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Ring Launcher Test Results

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LAN_403

FastMHz

Thu Feb 16 2006, 02:13AM

Registered Member #179 Joined: Thu Feb 16 2006, 02:08AM
Location: Hagerstown, Maryland - Close to Prime Outlets
Posts: 287

Still using my somewhat sloppy coil, I've been getting some encouraging results so far in my tests:

Ring - 3.5" hard disc platter
Weight - 22g
Speed - 57.3288 m/s
Efficiency - ~2.1%

Ring - 3.5" 5/16 self cut aluminum disc
Weight - 58g
Speed - 60.68568 m/s
Efficiency - ~6.2%

Is this in line with what others have gotten in ring launchers? I'm having a blast with this thing...pun intended

Guess I should specify power source. It's the same cap bank as I used for the coilgun...700v, 1.7kj, SCR switched

Dr. Shark

Thu Feb 16 2006, 01:59PM

Registered Member #75 Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711

Is that an electrolytic capacitor bank you are using? If so, I am surprised about the efficiency, as I thought you need a really fast pulse for these induction type launchers.
Um, may I ask, how did you measure the speed to six significan digits?

FastMHz

Thu Feb 16 2006, 08:02PM

Registered Member #179 Joined: Thu Feb 16 2006, 02:08AM
Location: Hagerstown, Maryland - Close to Prime Outlets
Posts: 287

Yes, it's an electrolytic bank. I'm not sure if they're pulse rated or computer grade, but the terminals are large enough for major current. I have them wired as 4 in parallel and then those 2 parallel banks in series for 700v. I use 3 SCRs in parallel to trigger them. I have a chronograph which can measure up to 7000fps...I take the FPS measurement and plug it into a standard to metric converter to get that number. The significant digits beyond hundredths probably aren't necessary or useful but I posted all data anyway.

I too am surprised at the efficiency. i just wound a "perfect" coil that's curing in epoxy at this very moment, so I'll see if it gets more efficient. The old coil is getting pretty deformed now and the epoxy is cracking all over. I finally got some pics of everything here:

Link

EDIT: OK, my new "perfect" coil is cured and I was anxious to try it...and it DID improve my results:

Velocity - 67.60464 m/s
Weight - 58g
Energy In - 1.7kj
Energy Out - 132.54j
Efficiency - 7.7%

Is that possible or am I doing the math wrong? I must have ended up with a very well matched system if this is correct. It sure is powerful...151 mph flying discs. It's disc-structive!

Quantum Singularity

Sat Feb 25 2006, 07:34AM

Registered Member #158 Joined: Sun Feb 12 2006, 09:53PM
Location: Central Ohio
Posts: 282

Did you change much with the coil... what do you mean by perfect? When I was launching disks I tried two coils, one that was #12 awg and 20-some turns and one that was #8awg adn 10 turns. There seemed to be not much noticable difference but had no chrono. How do you launch yours... vertical or other? And how do you position your chrono?

FastMHz

Mon Feb 27 2006, 08:18PM

Registered Member #179 Joined: Thu Feb 16 2006, 02:08AM
Location: Hagerstown, Maryland - Close to Prime Outlets
Posts: 287

Perfect meaning wrapped tightly and without any gaps in the wire, and no overlapping. It's then coated in epoxy. My coils are 14awg magnet wire wrapped to the 3.5" diameter with a nickel sized hole in the middle. I also use no center post. I launch horizontally and the setup I use is illustrated in this drawing:

Quantum Singularity

Fri Mar 03 2006, 04:08AM

Registered Member #158 Joined: Sun Feb 12 2006, 09:53PM
Location: Central Ohio
Posts: 282

Thanks for the info FastMHz. I will be buying a chrono sometime before summer. I'll probably buy one localy so if I toast it with EMP I can take it back and say it was defective

I'll probably have to space it quite a bit away from the coil. I am going to attempt to use both my maxwell caps for a couple experiments this summer like a disk launcher and maybe try shrinking some quarters. I am also going to try to actually build some kind of projectile for my disk launcher instead of just a disk (not very aerodynamic) - like take some pvc pipe with some kind of round nose attached and the disk attached at the base of the pipe. Maybe even make a barrel for it. Should also be more visible to the eye when launching, and when searching for it out in the field.

FastMHz

Fri Mar 03 2006, 06:41PM

Registered Member #179 Joined: Thu Feb 16 2006, 02:08AM
Location: Hagerstown, Maryland - Close to Prime Outlets
Posts: 287

I'm anxious to see your projectile with the cone...I was thinking similarly...it would be need to make a rocket looking thing and launch it straight up in the back yard

EDIT: I was contemplating my own RingRocket and your idea for PVC, however PVC is quite heavy. Do you know of another material which may be strong but without the weight? Perhaps thick cardboard like wrapping paper comes on, or one of those plastic Folgers coffee containers? I'm on the hunt for 3.5" diameter containers to use as a rocket tube

You've got me going in as new direction with this launcher!

Quantum Singularity

Thu Mar 09 2006, 01:48AM

Registered Member #158 Joined: Sun Feb 12 2006, 09:53PM
Location: Central Ohio
Posts: 282

Good luck and if you find a good material to use then let me know. I too was thinking pvc would be heavy but that was just an example - I was going to look at various plastic jars / containers etc. till I found something good.

I must say though that depending on the design, I think this type of launcher can drive a good amount of weight. A hard drive disk is very light. I put a short section of 2x4 on top of the disk just to see what would happen with the extra weight. The wood probably increased the weight by well over 10x. I was surprised that the disk and the 2x4 went probably half the hieght or more than just the disk alone. Perhaps the disk alone was too light and accelerated off the coil while it was still pulsing up. The extra weight would then slow the launch down enough to utilize more of the energy? I havent given it much thought or made any kinda simulation but there should be a way to optimize the pulse length vs. projectile wieght & acceleration.

Dr. Shark

Thu Mar 09 2006, 09:25AM

Registered Member #75 Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711

Fast MHZ, you have some great results there! I was at first sceptical about your figures for velocity, but seeing what your coil does to a can confirms that there must be some power there. I suspect that the thickness of your disk helps coupling lots of the magnetic field - other setups I have seen used much thiner disks.

Have you tried shooting _not_ at the chrono and checking if it displays something, due to EM interference?

Paralleling your SCRs is probably useless, as they dont have a resistance but a voltage drop, most of the current will end up going through only one of them.

What kind of backstop do you use? 100J could do some serious damage and kill your dog, if you are not carefull

Plasmaniac

Thu Mar 09 2006, 02:01PM

Registered Member #206 Joined: Sat Feb 18 2006, 03:17PM
Location:
Posts: 72

I calculate the projectiles speed by the height it travels, which is very inaccurate(air resistance). And I get efficiency <6% with my 100J design. A bigger 500J version is allready in work.

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