DIY Friction Drive Experiment

Discussion in 'Friction Drive' started by lowracer, Oct 10, 2011.

  1. lowracer

    lowracer Member

    I've been wanting to make a super-simple friction drive for some time now & think I may be onto something here that could work well on both a hardtail or a full suspension by allowing the engine mount to swing. It is attached to the set tube. Its basically a front wheel hub mounted in a 31.8 steerer stem attached to the seatpost with a 27.2 to 28.6 shim. Take a look at the pics....I'll probably run another arm off the non-drive side for balance & added strength. The clutch driver is a 1/2" Staton double bearing unit that I also use for V-Belt drive pulleys. I may use bungee cords & mount a brake lever & cable to lift the unit for coasting or pedaling without friction.
    -Lowracer-
     

    Attached Files:


  2. lowracer

    lowracer Member

    I've been thinking about it some more after posting these pics & will definitely add the opposite side 'L' arm & connect the 2 with some cross bracing & 2 alloy legs instead of the bungee/cable idea. I'm probably putting the Stage 7 pocket bike engine on it & it will need to be as sturdy as possible to handle the power.
    -Lowracer
     
  3. srdavo

    srdavo Active Member

    I'm liking it!!!
     
  4. loquin

    loquin Active Member

    I like it, too. Spring-loaded, I assume, to maintain proper drive roller pressure against the tire?
     
  5. bideronit13

    bideronit13 Member

    Well since its an expirament I hope you dont mind my 2 cents.
    Looking at it and some ideas I have for a shaft drive tranny maybe you could try to use a 1 inch drive swivle socket type assembly to top mount the clutch plate and run a vertical shaft motor.
    Looks pretty good for starten out. keep going thats what its all about.
    I really like thinking about stuff like this so my wife does too. See thinks if the clutch bell housing is reversed and use a gear or something for the drive the weight will be evenly distributed.
    I think its good this stuff goes on because eventually someone who doesnt care about money so much will come up with a winner and revolutionize the industry.
    Congrats
     
    Last edited: Oct 11, 2011
  6. lowracer

    lowracer Member

    loquin,
    I thought about using bungee to pull the arm into the tire, but will use an aluminum support bar & quick release instead. There is no spring in the attachment point. Its a bicycle hub with all the spokes removed so it can pivot if it needed to on a full suspension type bike (this one doesn't need to pivot much).
    -Lowracer-
     
  7. rawly old

    rawly old Member

    Quick release is probably a better idea than spring tension. I built sumpin
    similar with a spring; bucked like a green colt every time I hit a pothole cuz
    of spring bounce. Finally reversed it with a spring to hold the roller off the
    tire with a lever that hooked and unhooked easily to hold it down on the tire.
     
  8. rawly old

    rawly old Member

    Quick release is probably a better idea than spring tension. I built sumpin
    similar with a spring; bucked like a green colt every time I hit a pothole cuz
    of spring bounce. Finally reversed it with a spring to hold the roller off the
    tire with a lever that hooked and unhooked easily to hold it down on the tire.
     
  9. lowracer

    lowracer Member

    rawly old,
    I did go with a bolt & nut to lock it down tight against the tire.
    Worked ok, but ate the heck out of the rear tire on the 1st few rides even after I filed down the sharp points on the roller & had good pressure on the tire (pocketbike engine has a have power spike around 6000 & pulls hard like that all the way up to 11000 rpm's).
    Since I've switched that friction setup over to a rear v-belt drive, then added another front engine w/front v-belt drive for a dual engine machine (see pics). After a few weeks of senseless overpowered motoring, I removed the rear engine/drive altogether. It now sits in the garage as a front engine vbelt driven rig. I plan on removing the engine from the bike & building a lightweight aluminum push trailer with the same pocket bike engine/vbelt drivetrain...(see pics)
    stay tuned
    -Lowracer-
     

    Attached Files:

  10. rawly old

    rawly old Member

    Lowracer,
    Funny u should mention that, I too have just converted an old fric-drive
    to a v-belt with a 20" bike rim for a sheave. Geez, it works GREAT! My
    gx35 would only do 23 mph with a 7/8" fric roller on the flat. Same
    engine with the belt, 33 mph. Woohoo!
     
  11. rawly old

    rawly old Member

    Here's a pic of the mockup. It's the same as the finished version except
    the rope i used as a belt is looped thru the frame in the pic.(DUH!)
    In the final setup the belt goes behind the brake caliper with 3/16"
    clearance on both sides. That ain't much, but it's enuff.
     

    Attached Files:

  12. lowracer

    lowracer Member

    What pulley sizes & final drive ratio are you running here in the pic (using a vbelt, not the rope)?
    I had a whizzer sheave on 700c wheel with 1.5" vbelt pulley but the gearing was way too tall w/subaru robin eh035. When I made my own same size rim to rim pulley the gearing worked out much better. To test for the final drive ratio, mark your engine pulley & roll the drive wheel one complete revolution (from vertical valve stem around to vertical valve stem) with weight on the bike. Count how many times the engine pulley spins around.
    -Lowracer-
     
    Last edited: Jan 3, 2012
  13. rawly old

    rawly old Member

    Looks like my reply just got sent to the administrator, so I'll have to repeat it.
    My primary pulley is 7/8" made from 2 inverted belleville washers with a 1/4"
    spacer 3/4" in dia. the 3L600 belt wedges in a 1/16" from the spacer, hence 7/8"
    Since the tireless rim is 15.5 inside the ratio is about 19 t0 1.(hill/town pulley)
    I haven't yet used my 1.25 hwy/flats pulley which can be switched in 2 min.
    It should cruise at 22mph@4200rpm with about 45@8000rpm. It's really meant
    for my 52cc, but should work for the gx35 on the flat.
    If you plan to mount an old fric. channel, you'll have to cut some very precise
    spacers,( I used alu tubing from an old pr. of crutches), and find a suitable
    shaft.
    I may have led you to believe the is easier than it is. Some very close tolerances
    are involved. My initial break down resulted from a part 1/32" off. That fixed, it
    works just fine now.
    the trick on the pulley is 8 radiating grooves from the hole 1/64" deep. These
    grip the belt without wear making small dia. pulleys possible without the need for
    cogged belts or pulleys. I can even use 5/8" for the really steep stuff.
     
  14. rawly old

    rawly old Member

    :jester:p.S.
    It's a lot simpler to do the math than counting the wheel going 'round. The actual ratio is 17.7 to 1, my bad.
     
    Last edited: Jan 3, 2012
  15. lowracer

    lowracer Member

    rawly old,
    Sounds good...I like the way you solved the small vbelt pulley challenge.
    I too do the math 1st using the online ratio calculators. Vbelts ride into the pulleys so there is always a degree of inaccuracy trying to do just the math.
    The rollout method is more accurate & never equals my math (but close).
    Cheers
    -Lowracer-
     
  16. rawly old

    rawly old Member

    :confused:Golly, they have calculators? Now what am I supposed to do with all these pencils?
     
  17. loquin

    loquin Active Member

    At 8000 RPM, a 7/8 inch friction roller has a top end of about 21 MPH.

    Using a 7/8 inch primary pulley, and an (approximate) 18 inch secondary pulley results in about 20.5:1 reduction, with a top end about 30 MPH.

    A 1.25 inch roller would be equivalent to your pulley setup.
     
  18. rawly old

    rawly old Member

    Ah yes, but my secondary pulley is 15.5" giving a ratio of 17.7 to one
    yieldind a theoretical top spd. of 34.8 mph. Actually, as the belt never
    quite makes contact with the inside diameter of the primary it may be
    closer to 1". Remarkably, the belt does not need to be terribly taut to
    function well. AS a result it pedals with considerable more ease than a
    friction drive.
     

    Attached Files:

  19. rawly old

    rawly old Member

    Loquin,
    Perhaps this diagram will clarify how my primary pulley works.
    The belt effectively wedges to the sides of the pulley without ever
    contacting the center
     

    Attached Files:

  20. rawly old

    rawly old Member

    What, no comment?
    you know a bunch of people told me I couldn't build a better belt drive than
    G.E.B.E, but I have. It's sturdier, faster (with equivalent engine), and cost a
    a heck of a lot less, despite some unforeseen prolems in the making.
     
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