Painted drums

[jframe]

What is the best, SAFEST way to remove paint from my aluminum front drums that some dimwit applied? Don't know how long its been on, but it doesn't look like a pro job.

[JZRIV]

Media blasting with glass beads Using lower gun pressure around 50 psi. Or  Plastic media using 60-70 psi. I always paint the drum with Krylon dull aluminum which creates a uniform natural appearance and protects from oxidizing. 

[NC1968Riviera]

9 hours ago, jframe said:

some dimwit applied

Wow, you are making me feel bad for having had my drums painted

[jframe]

13 minutes ago, NC68Riviera said:

Wow, you are making me feel bad for having had my drums painted

Well, dimwit because he really didn't think the job thru before he done it, lol.

[Pat Curran]

I know the factory sprayed some black on the drums for the 69's when you opted for the road wheels so there was no contrast with the natural aluminum showing through the spaces in the wheel.  Not sure about the other years though.

[RivNut]

I thought there was a consensus of opinion that painting the drums caused the aluminum to lose some of its heat dissipating qualities.

[jframe]

I thought the same thing. That's one reason I want to remove it.

[Pat Curran]

The black paint I was talking about didn't cover the entire drum.  It was spray painted on just in the areas where you would see the drum through the wheel.  It wasn't masked either.  It was just enough to cover the areas I mentioned.

[JZRIV]

27 minutes ago, RivNut said:

I thought there was a consensus of opinion that painting the drums caused the aluminum to lose some of its heat dissipating qualities.

We'll, I'd like to see the test data from that consensus!  I understand the non-scientific thinking though. A typical scant 50 micron coat of black spray paint won't make any difference. There are so many variables in this application it would be very difficult to even do scientific test.

[PWB]

2 hours ago, JZRIV said:

We'll, I'd like to see the test data from that consensus!  I understand the non-scientific thinking though. A typical scant 50 micron coat of black spray paint won't make any difference. There are so many variables in this application it would be very difficult to even do scientific test.

Lets see - 

 

We could paint one half the drum. Uniform heat from an oven.

Then IR thermal imaging thru the entire cooling phase.

 

LoL  fun!

 

 

 

Edited January 11, 2018 by PWB (see edit history)

[RivNut]

14 minutes ago, JZRIV said:

We'll, I'd like to see the test data from that consensus!  I understand the non-scientific thinking though. A typical scant 50 micron coat of black spray paint won't make any difference. There are so many variables in this application it would be very difficult to even do scientific test.

No test data, just what you'd call word of mouth from a bunch of guys over a long period of time.  It's probably just an urban myth.  But I do remember some discussion a long time ago on Chris Knowles forum about chrome plating the drums.  That was a definite no-no. 

 

Here's something I found that refers to painting electric motors and heat dissipation.  I think it could probably relate to aluminum drums as well.  It supports Pat's info on painting the drums black.    Gotta change my thinking. But I like the looks of the raw aluminum. 

 

I'm a "Mechatronics" Engineer with 35-years experience designing electric motors. In addition, I teach for the Small Motor Manufacturers Association (SMMA) Motor and Motion College and present two separate tutorials on thermal issues in electric motors, "Continuous, Dynamic, and Intermittent Thermal Operation in Electric Motors" and "How to Improve Electric Motor Power Efficiency".

Having conducted numerous thermal experiments on all types of motors (AC induction, Brushless DC, Brush DC, Stepper), I must disagree with this conclusion. Instead, I 100% agree with Mr. Watts that the paint (thermally conductive or not) used on a motor's exposed surface area does not significantly impact heat transfer between the motor and the surrounding ambient environment so long as the paint color is black and the paint thickness less than 0.5 mm thick. If the motor is painted white (often used in the food industry) then a 2-4% reduction in heat transfer occurs, compared to painting same motor black, since radiation is a component of the heat transfer but not as significant as conduction and convection with typical 130-155° C motor temperatures plus the normally occurring ambient air. However, if the motor has been over-painted so many times that paint thickness becomes greater than 1 mm thick then I can understand that low thermal conductivity paint could inhibit heat transfer to the ambient.

Based on actual experiment, what does significantly impact the heat transfer from within the motor is the material used for its housing and the best material is Aluminum since it has higher thermal conductivity compared to a steel housing that's typically used for AC induction motors. Adding cooling fins to the housing plus painting it black is the best possible design. In addition, forcing high velocity cooling air across the housing's exposed surface area provides better heat transfer due to the "wind chill" affect.

 

[PWB]

Wow 

I did not know radiant heat energy (other than light energy) could transfer differently based on color absorption. Could the chemical constituent of pigment alone affect?

Love the science.

Check out the difference between the thermal conductivity of Steel and Aluminum:

 

Steel 50.2  (Assuming carbon steel)

AL 205.0

 

Holy Toledo! No wonder I burnt my hands on that dang thang.

 

Source: http://hyperphysics.phy-astr.gsu.edu/hbase/Tables/thrcn.html

 

 

[petelempert]

I'm guilty. I put newer road wheels on my 63 and the unpainted drums looked like tin pie plates peeking out. It was killing me. Looked like a mistake. Out came the Rustoleum satin black. No regrets. No heat issue. It's not like I'm heating up the drums running on the Nurburgring or down hill on Pikes Peak. PRL
 

[RivNut]

For anyone considering painting their drums black, you might consider using the same paint used to paint radiators.

Edited January 11, 2018 by RivNut (see edit history)

[retiredmechanic74]

....I use the same paint that is used on BBQ Grills. It can withstand 2000 degrees of heat and won't interfere with the cooling down process. 

[60FlatTop]

I guess that is a pretty thorough look at the aluminum front drums and technical down to half a millimeter. If you happen to be working around the car and get to making the rear drums pretty here is a tip that you can use a yardstick for.

 

When I went through my '64 Riviera around 1994 I found a beautiful pair of rear drums. To make it perfect I glass beaded them, Lightly skinned the braking surface, gave them a coat of red oxide primer, and a finish of satin black polyurethane. Absolute jewelry! Then I put them on the car... almost. They were small axle diameter, later drums. Oh, they are on the car today. After all that work they had to be. We set them up in a lathe and hogged out the center hole and shot some flat black on the bare machining.

 

Writing that is creating some shadows of other shenanigans that happened on that lathe, handy tools.

Bernie

[Pat Curran]

1 hour ago, RivNut said:

For anyone considering painting their drums black, you might consider using the same paint used to paint radiators.

The paint on my drums from the factory was the same paint used on the wheel webbing.

[jframe]

Maybe the dimwit was the guy at the factory who applied mine, lol. I just think the natural aluminum is a neat look.

[KongaMan]

I took a wire brush to mine.  They look great.

[PWB]

Which metal wire brush? Dissimilar corrosion fear. Beware 

[KongaMan]

Steel wheel on a drill.  I've had the car 40 years; they'd never been cleaned before.   In any event, they're only brake drums, and they're hidden behind the wheels.   I'm not going to spend too much time detailing them.