Replacement Coil Tar

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Model T Ford Forum: Forum 2012: Replacement Coil Tar
Top of pagePrevious messageNext messageBottom of page Link to this message  By James A. Golden on Monday, May 28, 2012 - 10:35 am:

Does anyone know where to purchase a small amount of replacement coil tar to fill in around a new capacitor and what kind to order?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson-Nicholasville, Kentucky on Monday, May 28, 2012 - 10:46 am:

Jim
Go to your local roofing supply store or contractor and ask if they have or use Type III Steep roofing asphalt. They will usually have it stacked in their stockyard in large 50# bricks and in many cases you will find a few small pieces laying about.
Carry a Model T coil with you and don't be surprised if you are asked what your using it for, one supplier told me it is also used by folks making illegal drugs.
Ron the Coilman


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson-Nicholasville, Kentucky on Monday, May 28, 2012 - 11:04 am:

Type IV steep would also work.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Anthonie Boer on Monday, May 28, 2012 - 11:09 am:

What is the max temp. of the Tar that the new capacitors can have ?
thanks Toon


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Patrick on Monday, May 28, 2012 - 11:53 am:

Look up type III steep roofing asphalt, where you can pullup the MSDS which will tell you the temperature at which it will melt. Since Ron uses it, it will be fine for your coils. Jim Patrick


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Cascisa - Poulsbo, Washington on Monday, May 28, 2012 - 02:23 pm:

Here is some data on type III and type IV tar.

Be_Zero_Be

(right click and save file to your computer then view with Adobe)

application/pdf
steep_roofing_asphalt.pdf (91.6 k)


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Dewey, N. California on Monday, May 28, 2012 - 03:06 pm:

Hmm, from reading that, I would avoid the type IV, as it requires a higher temperature to melt.
That MIGHT not be a problem, but I'm not Ron!!
T'
David D.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Cameron Whitaker on Monday, May 28, 2012 - 03:17 pm:

I do get a little nervous with tar...

A standard capacitor's temperature rating is usually 85 degrees celsius (185 Fahrenheit) and a high-temp capacitor is 105 degrees (221 Fahrenheit). I do believe that the new replacement capacitors are of the 85 degree type. If I'm not mistaking it takes more than that to melt the tar, but people have been potting new capacitors in tar for quite a while with no problems, so it must not be an issue.

Maybe if you wrap the capacitor in cardboard or something like that and then pot it with tar?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Thode Chehalis Washington on Monday, May 28, 2012 - 04:50 pm:

Cameron,
It is clear that the hot tar does not seem to effect the performance of the new capacitors. I believe that the temperature rating of a capacitor has more to do with changing capacitance values due to temperature rather then the maximum temperature that the capacitor can withstand when not in use.

Changes in temperature around the capacitor affect the value of the capacitance because of changes in the dielectric properties. If the air or surrounding temperature becomes too hot or too cold the capacitance value of the capacitor may change so much as to affect the correct operation of a circuit.

Jim


Top of pagePrevious messageNext messageBottom of page Link to this message  By John F. Regan on Monday, May 28, 2012 - 05:08 pm:

Cameron:

You are confusing "operate temperature" with potting temperature. The new capacitors are like the previous "old" capacitors in that they have an epoxy coating. Neither manufacturer will flat out guarantee the parts when potted but we did plenty of testing on the parts both new and old. If you overheat type 3 steep roof asphalt you will immediately notice it smokes a whole bunch. Nobody tries to pour it when in that state since mostly you get smoke and no tar. Just get yourself a hunk of tar big enough to fit into a large coffee can that you have squashed a bit to make a pouring spout. Heat that can with a torch or camping stove outside and stir on occasion with a piece of wood like a paint stir. Once there are no lumps in it then pour it into the coil and let it cool. If you have a deep hole then pour it only half full and wait a bit and then top it off. Otherwise you will get air bubble spatters of tar all over the outside of the coil rather than on the inside. Tar bubbles and spatters as it cools so don't wear any "Sunday clothes" to do the job.


Top of pagePrevious messageNext messageBottom of page Link to this message  By James A. Golden on Monday, May 28, 2012 - 05:11 pm:

Thanks Ron, I've learned a lot, now that I know the proper name to ask for and about. It is called Type 3 because it can't be used on a roof that slants up more than 1 foot in a 3 foot distance. I have always wondered how warm the tar had to be to pour. Looks like 250 to 300 degrees F should be warm enough to work with from the chart. I may have found a local source, but they are closed today.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John F. Regan on Monday, May 28, 2012 - 05:14 pm:

I forgot to mention that both Ron and I use type III steep roof asphalt in our coils. I have built several thousand now without issue. Not a single failed capacitor. I would not recommend that you heat the tar to the smoking point since there is danger of it "flashing over" in the pot - simply put this means it starts flaming. Keep a lid on the pot or nearby so you can put the lid on if it flashes over. I have one of those hand held temperature guns and those are great for telling you how hot the tar in the can is. I pour the tar just as soon as all tar in the can is melted thus I pour it at the lowest temperature.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Cameron Whitaker on Monday, May 28, 2012 - 05:39 pm:

Jim and John,

That's what I figured. When it comes to capacitors, I namely deal with electrolytics, and a bit higher than their rated temperature, the electrolyte can start to boil off. Don't worry, I'm not installing electrolytics in T coils!

When I pot T coils, I usually pour in enough tar to completely cover the new capacitor, let it cool off, and then I finish potting the coil.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Patrick on Monday, May 28, 2012 - 05:47 pm:

When poured should it be poured all the way to the top of the rim of the box or should there be a gap? If poured all the way to the top, will it shrink as it cools? Jim Patrick


Top of pagePrevious messageNext messageBottom of page Link to this message  By John F. Regan on Monday, May 28, 2012 - 06:25 pm:

Jim:

I am filling the entire box since I am installing everything not just a capacitor. Having said that, the main thing I do is use masking tape to cover the 3 slots on the top and sides that the door slides in. You should only fill the box up to the bottom of those slots but you can stop anywhere along the way so long as the coil windings and capacitor is completely covered. If you try to pour it all full on the first pour you will find that the hot tar will bubble with air bubbles and splatter all over as the hot tar forces the moisture and air out of everything it touches. Eventually when it cools completely it will shrink down a bunch so you made then a mess for nothing. Better to pour the box about half full but enough to just cover the winding and the capacitor. Then when it stops bubbling and seems to have solidified you can pour in the rest. I do it that way but I am pouring in way more tar than anyone who is simply replacing the capacitor and any attending tar that fell out of the coil while the capacitor was being dug out.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson-Nicholasville, Kentucky on Monday, May 28, 2012 - 07:32 pm:

Cameron
I have a box full of electrolytic caps in my coil archive tried by predecessors.
No doubt you will understand most them have one end blown off. grin
Ron the Coilman


Top of pagePrevious messageNext messageBottom of page Link to this message  By Patrick Martin on Monday, May 28, 2012 - 07:43 pm:

Someone here told me they were using the spray foam stuff for sealing household cracks and drafts in their coils instead of tar.
I used it and it actually works pretty super. I slid the cover on except for about a 1/4" gap, stuck the tube in and pulled out as I went so it filled from bottom to top then slid the door closed. That stuff expands and fills every void and dries hard.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson-Nicholasville, Kentucky on Monday, May 28, 2012 - 07:49 pm:

John
I finished rebuilt coil 15,431 today and have never had a replacement capacitor failure.
Wish I was as good at identifying the 80+ year old cold solder joints that can fail when everything is placed back in top working order.
Ron the Coilman


Top of pagePrevious messageNext messageBottom of page Link to this message  By Garnet on Monday, May 28, 2012 - 09:41 pm:

The problem in using spray foam is that it's the nastiest, stickiest stuff known to mankind. It also has a fair amount of pressure to it, so if there's any little opening in the coil case, the foam will ooze out. Nobody will get that cover off the coil again either in future. Some guys at work sprayed that stuff down along a door frame in an equipment hut in an attempt to keep winter winds out. Once it expanded and set they found that they couldn't get the door open again. They spent a lot of time getting back into that hut, and more time digging the foam out of the door jam.

Tar is easily chipped out and poured back in.

Garnet


Top of pagePrevious messageNext messageBottom of page Link to this message  By Terry Woods, Katy, Texas on Monday, May 28, 2012 - 11:33 pm:

Hugh Jass, once told me that he uses Bituminous Roofing Tar.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson-Nicholasville, Kentucky on Monday, May 28, 2012 - 11:43 pm:

Model T coils survived for 80+ years because of the tar potting.
I suggest you put them back the way you found them and forget all these alternative methods.
Ron the Coilman


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Eubanks, Powell, TN on Tuesday, May 29, 2012 - 08:02 am:

John and Ron, I had some coils leak tar and begin to fail on my 26 during the MN tour last summer. The heat was 100 degree plus at times. Should the tar have melted or was it possibly not the correct tar?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson-Nicholasville, Kentucky on Tuesday, May 29, 2012 - 10:44 am:

Jim
I cannot comment upon the tar in your coils, but a small amount leaking out of the bottom of coils on 1926/27 Model T's is very common because the the heat in the engine compartment.
A bit of lacquer thinner on a rag will clean it up.
Ron the Coilman


Top of pagePrevious messageNext messageBottom of page Link to this message  By James A. Golden on Wednesday, May 30, 2012 - 01:02 pm:

Ron, thanks for the lead and proper name for that tar. We now have 100 pounds, better than none at all anyway.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bud Holzschuh - Panama City, FL on Wednesday, May 30, 2012 - 02:13 pm:

James

Usually removing the old large caps and installing modern ones leaves a large void in the coil box.
I remelt the old tar I removed and that is usually sufficient to anchor the new cap so it won't vibrate or move in the box. The remaining void can be filled with a wood block or just left as a void.
I recently took apart 4 coils that were repaired this way and had been running in the car for a year. When I replaced the caps I left the void. Nothing moved and the caps were still securely in place.

Cheers
schuh


Top of pagePrevious messageNext messageBottom of page Link to this message  By James A. Golden on Wednesday, May 30, 2012 - 07:01 pm:

My friend got the tar home today.

The label notes it is Type 3, But the other stuff is hard to read.

Label

The package is difficult to deal with and the best way to removed the tar has not been decided.

Package

There is more information about the temperature here, but I'm not sure what it is telling me.

Temp


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson-Nicholasville, Kentucky on Wednesday, May 30, 2012 - 07:16 pm:

Bud
All the parts (components and wiring) inside the coil should be completely re-potted and encapsulated to avoid vibration related failures.
Ron the Coilman


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson-Nicholasville, Kentucky on Wednesday, May 30, 2012 - 08:20 pm:

Jim
Remove the paper tube coating. Place it in a deep wheelbarrow and go after it with a big hammer on a cool day. Fill a smaller box with broken pieces that fit your heating pot and take it to the shop for usage.
Ron the Coilman


Top of pagePrevious messageNext messageBottom of page Link to this message  By Michael Mullis on Wednesday, May 30, 2012 - 09:05 pm:

My personal “experimentation” into re-potting Model T spark coils yielded valuable scientific data that the most proficient “coil man” will inevitably find impossible to refute.


Experiment No. 1 (conclusion)
Counter Adhesion Force

My upper body strength is insufficient to facilitate adequate radial arm motion of the appropriate velocity needed to generate the necessary centrifugal force which is required to dislodge previously molten tar from one’s hand.


In other words, don't get none on ya'


Top of pagePrevious messageNext messageBottom of page Link to this message  By Garnet on Wednesday, May 30, 2012 - 09:21 pm:

The added benefit to Ron's above posting is that you can easily hand out pieces to relatives at Christmas and rotten kids at Hallowe'en !!

Garnet


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Stroud on Thursday, May 31, 2012 - 12:45 am:

And, if it is cold enough(30-40 degrees F.) and you hit the block with a single bitted axe, you will get to sweep up a LARGE area of the shop! Don't ask how I know this. Dave


Top of pagePrevious messageNext messageBottom of page Link to this message  By Michael Deichmann, Blistrup, Denmark on Thursday, May 31, 2012 - 04:51 am:

Here is my repotting setup:

It's a cast iron pot and an old electrical stove. The tar I dig out are put in the pot and some are added from a chunck of tar I got from the local wood shipyard.


Top of pagePrevious messageNext messageBottom of page Link to this message  By mike bartlett Oviedo,Fl on Thursday, May 31, 2012 - 01:35 pm:

I have asked several dumb questions in the past,so heres another.Why can't these coils get "potted" with a material like plaster of paris or epoxy? These materials wouldn't require much work.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Hal Davis-SE Georgia on Thursday, May 31, 2012 - 04:38 pm:

Epoxy is EXPENSIVE. I'll let someone else address the plaster of paris.

Tar is not really that much work. You just heat it and pour it and let it cool. You don't have to measure anything or mix anything. I do stir it just to make sure it's all melted, but I wouldn't consider it a lot of work.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Garnet on Thursday, May 31, 2012 - 05:02 pm:

Other methods may seem acceptable but you're really shooting for long time performance, and the Model T coilbox is not weatherproof. The parts need to be protected from the elements and the best way is potting in tar Mike.

Garnet


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bud Holzschuh - Panama City, FL on Thursday, May 31, 2012 - 06:28 pm:

Plaster of Paris wouldn't stand up to the vibration and would likely crack.

Hal's right, epoxy would be expensive and god forbid you should ever have to open the case and repair anything!

From a cost and simplicity point of view, tar seems ideal.

Cheers
schuh


Top of pagePrevious messageNext messageBottom of page Link to this message  By John F. Regan on Thursday, May 31, 2012 - 09:37 pm:

I think I want to comment again on a couple of points hopefully to help. I don't think the expanding foam is really a good idea. It is not a hard setup. It may be firm but not hard and it is really difficult to know when to stop and then be sure that you have enough to do the job after you close the lid. It expands but there are large air holes in it. Why does that matter? The idea of using tar is not just about a somewhat softer ride for the coil but poured in hot, it causes all air and moisture to be driven to the surface and exhausted. This has a lot to do with the long term life of the coil windings. Being totally and completely immersed in hot tar that then sets up pretty darn hard and gummy will result in a coil winding that is preserved almost indefinitely. This same tar removes any and all vibration movement of the parts which prevents joints from coming lose over time and also prevents things like capacitor leads and winding tap leads from working loose and eventually breaking due to metal fatigue. Tar does the complete job wonderfully and for the long haul it is clearly the stuff to use in my book.

Now having said that - I want to address 26/27 coil box concerns. Remember that Ford did not have to worry about any early coils being shipped in 26/27 coil boxes but you do have to be careful that you do not have an early coil in your mix since the early coils had tar with a much lower melting point and if you happen to have inserted one of those in your 26/27 you can have a coil that can fail rather easily or at the least tends to dump melted tar into your coil box which ends up causing poor connections. If any of you have ever dug tar out of some coils then you are probably familiar with how some coils have large chunks of tar that simply falls out and makes the job of digging very easy - those are the early coils with the low melting point tar and you should not use those coils in a 26/27 unless you remove all the tar and put in the type 3 stuff. Attempting to remove all tar is dicey so you might just be better off not using the coil in a 26/27 box. If the tar was gummy and hard to dig out - that is the later high melting point stuff and those are the best ones to use in a 26/27 coil box. You need also to keep the engine cool as you can by installing a good radiator and running the timing advanced and the engine on the rich side. Keep the engine cool for long coil life as well as long engine life.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Erik Johnson on Thursday, May 31, 2012 - 10:48 pm:

I seem to recall that the coils that were supplied with Fordson tractors marked "TRACTOR UNIT" were designed for higher temperatures (i.e. larger condenser and tar with a higher melting point).


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