broke clutch shaft today solution? stronger machined shaft???

Discussion in 'Friction Drive' started by uncleargenius1, Dec 28, 2009.

  1. see attached for where it broke

    my specs
    20" freestyle bmx dave mirra bike strong as ****
    my weight 140lbs wet
    dax friction drive running titan 4 stroke 50cc
    bmp friction drive kit
    1.25 roller
    riden 2 weeks daily at 50-100 miles per day trouble free until...

    going about 35-40mph downhill on smooth pavement full throttle
    got to the bottom of the hill stopped at red light
    light turned green gave her gas high revs rpms and no go
    hmmm so i look o no my clutch shafts broke

    the standard ones steel but...

    would a 6061 t-6 heat treated machine one be stronger?
    if so there would be 2 benefits
    1. less rotating mass weight better take off performance
    2. the main reason stronger and not breaking like mine did

    im sure no one makes one yet but if its stronger ill visit my machine shop
    i dont want to unbolt the engine twice a month or get stranded far away
    with no gas power

    also if 6061 is to weak for this application maybe 7075 aluminium?
    this ever happen to anyone? any ideas?

    see pic attached

    Attached Files:

  2. cycledude

    cycledude Member

    Am assuming that you have the standard bmp roller with the bearing inside, I packed mine with lithium soap grease before I put it together just in case it was dry, I dont know if I used the right kind either just hoping.
    I dont know if going up and down hill without pedal assist was also a problem, i gas up very little uphill and pedal as much as I can, use the breaks downhill.

    Hope comment helps.
  3. my bmp roller is the 1.25 with the one way locking bearing inside the roller still works and bearing are good the 1/2 shaft coming off the brass clutch plate just broke off where the clutch circle meets the shaft im thinking the shafts welded onto the clutch plate or its a forged mold

    i was thinking maybe a solid machined aluminum clutch plate/shaft that starts off from the same block of aluminum could be stronger since its all same metal no welded pieces or at a minimum maybe a 3/4 shaft thicker bigger shaft providing more strength

    the strange thing is it happened downhill and im a light rider 140lbs
    this is sumthin id understand more if i was 250lbs full throttleing up
    a steep hill then atleast theroticly it would make more sense
    also my motors a 1.5-2hp titan and bmp list engines all they way up
    to 4hp that can be used with there kit i like the kit and i dont see
    any parts from it ever breaking in the future except the clutch shaft
    i think i found this kits weak link hopefully bmp or some machinist maybe staton could build a stronger one and then maybe i can think about going over 2hp with the cyr420 2 stroke engine rated at 4hp or see if i can tweak my titan to 3hp with pipe/intake/jets
  4. 5-7HEAVEN

    5-7HEAVEN Guest

    Did the shaft break where it connects to the clutch drum?
  5. yup it broke on the outside of the clutch drum where it connects to the shaft

    the outer diameter of the shaft is smooth with no breakage or strees showing but the inner diameter of the shaft is all stressed looking and appears where the breaking took place
  6. cycledude

    cycledude Member

    Yeah, I was going to add a weld to that junction before putting the thing together, I didn't do it because I figured I didn't needed with my 35cc.
    But I will do it if I put anything else together larger than a 35.

    Anyway, thats 24 bucks with free shipping, how do you like that?
    The solenoid on my bike just went out of business, its about 100 bucks, I dont like that>
  7. 5-7HEAVEN

    5-7HEAVEN Guest

    I broke TWO Staton friction rollers right where they connect to the clutch drum. They snapped on my Mits TLE43 engine, just as I was reaching mid-to-high rpm range.

    It was all my fault, because I did not install the rear support strut on the engine side. I was using a MODIFIED version of Staton's early-version single rear support strut. When I installed two rear support struts and made sure everything was solid, I stopped breaking friction rollers.

    FWIW, the Staton friction rollers were installed on my BMP friction drive housing. I wanted to try 1.375" rollers and BMP didn't have spindles in that diameter.:whistling:
  8. i like that one person here who built a HF 79cc friction drive with a 2.75 aluminum wheel and no clutch bad thing though gotta hit kill switch when letting off gas alot or stoping and a 20lb engine on one side of the bike
    as a temp fix i orderd a new clutch bell/shaft but longterm im looking to mount a hf 79cc on top of the bmp carrier and do a sprocket chain drive setup then ill just have to worry about snapping my chain
  9. new bmp clutch drum drive shaft

    Well I broke my second replacement clutch drum today this time not at the weld or driveshaft but the clutch drum itself. So I go to bmp to order my replacement. Wow the holy grail to friction drive a solid machined drum and driveshaft with no welds. I have been wanting this along time. I was so happy I bought 2. Even if it breaks in 6 months that's ok by me. It beats my current rate of 1 per month. I can deal with disassembly 2 times a year. Also I noticed there 1.5 roller looks to be a diff color perhaps harder compound? I know the green one lasted a few miles. I might test the red one. Or even better a 1.5 steel freewheel roller for long lasting for a lighter rider like myself seeking top mph. Will you make a steel 1.5 with freewheel one way lock bearings Please bmp? I will buy 2
  10. 5-7HEAVEN

    5-7HEAVEN Guest

    BMP is not making the rollers. He's outsourcing them from other vendors.

    These rollers aren't specifically manufactured as friction rollers for bicycle tires.

    This MIGHT be where BMP'S spindles are coming from:

    FWIW, methinks you have the same problem I did when I was breaking Staton friction rollers at the clutch drum.
    Last edited by a moderator: Feb 16, 2010
  11. happycheapskate

    happycheapskate Active Member

    I have been waiting for them to come in stock to place an order (and maybe answer an email!).

    The 1.5" roller from BmP website is described as a 80a polyurethane "rubber" wheel. Isn't this a hard plastic like a skateboard wheel? Will this one work better in the rain? I'd rather not drive in rain, but sometimes there are sudden storms or flash floods where I live. (not like Katrina stuff, just water over the roadways in places or puddles)
  12. Happy Valley

    Happy Valley Active Member

    The urethane rollers are not a hard plastic like skateboard wheels, they're softer. They are more like the rollers that some boat trailers use.
    As to use in the wet I've not had much luck with them, I actually get a little better performance from the knurled steel but neither as good as wooden rollers in the rain.
  13. happycheapskate

    happycheapskate Active Member

    Kids are making friction drive bikes with weedeaters and skateboard wheels. The skateboard wheel material probably wouldn't do anything special in rain but ought to make a nice ride when dry.

    Probably the biggest obstacle to these friction drives is that the rollers are only 1-2 inches in diameter. A larger, rough roller that looked like a straight cut cog ought to have a lot more grip.

    Even bottle dynos use this pattern on 1/2-3/4 wheels, and don't slip on the tires much.
  14. 5-7HEAVEN

    5-7HEAVEN Guest

    Not Aluminum!

    I just realized that your clutch shaft is STEEL, not aluminum!:idea:

    I would never have imagined that there is such a thing as a one-piece clutch drum/shaft. In any case, that proves it's not aluminum.:detective:

    Check your rear support struts. I believe the one closest to your engine is not supporting. That's the reason I broke two Staton friction rollers in my BMP friction housing. They broke at the threads, so it'd cost more to remove the threads than to purchase new clutch drums.

    One more thing. If you're going downhill between 35-40mph with a 1.25" friction roller, you are so OVERREVVING your Subaru engine! That engine would NEVER pull your bike that fast on flat ground. You should limit your engine to 30mph if it's broken in.
  15. 5-7HEAVEN

    5-7HEAVEN Guest

    If your shaft breaks again, they sell heat-treated 1/2" shafts at various online sites. Orrr, you can buy non-heat-treated shafts, tap the end for the clutch drum, then have it heat-treated.
  16. Fred Fry

    Fred Fry New Member

    friction rollers

    How do you use Staton's rollers with BMP drive system?
    Last edited: Jun 24, 2010
  17. 5-7HEAVEN

    5-7HEAVEN Guest

    Both vendors use interchangeable 1.375" bearings; Staton's have .625" ID, BMP's ones are .50" ID. You can use Staton rollers with Staton-size bearings in BMP's housing. BMP's housing allow the bearings' outer edges to slip-fit. By lightly sanding the Staton rollers' ends, you can easily remove and reinstall the bearings and roller in the BMP housing. HOWEVER, you will need to fab a simple bearing retainer on the outboard side. This will keep that bearing from falling out.

    I like Staton rollers better. Since I try different spindle sizes, this setup works great for me.
  18. Brian Maldonado

    Brian Maldonado New Member

    Where do I find parts?

    I just got a bicycle with a Dax friction drive kit on it. On the way home the clutch wouldn't disengage and the clutch bell snapped off from the spindle. I went on to but of all the parts they sell, the clutch bell/spindle shaft is not one of them. That's all I need other than springs that they do sell. Aside from buying a whole new kit, I wanted to just get the part I need. I hear of people that have found and purchased replacement spindles but haven't posted a link to where they got them. Telling me they got them from bmp does absolutely no good because bikemotorparts is a search engine, not a parts store. I just love clicking on a link that's supposed to take me to my part just for another game of keep away and me tearing my hair out for the right keyword for the part I need. If you know where to get this clutch bell/spindle please post a link to the order form and make sure it will actually take me there.