Original photos and written procedure by
Ken Hastie:
http://www.hastie.org.uk/heatedjacket.html~~~
D.I.Y. Heated Jacket for Motorcycling
Toasty for a tenner...If you are determined to put your motorcycle away during the winter, these words may not be of much use to you. If you already venture out in cold temperatures, then you will know how uncomfortable it can be when the cold takes it's toll. Read on and you will find out how you can eliminate most of this discomfort at surprisingly little cost, and perhaps even be tempted to keep the bike on the road during the winter months, when a whole new opportunity is available to you to see a different environment on two wheels.
Winter motorcycling can actually be a lot of fun!As a newly-married and hard-up youngster, I remember travelling to work on my 250cc BSA C15 out of necessity. They were cold days, and I would frequently take quite some time to thaw out before I was of any use to my employer. These days were brought back to memory vividly when I rode from Newcastle-upon-Tyne to York one cold weekend in November to see one of my sons. I was so chilled, I had to stop at a Little Chef 15 miles before York to thaw out by way of a pot of tea, and gloves held under the hot air hand dryer in the Gents!
Motorcycle clothing technologyAs in all areas, technology has advanced, and not least in respect of your beloved two-wheeled activity. Modern motorcycle clothing tends to be of better quality, offering greater protection against the elements, and I can attest to this by recently completing a 700 mile weekend trip to the Isle of Mull on my 750cc BSA Rocket 3, sometimes in ideal conditions, but at other times in horrendous and very wet conditions, yet my good lady and I stayed bone dry. It has taken me something like 25 years to settle on a good combination of clothing, which is basically Hein Gerecke leathers with quilted liner and flexible Hiprotec body protection, a Moto-line waterproof oversuit, Alt-berg made to measure leather boots with waterproof membrane, and Rukka overmitts.
Keeping warmSo that takes care of wet weather protection; warmth is quite another matter. It is best to avoid the body core temperature dropping, because once this has happened, it is extremely difficult to restore it. Also, it is a natural function of your body to reduce the blood supply to your outermost extremeties when the core temperature drops too far. Hence your fingers and toes feel the cold first, followed by your hands, arms and legs. Such modern devices as electrically-heated handlebar grips and heated clothing are wonderful things, but can be expensive, and on older motorcycles can draw more current than the bike can produce. I have heated grips which cost £39.00 but have the nice feature of a manually selectable start-up power consumption of 45 watts, and an ongoing consumption of 15 watts, which is no more than a rear stop/brake light bulb. It is only necessary to run at the 45 watt setting for a couple of minutes, and then 15 watts is quite sufficient to maintain that temperature.
Commercially available heated vestsHeated vests are available, mostly from USA manufacturers such as Gerbing and Widder, but they can be expensive, starting at around £120.00. They work on the principle that high resistance wires are used which generate heat when a current is passed through them. A new jacket about to be launched has used a new concept which is to use electrically conductive carbon woven material, which is claimed to be more reliable and effective, but will only be available in North America, and the cost is expected to be around US$ 200.00.
The "do-it-yourself" optionHowever, there is another option, which is to make your own, and it is not as difficult as you may think. Being a Northerner, where we have a reputation for being 'careful' with our hard-earned readies, I recently set about doing just that and was surprised how inexpensive and easy it was, especially given my limited knowledge of electronics. I located a couple of items on the internet that described how to do it, and it was the webpage of Sue Diaz that appealed to me, because it looked the simplest way to do it. If you have access to the World Wide Web then the U.R.L. is
http://homepages.luc.edu/~sdiaz/electrics.html I selected this method because of it's simplicity. It uses a single length of thin wire which acts as your heating element, and is therefore quite easy to work with, and avoids the need for too many cable joins, which can be a source of difficulty if you don't have nimble fingers and good eyesight !
I have been using the heated vest now for two years, and no problems apart from one occasion when I had to repair the connection between the heating element and the power supply cable.
The technical bit (you can skip it if you want; you don't need it)Here are some derivations of Ohm's Law which may help you in your calculations. It doesn't really matter if it is all gobbledegook. I am not an Electronics Engineer, and managed quite adequately without it.
Volts = Amperes x Ohms
Amperes = Volts / Ohms
Ohms = Volts / Amperes
Watts = Volts x Amperes
Watts = (Volts x Volts) / Ohms
Watts = Amperes x Amperes x Ohms
Ohms = Watts / (Amperes x Amperes)
The heating elementWire is available in many thicknesses (gauges) and you need to select one which will provide sufficient resistance to generate the heat you are seeking, yet without drawing too much power from your electrical system. I used a 100ft reel of 30awg (American wire guage) wire from RS Components for £8.00; R.S. Part Number 177-0621, and here is the specification if you are really interested (you don't need to be):
30 awg conductor 7 x 0.1mm strands 4 amp maximum current Total thickness 0.81mm Temperature rated to 200 deg c - much more than you will ever see!
This is a relatively low resistance PTFE coated wire which is U.L. listed, so I didn't have to translate into swg (Standard wire gauge). The PTFE insulation on the wire is suitable for high temperature, and also has a slippery feel which makes it easier to thread into any garment. This particular wire has a resistance of about 0.1 ohm per foot, and I started by cutting off a 40 ft length, then gradually cutting down two feet at a time until I reached my target of about 3.0 ohms. In fact, the 30 feet length I ended up using, provided 2.9 ohms which was near enough to what I was looking for.
As the resistance is 2.9 ohms, the current draw is 13.8 volts/2.9 ohms = 4.75 amps.
Wattage is (13.8 x 13.8 volts) / 2.9 ohms = 65 watts
The embarrassing bitThis is where you have to hide from your friends (and your wife) in case they see you with a sewing needle in your hand ! I bought a knitters sewing needle and ground a sharp point on to it, as they are normally quite blunt. The eye of the needle was just the right size to grip the wire as it was pulled through, so I didn't 'lose' the end. I sewed the wire into the torso area of my quilted vest which zips in and out of my Hein Gericke jacket. It is best to try to sew the wire into the quilt itself to avoid too many bits of wire showing. You can do this by sewing up the liner a few inches then come out again, and then sew back in to the same hole you just made for the next few inches.
If you don't have a detachable liner, then buy a cheap quilted bodywarmer instead, the thinner the better. How you sew the wire that is to act as your heating element is up to you, but I calculated that I had enough wire to manage four runs up and down each breast, and then 7 runs up and down the back, and a couple of runs horizontally across the lower back. Don't be fooled into believing you need all the heat at the front of the vest - you don't! Runs across the lower back are very important.
Cable connectionsIt is important to have both loose ends of the wire exiting the vest at roughly the same point, as you have to attach a twin core cable to the ends. In my case, I used a 6 amp multistranded twin-core cable and Lucas-type traditional brass bullet connectors
Strip about 15mm of insulation from the ends of the thin and thick cables, and feed them in to opposite ends of the bullet connectors. Then heat up the connector with a soldering iron and fill with solder. I used lengths of heat shrink sleeve material to cover the resultant join. As an alternative to a soldered joint, you can use a vice to just crimp the bullet connector closed, and then cover with heat shrink tubing. I did try crimping pliers but could not get sufficient force to compress the bullet connector properly, so in to the vice it went. Perfect.
The power supply leadThe trailing lead of the 6 amp twin core cable should be about 30cm long, so that you can make a loop and secure it to the vest to avoid pulling. You can do this by stitching the cable into place, or by using a few small nylon cable ties, and looping them through the quilted fabric by piercing it. A small plug was attached to the end of this cable which then lies just at the base of the jacket, so it accessible by you when you are ready to plug in. This fitted into a matching socket which I attached to more twin core cable, which ran to a little plastic control box I made up to attach to the handlebars, housing a rocker switch, a 12v LED, and a 5 amp blade fuse. This then ran to the power supply on the bike.
You can choose your own plugs and sockets, but I would mention two things:
You need plugs and sockets that are capable of carrying a load of around 5 amps You need plugs and sockets that will easily come apart should you dismount from the bike and forget to unplug yourself first ! You don't want to exert undue force on the cable leading to your jacket. Remember the heating element cable is only 0.8 mm thick !
I used plug and socket connectors from RS (part number 424-579) which are like "chocolate block" connectors, but with slide in pins. They are easy to wire up, the screw terminals can be sealed with silicone, and they take 10 amps. I did once forget to unplug them when I got off the bike, and they plug separated from the socket easily without any damage.
TestingWhen I came to test the finished item, at first I couldn't work out why there was no apparent heat in the vest, but my bench testing (literally) used a normal battery I removed from my BSA Rocket 3. A friend on the Internet (Mark Robinson) who is an electronics engineer, suggested the battery on it's own wouldn't provide the power and suggested attaching a battery charger as well. This did provide lukewarm heat, which led me to believe I may have unsatisfactory connections from the 30awg heating element wire to the 6 amp power supply wire.
However, this was not the case, because when I first plugged the set-up into my Triumph Trophy 1200 power supply, and made a test run up to the Cheviot Hills, where I knew there was a bit of snow, it worked perfectly ! Clearly, my vest needed the extra power produced by the bikes alternator to give sufficient power to heat up the vest. I also found that my BSA Rocket 3 alternator also generated enough power to heat the vest. The heat that is generated is at a level that really gives you some comfort. I have used it many times since, and in temperatures below freezing and it has proved to be worth it's weight in gold. In fact I masochistically switch it off for ten minutes or so just to remind me (smugly) how effective it really is, and all for a cost of a few pounds. In fact the reel of wire I bought has also been used by my friends to make another two heated vests.
Other garments can be heated in much the same way, such as gloves and leggings, but wire length and thickness have to be calculated to provide sufficient heat, without drawing too much power.
Try it for yourself.....it gives a whole new take on Winter motorcycling.
© 2006
Ken Hastie, all rights reserved
