UPDATE 10/31/2009: I finished remaking my pants and I think I've come up with a better stitching pattern. I'll leave the pictures of the old style just in case someone wants to do it that way. I'm also updating the parts section.
This is for those motorcycle riders, who like me, don't know when to quit and can't afford store bought heated clothing. I'll show you how I made my pants, but the same can be done for a jacket or whatever else you can think of. I made these last year during the middle of a road trip to battle the bitter cold, and it worked wonderfully. This is how I did it, I'll put some links to other ways on the last step. Also, I took the pictures while taking my completed pants apart (I think I can make them better), so there are not many action shots. Sorry and enjoy the instructable.
* The chief concern with anyone I tell this to is always "Can you catch on fire?". Well to answer your question, no. If you follow the steps as outlined, there is no chance of you catching on fire. There are companies that sell clothes made the exact same way, just with nicer looking materials and a higher price tag. The flash point of most fabrics is much higher than this suit is capable of producing.
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Step 1: Materials
Everything but the Teflon wire, clothing material, and needle can be purchased from radioshack. All together the materials cost me about 50 dollars, and you'll have enough wire left over to make a jacket and more.
- 30ft of 30 AWG Teflon wire
- Some normal copper wiring (16 AWG)
- Connectors (See note 1)
- Ring connectors for connecting to the battery (See note 2)
- Fuse (Over 4 amps with just pants, over 10 if you make a jacket)
- Fuse holder (See note 2)
- An SPST switch (optional but recommended) (see note 3)
- Thermal underwear (or whatever you want to use)
- Cloth to make a lining
- A thick sewing needle
Note 1: You'll want to chose a connector that can be can be quickly disconnected. This is for the cases where you forget to disconnect from the bike and you try to walk away. Rather than tearing anything apart, the connectors will just come apart. There is an instructable on how to make one that's pretty cool. Here's the link: https://www.instructables.com/id/ThinkSafe%3a-A-Magnetic-Power-Connector-for-Thinkpad/. But if you don't want to make one, you should get a coax type plug or maybe a quarter inch plug, like the ones used on guitars. The coax plugs are what is used on professional clothing. I have a bunch of bullet connectors laying around, so that is what I'm going to use.
Note 2: You can buy a pre-made battery harness with fuse holder for pretty cheap. It's actually cheaper to buy the pre-assembled one than it is to make one unless you have the parts laying around. This second time around I'm using a pre-made one. http://cozywinters.com/shop/wg-dcjk15amp.html
Note 3: You can also buy a pre-made switch which looks pretty nice and is waterproof. This is what I'm using this second time around: http://cozywinters.com/shop/wg-oocoax.html
Step 2: Theory
This works on the same principal as a light bulb or a toaster. Pass electricity through a high resistance, and you get heat. In this case though, we are controlling how much heat the clothing will put out by varying the length of wire we will use. To figure out how much wire to use, we will use ohm's law or
Current [Amps] = Voltage [Volts] divided by Resistance [Ohms]
The wire we are using has a resistance of .1 ohms per foot. So if we used 30 feet of wire, the total resistance would be 3 ohms. This is ignoring the resistance of the connectors and wire going to the battery but it should be negligible in our calculations. The voltage of most modern motorcycle batteries is 12 volts. So 12V/ 3 ohms = 4 amps. Now we know how much current our pants will draw.
So you want to know how hot this will be? Here's an excerpt from this site
Power [Watts] = Current [Amps] x Voltage [Volts]
Based on our project consisting of a 12-volt battery and a current of 4-amps, the power consumption would be (4-amps x 12-volts = ) 48-watts. The heat output of 48-watts, can be expressed in British Thermal Units (BTU) per hour by performing the following conversion:
BTU / Hour = Watts x 3.413
Put simply, one British Thermal Unit (BTU) is the amount of heat required to raise the temperature of 1-pound ( lb) of water 1-degree Fahrenheit. Thus the vest in our project would output ( 48-watts x 3.413 = ) approximately 164 BTUs per hour. If this value isn't intuitive to you, consider that 48-watts is similar to a 50-watt light bulb, and imagine the amount of heat that a 50-watt light bulb outputs. That may not sound like much, but when that amount of heat is contained under a jacket, you will find that it is plenty warm.
Also, if you were to look at the power output of Gerbing's heated pants, you'll see that they put out 44 watts of energy, so our pants will be warmer than theirs. If you want to go even hotter than that, just use a shorter length of wire. Just remember ohm's law and you'll be all set.
Step 3: Threading the Wire
After measuring out 30 feet of teflon wire, you'll want to thread it through the pants. Plan your layout. Otherwise you'll have a hard time figuring out where to put 30ft of wire. You'll want to put most of the wire where the wind will hit you. So for me, I put a bunch on my shins, and on my thighs. Turn the pants inside out. If you are using thermals, it helps if you wear them to stretch them out, otherwise you'll have a hard time putting the pants back on.
Measure out 15 ft (or the halfway point) and mark it. Now starting at the middle point of the crotch, feed the wire all the way up to your halfway mark. Now tie a loose nut or put some tape to keep the other half from passing through. Make your way down the inseam, and then follow the pattern that I drew below. You'll want to finish around the waistband area. This is where we'll attach a connector. Once you finished with the one pant leg. Repeat the process for the other pant leg with the other half of the wire.
This new layout is better as well because it doesn't constrict the legs like the spiral pattern does. It makes it much easier to put the pants on.
Step 4: Soldering the Wires
After you have finished passing all of that wire through your pants, you'll want to connect them to the thicker gauge wire. After I soldered them, I bent the thin wire down leaving some slack and taped it the the thicker wire. I did this to act as a sort of strain relief. If there is a better way to do this, please let me know.
Step 5: Adding a Connector
Now it's time to add a connector to the end. Tie a knot in the thicker gauge wire and then pass them through the pants; the knot will act as a strain relief. Now solder and or crimp whatever connector you bought. Always make sure to put the female side on the bike.
After all of that is done, you'll want to add a liner. This will serve two functions. One it will protect your wires and two, it will keep you from getting burned. Trust me, this wire gets hot, it WILL burn you...I found out the hard way. I think an easy way to do this would be to buy another set of thermal pants, and sew them on the inside.
Step 6: Final Steps
Now put together the female connector with the switch and fuse housing, and end it all with a ring connector on each end. To brake it down, take two lengths of your thick wire. Attach a ring terminal on one end of each wire. Now, connect one of those wires to the fuse housing, and the other wire to one of the terminals on the switch. Now attach another wire to the other terminal on the switch and have that go to one side of your female connector and the other end of your fuse housing to the other side of your connector. Don't worry, I drew a diagram. And there you have it, your own heated pants. Now you can do the same thing for any other article of clothing you want to electrify.
Step 7: More Info
If you want more info, just search "DIY heated clothing" in google. That's how I learned about it. Below are links to sites that I think have good information.