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Bbshd. Slack in drive shaft?

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    Bbshd. Slack in drive shaft?

    I recently upgraded from a 52v bbs02 to a bbshd, and I noticed that when apply power quickly, there seems to slack be slack in the crank that sends a shock though the bike, jarring the chain and derailleur sideways a bit. The motor was torqued to 45 ft lbs and seems snug the bling ring is tight, there just seems to be a few degrees of play

    Is this expected? Do I just need to adjust my acceleration to accommodate?

    Thanks,

    #2
    Is, by chance, the motor rotating up and hitting the frame down tube?

    You might be able to see what's going on by carefully bracing the front wheel against a wall, and momentarily applying the throttle - nothing should move, twist, etc.
    Last edited by ncrkd; 08-11-2019, 07:03 AM.
    2nd build, 2018 Crust Scapegoat, BBS02 or BBSHD, Rohloff IGH
    3rd build, 2018 Crust Evasion step-thru, BBS02, Shimano Nexus INTER-3 IGH
    4th build, 2016 Salsa Marrakesh flatbar frameset, BBSHD, Alfine 8 IGH
    Other, Electronic throttle lock

    Visit the forum knowledge base

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      #3
      Motor is mounted tight. There's 2 mmb or so lateral play in the driveshaft, but that's not material. It seems like the play in the clutch splines is not than I'm used to from my bbs02 when the extra but if rotation catches up under heavy throttle, it's a bit jarring to the drivetrain. Everything is mounted tight. I'm testing with it up on my work stand.

      Marc

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        #4
        My BBSHD motors hit harder than my BBS02 ones do, and I try to lessen it as much as possible as all my bikes are IGH. Matching road/gear speed as best I can, use a shift sensor, don't shift at high throttle.

        As you thought about, you could adjust acceleration to accommodate or somewhat, alter the throttle response via the programming,
        2nd build, 2018 Crust Scapegoat, BBS02 or BBSHD, Rohloff IGH
        3rd build, 2018 Crust Evasion step-thru, BBS02, Shimano Nexus INTER-3 IGH
        4th build, 2016 Salsa Marrakesh flatbar frameset, BBSHD, Alfine 8 IGH
        Other, Electronic throttle lock

        Visit the forum knowledge base

        Comment


          #5
          Thanks for the feedback. I figured it was the extra torque at work, but wanted a sanity check. I was a little too enthusiastic about a "bomb proof" motor after babying my bbs02. I'll be more realistic.

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