15 replies to this topic

[Junior8]

What type of epoxy can I use to coat the resistors on my Parma econo controllers. Even though they are working fine except for 1 that had the windings work loose I have 4 of them that I would l like to coat to prevent this.

[Jairus]

I have used Devcon 15 min two part epoxy but find it might be a bit soft for the constant friction and heat build up although I have not had a failure on any of my controllers. I would look for some high temp epoxys and try it on one controller first. (hey, I said MIGHT!)

Hey, let me know how it goes!


Generally I coat the friction surface with a nice thick layer and let it cure for a day. then get some 220 and 400 grit wet/dry sand paper and slowly block sand the wiper surface with the 220 and then the 400 until it's baby butt smooth. That wiper action is sooooo nice!

[Junior8]

Thanks for the reply. I will try the sanding tip as well. These are pretty good cheapo controllers and they have been very reliable other than the loosening windings on the one. It happens to be the oldest of the 4 also.

[Ron Hershman]

The epoxy that Parma uses on their wet wound resistors is a two part aluminum filled epoxy, same as we use in body molds. Devcon makes one.

When sanding a resistor, be careful to not take too much "wire" off as when you do, you will change the ohm's of the resistor.

[Pappy]

I've heard JB Weld works good on resistors.

[Junior8]

I thought about using the JB weld but the type that I have is the metal filled. It's very strong epoxy but I thought about it being metal filled and wondered if there would be a possibility of shorting the resistor. I'm not an electrician by any means but is that a possibility ? Since I don't use anything near a hot motor on my track are the resistors going to get hot enough to worry about melting the epoxy ? By the way I use a Pyramid PS26KX and normally run my cars at 11/ 12 volts and the controllers are 25 ohm. I use the Fox motors almost exclusively. Not hot by any means but they really scoot on my track.

[Pappy]

I don't know if the metal in JB Weld would short out the resistor or not. I've never heard anyone say it did. I can't imagine a Fox motor creating enough heat to melt any epoxy unless you had a kid just hold the controller at one constant speed.

[slotbaker]

What type of epoxy can I use to coat the resistors on my Parma econo controllers. Even though they are working fine except for 1 that had the windings work loose I have 4 of them that I would l like to coat to prevent this.

I've used Super Glue. Works great.

[Ramcatlarry]

FACT of life: Resistor wires burn out at the top end and need repairs. You can usually repair a slotcar resistor three or four times. The only way to prevent it is to use a fuse lower than the resistor limits - single barrel is 25 watts or two-three amps; double barrel is less than 50 watts or four amps. Wet wound type epoxy allows the heat to dissipate quicker and keeps the winds together longer.

[Mopar Rob]

FACT of life: Resistor wires burn out at the top end and need repairs. You can usually repair a slotcar resistor three or four times.

Yeaaaaa, if you don't mind them working like a light switch

[team burrito]

I've used JB Weld for years before the arrival of electronic controllers. Thin it out with lacquer thinner & spread a thin even coat with an index card. You want a thin coat so it won't trap the heat. Sand of the excess epoxy off the bands & finish with 400 or 600 grit sandpaper.

[Ron Hershman]

I forgot to add this before........ just putting epoxy on the resistor will not fix the problem of the wires lifting due to heat.

The wet wound resistors were exactly that....... wound while the epoxy was wet.

The resistor cores were coated with epoxy before the wire was wound on the cores. When dried, the wire was bonded to the core with a small film of epoxy between the core and wire. The epoxy "stuck" the wire to the core.

The sanding lowered any "high" bands due to excessive epoxy in spots along the core.

Unless you can get epoxy between the wire and core on a finished resistor.... I am afraid your wasting your time.

Normal resistors are wound then coated afterwards...... this is why wire lifts on them from time to time.

[Guy Spaulding]

We used JB weld, like forever!

Remove all the colored ceramic coating you can, using a dremel or whatever. Then apply generous coats with a Popsicle stick, one side at a time. (let one side dry before coating the other.) When applying to the face that the wiper arm touches, scrape off much of the excess with your Popsicle stick. When dry, carefully skim the surface with a Dremel cut-off blade, until the bands are exposed for the wiper button. Finish off with 220 or 340 grit wet-or-dry sandpaper. Some wiper buttons have a tendency to stick if the surface is too smooth. Changes in resistance, due to JB Weld metal content is negligible.

Resistors refinished like this are smoother, easier to maintain, resist lots more heat and last much longer!

[Dan Ruddock]

If parma really wanted to make a good resistor they would wrap the wire around a double anodized aluminum core which would draw the heat out of the wire much better than the ceramic core they use now. The only possible problem I see with this is as the aluminum expands and contracts could cause problems with the wire becoming lose. Dan

[team burrito]

When dry, carefully skim the surface with a Dremel cut-off blade, until the bands are exposed for the wiper button.

If you're going to do that, I recommend a belt sander (much faster).