Author Topic: Stripped axle and nut on MP3 rear kit  (Read 7096 times)

Offline jbc@jcudney.com

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Stripped axle and nut on MP3 rear kit
« on: September 25, 2012, 02:20:15 AM »
Has anyone ever replaced the axle on a MP3 rear wheel kit? I'm about to embark on new territory here and I'd like a heads up before I do any more damage. Thanks

Offline Bikemad

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Re: MP III Axle removal
« Reply #1 on: September 28, 2012, 01:06:32 AM »
Hi andto the forum.

As far as I'm aware, no one on the forum has replaced the axle on the MPIII, but it appears to be pressed into a steel sleeve with a key-way slot which receives the locating key.
The axle looks as if it has been fitted from the controller side of the stator, and it has a circlip fitted on the opposite side to ensure that it cannot slide out if the fit becomes too loose.
This circlip (see picture below) must be removed before you can attempt to gently tap (or maybe press) the axle out.

If the axle is machined for a precise sliding fit (transition fit) it may be possible to simply remove it with a wooden or copper mallet by gently tapping the R/H end of the axle.

However,  if it has been machined for an interference fit, it would have needed a lot of force to press it into place. If this is the case, it will probably need to be pressed out again using either a mechanical or hydraulic press, ensuring a suitable piece of tube is placed over the axle on the controller side (seating directly against the steel insert) to oppose the applied force of the press.
The inner diameter of the tube would ideally be very slightly larger than the outer diameter of the axle where it seats against the stator inside the controller housing.

If the inner diameter of the support tube is too large, the steel insert will not be properly supported on the tube, and the large force exerted by the press would then act upon the body of the stator casting instead. This could result in the stator assembly becoming damaged (and unusable) if the force applied to the axle was sufficient to break the joint between the steel insert and the stator.

Have you made enquiries as to whether GM are willing to supply just the steel axle?

Alan
 

« Last Edit: July 04, 2017, 09:47:42 PM by Bikemad »

Offline jbc@jcudney.com

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Re: Stripped axle and nut on MP III rear kit
« Reply #2 on: September 28, 2012, 05:48:36 AM »
Thanks Bikemad for your post:

I ordered a front motor kit to tide me over until I fix this rear axle. It is going to be my winter's project. Gary is looking into what GM can do for me, so we'll see what my options are. This whole mess is my own stupidity and I intend to treat it as a learning opportunity. I'm in no rush. Thanks again you've given me a sense of what I'll be dealing with when I open this thing up. I may have to confer with the other retirees crowd at the local McDonalds and see if anyone has access to a press.

Offline Duck

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Re: Stripped axle and nut on MP III rear kit
« Reply #3 on: October 02, 2012, 02:58:00 PM »
Depending on how bad it is stripped you very well could repair the threads with a Thread Die... You can buy them individually at Sears. They clean up threads quite easily and you can just get another nut to fit it... Would definitly be the cheapest and fastest route...

~Duck
Everything is better with more horsepower!

Offline jbc@jcudney.com

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Re: Stripped axle and nut on MP III rear kit
« Reply #4 on: October 03, 2012, 05:43:25 AM »
Thanks Duck, I'll check into re-threading the axle. The axle threads are definitely stripped but they don't appear to be in that bad of shape. I think the nuts took about 50% of the damage. I had over tightened them, and the one side gave out while the bike was operating. I wasn't stressing the bike very much at the time and I felt the wheel sort of bind when I came to a normal stop. Since I've had absolutely no experience with electric bikes, I thought it might be the regen kicking in or something like that. After riding for another 10km or so I noticed a gentle whine (nothing horrific) from the motor and then saw the loose nut. The nut and axle turned out to be stripped on one side. On closer inspection I now see damage on the other end of the shaft as well, and it looks like it is ready to give out pretty soon. The whole process started after a particularly rough stretch of the Kettle Valley Railway bed where I tore out the side wall of my rear tire and had to replace the tire under tough conditions. My ensuing temper tantrum resulted in all the damage. At 65 years of age you'd think I'd learn. We have a very good bike shop here in Penticton, BC and I'm pretty sure they can help. A new replacement MP3 arrives tomorrow and I'll be motoring again soon. All's well.
Jack

Offline Duck

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Re: Stripped axle and nut on MP III rear kit
« Reply #5 on: October 03, 2012, 06:27:59 AM »
One thing that I quickly learned with running a MP3 is that you definatly need that rear wheel suspension with a shock. My next bike I plan on doing a mountain bike with a FULL suspension and then just putting wide street tires on it. Right now I have a city bike with skinny tires and at 20+ MPH the bike sure takes a beating! Without a full suspension I constantly worry about the MP3 rim from road hazzards...

~Duck
Everything is better with more horsepower!

Offline jbc@jcudney.com

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Re: Stripped axle and nut on MP III rear kit
« Reply #6 on: October 07, 2012, 08:58:23 PM »
Thanks again Duck: I took your advice and got hold of a tap & die set and cleaned up the threads on the axle. They look pretty good, so I bought a new set of nuts (M14 x 1.5 pitch) at Lordco. Every thing fits perfectly. Now I'm looking for a full suspension bike to convert. Perhaps an el-cheapo from Canadian Tire will do the trick.

Offline Morgen 3Eman

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Re: Stripped axle and nut on MP III rear kit
« Reply #7 on: October 08, 2012, 04:49:43 AM »
Hi JBC,

Regarding a source of cheap bikes, I have  been building "toys" for my grandchildren for a few years, and when I need bike components,  I go to Good Will, or the Salvation Army  stores.  I have no idea if you have them in Canada, but perhaps you have something similar?  I've bought  good suspended bikes for less than $15 US. :)

TTFN,
Dennis