Re: Ring Launcher Test Results
Dr. Shark, Thu Feb 16 2006, 01:59PM

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?

Re: Ring Launcher Test Results
FastMHz, Thu Feb 16 2006, 08:02PM

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!

Re: Ring Launcher Test Results
Quantum Singularity, Sat Feb 25 2006, 07:34AM

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?

Re: Ring Launcher Test Results
FastMHz, Mon Feb 27 2006, 08:18PM

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:

Re: Ring Launcher Test Results
Quantum Singularity, Fri Mar 03 2006, 04:08AM

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.

Re: Ring Launcher Test Results
FastMHz, Fri Mar 03 2006, 06:41PM

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!

Re: Ring Launcher Test Results
Quantum Singularity, Thu Mar 09 2006, 01:48AM

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.

Re: Ring Launcher Test Results
Dr. Shark, Thu Mar 09 2006, 09:25AM

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

Re: Ring Launcher Test Results
Plasmaniac, Thu Mar 09 2006, 02:01PM

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.

Re: Ring Launcher Test Results
FastMHz, Thu Mar 09 2006, 07:05PM

"Good luck and if you find a good material to use then let me know."

I've been searching, and noticed that a Planters medium sized peanut can is the perfect diameter, strong and light weight. I trimmed all excess metal I could and siliconed the aluminum disc to the bottom, placed it upon the launch pad out back, and prepared to launch. I had an audience of family members. We expected it to go a few feet into the air...well, I pushed the "detonator" and it disappeared with a noise of gunfire!! It went way up, I have no idea how high but it took a bit to fall. Now that I know what to expect, I'm reinforcing it and will take video and time measurements. Stay tuned!

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

Yup, it just keeps rolling the ready symbol on the screen. It's a metal unit, I think this helps prevent EM interference.

"Paralleling your SCRs is probably useless"

I have a seperate resistor in front of each gate to prevent this...saw this posted somewhere in the old forum.

"What kind of backstop do you use?"

A pile of sheets and cardboard boxes

Re: Ring Launcher Test Results
Maz, Fri Mar 10 2006, 03:23AM

around where i come from paper is a big industry. i used to work for a box making plant and they had a thin sheet plastic that was durable, light and easily worked with. they called them die boards. they use them to cut patterns for boxes by gluing knives to one side. that would work. good luck finding a ox manufacturer around you!

Re: Ring Launcher Test Results
Quantum Singularity, Fri Mar 10 2006, 06:04AM

Is there a proper name for this type of ring/disk launcher? When I get to working on my new improved one I will be documenting it on my website and was wondering if there is a more appropriate name. I have tried researching and a Thompsons Gun typicaly utilitizes a selenoid style coil and a ring, along with a center section of ferromagnetic material. An Induction Coilgun also uses selenoid field coils but uses a slug that passes through inside the coils. What I am building - and I think FastMHz - utilizes a flat 'Archimedes' sprial field coil and a similarly shaped flat disk, which is just single stage. Did I miss the common name in my research or is there none?

Re: Ring Launcher Test Results
Dr. Shark, Fri Mar 10 2006, 08:45AM

I don't know whether you guys are aware of the work of Thomas Rapp here . He uses the aluminum disk as a sabot to launch a ball bearing ball as the main projectile. Of course you loose about 50% efficiency this way, but I think this is affordable with a ring launcher. This allows you to use any type of projectile you like!

I have also seen some IEEE Magnetics paper on this kind of launcher, they used two coils at 90 degrees with the projectile in between, and got some unbelivable efficiency like 30%.

Re: Ring Launcher Test Results
FastMHz, Fri Mar 10 2006, 06:32PM

That's some neat stuff on the German page...I'm also interested in knowing more about the 90 degree double coil launcher...

I think the proper name for these things is "Mass Driver"...at least, that's what Nasa calls them IIRC.

I think I'm going to try and form a rocket out of "great stuff"...could be messy, but it might just work. The Peanut can I mentioned earlier "accordioned" after one launch.

Re: Ring Launcher Test Results
Quantum Singularity, Fri Mar 10 2006, 07:01PM

Yeah, I have looked over that German page a few times but since I cant read German I just look at the pretty pictures I have seen the "mass driver" name too, but c'mon, thats not as catchy as Gauss Cannon or something like that

90 degree double coil launcher? Are you refering to the 'Lateral Disk Launcher' illustrated here also known as the 'Reconnection Coilgun'. I am curious to try this design but I am not certain how it could be nearly as efficient. Placing a disk on a flat spiral will yield high coupling and large induced currents, wich repel the disk strait away. Trying to sandwich a disk between two coils and launch it sideways wouldnt seem to be as efficient. And with the really high power levels I would be scared of the possibility the disk might shoot out at different angles. Would have to build a serious safety chamber around the thing. I have already shown my earlier design could penetrate into a good thickness of wood with a 5" hard drive disk. If I used a 3.5" or smaller disk (which I will probably do) with over twice my original energy...

Re: Ring Launcher Test Results
FastMHz, Fri Mar 10 2006, 11:02PM

Finally - video of the ringrocket launching!! This one was a metal coffee can with the 5/16" aluminum ring screwed into the bottom. After launch, the can was about 1/3rd less in height as it accordioned, meaning that a ton of energy was wasted in smashing the can instead of altitude:

DVD Quality Footage

Re: Ring Launcher Test Results
Quantum Singularity, Sat Mar 11 2006, 01:39AM

Pretty cool! Keep the camera rolling in your future runs! How did you form the cone - looks homemade? I take it the rocket didnt come down in view of the camera... or else it must have went really high...

About the pvc suggestion... I havent really worked with the stuff much, but they sell thinner pvc for like sewer drainage or something like that, would be thinner and lighter than say the common sched 40/80 stuff. Or take a plastic jar / container and coat em with several coats of polyurethane or epoxy to give em extra strength? Probably too much hassle, just thinking of ideas thats all.

Re: Ring Launcher Test Results
FastMHz, Sat Mar 11 2006, 06:37PM

In the video, the cone was formed from sheets of paper. I then mixed wood glue with water and painted it with that to harden it. I figured they better be easy to make and cheap since they get destroyed after each launch.

The rocket came down to the left of the field of view after landing on the roof and bouncing off. That's why you hear two crashes after launch. I'll get a cameraman to follow the rocket in some future footage. I still need to design a strong, yet light weight rocket that won't compress during launch.

I'll dig through the PVC at the home center and see what I can find...The Gs being experienced by the rocket must be sky high...pun intended

Re: Ring Launcher Test Results
FastMHz, Fri Mar 17 2006, 08:35PM

Two things:

I just finished making a new rocket out of Great Stuff...it's surprisingly solid, weighs less than the cans, and shouldn't crush...I hope...

I also won another 1.7kj cap bank on ebay...so I'll start planning a 3.4kj launcher