How to swap a MA motor?

[disturbman]

I have a motor unit that shorts. It runs (almost) perfectly without the body on but consistently shorts when the body is installed. Which makes me think the issue is isolation-related but I don't have the tools to track down and identify the problem. My intention is to swap the motor for a new one. I have a couple of replacement motor units lying around but the chassis are not the correct length and I was wondering if anyone had ever tried/manage to swap a MA motor? And if yes, if you had recommendations or tips to share?

[railsquid]

What kind of motor unit is it?

 

If it's the typical multiple unit design, it's conceivable that the copper strips under the "floor" might be making contact with the chassis when the body is on, causing the short. If that (or something similar) is the case, then changing the motor probably won't help.

 

(The only persistent shorting issue I've had with MA is a DD16, which has the old split chassis/split bogie design, which needed some additional insulation).

[disturbman]

Typical multiple unit design. I tried taping in place the transparent plastic part that isolate the motor from the copper strips as I thought it might be slightly too loose but it didn't help. I could try and look again at the copper strips, how they rest.

If the issue is with the chassis I might have to find a E0003.

[railsquid]

45 minutes ago, disturbman said:

Typical multiple unit design. I tried taping in place the transparent plastic part that isolate the motor from the copper strips as I thought it might be slightly too loose but it didn't help.

 

Oddly I've never had any issues with older models after removing (without replacement) the thin black membrane they used to use, which mostly hardens and splits into useless pieces.

 

Another possibility might be damaged/missing insulation on the motor itself, apologies for the gunk picture but you can see this one has some insulating tape on the side (which has developed a slight hole, I notice):

 

Overgreased motor bearings (2) by Rail Squid, on Flickr

 

 

[disturbman]

Further investigations. It's not the copper strips. I remembered I had an older, temperamental and discarded 21m chassis and it works perfectly. It seems that the motor on the original chassis is not insulated, I can't see any electrical tape on it. I'll have to remove it to check. But if that's the case, I'm surprised it does not short constantly and works without the body.

Edited February 3, 2022 by disturbman