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ben5017

Fri Nov 30 2012, 03:25AM

Registered Member #3315 Joined: Thu Oct 14 2010, 04:23PM
Location:
Posts: 156

After my proof of concept S.C.A.R. 1000 project, I have been lurking around the forum and have slowly been making progress on the upgraded model. I decided to lay out an experimental benchtop version to finetune the design before I complete the V3CC portable version.

Project Goals of X3CC:
-To create an easily modified experimental testing rig as a stepping stone for the final version (V3CC)
-Learn to optomize a multi-stage coil gun.

Future design Vision of V3CC:
-A 6s Lipo powered, 4+1 stage, select fire, drum fed, portable coilgun

Project Goals of VC33:
-Rate of Fire: 150 rpm
-Velocity: 50 m/s
-Efficency: 8-10%

The pictures attached show my progress to date, as well as a picture of the completed S.C.A.R 1000.

Progress:
-Injector is completed and operational.
-Optical Sensor is Completed and operational.
-Stage 1 Completed

PSCG

Fri Nov 30 2012, 03:41PM

Registered Member #3792 Joined: Sun Mar 27 2011, 06:07PM
Location:
Posts: 136

Good to see you with a new built! Are you using the design that Saz43 follows with his own multistage coilgun?

ben5017

Fri Nov 30 2012, 03:56PM

Registered Member #3315 Joined: Thu Oct 14 2010, 04:23PM
Location:
Posts: 156

PSCG:
Saz has deffinatly given me some motivation to keep making progress, and my design is somewhat similar. However there are some major diffrences.

1. It will be ran off of 6s instead of 12s
2. It will have a cap bank to increase the discharge rate as opposed to running it just off of the lipo. Hopefully it will give it some more punch.
3. It uses an "injector" to smack the projectile out of the magazine, as opposed to having the 1st stage pull the projectile out of the clip
4. It will be a 4+1 coilgun (4 stages + Injector) as opposed to 8 smaller stages

PSCG

Sat Dec 01 2012, 09:10AM

Registered Member #3792 Joined: Sun Mar 27 2011, 06:07PM
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Posts: 136

Very interesting changes. I'd like to see how the "battery - capacitor bank" combination will work.

Yandersen

Mon Dec 03 2012, 08:15AM

Registered Member #6944 Joined: Fri Sept 28 2012, 04:54PM
Location: Canada
Posts: 340

Ben, you asked me to enlight my design of recuperational gauss technology, but your current battery-driven design is completely incompatible with it. See, the keypoint of mine is using non-polar caps as power source for the coils. If you are going to start from scratch, let me know. By now, my 6-stage gun shows average efficiency 20.6% (recuperation is taken into account) by accelerating 6.57gramm projectile of 9.4mm caliber to the speed 54m/s while initial energy stored in 3 caps is just 55J. If such perspective will initiate you to try my technology, I'll tell in details how you can build one.

ben5017

Mon Dec 03 2012, 06:26PM

Registered Member #3315 Joined: Thu Oct 14 2010, 04:23PM
Location:
Posts: 156

Yandersen,

To clarify, I am still at the beginning stages of this build, and moreover its entire purpose is as a research and testing platform for later builds. I most definatly want to experiment with your design, with modifications of course (neither of us would get much out of simply duplicating your work).

To your point. I kind of figured that it would not be compatible with a battery driven gun. However I am still interested in seeing if it can be used to capture the leftover energy in my coil and the dissipate it elsewhere after the coil shuts off. I realize that this would not allow me to reuse the captured energy in additional stages, but i am thinking it would still be more effective way to minimize suck back, compared to an anti-parallel diode, and still have the rapid rate of fire I am looking for.

Thoughts?

Yandersen

Mon Dec 03 2012, 06:44PM

Registered Member #6944 Joined: Fri Sept 28 2012, 04:54PM
Location: Canada
Posts: 340

Easy. Just put a couple of high power zener diodes in series with dempher diode. When coil disconnected from the power source, the speed of energy dissipation will be proportional to the voltage spike over the coil. Choose the highest possible voltage your commutation elements can handle.
To determine the voltage spike' magnitude check the peak current in a coil. Multiply this value by coil resistance, add 1V for dempher diode and around 1.5 values of zener diode voltage rating. Make sure zener can handle the spike current for a time it will run (this characteristics are rarely shown in the datasheet, howhether). I think, couple of 5W zener in parallel will handle the spike. To be sure, put 5 or so of them in parallel and check the voltage over them during the spike. If it is just 1-2 Volts over their rating, you don't need that much - remove some and check again. Zener diode, when burned with moderate overwhelming, become a shunt resistor with few ohms of resistance, so don't be worry much about the rest of the circuit.

ben5017

Mon Dec 03 2012, 07:31PM

Registered Member #3315 Joined: Thu Oct 14 2010, 04:23PM
Location:
Posts: 156

Is this setup worth pursuing since it wont be able to use the captured energy, and therefore could not give me the same magnitude of efficiency gains you achieved? It should still give me a good boost in velocity due to almost eliminating suck back true? Can you give me a reasonable guess of % increase in velocity I can expect?

What if I were to charge nonpolar caps directly off of the lipos and use it to fire the coils?, could it then recoup and use the energy if I gave the batteries some sort of protection so they couldnâ€™t see the reverse voltage, kind of like a hybrid between a cap bank and direct lipo driven coils gun

Yandersen

Mon Dec 03 2012, 07:57PM

Registered Member #6944 Joined: Fri Sept 28 2012, 04:54PM
Location: Canada
Posts: 340

Well, eliminating suckback may give you up to 10-20% of efficiency in total, while recuperation will not increase bullet's energy but doubles efficiency by reusing energy leftovers. If you would wire your coils in a proper shape (length is equal to the inner diameter, 3x outer diameter to inner), use the shortest possible projectile and add external iron (at least washers at the ends of a coils), then you can be totally sure about those numbers. But by now, just put zeners in series with your dempher diode and see the difference.

ben5017

Mon Dec 03 2012, 08:12PM

Registered Member #3315 Joined: Thu Oct 14 2010, 04:23PM
Location:
Posts: 156

what do you think about my proposed "hybrid" setup

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