What's New

November 8, 2005

My day job has taken up most of my time for the past 2 months, but I still managed to make
some progress on the coil pistol. I apologize for the many emails I have not had time to
respond to properly. Everyone who contacts me is being added to the list and will be notified
when products become available.

I have simplified the overall design to reduce cost, eliminating some of the batteries so it is
now somewhat lighter. Instead of adding more batteries to achieve a higher gate voltage on
the IGBTs, I added a DCDC converter to provide 18V to run the IGBT gate drivers. So
instead of adding two batteries as I originally intended, I am removing two. This also makes
the pistol more balanced (less front-heavy), since all 8 batteries are centered at the grip.

I am removing the battery charging IC (MAX713, which cost me almost $8 apiece) and am
now using the PIC to manage the battery charging. I also found a much cheaper source for
the laser sight which reduces costs by another $20. My goal is to make the kit as affordable
as possible without sacrificing performance.

I wound a few test coils using a "bonding" magnet wire. This wire makes it much easier to
make strong coils and beats the snot out of adding epoxy resin between each winding. After
I wind a coil with this wire I bake it in the oven for a few minutes, which cements the windings
together. The coils in the original pistol contracted a bit when fired, but these new coils are
very stiff. Thank you Bob Humphrey of Sarcem America for recommending and mailing
me samples of this wire.

The original capacitor charging circuit delivered less than 10 Watts, and not very efficiently
either. I am improving this circuit to increase efficiency and to reduce the time between shots.

I am making the pistol case out of transparent acrylic instead of sheet metal. This makes it
lighter and also makes the innards visible through the cover. A transparent cover fits the
primary purpose of this pistol as an educational product. It also increases user safety; for
example, if a high voltage wire comes disconnected a metal case would be much more
dangerous than an acrylic one.

And last but not least, I have an attorney working out the liability issues to offer this product
for sale. I will not sell anything until this is work is complete.

September 3, 2005

It has been some day, someone put my site on hackaday.com so it was overwhelmed for a
while. It's obviously back up now. Thank you to each of you who communicated your
encouragement and interest!

My focus on this project has always been half hobby, half entrepreneurial. As soon as my
firing tube improvements are prototyped and proven, and all liability issues are satisfied, I will
begin offering full plans and kits. I may forgo offering fully assembled gauss pistol though, I
like the idea of having to build it before you can own one, kind of like a light saber.

August 31, 2005

The Garolite tube I ordered has come in, so time to build the new firing tube.

I also bought some 1" ID steel pipe, which I have cut a 30mm section out of, and then cut it
in half. I am going to use these pieces with some new thicker washers to enhance the flux
linkage around each coil. The pipe walls and the washers are both 1/8" thick.

I am also going to apply epoxy resin to each layer as I wind these coils to strengthen them. I
used an acrylic spray when I was winding the present firing tube, but I don't think it adds
much strength.

August 28, 2005

I have plans to improve the performance of the gauss pistol as time and budget permits.
Some of the ideas I am considering are:

Replace the brass firing tube with a nonmetallic one. I have slits cut in the brass
tube to reduce eddy currents, but I would rather take them out of play entirely by going
with a nonmetallic tube. I have ordered two different sizes of Garolite tube to
experiment with. Garolite is a "continuous-woven glass fabric laminate with an epoxy
resin".

Increase iron around the coils. I have one washer at each end of each coil, the new
firing tube will have increased thickness either by finding thicker washers or stacking two
washers. There are also currently thin steel strips strapped around each coil, I want to
try to encase the coils in an epoxy/iron filing mixture ala this Coilgun Systems
experiment.

Experiment with alternative projectile loading method. The pistol is currently one-
shot, I am looking into both a clip system and a revolver-type cylinder. I am currently
leaning toward the revolver idea.

Experiment with alternative coil windings. I may be able to get away with using
coils with lower resistances if I set the low battery lockout high enough. The reason the
battery level matters is the gate voltage of the IGBTs has a large effect on the maximum
current. If the gate voltage triggering these transistors is too low due to low battery, at
least one of the transistors in the pair will overload and burn out. I may be able to trade
off some capacity of shots per battery charge for some more muzzle energy, which is
my highest priority.

I see 3/4 of these items involve building a full new firing tube. I will build one and test it,
comparing it to the present coils/tube/shielding configuration and post the results. The
revolver system is going to have to wait a while.