After installing new capacitors in coils should you use tar potting material to fill them up or can you use other material such as foam or silicon? Any help would be appreciated! Thanks, John
As i understand it silicon is thought to cure acidic and foam is thought to hold moisture.
John some will say the box needs to be filled up as it was when you opened it. I don't see this as being necessary. I've always had enough tar that was chipped out of the coils to remove the old cap to pour into the box and trap the new cap & wiring. That's the whole point of the tar. To insulate & retain components. Silicone will retain water if it's present when the silicone is applied but if it's not wet when you do the job (and the coils don't get wet after) it's OK. It doesn't attract water on it's own. Then again if you must make it look orig. use wood spacers and a lot less tar is needed.
John
The coils you rebuilt lasted 90+ years because of that tar potting. Silicone and foam have several issues. Now that you have replaced the failed capacitor put the coil back the way you found it and they will last another 90+ years.
If you don't know where to get some tar just ask, it is easy to find in small quantities.
Ron the Coilman
Thanks everyone for the information, I appreciate the help! John
ive heard of it refered to as "steep slope" and i think its a roofing tar. thicker than most and sets up fairly hard.
Matt
The technical name is "Type III or IV Steep" roofing asphalt.
Ford gave it the fancy name "Hydrolene" but it was nothing more than the sludge at the bottom of the crude oil cracking process.
Ron the Coilman
It comes in "kegs" that are in fact paper wrapped containers that weigh in at about 100 lbs. If you need a chunk of it, call a commercial roofer not a roofing supplier. Drive over to his house and let him see your car and you likely will come home with all you need - it is pretty cheap stuff but if you bring home a 100 lb container of it, you wife ain't gonna be happy with you. You can get away with melting the stuff just one time and she will never let you do it again so make sure you do all your coils at that one event and have reservations for dinner already set up. Even flowers won't get you a second shot at tar melting.
I went to the local shipyard that do ships in wood and got a chunck of tar for 5$ to their coffee (or beer) pot.
I managed to find an old cast iron pot for the melting and have a 2 hob camping stove in my shop that i use for tar melting:
I have found a small oven also that I use to heat up the coils to make the tar soft:
It's much easier to wait for winter. The tar will chip out very easy with a few taps. And there's no danger of cutting a winding with a chisel!
Garnet
I'm with Garnet; I like to work on them when they're cold. I typically put a batch of them in my shop fridge for a few hours before I work on them. The beer never seems to mind sharing space with a dozen coils.
I like the refrigerator idea. Good one. What I've found on the dozen or so I've done is that the wood side of the coil that the cap is on can usually be pried off. Tap a thin blade between the wood and the cap to break it free and off it comes. You can't believe how much easier the job is with it out of the way. For melting tar I use a tin can on the barbecue. I've also used a tin can and a propane torch.