# AF 18B transformer wiper arm rebuild



## The New Guy (Mar 11, 2012)

Anyone ever have a rivet fail on a wiper arm?

Crazy bugger - I don't believe that odd rivet contraption is available anymore, not that it matters really as the brass bushing is so worn the arm was contacting the coil even with the dead man lifted.

I think what I'll do is drill the bushing true, solder in a rod, drill and tap to 4-40, and re-assemble with a shoulder screw. I believe the RC crowd should have a screw near that size.

anyone see an issue I haven't thought of?


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## Nuttin But Flyer (Dec 19, 2011)

Not sure which part you are referring to here....would this be the brad that fastens the carbon roller to the contact arm assembly?


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## The New Guy (Mar 11, 2012)

This is one of those "useless w/o pictures" moments - Ed must be napping...










The whole assembly is the good side from an 18B. The other parts you see are the crap ones. I just turned a base, it's the one with the smaller hole 

Haven't tapped it yet.

It's difficult to see in that picture, but the old one is so elongated that the carbon roller would rest on the coil even with the dead man lifted.
It was cheap though.


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## Nuttin But Flyer (Dec 19, 2011)

Oh, so it's the "pivot" point of the contact arm assembly. Any thoughts how you intend to repair this? I ask because I have both an 18B and a 30B that eventually need my attention. Now would be a good time to learn the "innerds" of these things.


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## The New Guy (Mar 11, 2012)

Nuttin But Flyer said:


> Oh, so it's the "pivot" point of the contact arm assembly. Any thoughts how you intend to repair this?..


I turned a new base pivot point, tapped 8-32 (because I goofed, would have preferred 6-32) put the new base in the fiber strap, peened the edges to swell the brass so it holds good, and installed a brass screw w/ red locktite.

I also played with the old one some - soldering a 1/4-20 into the elongated hole last night, I plan to chuck it up and smooth out the shoulder, and drill a proper hole for 6-32. Essentially making a threaded insert.


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## Nuttin But Flyer (Dec 19, 2011)

Can you post photos of your rebuilding work before you reassemble it....or am I too late asking for that?


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## The New Guy (Mar 11, 2012)

Nuttin But Flyer said:


> Can you post photos of your rebuilding work before you reassemble it....or am I too late asking for that?


Everything is past tense, sorry. I can pull the case again and snap a finished picture if that would help.

If you have this type of contact arm, and if you need to, once you take it apart what I did will be clear. If you have a lathe (wood lathe will work, it's just brass) it's a simple fix.


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## Nuttin But Flyer (Dec 19, 2011)

Naw, don't bother. I'm sure I'll find out soon enough. If I have difficulty at that time, I'll be writing to you.


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