1969 SB build - the journey begins

[demonufo]

Can't seperate the coil from the lam's without destroying it. They bake it all. But by bake, they mean at around 60-70 deg Celsius, in a proper oven, rather than your domestic affair with it's very iffy accuracy.

[young flower]

Today, I brought the trannies to the company I mentioned. For your information: The "baking" is not at 60 to 70°C - it´s at 120 to 130 °C. That´s a bit much I think. Also - the varnish can be air cured too, just takes it a bit longer: that would be the way to go in my opinion. They said the superficial rust is just a cosmetic flaw - as I already assumed. Unfortunately varnish coating the trannies is more expensive than they quoted me on the telephone. When I showed the trannies to them, they said it would cost about 50€ for PT+OT+choke. That´s a bit too much in my opinion. I´ll inquire again tomorrow and ask if it´s maybe possible to buy the varnish from them or if they can give me a discount if it´s air cured.

Alternatively, I´m thinking about applying a coat of clear laquer myself after cleaning off the rust with WD40.

I also brought the chassis to the galvanizer today. He said the zinc chromate layer on the chassis looked perfectly allright. What I assumed to be zinc-oxide residue on the corners, is actually just the way galvanized welding seams+a bit of dirt look. So - I obviously saw ghosts there.
It is however true that the yellow chromate conversion coating is more resistant to corrosion than the clear/blue version. Unfortunately hexavalent chrome which yields the most corrosion resistant coatings (and probably was used on the original Marshalls) was banned by EU law in 2000. Since then - the strongest zinc passivation technique is illegal in the EU - damn you EU and your whole exaggerated bureaucracy . All the good stuff slowly vanishes because it´s supposed to be too toxic. I think that´s bullshit. All you guys over the pond can probaly still get the good stuff.
Anyways - the fact that the yellow crhome coating is stronger and that some of the chassis holes are not zinc coated on the inside, convinced me to give it a new coating anyways. It will be done in a few days.

[demonufo]

For impregnating varnish I HIGHLY recommend Humiseal 1B31.

But like I said, don't smoke, and DON'T use it indoors.

[young flower]

Thanks - just checked it out: laquer for circuit boards. That seems to be the right stuff. I´m still hoping to get the varnishing done by that company. The employees said that the boss is on vacation and will return the week after next - I could talk to her and there is a chance that she´ll give me a discount for the varnishing. They also do vacuum varnishing where the varnish is sucked into the laminations and coil providing excellent isolation for years - which would be even better. Or maybe they sell me the varnish and I do it myself - we´ll see...

[young flower]

Oke - I went to the galvanizer again today because I was thinking all the time about how the chassis would look if it was glass-beaded before galvanizing. When I was there yesterday to bring him the chassis and I asked him to show me some samples of how glass-beading looks on steel, he just had some heavy-duty, previously beat-up motorcycle parts as examples. Seeing these didn´t really help me to get an idea of how it would look like on my chassis. Since the parts had quite a rough surface texture, I didn´t like, I told him not to glass-bead the chassis, but still I couldn´t stop thinking about the possibility to get the steel surface totally cleaned and looking like new. But today, he had a nice steel gear-wheel with a fragile chain, made of steel of similar thickness to the one on my chassis, that had been glass-beaded. It really looked great - down to each little chain link (the links having been about 5 mm long and 3 mm wide and made of about 0,5mm thick steel). So I decided that I will have the chassis glass-beaded before it will be galavanized. I´m quite sure now that this will turn out great !
Trannies are the last thing left before I can start reassembling - and I have some very hot leads on how to get them right.

[demonufo]

There are different grades of glass bead media, that can give variations of finish. The smallest beads can actually give a nice uniform finish. I used to do a lot of alloy wheel refurb-ing using glass bead on the rougher wheels. Can't recall what grades they were though, as I wasn't in charge of ordering the blast media. All I remember was it was Honite. If you look here, you'll see the different bead sizes, and I'm sure you can imagine the different finishes with such a HUGE range of bead sizes.
http://www.guyson.co.uk/assets/uploads/ ... et.pdf.pdf" onclick="window.open(this.href);return false;

[young flower]

Yeah - I know. I also asked the guy if he has different sizes of glass bead media. He said he´s using just one size which I assume to be one of the bigger ones as he´s mainly doing automotive and motorcycle parts. If I wanted another size he´d have to custom order it and readjust the machine which would make the whole thing very expensive.
But the example of the steel gear-wheel and chain (I think it was just ordinary steel) convinced me that the size he´s using will yield a good result.
I did find another shop who use fine beading media of about 120-130 microns - which would be medium sized according to the diagram you sent me. But I think what he´s using will be just fine.

From your experience - which size (about) would you recommend to get a nice finish on a chassis?

[demonufo]

You don't have to readjust the machine, that's nonsense. You just clean the filter, empty out the bowl, and change the media.

But like I said, I can't recall what size we were using. It wasn't too fine a grade, as it was too much time and effort to get the imperfections out when it was too fine, but it left a perfectly good finish. We didn't need particularly super fine as we already had a seperate blasting cabinet loaded with prunus shell which stripped paint and left metal untouched.

[young flower]

Yeah - but he´d still have to do additional work and he´d have to order the blasting media just for me. All of that taken together would obviously make it very expensive.
It doesn´t matter now - as I said: What he uses delivered satisfying results on steel. I guess it´s one of the medium bead sizes. Today I told him that he can proceed with the work - in a few days it will be done.
Next step: trannies.
I think I´ll coat them with lacquer myself.This is what I´ll probably use because it´s available locally and seems to be the right lacquer for the purpose: http://www.crcind.com/wwwcrc/tds/TKC3%20PLASTIK70S.PDF" onclick="window.open(this.href);return false;

Last thing I don´t have entirely planned out is how to best remove the rust from the lams and keep it from coming back while leaving a surface which allows the varnish to adhere. I won´t sand the surface of the lams or use any other abrasive cleaning method.
There are two things I´m concerned about when using common rust removers/lubricants like WD40 or Deoxit:
-insulation properties: Most of these rust removers are oil based/oily. Question is: are they insulating or do they conduct current? If the oil is conducting it could short out the lams creating one giant mess of eddy currents. Especially because most of these cleaners are penetrating - meaning they advance into every last nook and cranny. If they get into the (miroscopically thin) gaps between laminations that could be good or bad - depending on insulation properties and also I ask myself what happens to the oil trapped in there after varnishing? Does it get gooey? Does it slowly evaporate from the inside of the core/chemically degrade and vanish?....
-preparing the surface for the lacquer: the surface should be free of fat/oil of course - that´s contradicting the nature of most rust removers, as I said above
other possibilites: rubbing alcohol, water dilutable phosphoric acid based rust removers
the transformer company I talked to are using rubbing alcohol and nitro thinner to remove rust, Heyboer themselves advised me to use abrasive paper/steel wool to remove the varnish and re-varnish the tranny - I on the contrary want to remove as little as possible of the original finish and just remove the rust and seal the surface so it can never rust again.
I´ll soon run some tests...

[demonufo]

Personally I'd just lacquer over the rust. Not only is the rust not a bad thing, it is inherently good in reducing eddy currents.
Any oil left on the surface will stop any lacquer from adhering. The lacquer will actually "move away" from the oil, to a degree, although a proper brush on impregnating varnish will generally be so thick that it will cover it regardless and dry around it. Anybody who has done any spraying commercially and has experienced "silicon fish-eyes" will tell you just how paint moves away from it.
As for the lacquer, that one doesn't say anything about being an impregnating varnish. There are so many different types of conformal coatings available. Most of the impregnating ones are modified polyester. Not sure as I've seen an acrylic one before.

[young flower]

Oke - I think for removing the (really minor) surface rust, I´ll simply wipe down the core with rubbing alcohol repeatedly. The alcohol gets under the rust and helps removing it with a plastic bristled brush, like a tooth brush.

I ordered this laquer today: https://www.buerklin.com/default.asp?ev ... e&ch=30399" onclick="window.open(this.href);return false;

I think it is the absolute perfect fit for the job - I have a good feeling about this.

the journey will continue soon
YF

[demonufo]

I ordered this laquer today: https://www.buerklin.com/default.asp?ev ... e&ch=30399" onclick="window.open(this.href);return false;

That stuff will have an unnatural purplish hue to it. Not completely clear translucent. Also, wear a GOOD MASK when spraying polyurethane (even outdoors). It's still not an impregnating type varnish though...

[young flower]

The English technical data sheet on that site links to the wrong article.

Here is an excerpt from the product description on the site:

"Can be used as insulation lacquer on motor windings, coils and transformers, or as anti-corrosion varnish for metal surfaces."
That´s all I want in a box.

and here from the correct German data sheet translated into English:

"URETHANE CLEAR is a transparent protection varnish with excellent electrical isolation properties. It has excellent adhesion properties within the temperature range between –40°C and + 120°C. URETHANE CLEAR is a reliable protection laquer for circuit boards, especially in warm and humid environments. It is also suitable for motor windings,
coils, transformers or as yellow-transparent anti-corrosion varnish for metal surfaces."

Doesn´t say anything about purplish here - says "yellow-transparent", which reminds me very much of the stuff (the goo) that already was on the trannies in places originally. BTW: Why "unnatural purplish hue" - I thought you like purple ?

Also, wear a GOOD MASK when spraying polyurethane (even outdoors)

Thank you for reminding me - I have quite an expensive, high-quality one I will wear.

[demonufo]

I didn't even look at the data sheet, but in the description on the page...

The varnish contains a fluorescent dye to facilitate UV checks

This will have a slightly opaque purplish hue to it. These types of lacquers normally go slightly misty when it's more humid too unless you spray in really thin coats and allow plenty of drying time between coats. Unfortunately thin coats isn't the way to get the stuff to impregnate. Personally I have NO issues with a purplish hue, just warning you that the lacquer won't look quite so natural, if indeed the description does match the product.

[young flower]

Oke - understand. I´ll test the lacquer on scrap material before using it on the trannies.