Covering silver conductive paint with fingernail polish may break connections

[Bill H]

Group;
In the process of converting 400+ to resistor wheel sets, I have observed an interesting occurrence. The side of the resistor that touches the plastic insulator, requires just a bit of conductive paint from the resistor to reach the metal tire. Recently, I became concerned about the cured silver conductive paint being damaged by handling, specifically wheel cleaning. So I decided to put a layer of clear fingernail polish over the paint just to protect it. On wheels that were historically working just fine as resistor wheel sets, that had tested with the correct resistance, suddenly the circuit was broken after "updating" with the "protective" top coat. It appears that as the nail polish top coat cured, it shrank and broke the conductive paint circuit from the resistor to the metal tire. Just to be clear, unlike a lot of HO applications of resistors, I do not angle the resistor to directly touch the metal tire, out of concerns that the resistor may dislodge in wheel cleaning or other handling. All my resistors lay flat on the axle shaft. Just in case this may help others who wonder why their resistor wheel sets stop working...

FWIW this is the top coat I was using... https://www.amazon.com/gp/product/B00HFTXXIU/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1

And this is the conductive paint i have been using for some time with good results. The conductive paint is much better than the frequently clogging pens. https://www.ebay.com/itm/124488315234 grainy.

Kind regards,
Bill

[peteski]

Bill, could  you post a  closeup photo of how the resistor is installed?

Most resistor equipped wheels I have seen have the resistor located close to the axle and the back of the wheel.  Again in my experience wheel (tread and flange) cleaning is usually done with the wheels still installed in the truck and whatever item is used for cleaning shouldn't even gets close to the area in the back of the wheel and axle.  How do you clean your wheels, or what do you suspect can affect the resistors and conductive paint?

Seems like I need some education.

[Bill H]

Pete;
I will try to shoot some closeups over the weekend. Thanks,
Bill