1G Pics of my alternator heat shield

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Late last summer I started working on a heat shield for the alternator in stock position. (1990 Talon)

At the moment, it fits and doesn’t seem to be causing any new problems. So here are pics and design notes for it.

Aluminum reflects somewhere around 90% of infrared radiation hitting it, and absorbs the rest. Some of the absorbed heat would be re-radiated from the side facing the alternator unless you put a layer of something there that is a bad conductor of heat.

Aluminum alloys like 5052 and 6061 are fairly strong and are really easy to work with.

So:

I built it from .063” thick aluminum sheet (5052 with H32 temper) and coated the side facing the alternator with red silicone RTV high temperature sealant/adhesive made by ASI Sealants. I have .008” thick fiberglass cloth embedded in the silicone sealant.

The silicone/fiberglass is a bad conductor of heat, and it is also a good electrical insulator. That is important because the electrical terminals on the back of the alternator are very close. It is very tough, and it adheres really well to bare aluminum (which I did a bunch of testing on before deciding to use this stuff).

 

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I spent a lot of time mocking it up with the thick paper that file folders are made from. This paper will hold a folded angle fairly close. Then you can flatten it back out to use as a flat pattern for cutting the aluminum sheet to shape. Here’s a scan of my final flat pattern, the one that worked.

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I cut the aluminum to shape, then started dialing in the bend angles with a lot of test fitting to the car. Back and forth a couple times between the car and a large bench vise.
I don’t have a proper bending press.
To make the bends, I put the aluminum in a large bench vise and put a wood 2x4 endwise against the aluminum and hit the the other end of the 2x4 with a hammer.

Then I squirted red silicone all over the side of it that faces the alternator, rolled that out flat with a dead AA battery, and pushed the fiberglass cloth into it.

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[motomattx]

Good thinking! carbon fiber would also work well I would think.

 

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The upper part of the shield is made separately and is actually a heat shield for the PS pump. It bolts to the alternator heat shield with two 6mm bolts/nuts.

The whole assembly is attached to the engine with one 10mm bolt. It is the bolt that goes through the PS pump bracket and screws into the PS pump, on the inboard side of the pump.

Being attached by only one bolt, it needed something to keep it from rotating, so there is a trick in the upper part of the shield that stops the rotation.

The trick is the exact location of the saw kerf which is labeled in the flat pattern for the upper shield. The part above that kerf gets bent almost 90 degrees to become like a flange that bottoms out against the PS pump bracket. I made the saw kerf a little low so I could file it back, bit by bit, to dial in the rotational position of the alternator shield, a few thousandths at a time.

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[We're on Boost]

Good thinking! carbon fiber would also work well I would think.

Probably so!
I've never built anything from carbon fiber but would like to sometime.

 

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The single 10mm bolt goes through both shields, where they overlap each other. The whole thing can be taken in or out of the car by removing just the one 10mm bolt.
In these 2 pictures you can see pretty well the bent part above the saw kerf and how the bottom edge of that would come down against the PS bracket.

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[We're on Boost]

Here's a couple pics of it on the car.
You can see things are pretty close down there.
The bent flap at the bottom is to clear the O2 sensor.
The red wrap you see on the wires there is self-fusing silicone tape (X-Treme Tape TPE-XZLBRD).
I had never used this tape before. It's pretty incredible how when you press 2 pieces of it together for a few seconds they like meld into each other. Totally alien.

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[ist dwa]

I built one of these for my cars years ago, haven't replaced an alternator since. I was going through one every 5K miles up to that point.

 

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I built one of these for my cars years ago, haven't replaced an alternator since. I was going through one every 5K miles up to that point.

Well that's good to hear. The alternator that I put on with this heat shield is the 4th alternator I've had on this car, if you count the one that was on the car when I bought it in ~2004.
I haven't been in hot weather yet with the shield and the new alternator. If it makes it through this summer, that will be a good start.

I still don't have a voltmeter on the dashboard but I bought one and it's sitting around here waiting for me to work up an install for it.
What I've been doing is, every time I drive this thing, I first look at the CTEK battery maintainer, looking for a green light on it, then disconnect it and check battery voltage with a multimeter right on the battery terminals. Then start the engine, warm up for a minute or 2, check battery voltage with engine running expecting to see about 14.3 volts. Then I take the multimeter with me on the drive. When I get back, check the battery voltage again before shutting engine off expecting about 14.3 volts again. Then shut off, and hook the CTEK back up.

The 14.3 volts is not a magic number except that I want to watch that number to see if it changes over time. I imagine that initially it depends on the voltage set point of the alternator, and the load on it in amps, and the engine RPM. My alternator never gets a break because there are 3 fans running all the time, hot or cold. That's about 27 amps going just to fans. Two of those fans (pusher and puller) are on the left side of the radiator, so there should be a lot of airflow where the alternator is.

 

[psychbiker1966]

Thanks for your write up. I just fabbed up my heat shield and your method was very helpful. The measurements didn’t work for me but I used cardboard and cut a thin aluminum sheet that matched. I found a bolt hole on the bottom behind my oil filter and bought a very short bolt that I could sneak back there without having to remove the oil filter. Up top I found another bolt hole and then I cut 2 pieces of aluminum drilled holes and riveted the pieces together. The aluminum is very thin so I could bend it by hand. I then used the same high temp red RTV on the side by the alternator and cut strips to fit And covered the inside completely. It almost looks like carbon fiber now! I was in a hurry so I didn’t take pics of the final piece off the car but I did take pics of it in place. Gonna let it dry overnight and hopefully she will be sturdy and do the job. Lastly I added a couple strips of DEI heat wrap material by the flange because it’s very close to my aluminum. See pics ...

 

[We're on Boost]

Thanks for your write up. I just fabbed up my heat shield and your method was very helpful.

Cool, and thanks for the pics!
Yeah, test fitting with paper or cardboard templates is pretty much a must before cutting metal.
I'm keeping an eye on mine to see if it ever moves or takes damage of any kind.
Since mine is only attached by one bolt at the top, the lower end of it does flutter a little bit with engine vibration.
There could be metal fatigue eventually due to that. So I might look for some way to attach it also at the bottom, or to at least restrain the bottom of it in some way so there is less flutter. But for now I am just keeping an eye on it, and I like that it is so easy to remove and replace from above whenever I want to get it out of the way for whatever reason.

 

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When I made this thread I forgot to post this chart that shows reflectance vs wavelength for aluminum, gold, and silver. You can see they are all good. Infrared wavelengths are 750nm and longer, up to 1mm.

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Just lately, I noticed that the James Webb space telescope uses thin aluminum coatings on the heat shield:
"Webb deploys a tennis-court sized Sunshield made of five thin layers of Kapton E with aluminum and doped-silicon coatings to reflect the sun's heat back into space." https://webb.nasa.gov/content/about/innovations/coating.html
This is super important because Webb is an infrared telescope, so they have to block infrared pollution basically, from it with this shield.

There is a pretty good short summary I think about IR reflectance of materials in the Physics Stack Exchange that I copied out and saved back in 2018:
"Any electrically conductive material will block IR. The greater the conductivity, the greater the blocking. Aluminum foil will kill all IR, both high range and low. Most plastics allow IR to pass through. Glass will block low frequency IR (red hot), but allow the passage of high frequency (white hot) IR. Hence, the heat of the sun will easily pass into a greenhouse, but once this energy is converted into low frequency heat by the objects within that absorb it, then the resulting low frequency heat is trapped. Hence, the Greenhouse Effect."