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    Fat Bike build

    Hello Ebike folks,

    I just did two BBS02 builds on two Trek 29er hardtail MTB which have been a blast. It would have been better to have waited since we just got a Motobecane Boris & Natasha fatbikes . After the Trek builds and dealing with the chainline issues of the BBS02 I would rather build these without disturbing the 2x10 drive trains.

    Having read extensively the pro and con of the different drives, the front hub motor seems to be worth considering.

    1) doesn't disturb the drive train
    2) better power input peddling with gear choices not as limited
    3) both wheels driving
    4) may easily remove battery and replace wheel/motor with stock wheel for those trips when electric is not wanted

    So having one 135mm QR and one 150mm x 12mm thru bolt set up front forks I am wondering what the choices are? Will the double torque rear 145mm work on the front of the 135mm forks(cromoly). The disc mount would be on the correct side though not sure about the spacing? The 750 watt might be fine for the 135mm fork but what about the 150mm? The 150mm is aluminum alloy so I would need to get a cromoly fork if the axle is long enough.

    I do like the double torque/double speed idea and have a small metal lathe at home to machine spacers, bushings ect. also working on adapting a single wheel trailer to the fat tire format.

    All opinions welcome..........what do you think?

    Thanks Dave

    #2
    I have a custom FTB with front drive hub. There are some issues to consider: The front drive causes torque steer. If you hit the throttle in a turn it will tend to straighten out the line. Not a huge deal but noticeable. Also, the front drive puts a traction load on the steering tube where it meets the downtube. For most bikes the frame can handle this but I suspect some frames could crack over time. The torque on the axle can loosen the nuts and I think the front wheel could try to "walk out" of the dropouts.
    I welded extra tabs onto my fork and used torque arms to lock the axle in place on both sides. Much safer I think. It would make the wheel harder to remove quickly.





    Sorry, I cannot help you with the spacing questions.

    Robert
    Last edited by Robert62; 11-11-2017, 11:18 AM.

    Comment


      #3
      Its a really fat tire!


      Robert

      Comment


        #4
        OK that is just crazy :)

        I am not concerned about a little torque steer at the speeds we are riding. Think low range off road crawling along compared to many MTB folks. I thought about a rear motor but one is 170mm and the other 197mm spacing so the purchase of a motor would be needed just to disassemble and see if it would be practical to machine a new axle and spacers.....fortunately there is a full machine shop at work.

        There are some companies selling front wheel geared motor fatbikes lately based on the 135mm front spacing forks so the idea does appeal to others besides me.

        I was searching today for a motor that was being developed with a modular axle/bushing design so it could work with several hub spacing options, could not find it though. Memory was ebikes.ca but no joy when I looked.

        Told the wife if Ebikes are that much fun and fatbikes are that much fun an electric fatbike must be the most fun you can have.

        Hey thanks sharing the pics...Dave

        Comment


          #5
          After looking at available components to make the front hub motor fly perhaps the easiest route would be to use steel forks with the 135mm drop-out spacing which aren't too pricey. The ones I'm seeing are 1 1/8" steerer but reducers are available to bush down the 1.5" lower headtube bearing. Not as neat as simply changing the front wheel to convert from electric to non-electric but not bad if one wanted to put the bike back the way it was.

          Comment


            #6
            I like that plan. Machining a new axle is doable but I think it would be painful. Please let us know how this works out.
            Robert

            Comment


              #7
              I have this Hardtail Fatbike, with 197mm rear dropout. Chang Zhou SuRing Motor company on Aliexpress supplied the Mxus motor with a Custom 197 mm axle, laced into a matching rim to my OEM wheels, enabling me to fit a 10 speed freewheel, and retain all my original derailleur components.
              Everything lined up perfectly, and I didn't even have to adjust the derailleurs to make it all work perfectly.
              A brilliant conversion. They also supply it with a 170mm axle..
              Highly recommended
              ​​​​​​​

              Comment


              • marek7805
                marek7805 commented
                Editing a comment
                couldnt fint it ...have also 197mm rear hun pn my Surly ict....would like to buy it
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