Black Shadow engine painting

vibrac

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In the period 48-50 at the Stevenage works for which I have a detailed factory layout (which I will extract from an old computer when I get time and pass to the archives on the main site) there is no Paint shop or paint area and the only air compressor is ajacent to the end of the assembly area and a long way from the crankcase assembly
 

craig

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Thanks chstorm, I was under the impression that ceramic coating would inhibit heat transfer. Are there different types of ceramic to allow/not allow heat transfer? I have seen ceramic coatings used on exhaust components to keep heat to a minimum and they work quite well.

When rebuilding my Shadow C-series engine, we decided to use ceramic coating on cylinders and cylinder heads, a coating which will stand very high temperatures. The result was very good and can be recommended. The work was done by Camcoat Performance Coatings, Hoyle St, Warrington, Cheshire WA5 0LP. Tel.: 01925 445003 or 01925-445688
 

Magnetoman

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I hope you can post what the clue is............
I couldn't wait for the clue, so looked it up:

The Birth of The Black Shadow. ...the two original models were completed. Fully machined crankcases arrived from British Salmson in matched pairs... Timing cases and chain cases... were temporarily attached to the crankcase so that all mating edges could be trimmed up and all visible surfaces highly polished... treated chmically with 'Pylumin'.. and a finishing coat of the enamels supplied by Pinchon-Johnson for the frames. George Aylott took great pride in the lustrous finish he obtained, yet ensured that all machined surfaces and tapped holes were free from enamel by blanking them off or using slave plugs. This work was done in the No. 2 factory and then the parts were then transferred to... the No. 1 factory..."
 

Magnetoman

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Ah that explains the lack of the paint shop, it was in No2 ,I dont have a plan for that
But it still is only a clue, because the description is of the how the first two Black Shadows were built in semi-secrecy. It doesn't describe how things were done when they went into production. Still, aside from the B.S. engines, they had to paint the frames for all the bikes somewhere, and if your drawing doesn't show a paint shop of any kind in No. 1 factory, the finger points to No. 2.

With nothing definitive yet posted on sprayed vs. dipped, we're still left examining clues.
 

chstorm

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Thanks chstorm, I was under the impression that ceramic coating would inhibit heat transfer. Are there different types of ceramic to allow/not allow heat transfer? I have seen ceramic coatings used on exhaust components to keep heat to a minimum and they work quite well.

There are indeed different types of ceramic coating, and I followed Camcoat's advice to choose a type which according to them would improve heat transfer. They had coated Vincent cylinder tops and cylinders before and obviously knew very well which type to use. I suggest that you contact them to discuss the matter. I am very satisfied with their service, and glad that I could avoid using paint or powder coating.
 

Magnetoman

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choose a type which according to them would improve heat transfer.
Lots of semi-technical, semi-correct, semi-misleading "information" exists on the web about coatings of all kinds, including ceramic. First, any black coating of any kind on a head will increase the emissivity and thus increase the heat loss to the air due to infrared radiation. The emissivity of black paint is ~5x better than bare Al, and even shoe polish would be better than bare Al. Unfortunately, there are two catches to this. First, the heat has to travel through the relatively low thermal conductivity paint to get to the top surface where it can be radiated away. The further the heat has to travel (i.e. the thicker the paint, and the lower the thermal conductivity of the paint), the greater the temperature drop across the paint, and thus the worse the heat transfer. Only in the sense that a high thermal conductivity black coating is "less worse" than a low thermal conductivity one could it be said to "improve" the heat transfer.

Second, thermal radiation is a relatively small part of the heat equation anyway. Convection carries away much more of the heat than thermal radiation, and any coating on the head is worse than no coating. That is, even if the head could be coated with crystalline diamond (which has very high thermal conductivity), the heat transfer to the outer surface would be lower than if the head were left bare (albeit, in the case of diamond, only a tiny bit lower). Again, one coating could be said to "improve" heat transfer only if that statement were properly qualified to say it was iin comparison to the use of a worse coating, not in an absolute sense (e.g. "A head coated with silver improves heat transfer over that of a head coated with paint").

The above isn't directed at any specific company offering coatings. Whether or not such coatings had higher thermal conductivity than black paint only could be determined by examining the technical specifications of the material they used (both its thermal conductivity, and the thickness of the coating).
 

Magnetoman

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I followed Camcoat's advice
I searched Camcoat's web site and the only relevant information I found was:

To give the head a pro-look you also get the black TLTD heat shedding coating on the outside surfaces.
TLTD Thermaldispersant coating designed to expedite heat loss from cooling surfaces.

These are just advertising claims, not technical information, and there's no way to evaluate what they mean. As I wrote in an earlier post, any black coating whatever would increase the emissivity of the outer surface, so would expedite the heat loss due to infrared radiation of whatever heat actually made it to the outer surface. The problem with the above statements is both would be equally applicable to a 1"-thick layer of black asbestos wrapped around the head -- very little heat would make it from the head through the asbestos to the outside surface, but the heat that did manage to get through would be radiated more expeditiously by the black surface than if the asbestos were left white. Once again, though, the major factor is convection, not infrared radiation, so overall that 1"-thick layer of asbestos would be a disaster for cooling. Absent any technical information on the Camcoat web site there's no way to know whether the TLTD coating is better or worse than black paint.
 
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passenger0_0

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Just adding food for thought........
Radiant heat transfer is a little more complex than just colour. The highest theoretical emissivity of 1 may well come from a 'black body' but this has nothing to do with its colour. Snow (coloured white) has an emissivity of 0.98 which is higher than flat black paint. Heat needs to conduct to the surface before it is lost through convection and radiation mechanisms. Any coating adds thermal resistance and very likely negates any benefits of enhanced radiation. Furthermore, heat lost by radiation is driven by temperature difference raised to the power of 4. It only becomes significant when the surface is really hot - we often see electromagnetic radiation as 'glowing red' from steel surfaces as it moves into the visable wavelength. I don't want to upset Black Shadow owners so I'll sign off now. Cheers David
 
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