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Registered Member #2292
Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795
Wizzup wrote ...
Very nice shot :) What was the capacitor configuration in that shot? I tried shooting a 2mm steel plate with the old 1.4kJ bank but my projectile tip just crushed and made a large dent on the plate, I guess I need to use harder steel to make it penetrate steel.
Before getting any more capacitors I need a new chamber that can hold the current pressures without blowing up so I have been looking for a small lathe to do the parts for my cannons, I am considering this one as the working space of the lathe is 550mm long so I can do small and medium size parts with it and have some space to work. In Finland that same model costs about 1400 euros but just 900 euros if I buy it from Netherlands. You have experience with machining equipment Kizmo so do you think it is a good price for the machine or should I maybe look for an older used machine? I would use it to machine small parts such as ETG chambers and similar size parts from aluminum and steel and sometimes maybe a bit larger parts too.
I appreciate it that you could do the machining for me but I have a few other projects in my mind too that I would need a lathe in so I see it is better to get my own lathe. I will be interested in those 3300uF capacitors though when I make a new chamber so I will send you a PM here or in youtube when the time comes :) I can also send you my skype if you want to talk more.
Have you considered using micarta for your chamber design?
Registered Member #3302
Joined: Sun Oct 10 2010, 02:21PM
Location: Finland
Posts: 42
No I haven't, I had actually never heard of the material before I searched it now but I will stay with nylon in the future because the fault with the current chamber is that the nylon piece is in place with just about 15mm of nylon threads and that is obviously not enough to keep it in place as seen in my video. With the next chamber I will use a design something like this: the grey parts are nylon and black is steel so the nylon part is supported from the back.
Registered Member #2292
Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795
G10/micarta is many times stronger than nylon but still offers the same electrical insolation benefits. This is because it is built similarly to carbon fiber using layered fabric and epoxy resin. I would highly recommend it.
Registered Member #1938
Joined: Sun Jan 25 2009, 12:44PM
Location: Romania
Posts: 701
Why not use a car sparkplug connected to a steel chamber (with an opening for the barrel and one that matches the thread size)? Of course, you would need to cut off the "ground electrode" and leave only the central electrode pin. The aluminum foil would contact the chamber and the central electrode. A much better choice I'd say considering these are actually designed both for sparks and high pressure.
Registered Member #4603
Joined: Wed Apr 25 2012, 07:33PM
Location: Austria
Posts: 159
Hi Guys. Inspired by Wizzups ETG i also decided to build one. The design is very similar to Wizzups first construction. I use a Nylon cylinder. 60mm diameter, 100mm in lenght. The electrodes are made of M6 threaded rods. As a switch i use a massive contactor. The inner diameter of the barrel is 6mm. I use 6mm steel BB balls, 0,8g. I was wondering how to adjust the two electrodes as the gun "only" shoots through one plate of 16mm medium-density fibreboard @ ~1kJ (24000µF ~300VDC) The distance between the electrodes is about 4mm. I used a small piece of wet aluminum foil between the electrodes. How could i get more power?
Registered Member #3302
Joined: Sun Oct 10 2010, 02:21PM
Location: Finland
Posts: 42
Its nice to see someone else has built one of these too :D
The first thing I would probably try to get more power is rearrange the capacitors for a lower capacitance setup. The highest capacitance I have used with my builds is 14100µF and I think that even that is pretty high. So if there is a chance you could rearrange them to for example 6000µF at 600V I think it would be better.
When I first tested my ETG I did some shots at about 300V that was about 640J, and it did like a small mark or dent to the plywood that I was shooting at but when I increased the voltage to about 400V the power I was getting out of it was in no way linear to the electrical energy. At 300V I had 640J energy and at 400V I had 1130J energy, but at 640J it made a small dent to the plywood and at 1130J it went completely through the plywood, so the increase in output kinetic energy was way over that compared to the electrical energy increase. I am not sure what causes it but I think that under 400V is just not enough voltage to get the plasma hot enough or something so even if the energy is the same you will probably get better performance with higher voltage.
Also I think that the distance between the electrodes and the amount of foil is not very critical, I tried many different amounts of foil but I didnt see any major difference. You said you use wet aluminum foil but have you tried for example filling half of the chamber with water before adding the foil or something? With my ETG I just usually put some water in there and then tap it a few times with the chamber upside down so it was not full but had pretty much water in it. The water decreases the amount of air in the chamber so it can increase the pressure in the chamber quite a bit I think.
Registered Member #4603
Joined: Wed Apr 25 2012, 07:33PM
Location: Austria
Posts: 159
Hi Wizzup! Thanks a lot! I will try to use a higher voltage. No I did not use much water. Just a few drips over the foil. I think the water vaporizes and so increases performance producing steam!? Maybe it even produces oxyhydrogen...? Some tests showed me that a wider distance between the electrodes also increases performance.
If you don't mind I could post some pictures and further results?
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1.4kJ electrothermal gun
