Homemade Cool Suit System

It looks like Zack Steinkamp’s specthismiata.com is no longer online. A local racer contacted me about some of the parts numbers that I provided to the cooler component. I’ve grabbed the original contents from a cache and am placing them here for posterity. All credit goes to @thenobot.

Homemade Cool Shirt System

Usually after about 20 minutes in the car on a hot day, I start making mistakes. Nothing horrible, but I know that it’s fatigue setting in that makes my brain work less well. Driving a Miata is a physical experience, but less physical than doing something really physical like playing basketball. So the fatigue isn’t the same kind of fatigue as what you’d feel after running 5 miles, instead it’s a mental fatigue that is mostly due to overheating.

With a race at Thunderhill in July approaching, Derek and I decided to do something about the heat. A typical summer afternoon in Willows can be 105 degrees or more, so of any race this season, that one was likely to be the hottest.

We looked at the existing cool shirt systems out there. All look very well made and definitely have the kinks worked out. However, there were two big issues with them from my perspective: they’re expensive, and they look like they’d be easy to make. Time for some D.I.Y.!

The overarching concept with the shirt is that cold water is circulated in a lot of tubes attached to the shirt. A small cooler serves to contain icewater. The water is forced out the cooler using a bilge pump, through tubing into the shirt where it pulls heat out of your torso, flows out of the shirt, and is dumped back into the cooler where it mixes again with the icewater. An important part of the system is a way to quickly connect and disconnect the shirt from the cooler — this is accomplished with dry-break fittings normally used in medical and industrial applications.

Parts

8+ Quart Cooler – Make sure the one you pick will fit where you want to mount it. Measure the available space, and get the biggest cooler that will fit. We got ours from Target for $10 or so. In hindsight, we TOTALLY should have gone with this one, since it looks to have a WAY better seal and the one we got leaks unless we cover the whole top in racer’s tape.

Pump – I got a 600 GPH Bilge Pump from West Marine for $25. The ones at OSH take AC power so those were out. The one I bought takes 12VDC power, so wiring it up to the car is easy.

To get the water in and out of the cooler, we used 1/2″ diameter, 3″ long nipples (pipe threaded on both ends). We may have been able to use 2″ long ones.

Fittings And Such – We found all of this in the plumbing aisle at the local hardware store (NOT HOME DEPOT).

- (1) 3/4″ female to 1/2″ female adapter

- (2) 1/2″ diameter, 3″ long nipples (pipe threaded on both ends). We may have gotten away with 2″ long ones.

- (4) Thin nuts, 1/2″ coarse thread. The nuts need to be able to thread onto the nipples.

- (16) washers that can slip over the nipples.

- (2) 1/2″ female to 1/4″ compression fittings with inserts to fit in 0.170″ ID tubing

- Roll of teflon tape

Tubing

- 50 feet of 1/4″ OD vinyl tubing. This is what goes in the shirt.

- 10 feet of 1/4″ OD polyethylene tubing. Typically used as the cold water supply for refrigerators. This is what goes from the cooler to the shirt. It needs to be different tubing because you use a compression fitting on the cooler end of the tubing.

- 5 feet of foam pipe insulation. 1/2″ inside diameter works fine.

Quick Disconnects

- (2) Sockets – McMaster-Carr part number 5923K31 – $8 each or so

- (2) Inserts – McMaster-Carr part number 5923K61 – $7 each or so

Optionally, get an extra insert so that you can connect it to the ouput line from the cooler and run the pump to drain the water from cooler without throwing away ice if you’re going to be running closely spaced track sessions.

From Brian…

Btw, I ordered the real FAST Carbon-X shirt so if you ever want to build the cooler again, you need to use the PLC line of couplers (metal thumb clasp) rather than APC line (plastic thumb clasp). The male end on the FAST shirts requires the thin metal connection. Luckily McMaster-Carr sells them also. It’s McMaster-Carr #5012K662 for $9.93/ea. The general parts number btw is Colder P/N #PLCD13004

Mounting – keeping the cooler in position

- (3) pieces of 90-degree aluminum, 1.5″ on a side, 6″ long

- (6) 1/4″ Bolts and nylock nuts

- Nylon strap with ratcheting tightening mechanism

Shirt – Get a TIGHT shirt. If you wear a Large, get a medium. It needs to be skin tight.

Fabric – An old cotton pillowcase is great source of the fabric. You sew the fabric onto the shirt to hold the tubing in place. Details to follow.

Silicone – A small tube of GE Silicone II works well.

Putting it Together

Cooler

Start by setting the pump in the cooler. Put the outlet against one of the sides of the cooler and mark its location. Find where the center of that circle is and drill a hole just big enough for the nipple to slip through. Drill another hole the same size toward the top of the cooler for the return line.

Spin one of the thin nuts onto one end of one of the nipples. Then, wrap that end with teflon tape and thread the 3/4″ to 1/2″ adapter onto it. Tighten. Slip one of the washers onto the assembly so it rests against the nut and goop up the washer on the side facing away from the adapter with silicone. Slip it through the lower hole in the cooler from the inside to the outside. Put the pump in the cooler, put teflon tape on the 3/4″ threads on the pump, and thread the nipple and adapter assembly onto the pump. Tighten. Goop up the hole on the outside of the cooler, and stack up enough washers on the nipple so that you can tighten one of the nuts onto the nipple’s threads all the way to the bottom of the threads. The goal is to maximize the threads exposed on the nipple after you tighten the nut.

Slip the other nipple through the top hole in the cooler and goop up around it inside and out with silicone. Don’t be shy. Use one or more washers on the inside and out. Stack up the washers just enough so that you can tighten the nuts on the inside and out all the way down — so the nut is threaded as far down as the threads on the nipples go. I used all 16 washers for this.

So at this point you should have both nipples mounted firmly in the cooler, with the pump attached to the lower nipple. We used some short sheetmetal screws to attach the pump to the cooler floor. We drilled holes first and squeezed silicone into the holes so that the water would not leak through.

Drill a small hole through the side of the cooler near the top for the pump’s wires to pass through. Goop up around the hole with silicone so this is not a source for leaks.

Put teflon tape around the exposed threads on the nipples on the outside of the cooler and thread on the 1/2″ to 1/4″ compression fittings. Tighten. Cut the polyethylene hose into equal lengths, slip in the compression insert to the tubing, and attach to the compression fittings. Wait to install the dry-break connectors until you get everything together and know exactly how long you want the polyethylene tubing to be.

Shirt

Hopefully you or someone you know has a sewing machine and is not afraid to use it! The concept here is that you will need to sew two panels onto the shirt — one on the front and one on the back. You will only use vertical stitching on the panel since the tubing is going to thread up and down between the panel and shirt. The tubing enters the front of the shirt one one side, goes up and down through the “channels” in the panel, hooks around to the back, does the serpentine thing again, and ends up next to the inlet tubing.

Here are diagrams of the front and back. The grey shaded area is the panel you cut out of pillowcase or sheet material. The red lines are the stitching, and the blue lines are the clear vinyl tubes.

Start out by putting on the shirt (TIGHT!) and your HANS and sit in a chair. Mark on the shirt (water soluble markers from my daughter’s art box worked great) where the HANS lays. Also mark 3″ or so above where lap belt falls – that’ll be the bottom of the panels.

Cut out the panels. Center them on the shirt horizontally, and line them up with the line you drew that’s 3″ above the lap belt. Sew up the sides of the panels, then sew the channels that will guide the tubing. The channels should be 1.5″ wide or so — but make sure there is an even number of them so the tubing works out. I used 12 channels on both the front and back.

Thread the vinyl tubing through the shirt, being careful to not twist it in the shirt — it’s not a huge deal, but it will not lay flat if there are twists. Leave 5 feet or so of extra tubing at the beginning so you can have flexibility in where things go at the end. The tubing should enter and leave the shirt on the same side, e.g. in the front on the left, and out the back on the left.

Finish Up

Cool! So now put the shirt on and get in the car. Play with different positions of the tubing to figure out what’s best for you. Don’t forget that the shirt tubing needs to get outside your firesuit somehow — I put mine through the lower zipper opening. Some people will cut slits in their pockets, which seems like an OK idea too.

Once you figure out where everything should go, trim the tubing and hook up the dry-break fittings. Also figure out where you want the cooler to mount in the car. Use the aluminum and nuts and bolts to locate it. Figure out how to mount the nylon ratcheting strap to keep everything tight. I used eyebolts that were already there for the passenger side lap belt.

The nice thing about this mounting setup is that to remove the cooler to dump it, all you have to do is loosen the nylon strap and pull the cooler out. No tools required.

Wire up the pump, ideally with a fused and switched circuit. You don’t want it on all the time, and if the pump burns up you don’t want to take down the car’s electronics. I made a power distribution block and fuse block that sits in the center console and used a metal toggle switch for the pump circuit.

Aftermath

I was excited to give the system a try at the Thunderhill race. The forecast was for 95 degree temperatures. In the first practice session, I hooked up the system and powered it on at the 3-minute board on grid. To my dismay, I didn’t feel or see any flow in the system. After all this work, I was really bummed out. I resolved to work out the system after this practice session. So I went out not expecting anything. Well in Turn 6 on the first lap, the cold goodness started flowing! OH IT WAS SO NICE!

I’d fill the cooler with ice, then pour in just enough water to run the system. This gives maximum cooling for the longest time, since the warmer water returning from the shirt will start melting the ice right away. If it’s too cold, run less ice and more water in the cooler, though I don’t see this as a possibility unless it’s really cold outside. After the session, I’d either remove the cooler from the car and dump it, or attach an extra insert to the line coming from the pump and run it to pump out most of the water, add more ice, then go out again.

It worked great through the whole weekend. Through the entire 30 minute races I felt sharp, and not once did I wish for the end of the race. Where I’m usually totally beat at the end of a session or race, I was not fatigued a bit.

I’m sure the $400 systems would work better to some degree, but for 1/4 the cost and a day or so of work, I’m satisfied.

Editor’s note: I followed Zack’s advice and built the cooler but bought the real FAST Carbon-X shirt from SafeRacer. I wanted Carbon-X for the comfort and a second layer of fire protection but it also looked like it was sewn really well. In retrospect this was definitely the right move. The shirt fits well, the tubes are awesomely sewn on and there is no goofy bulging. The shirt is pricey but it’s the last piece actually touching your body so I feel the price was worth it. I used it just yesterday in 60F weather at Willow Springs and it was nice! Don’t underestimate how much heat you generate trying to hustle your car around.

Here is a photo of my parts laid out. I used a combination of PVC and brass fittings from Home Depot in conjunction with the cooler and pump I noted above. System has traveled across the country for 3 seasons and is still working like a champ.