.. "Knocking" MP5 ...

[diverdon]

    Hello Everyone .. I searched and read what I could find on this ... Mines a little different as it's "not new" ..at all .. MP5 front wheel of a 26 inch townie 7 speed .. I ride average 8 mph most days between 1-2 hours for some exercise .. i'm handicapped and walk far but can pedal this thing and have lost weight doing it ...
           Over 10,000 miles showing on the speedometer app I use on my phone for the bike ..On the 3rd set of tires ... So it's been used a LOT but pretty easily ..
      2 ? weeks ago as I first left home I got this disturbing knock knock knock from the wheel ... 15? seconds and it was gone ....  2 weeks later .. Today .. I got the knock mid-ride lasted a little longer ...30? seconds ..seemed to get worse (harder) with acceleration ...  1 Hour away from home at 6:30 AM ... I just "gassed it" for a few seconds ... And it went away ... Again ... For the Hour Ride Home ...
    I want to check the Axle Nut .. Anyone know the Torque Spec ? Don't want to strip it with the 1/2 axle threads ... Thanks for any Help you can Give ... Don

[Bikemad]

I want to check the Axle Nut .. Anyone know the Torque Spec ? Don't want to strip it with the 1/2 axle threads ... Thanks for any Help you can Give ... Don

Same advice as before:

Hi Don,

If you read that post again, you will see that I actually recommended 39.5Nm, or 28.76 foot pounds, so if you are happy to tighten yours to 40ft/lbs it should be plenty tight enough for the standard axle nuts.

As I've previously mentioned, I always tighten the axle nuts by feel, as I can usually "feel" when a nut is approaching its yield point.

I will admit that I probably tighten mine a bit more than they need to be because I have steel frames and I run a modified Pie at up to 50 Amps with no torque arms fitted.

I have previously measured the torque output of my modified Magic Pie, which worked out to be ~93Nm @ ~66Amps. Therefore a standard Magic Pie will probably produce ~42Nm of torque @ 30Amps.

My modified controller was eventually pushed to it's limit, but before it finally died, it delivered a whopping 97.75 Amps to the motor:


As torque is proportional to the current, this should theoretically have produced almost 138Nm (101ft/lbs) of torque, which my overtightened axle nuts were able to withstand without allowing the axle to move within the frame dropouts (and that was also without any torque arms fitted).

The most important thing to consider is that the torque on the axle is not one directional, as each time you engage regen, the torque on the axle is applied in the opposite direction to when the motor is being powered.
Any movement at the axle fixings whatsoever should be avoided at all costs, as it will inevitably result in the loosening of the axle nuts.

I regularly put a spanner on the axle nuts just to check they are still nice and tight and I haven't needed to retighten them yet, so presumably nothing is moving where it shouldn't move. 

Alan

[diverdon]

 
     ..  Thank You for the Reply .... And ... Dummy me ... I posted the "problem" before even checking anything .....
       
           Both axle nuts were barely past finger tight ... I remember the Torque spec being sorta low ...seemingly to me ....  But the axle with the machined in flats ...limits the thread area ....  I understand why one wouldn't want to overtighten it ...

    So anyhow I check the nuts before looking at your reply and cranked them down pretty good ... I had/have an extra nut on the axle end the theory is the double nut locking ... I didn't actually use 2 wrenches to lock the nuts together when I first did it ....   Their LOCKED Together now ....

       So I will get back to you after a couple of days to update if I have any more knocking .... Thinking the lose nuts was it thou .... Thanks Again For Keeping me Going ...  Don

[diverdon]

   
       The loose axle nuts seems to have fixed the "knocking" noise .. 3 hours on the bike and no noises ... 
       A couple of other things I noticed may have been caused by the loose nuts ....  I had a "clunk" when I went into the throttle to fast and when I hit the front brake ... Thought it was "normal" ....  Now that's gone too ...no more clunk ..  I must have rode it this way for a year ... Don't want to see what my fork drop out looks like ... I have 2 Torque arms .. 1 is the thick one from Grin Tech. ... perhaps I will put 2 new ones on ....  The other thing is I was constantally needing to adjust the front brake as it rubbed the rim .. That seems to be "fixed" now to ....
       I still use the tip you gave me about the home watt meter to fully charge the battery every now and then ...  Mine goes down to about 4 watts when full ...
      Once AGAIN ... THANK YOU .. Don't know what I'd do without this help ...  If this motor crapped out tomorrow ..I'd say I got my moneys worth out of it ...  But it just keeps going and going ....   Thanks Again .. Don