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Painting Your Head.

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fetor56

Guest
Painting Your Engine and Cooling.

I havn't seen any hard scientific research on this subject but the general consensus of opinion on motorbike forums is that it doesn't help with cooling if u paint your lower engine & head & barrel fins.
It doesn't particularly hurt either so if u wanna enhance the look of your bike then go ahead,just make sure it's absolutely clean first and use a good quality heat resistant paint.
 
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L

Large Filipino

Guest
OH MAN! I thought you shaved your head and like did a Patriots or Giants thing on it.

I want to add too that color makes a difference. They proved it on Mythbusters. White absorbs 5 degrees less heat than black.
 
A

andyinchville1

Guest
Interesting question.....as another method of coloring engine parts, I wonder how anodizing would work out on an engine (both in terms of durability (I think it would be superior) and heat rejection (not sure about this one)....You might be able to color the whole head and cylinder and maybe through use the piston would wear the color coat off the cylinder wall (hopefully without damage)...Most of the exterior of the engine is aluminum anyways so it could really be colorful!

Andrew
 
S

SirJakesus

Guest
Interesting question.....as another method of coloring engine parts, I wonder how anodizing would work out on an engine (both in terms of durability (I think it would be superior) and heat rejection (not sure about this one)....You might be able to color the whole head and cylinder and maybe through use the piston would wear the color coat off the cylinder wall (hopefully without damage)...Most of the exterior of the engine is aluminum anyways so it could really be colorful!

Andrew
Anodizing works really well on aluminum. Just look at paintball guns. They get really cold and get the **** beaten out of them and the anodized layer stays strong. I think the metal is actually chemically bonded to the aluminum so heat shouldn't be an issue especially if certain types of high temp paint can resist bubbling or peeling. Then again you never know until you try, sounds expensive though for a chinese engine. I'd much prefer the sand n' paint method.
 

cooltoy

Member
Joined
Jan 6, 2008
Messages
341
I was a painter/ auto body guy and would say that powdercoating would be the best. The parts are put into an oven to dry at a temp of about 400.That is how it turns from powder to a paint coating,it melts and then bakes to a rock-like coating.
Also , Any paint should be a "flat" paint. "High solids" in a gloss paint would tend to "seal the heat in" That is why I would never use a clear-coat.
By the way...lol....you would mask off the inside of the cyl. and not let the rings wear it off.I'd bet they would break.
 
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Scottm

Guest
The auto parts store (Autozone) sells engine paint, but I'm sure the colors are limited to grey, black and orange. All my products I sell are powdercoated, I'd love to have my engine done in a dark blue.
 

loquin

Active Member
Joined
Jan 11, 2008
Messages
2,214
There are three sources of heat transfer from the engine piston/head area - conduction, convection, and radiation.

The simple physics primer on the subject is as follows:

  1. Conduction: Conduction is the direct transfer of heat from one material, in contact with another. Essentially, heat can be considered to be the 'vibration' of molecules in the material. The greater the molecular vibration, the higher the temperature. If all molecular motion stops, you have zero heat present. The temperature where molecular motion essentially stops is called "Absolute Zero." (Absolute zero is defined as precisely 0 K on the Kelvin scale, which is an absolute temperature scale, –273.15 °C on the Celsius scale, and −459.67°F on the Fahrenheit.) If a hot engine cylinder is in physical contact with a cooler engine body, some of the molecular vibration gets passed from the cylinder to the body. Likewise, some of this heat gets passed to the mounting bolts and frame. Unless you have a large surface area in contact, not a lot of heat will be transferred, as the heat transfer is proportional to the area in contact, and the temperature difference between the hot and cold objects.
  2. Convection: Convection is actually a specific form of conduction, where the heat is transferred from a hot object to the surrounding air. THIS is the primary method of heat transfer between the engine and the surrounding air in an "air cooled" engine. This is also why an air-cooled engine will have large fins on the cylinder and head. Since the amount of heat transferred by convection depends upon surface area and heat difference between engine and air, the fins act to greatly increase the surface area in contact with air. Now, if the air stood still, the air in direct contact with the engine would heat up until it approached the heat of the engine. But, since heat transfer also depends upon the difference in heat, eventually, no more heat could be transferred. Two effects happen here, though. First, hot air rises. As it does it lifts itself away from the hot engine, allowing cooler air to replace it. Second, many air cooled engines have a blower of some sort on the flywheel, which sucks in cooler surrounding air and forces it through the cooling fins. By forcing air through the fins, you keep the temperature difference between engine and air to a maximum, and maintain the highest heat transfer. On engines that do not use a fan, as the engine moves through the air, it moves into regions with cooler air, again keeping the temperature difference at a maximum.
  3. Radiation: Finally, the third area of heat transfer is direct radiation. Heat is released as a form of electromagnetic radiation, in a frequency range "below" the red portion of the visible spectrum. This frequency range is also called "Infrared" Night vision equipment converts the infrared (or heat) portion of the spectrum to the visible portion of the spectrum. The amount of heat released by radiation depends upon the area, as well as the reflectivity of the surface. A mirrored surface reflects most of the light which strikes it back. Likewise, it reflects most of the light hitting it from the BACK away also. The lighter the color of the surface, the greater the reflectivity of light and heat. In the other direction, the darker the surface, the greater the amount of heat absorbed or emitted. A black object DOES emit more heat than a light (chrome) surface. However, the amount of heat radiated is much less than the amount transferred by air convection. A chromed engine will definitely run hotter than an identical engine that is anodized or painted black. But, this probably won't be by a lot - maybe 5 degrees or so, as a guess. One of the reasons for this is that the greater surface area of the fins don't help too much with radiation, as a lot of the of the heat radiated by a fin will be reabsorbed by its adjacent fin...
In conclusion, unless the engine is already running hot, it probably won't hurt it to chrome plate it, or paint it a light color. On the other hand, it WILL help to cool an engine to paint it a flat dark or black color. (A flat paint has more surface area than a shiny surface.) But, not by a lot. (However, also note that a layer of paint WILL add a tiny layer of insulation to the engine, which will act to reduce the convection by a bit...) Which is why anodizing is usually used for electronic heat sinks, as the color of the surface layer of the aluminum is altered.
 
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cooltoy

Member
Joined
Jan 6, 2008
Messages
341
I used to powdercoat all the parts for those 6 wheeled military "tanks" and I know that if a person would have walked in off the street asking for us to paint a couple of parts, we would have done it for a very fair price. The only thing is that that would only work if a person was willing to get the colour that we were using. Way too much work involved in changing colours and everything involved. It takes one minute to coat the part, but an hour just to get things set up,that is where the cost comes into play.Powder comes in all colours and textures and I would phone around to all the paint shops (not auto body shops) and ask about it. When looking in phone book try using the word "coatings", not just "paint". I would bet that there are ways to do this yourself at home and this could be found on the net. As far as I can tell , the powdercoat gun allows you to spread the powder out evenly, along with a "charge" that draws the powder towards the part.It's the oven that wets the paint, allowing it to flow out and then dry.I can picture a battery, a handful of powder and a good blow from your mouth.The negative would go to the part, I'm just not sure where the pos. would go.lol
 

pedal pusher

New Member
Joined
Feb 2, 2008
Messages
16
A method of making alum. look vintage is to use spray graphite. use it like spay paint about a foot away. They use this trick in restos on ol road race cars. AC Cobras,Jags ect,ect... Thats if your into the used for along time look like I am. Not ragged, Just old. I dont like this look on ladys though, just aluminum.
 

cooltoy

Member
Joined
Jan 6, 2008
Messages
341
So will the graphite dry to the touch? will the heat bother it? Interesting!
I went and looked up powder coating (DIY) and you can buy a kit/gun for just over a hundred bucks in the USA. Not bad if you think of what you can do with it.
Anyways all the salt has mine looking really sad and I can't wait for spring. I've put an ad in my local paper asking for that 50 year old bike that is in the old barn-Wish me luck!
 
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