultimately, I have found air pistons that simplify the process... however they are for several hundred dollars, and not really cost efficient. Really if done right it should be a rather sleek set-up, running the lines zip-tied to the bike frame... Obviously the 3-way valve would need to be mounted... my idea is mounting it just back from the handle bars on the top cross bar.
  12. 5-7HEAVEN

    5-7HEAVEN Guest

    I Can See It!

    bigkat, I see your idea very clearly, but using 50-pound springs, turnbuckle and lever. I can visualize the engine mounted on a steel plate and central pivot 1/2" bolt which is perpendicular to the vertical mounting bracket. Under the engine plate are two Staton friction rollers suspended by 5/8" bearings and hangers. The rollers' threaded ends screw onto 2" stubs which mount 10-tooth sprockets. These sprockets align with the centrifugal clutch. The engine's 10T sprocket clutch chains to one friction roller, which then chains to the other spindle. Of course, the bearing's pillow blocks mount via elongated holes which allows chain adjustment. Spacers under the engine adjusts tension to the first friction roller. Springs provide 50 lbs. tension onto the tire w/1.25" roller. A strong cable with locking lever controls the shift to the 1.5" friction roller.

    I would have considered thid option a few months ago, since I was very interested in shifting for more engine rpm. Instead, I chose the simpler, easier but costlier way by using one engine per wheel, each with different size friction roller.
  13. sparky

    sparky Active Member

    Yes, this is very similar to SimpleSimon's idea a few weeks ago.

    I don't think he used CO2, and I sure wouldn't even consider it because I'd be switching at every stop. That means I'd have to change CO2 cartridges every other day, if not every day.
  14. SimpleSimon

    SimpleSimon Active Member

    I posted a diagram and an explanation of how to implement just this idea bout a month ago. I believe in K.I.S.S in any mechanical device. All that is needed to make it workable is a compression spring, an after market manual choke cable with a variable locking capability, and a little ingenuity. No need for air, or compressed gas, or valves, or any of that.

    See: http://www.motoredbikes.com/showthread.php?t=14302 , post #8 and on.
  15. loquin

    loquin Active Member

    A simpler approach (no power loss, anyway) may be to have a sliding outer tube over an inner, grooved (or splined) shaft.

    The inner, grooved shaft is directly driven by the clutch bell.

    The sliding outer tube is the 'roller,' and is machined with two diameters, and knurled on the drive surfaces.

    In the sketch below, slide the roller to the left, so that the larger diameter portion of the tube is contact with the tire, and you have the high speed. When you slide the roller tio the right, so the smaller diameter portion is in contact with the tire, you have low speed. The drive has to be spring loaded, so that you can go to high speed on the fly. Essentially, you'll have a throwout bearing at each end of the roller.

    Ref. the attached sketch

    If you decided to try the dual roller approach, use a timing belt instead of a chain. It's much less noisy, and would be much lower maintenance, especially since you could use a short, wide belt.

    Also, rather than spring loading the entire drive, mount it on a 'rocker'. Tilt it forwards at the top, and the front roller is in contact and the rear roller spins freely. Tilt it back, and the rear roller makes contact, and the front disengages, per the second sketch. You could also have an adjustable stop at each position to be able to set the down pressure individually ...

    Attached Files:

    Last edited: Oct 23, 2008
  16. sparky

    sparky Active Member

    What?!? If the roller was cone shaped... it could be made into a CVT, right?

    Imagine that... a friction drive CVT.
  17. loquin

    loquin Active Member

    Yes... but it would wear the tire unevenly, (and would have very poor efficiency) as the different diameters on the cross section of the roller would be spinning at different linear speeds. While this would be acceptable for a few seconds when shifting, you definitely wouldn't want to run in this mode continuously. You need a 'flat' (fixed diameter) portion, at both the high and low speeds, to be be in contact with the tire.
    Last edited: Oct 23, 2008
  18. sparky

    sparky Active Member

    Bummer. At least with your idea, the possibility of a third roller is more likely than the other method.

    I wonder how easy it would be to "shift on the fly" with any of these multiple roller designs?? Would compression spring really be all that's needed for Loquin's method?
  19. srdavo

    srdavo Active Member

    I've been gone for a while......but.....

    ...It's great to see the MBc "think tank" at work!!!!

    keep the fresh ideas flowing!!
  20. SimpleSimon

    SimpleSimon Active Member

    I like that sliding roller idea quite a lot - no reason it couldn't be a three-speed, depending on tire width. The pivot idea is basically what I was addressing - I suggested a compression spring mostly to simplify control - if default is one roller being pressed against the tire, all you need is a single pull choke type cable to shift to the other. I agree that a timing (toothed) belt is a good alternative.