what is correct color of black for norton 850 barrells

Aside from being resistant to high temperature, the manufacturers data on the link provided by rvich provides no information as to how the paint "heat dissipates". It is likely a good high temp. paint...just use black on an air cooled engine. I am skeptical that their black paint radiates significantly more heat than any other black.

The physics of the matter is that radiation heat transfer is maximized by the color black, flat being better than gloss, and a black surface will radiate about 3 times more heat than a silver or white surface.

Convective heat transfer is enhanced by a rough fin surface.

Conductive heat transfer is reduced by any additional layer on the surface of a fin, thus minimize the paint thickness.

All three modes of heat transfer determine the overall cooling....reduce the heat transfer of any one mode, and the engine WILL run hotter.....hotter does not necessarily mean it will overheat.....that is the physics.

The Norton has a good tolerance against "heat stroke" as Hobot puts it. I posted above that I seized a piston...yes when the fins were white and with some salt crust, and air temp was in the 80's. The same machine crossed the Mojave desert earlier in my trip when the air temp was in excess of 114 F and took it in stride. The white color reduced the tolerance to the critical point.

I am not arguing here with anyone. I just want all to understand how the physics applies to your mods of the machine.

If you like gloss black, go for it....the reduction in radiation heat transfer may be 3 to 5 % over flat black ( these values must be experimentally determined), and that is not enough to obsess about.

As for other mods such as high build or fin polishing, silver, or gold paint, etc, each such mod reduces the tolerance to "heat stroke", so proceed with caution, giving proper attention to other go fast mods that may increase engine temperature.

Slick

Its a sliding scale of heat production dumping by fuel amounts burning speed with ambient temps and humidity and wind direction. Salt and thick dust layer covers up the radiant and convective heat flows. Check these out for extra heat dump options.

Weapons coatings rattle can. I used GunKote on Peel.
https://www.google.com/#q=firearm+coating+GunKote+
https://www.google.com/#q=firearm+coati ... 1436545876


This method is known to be fragil to maintain with razor dangerous saw teeth to handle but claimed 30% more heat dump.
http://www.hotbikeweb.com/diamond-heads ... -your-bike

Re: diamond cut fins and 30% greater heat transfer:

In my professional opinion - this is snake oil.

The edges of a fin contributes so little to overall heat transfer, engineers do not bother to account for it. Convective and radiative heat transfer is a function of both surface area and temperature. The fin edges are of minimal area compared to the overall surface, and the temperature at the edges is the least over the fin surface, thus very little can be gained. If the fin edge temperature in a given design was sufficiently high to warrant attention, then the engineer would better extend the fin length....extending the length by twice the edge thickness would gain over 4 times the transfer that can be obtained at the edge. Moreover, this cutting is actually removing fin surface area!!

Regarding gunKote: A viable alternative to paint....but physics limits the emissivity of a black body to a value of 1.0. No paint or coating can exceed this value. A metal surface treatment such as anodizing, plating or chemical coloring that duplicated deep black can achieve similar values of emissivity as paint, but have the added advantage of increased conductive heat transfer owing to a molecular level thickness, rather than the several mils of paint. The claim that this coating does not attract dust is valid, but a proper wash at times will obviate that.

Slick

Yeah I'm pretty much up on all that a long time but I see a lot of diamond edge fins on the HD's out here so showed it here d/t their claims as heat helper to help sell it. Take too much out with holes lowers surface area more than helps flow dump heat unless the holes are about same dia. as fin thickness. Some black surfaces definitely radiate better but Gunkote type 'paints' main help is its very thin and several coats should be put on barrels but still will not hide any the texture imperfections such as paint or powder will. Ms Peel whole engine accidently got black coated so thinking to file off head fins to leave the neat shape highlights and maybe silver paint the valleys of the barrel to help it show up other than dark lump.