[jakeru]

Thanks for the tips, I think I will do just that (practice & attempt the "keyhole" filling method, for more complete penetration). The other idea I had was, experimenting with some heat sink compound I've got (clay / putty like like stuff) - I was thinking I might try forming it into a rope, and "smooshing" that into the backside of the weld joint before welding, to see if it might aid with more complete penetration.

Oh yeah, I also thought about using cut strips of the parent metal for filler rod; I think that would be quite strong and ductile, but I have a feeling it would be overkill.

[jakeru]

Update: The last piece of sheet metal on this end tank welded on nicely. I'll be ready to weld the round tubing piece on as soon as I get the bead formed for the rubber hose connection.

[jakeru]

I've completed the first end tank now. Got the bead formed on the second round tube, and welded that to the rest of the intercooler.

I have been able to fuse weld (no filler) the back side of many welds that are tricky to access, but possible, with the TIG torch; such as pictured below, through the round opening. I can do this without necessarily having full vision of the puddle; I just do a little bit of metal melting (or attempted melting) at a time, pulling the torch out so I can check my work in between torch blasts. The angle-ground TIG cup is proving handy for allowing me to reach narrow angle surfaces I would otherwise not be able to get adequate inert gas shielding.

[speed g40]

hhmmmmm,why are you making the ic with 2 entries?
is your car equiped with g-charger and turbocharger?

[jakeru]

It's a dual pass intercooler, with the inlet and outlet both sharing the same end tank. At the other end tank, the air makes a "U-turn". Here's a photo of what it looked like before I pulled the plastic off. (epoxied on aluminum tubing connection is where the failure occurred.)

[speed g40]

aahhhh. ok thanks.
keep up the good work

[jakeru]

I got the second end tank done! While the design of this one was a simple three pieces of sheet, I challenged myself by trying smoothly rounding over the edges where the sheets mate together. (I made a homemade "T-dolly" for this, by grinding a hemispherical shape into the end of a steel rod and chucking that into a vice.)

I welded this end tank inside&out and also "smeared" the inside weld beads (to make it easier for air to flow), before welding it to the core.

[Rugar]

What machine are you using?

[jakeru]

I'm using an Everlast "Super200P"

[ogorir]

that's lookin' really nice, the welds on the other tank are purdy.

[jakeru]

Thanks ogorir! I feel like I've definitely gotten better at "TIG sheet aluminum" since I started this project, and I really appreciate your helpful advice on the techniques also.

I welded on the first two of three mounting flanges to the intercooler today. Its looking like a totally perfect fit in the car (as it should, given this level of customization.) I went until my argon tank blew its last breath, with just one more mounting bracket to go. I can almost hear the car running again.

[jakeru]

The intercooler is all done now. I was really proud of a couple of beads I put down today welding on that last mounting bracket. I made them all in one shot, with no stops. I've finally got my filler rod feeding hand working.

[TT350]

Could you do a little show and tell on how you made the round to square transitions.

[jakeru]

Sure -

First I used a tubing expander tool (see picture below) patially inserted into the tubing, to flare out the end. These can be had for cheap (I recall spending about $8) from harbor freight. They come in three different sizes.
http://www.harborfreight.com/catalogsea ... q=expander

I've learned from experience playing around with this tool that if you don't insert it all the way, it will flare the tubing out into a cone shape, rather than evenly expanding it. So I used that behavior to my advantage as I wanted to flare out the tubing as a first step of making it adapt evenly from round to square.

Before you make the flare, you should plan how much to flare the tubing to (the diameter of the flare) and also how long the taper should be (how long the round to square transition will take.) To calculate the diameter of the flare, I figured the circumference of the flared out end I wanted, by adding up all the edges of the square or rectangle you want to adapt to. So in my case, a square with edges having 2"x2"x2"x2" lengths gave me a target circumference of 8", which implies that it could be formed (without any shrinking or stretching) from a circle having exactly 2.55" diameter (Using the ol' trigonometry formula: Circumference = PIE * Diameter). When you are making the flare, periodically check the flare diameter and stop the flaring operation when you reach it.

After you have made the round flare, I just pinched the square shape into it with a vice. It will help to mark the center of the four faces on the tubing, or the edges (where the faces are going to meet) so you can work it evenly on the vice. You can also reset the expander tool into a cylindrical shape of the minimum dimension and leave that inserted in tubing if you want, to keep the vice from pinching the tubing smaller than that diameter. You can also use pliers to make small adjustments, although I found I was able to accomplish it pretty much all on the vice. And don't try and form the flats all in one vice pinch, but instead make them a little bit at a time and work them in different spots and also doing all four edges about evenly on the vice. Take your time. I managed to get a good result on my first attempt. The malleable grade of aluminum I used for these pieces (I don't know the grade for sure, but if I had to guess I'd say it was 3003) probably helped.

Finally, I made the bead with the tool shown pictured below, which I made out of a pair of vice grips. No need for an expensive bead rolling tool. I just go a little bit at a time around the tubing and progressively make the bead deeper until I am satisfied with it. However for this project I also decided to try adding a weld bead around the inside of the formed bead part, for smoother airflow. I cleaned it up with a cartridge roll on a die grinder afterwards to smooth out the welded bead (you can barely see it.) To idea was to make minimal turbulence for airflow. A nice unexpected beneift of the weld bead inside the rolled bead was that it helped stiffen the open end of the tubing.

[jakeru]

(above post continued...) and below is a picture of the end result, after being welded on.

[kevn]

Nice intercooler design Ive thought of doing that style in the past.

What car are you using it on?

I made my end tanks on My Talon. I can post some finished pics if youd like to see what I did with mine.
I used a lincoln squarewave 175 that we have at work to do it. I just bought a powermaster 256 yesterday so Im excited to have a tig with the bells and whistles to try out.

I was under the assumption that most fabricated end tanks were made with 1/8 aluminum.

I would have thought 16-14g would be too thin and burst under pressure. Im not expert so Im not saying Im right its just what I figured. I dont know how much pressure you run But I run over 25psi.


You did a nice job on your Ic and I hope you do alot more in the future Its nice to see thought you are putting into it.

[jakeru]

Hey Kevn thanks for the compliment! I'd love to see other intercooler / end tank designs, especially any that are innovative.

This cooler is for a VW in an autocross racing application where the class does not have a minimum weight, and the boost pressure is in the upper 20's psi range. Weight savings in this case is pretty important (pounds or even ounces here and there can add up!), as are good performance characteristics of the intercooler (good cooling efficiency, and minimal pressure drop.)

You may be right that most sheet metal fabricated end tanks people make are out of 1/8" thick aluminum, but that may be a good idea for designs incorporating large, flat surfaces that are subjected to pressure. The flat surfaces I believe, (kind of like the base of an oiling can), flex a lot more and have higher resulting stress concentrations from the bending forces as a result, basically because they are less rigid than other shapes from holding back the boost pressure. Examples of shapes that would hold the pressure back better and more "rigidly" would be ones incorporating simple bends (IE: cylindrical or conical shapes) or even compound bends (spherical or balloon-like shapes). The simple bends take more work to form than just cutting flat pieces, but less effort than hammering out or pressing complex curved shapes. Incorporating bent shapes into the design has another benefit, of being able to better shape the air flow through the end tank, for smoother more laminar flow (resulting in less pressure drop through the intercooler.)

If you want to look at what types of fabricated shapes hold back pressure the best, take a look at pressure vessels. Notice their use of simple bends (cylinders) and compound bends (spherical shapes):
http://en.wikipedia.org/wiki/Pressure_vessel

(For intercooler end tanks, we'll of course need to use shapes that have fairly large openings for air to flow in and out.)

There is more to think about with an intercooler end tank than just holding back boost pressure however. Engine vibrations or any torquing motions of the engine moving in the mounts can push and pull on boost tubes and the intercooler (and boost tubing system) will need to hold up to whatever those motions are. Also rapid, uneven changes in temperatures might also make the material expand and contract unevenly, adding to the material's stress.

Finally, you've got to select a thickness that you are able to work with. 16 gauge was just about as thick as I'd want to bend by hand on something like this, at least with my simple tools (vice, some pipe/rod, hands.) Dinging the compound radiused edges would have also been a lot harder and maybe not worked if the material were much thicker. Also thicker materials might be easier for most folks to weld than thinner materials. I was definitely on the learning curve with welding the 16 gauge aluminum here. 16 gauge aluminum is also on the thick end of what I can comfortably trim with tin snips.

[jakeru]

Here is my completed intercooler, taken before installation in the car. I went over it with a blue 3" scotch brite disc, which cleaned up the uneven oxide finish from old and new materials, and removed the random odd burned-in sharpie and masking tape residue. I didn't go crazy doing fine grit polishing, I just went for a somewhat uniform "brushed grain" look.

Also the cinderella intercooler fairy made her appearance in the photo shoot...