(or) Cutting the AirMan portable air compressor down to size

In anticipation of doing some longer road trips, I desired to have an emergency tire repair kit so I could repair a tire puncture without removing a wheel or leaving the bike alongside the road in unfamiliar territory.

I rely on Motorcycle Consumer News (U.S.) to help me make decisions in such matters. In their March 2002 issue, they did a good evaluation and write-up of emergency tire repair kits for repairing punctures and for inflating a tire. They especially liked the Stop & Go Tire Plugger for repairing punctures, and while they felt that the better CO2 cartridge-based inflators were more practical than the hand pumps or the engine pumps, they weren't really happy with the CO2 cartridge gadgets either. In the October 2002 issue, they did a follow-up where they stripped a small 12V air compressor down to its bare bones.

I was inclined to follow that approach, but then when I saw some small compressors in the Aerostich catalog, I decided to order the lesser expensive of those two units for $30.

The picture above shows the shortened AirMan compressor stored under the Yamaha FJR1300's seat, left unwrapped so that you can see how it fits but then subsequently wrapped in a protective sack. Out of the box, it would not have fit there because it was nine inches long as compared to 5 1/2 inches as you see it here.

When I initially saw that it was larger than I wanted I was inclined to return it then buy a small compressor at a store and strip it down. But I liked the AirMan's compact, sturdy ventilated case, and that when running, it was quieter and vibrated less than the somewhat larger battery-powered portable compressor that I keep in the garage. After considering that if I bought one at a store it would still cost as much and wouldn't have any housing whatsoever after I stripped it down, and after studying the AirMan's case for a few minutes, I concluded that the best option would be to keep the AirMan but cut off the excess part of the case.

The picture above shows the AirMan as it comes out of the box. You can see the step pattern on the compressor case corresponding to the stepped shape of the orange piece in the foreground. Note also the electrical contact on the left end of the orange part; there is another opposite and underneath where you can't see it. This orange part is hollow and the power cord stores there, but it was very difficult to get the wire in and out. An AC/DC adapter was also shipped with the unit, which is bizarre since there is no jack anywhere to accept it. The adapter confirms that in another version of AirMan, a rechargeable battery fits where the orange part goes, and this orange part is the accessory that allows it to be powered from a cigarette lighter.

I was going to have to change the power cord anyway so that I could connect it using the heavy gauge coiled cord that I use for my electric vest. I decided that the orange part provided no value, and that the obvious solution would be to cut off the portion of the compressor case that serves only to accommodate the orange part.

The picture above shows AirMan taken apart and with the wires cut so that I could cut off the excess length of the case without getting plastic junk all over the moving parts.

The picture above shows what AirMan looks like after cutting off the excess part of the case and with the wires re-connected, including an in-line fuse holder that I added. I didn't know what size of fuse to use but I put in a 5 Amp fuse and it didn't blow when I tested it. I had to re-do this because when trying to reassemble it, I discovered that the fuse holder needed to sit in the empty space at the bottom of the motor, which required lengthening the red wire on both sides of the fuse holder as compared to what you see in the picture above.

Putting it back together was a little tricky as you would expect, but it was made more difficult by the fact that I had shortened the yellow wire slightly when I cut it and then soldered it back together. It is tricky not only because several parts have to be held in place while bringing the two halves together, but also by the fact that all of the wires have to be carefully routed so that there is no possibility that any of them could come in contact with the crank pin or the large white nylon gear. I spent a fair amount of time fiddling with it before I was entirely confident that the wires were in safe locations and that there was no possibility that they might move.

The picture above shows the result. That short length of wire is all that I needed because the power cord for my vest has a section of heavy gauge coiled wire that will stretch out and reach from my vest socket to the rear wheel by itself. With the additional length of the air hose, this is all the wire that I needed, and it easily tucks into that hollow space. The overall dimensions are now 5 1/2 inches long by 5 inches by 2 1/2 inches. The plastic is exceptionally strong, and the AirMan overall seems to be of unusually high quality.

My vest socket is controlled by a HeatTroller variable controller, which does not pose any problem whatsoever. In fact, the HeatTroller's PWM circuit is the circuit that is used to control the speed of DC motors such as fans, but given the low operating frequency of the HeatTroller's PWM cycle, it is probably best to have the HeatTroller turned fully up before turning on the AirMan, as I did when I tested it.

The picture above shows the complete emergency tire repair kit. I hope that I never have to use it, but if I ever do use it even once and avoid having to leave the FJR alongside the road in some unfamiliar location or in the middle of nowhere, it will more than have paid for itself.

Tom Barber

Copyright © 2003, by H. Marc Lewis and Tom Barber.
All rights reserved.