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Aluminum Heat Diverter
https://slantsix.org/forum/viewtopic.php?t=46953		 Page 1 of 2
Author:  Danarchy [ Sat Nov 12, 2011 8:05 am ]
Post subject:  Aluminum Heat Diverter
What thickness of aluminum plate to use? Is thicker better?(not to effect linkage)
Any reason for not rounding off corners?
Future project before next Texas summer.-Thanks
Image
Thanks to:Aggressive Ted for the picture!
Author:  wjajr [ Sat Nov 12, 2011 3:35 pm ]
Post subject: 
I would think function would be the same with either square or rounded corners. However, when passing a cleaning rag over & under that heat shield, rounded corners maybe a bit more cleanaholic friendly on the hands.

Take it from an old damp rag dragging cleaning fool.
Bill

Or, how would Duisenberg have made such a thing.
Author:  DusterIdiot [ Sat Nov 12, 2011 3:44 pm ]
Post subject:  Aluminum
I'd use .032 or .040 aluminum sheet, .062 would be nicer but is not workable with tin snips.

-D.Idiot
Author:  Aggressive Ted [ Sat Nov 12, 2011 7:26 pm ]
Post subject: 
That one is .090 thick aluminum straight from the K&S rack found at your local hobby shop or hardware store. That was on my aluminum manifold and worked perfectly. I did by some 1/8th material this year to make several slightly bigger.......a little wider and longer for the cast iron manifold. The iron manifold doesn't cool down quite as fast and takes a hair longer to warm up so larger piece was needed.

Thickness is just a convenience and provides rigidity. I can slide my cut down Folgers plastic coffee can on it and under the bowl, pull the four bolts, change the jet, re-lube the gasket and have it running again in 3 minutes with out spilling a drop of gas.....

I didn't make it to be pretty, just functional and it was on the car in about 20 minutes. Adjusting the choke linkage and kick down linkage took longer........
The new ones I made extend out further over the front intake runner to keep it warmer. I also got rid of my 16" electric fan and went with two 9" fans which work far better. They seem to provide a better balance in terms of faster heat reduction when needed since they are closer to the tank and let me run a little warmer for better mileage. They also draw a lot less amperage. To force more air into the radiator I built a air dam which seems to be the ticket for pushing more air into the radiator. The front dam has bolt on strips, 4", 5" or 6" wide. The 6" really forces a lot of air up into the radiator at cruise. I run 4" in the winter and 6" in the summer. I have a few shots on the red link below my name.
Author:  olafla [ Sat Nov 12, 2011 10:05 pm ]
Post subject: 
I am in the process of making one myself, and from what I see in your photo, I would round the corners to avoid any finger cuts. I would also add a piece, at a slight upward angle toward the cylinder head to protect from the heat radiation from the visible parts of the exhaust manifold, and possibly extending a little under the hoses. Making sure that the fuel line is protected from direct heat radiation from below, is perhaps easier done with a protective hose sleeve.

One other thought that came in the process, is to polish the underside of the heat shield before final fitting. I know the polish won't last, but any small action adds up to a large one!

Olaf
Author:  Brussell [ Sat Nov 12, 2011 11:28 pm ]
Post subject: 
Just a thought, the idea is to deflect heat is that correct? If that's the case than you generally want a material that has a low conduction coefficient, the conduction coefficient is dependant on the temperature it'll be exposed to but I would think stainless steel would work better than aluminium, or if you could get a 'sheet' of exhaust wrap or better yet a ceramic. Whilst some of these are impractical could give an extra benefit?

http://en.wikipedia.org/wiki/Thermal_conductivity There is a table on that link of thermal conductivity.

Hopefully this is of some use.
Author:  Dart270 [ Sun Nov 13, 2011 4:42 am ]
Post subject: 
I don't think that is right, Brussell. I seem to remember doing a calculation on heat shields long ago and the best material has high thermal conduction. In this application, I'm not sure, since you have the shield partially attached to the carb. But if you have a shield simply suspended between the heat source and the absorber, I think you want highest thermal conduction. I'll try to look this up again.

Also, I'm pretty sure that if you are simply reflecting heat (not quite case here), then higher conduction is better than low.

Need to think more about this...

Lou
Author:  Jeb [ Sun Nov 13, 2011 5:20 am ]
Post subject: 
Here is what a factory heat shield looked like.

Image

Thread on the factory heatshield.

http://www.slantsix.org/forum/viewtopic ... heatshield
Author:  Sam Powell [ Sun Nov 13, 2011 6:14 am ]
Post subject: 
I cut 1/16" aluminum sheet with a hand held saber saw, (jig saw) and a metal cutting blade. Clean up the edges with a file, and you are good to go. I have a very elaborate heat shield on my slant, to keep the turbo heat away from the engine and fuel, all made from 1/16" cut with the jig saw.

Sam
Author:  Brussell [ Sun Nov 13, 2011 7:10 am ]
Post subject: 
Dart 270

I'll double check as well. I was thinking you would want to deflect the heat away from the heat shield so that all heat would be in the manifold instead of the shield. However I have no idea about air velocity under the bonnet which would change alot. And unlike you I haven't done any calculations or tests this is just an educated guess.

To deflect heat you want a material that doesn't readily absorb heat, which means to have a low thermal conduction coefficient.

"Heat transfer across materials of high thermal conductivity occurs at a faster rate than across materials of low thermal conductivity. Correspondingly materials of high thermal conductivity are widely used in heat sink applications and materials of low thermal conductivity are used as thermal insulation."

In this case you would want a material that has a lower coefficient than that of your manifold. Doing this would heat the manifold more efficiently.

But having thought about it more I can see pros and cons for having a material with a low or high coefficient, and depending on temperature and air velocity it might not even make much difference.
Author:  Aggressive Ted [ Sun Nov 13, 2011 9:37 am ]
Post subject: 
Quote:
Just a thought, the idea is to deflect heat is that correct?
That is partially true, and yes the bottom side is polished. The other point is that the aluminum acts like a heat sink during heat soak and wicks away heat from the carb and keeps it from getting too hot and vapor locking or boiling. The electric fan's cool the aluminum very effectively after shut off. The carb only gets luke warm. Hot starts are instant!

To summarize, yes it deflects heat and helps keep the manifold warm while the engine is running but it also acts like a heat sink for a cooler carb after shut off.

As you know most heat sinks are made from aluminum for their cooling properties.
Author:  Brussell [ Sun Nov 13, 2011 10:35 am ]
Post subject: 
Thanks I get it now. So it's about finding that sweet temperature spot to avoid vapor lock or boiling as you said.
Author:  WagonsRcool [ Sun Nov 13, 2011 3:50 pm ]
Post subject: 
Aluminum is also cheap, readily available, & easy to work with- a three time winner in my book.
Author:  Danarchy [ Sun Nov 13, 2011 5:19 pm ]
Post subject: 
Years ago I had a DKW (3 cylinder 2-Stroke) car that had a unique carb. sheild, it was made out of plastic (or maybe Bake-o-lite?) I don't think it was designed for heat problems, but maybe cold problems. The car also had a grill cover that worked like a horizontal roman shade from a pull handle under the dash.
Image
Author:  nuttyprof [ Sun Nov 13, 2011 5:54 pm ]
Post subject: 
NE. uses aluminum license plates with no embossing. Would one of those work good for this?
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