If you need assistance, please send an email to forum at 4hv dot org. To ensure your email is not marked as spam, please include the phrase "4hv help" in the subject line. You can also find assistance via IRC, at irc.shadowworld.net, room #hvcomm.
Support 4hv.org!
Donate:
4hv.org is hosted on a dedicated server. Unfortunately, this server costs and we rely on the help of site members to keep 4hv.org running. Please consider donating. We will place your name on the thanks list and you'll be helping to keep 4hv.org alive and free for everyone. Members whose names appear in red bold have donated recently. Green bold denotes those who have recently donated to keep the server carbon neutral.
Special Thanks To:
Aaron Holmes
Aaron Wheeler
Adam Horden
Alan Scrimgeour
Andre
Andrew Haynes
Anonymous000
asabase
Austin Weil
barney
Barry
Bert Hickman
Bill Kukowski
Blitzorn
Brandon Paradelas
Bruce Bowling
BubeeMike
Byong Park
Cesiumsponge
Chris F.
Chris Hooper
Corey Worthington
Derek Woodroffe
Dalus
Dan Strother
Daniel Davis
Daniel Uhrenholt
datasheetarchive
Dave Billington
Dave Marshall
David F.
Dennis Rogers
drelectrix
Dr. John Gudenas
Dr. Spark
E.TexasTesla
eastvoltresearch
Eirik Taylor
Erik Dyakov
Erlend^SE
Finn Hammer
Firebug24k
GalliumMan
Gary Peterson
George Slade
GhostNull
Gordon Mcknight
Graham Armitage
Grant
GreySoul
Henry H
IamSmooth
In memory of Leo Powning
Jacob Cash
James Howells
James Pawson
Jeff Greenfield
Jeff Thomas
Jesse Frost
Jim Mitchell
jlr134
Joe Mastroianni
John Forcina
John Oberg
John Willcutt
Jon Newcomb
klugesmith
Leslie Wright
Lutz Hoffman
Mads Barnkob
Martin King
Mats Karlsson
Matt Gibson
Matthew Guidry
mbd
Michael D'Angelo
Mikkel
mileswaldron
mister_rf
Neil Foster
Nick de Smith
Nick Soroka
nicklenorp
Nik
Norman Stanley
Patrick Coleman
Paul Brodie
Paul Jordan
Paul Montgomery
Ped
Peter Krogen
Peter Terren
PhilGood
Richard Feldman
Robert Bush
Royce Bailey
Scott Fusare
Scott Newman
smiffy
Stella
Steven Busic
Steve Conner
Steve Jones
Steve Ward
Sulaiman
Thomas Coyle
Thomas A. Wallace
Thomas W
Timo
Torch
Ulf Jonsson
vasil
Vaxian
vladi mazzilli
wastehl
Weston
William Kim
William N.
William Stehl
Wesley Venis
The aforementioned have contributed financially to the continuing triumph of 4hv.org. They are deserving of my most heartfelt thanks.
Registered Member #1819
Joined: Thu Nov 20 2008, 04:05PM
Location:
Posts: 137
I have decided to post ideas and plans for my first coilgun.
Current Planned Specs: Storage Energy - 1903.5 Joules (450V on 18800uF) Muzzle Energy - 285.525 Joules Efficiency - 15% Projectile Diameter - 3.8 cm Projectile Length - 12.7 cm Projectile Mass - 388 g Projectile Material - Aluminum Muzzle Velocity - 38.319 meters / second Rate Of Fire - 15 rpm Total Weight Of Coilgun- 13.6 kg
Goal Specs: Storage Energy - 1903.5 Joules (450V on 18800uF) Muzzle Energy - 475.875 Joules Efficiency - 25% Projectile Diameter - 3.8 cm Projectile Length - 20 cm Projectile Mass - 612.422 g Projectile Material - Aluminum Muzzle Velocity - 39.421 meters / second Rate Of Fire - 40 to 60 rpm Total Weight Of Coilgun- 23.178 kg
The capacitor charging circuit is a 1500W to 1700W Push-Pull converter using a custom made 1:37 ratio transformer, or, as an alternative, a constant-current boost converter (both of my own design). Hopefully, either of these will be able to charge the capacitors fast enough to achieve the rates of fire that I have planned.
As stated above, the capacitor bank will consist of 4 capacitors (450V 4700uF) in parallel connected using bus bars.
The main power switching device will be an Ixys MCC162-16-io1 with an average gurrent of 160A and a peak current of about 6000A per SCR. The first one will actually switch the coil, and the second one acts as a protection diode (self-triggered SCR when forward voltage is applied).
The coil itself will be made of two layers of 96 turns with 48 turns per layer. This will have an inductance of about 100uH and a resistance of about 0.04 ohms.
The shunt circuit will be designed to absorb a full power discharge without a projectile, but hopefully this power dissipation capability will not be needed with a projectile inserted, because that would mean wasted power. It will consist of the second SCR in the MCC162-16-io1 wired as a protection diode to the dissipation circuit consisting of a capacitor and a resistor in parallel, but with an MOV between them. The capacitor will ramp up the voltage across the inductor so that either SCR's dV/dT rating will not be exceeded. After the voltage exceeds a certain level, the MOV will divert the rest of the inductor's stored energy to the resistor, where it will dissipate it as heat (as with most designs).
The entire circuit will be placed inside a metal casing made to look almost exactly like the Fuel Rod Cannon from Halo 2, shown below:
The coil and circuit will be magnetically shielded to prevent eddy current losses from occurring in the casing.
Comments and suggestions are highly appreciated, especially regarding the feasibility of the specs (in my opinion, both planned specs are achievable, but the goal specs will take much longer to achieve).
Registered Member #1774
Joined: Wed Oct 22 2008, 02:51AM
Location:
Posts: 135
Well the first problem I can see is that the projectile is made out of aluminium. Aluminium is not ferromagnetic so in a conventional coingun it would do nothing, unless you're planning to made an induction launcher rather than a coilgun? Also an efficiency of 15% is extremely generous for a coilgun Id say closer to 2% or 3% would be more realistic. And if it is infact a coilgun you want to make then id suggest you try a multistage one, this would make it more effective. Also 23kg is pretty heavy for a gun...(I think). I think your goal with rate of fire is good though, not many (None that I know of) have tried this with a high powered coilgun, Youll need extremely thick wire (8AWG?) and probably active coooling to prevent it from overheating as my coilgun (400j, 19AWG single coil) overheats after about 3 shots!
Edit: Also those Switches are only rated for 6000A peak I have estimated (Using the info given) that the peak current will be closer to 6160A.
Registered Member #1819
Joined: Thu Nov 20 2008, 04:05PM
Location:
Posts: 137
El_Roberto wrote... Aluminium is not ferromagnetic so in a conventional coingun it would do nothing, unless you're planning to made an induction launcher rather than a coilgun?
That is correct. I'm making a coilgun that uses induced magnetic fields to repel the projectile. I also might use copper as a projectile material as it has a lower resistance.
El_Roberto wrote... Also an efficiency of 15% is extremely generous for a coilgun Id say closer to 2% or 3% would be more realistic.
The following is just my pure, theoretical logic (as is most of my thinking), so if you see something horribly wrong with it, please comment.
PowerLabs has made a single stage coilgun that achieves a muzzle energy of 360J with an efficiency of 12%, so it is achievable in my opinion. The reason why I predict higher efficiency figures is because I don't have to worry about things such as suckback (since it is being repelled) and projectile saturation (of course, up to a point where the projectile melts due to resistive losses).
Also, AC induction motors are very efficient (I think >90%) and they work on the same repulsive principles as an induction coilgun. Both of these devices are basically transformers with mobile secondaries, and transformers are also efficient.
El_Roberto wrote... Youll need extremely thick wire (8AWG?)
Thanks for mentioning... I was thinking of using 10 AWG wire, but I'll look into 8 AWG wire and see how much of a benefit (in terms of dissipation) it offers. PowerLabs' single stage coilgun uses 10 AWG wire hooked up to a 3000J capacitor bank with fairly good results.
El_Roberto wrote... Also 23kg is pretty heavy for a gun...(I think).
That's very true... The military probably wouldn't adopt this as a weapon, considering the fact that they thought the M60 machine gun (~25 lbs, I think) was heavy. I might still make the final coilgun like this so it will have the same weight as the real Halo Fuel Rod Cannon. This comes with a nice melee attack...
El_Roberto wrote... Edit: Also those Switches are only rated for 6000A peak I have estimated (Using the info given) that the peak current will be closer to 6160A.
Thanks for pointing that out. I have another dual-SCR by Semikron very similar to the Ixys dual-SCR, and I accidentally used its peak current specification instead of the one from Ixys. The peak current rating for an 8.3 ms pulse using the MCC162-16-io1 is actually 6400A.
What I am wondering now is if that is a big enough margin.
Thanks for your suggestions, as this is my first coilgun.
Registered Member #1389
Joined: Thu Mar 13 2008, 12:50AM
Location: Pittsburgh, PA
Posts: 346
The peak current that an SCR can handle goes up as the pulse length goes down. If you have an inductance meter with the appropriate range, you can use this simulator to find your pulse shape and length. If your pulse is shorter than 8.3ms, but only a little bit higher than the pulse rating of the SCR, then you should be ok.
Registered Member #1262
Joined: Fri Jan 25 2008, 05:22AM
Location: Maryland, USA
Posts: 451
I think you might be able to approch those insane efficiencies with cryogenic cooling. Someone tried that a couple years back and got some good results but it never took off due to the obvious need for a cryogen.
Registered Member #95
Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308
I must say it's an ambitious project! I'd like to see how it turns out. 15% with a single stage sounds like a long shot to me, but we'll see how it goes. You have better chances at greater efficiency with multi stage designs.
Registered Member #511
Joined: Sat Feb 10 2007, 11:36AM
Location: Somerset UK
Posts: 55
Hi killah573 and welcome to the forum.
I think this is an excellent project and I look forward to seeing how it turns out. I think the overall aims and specs are perfectly reasonable, here are my thaughts so far.
1. The efficiency is a bit optimistic, I would use 15% as the ultimate goal. Your first prototype could be 0.1% to 10% depending on how successful the design is.
2. That SCR is probably capable of switching a 1.9KJ bank but it will depend on the total resistance of the circuit not the peak current.
3. An induction coilgun needs high current and high dI/dt, at 450V and 18,800uF a 100uH coil is way too much, the pulse will be too long and the peak current too low. For this bank you want 5 to 10uH this gives you 10 to 20 turns of 10AWG wire. If you put all the capacitors in series for 1800V and 1175uF the bank will be better matched to a 100uH coil.
4. Single stage induction launchers based on the pancake coil geometry with the armature as a flat plate are generally successful and can be efficient. Single stage induction launchers with a solenoid coil and rod armature are spectacularly un-successful. I have a theory as to why this is the case, the force on the armature is proportional to the inductance gradiant, or more correctly the gradient of the mutual inductance between the coil and armature dM/dx. In the case of the pancake coil when the plate is close to the coil the gradient is huge but drops rapidly with distance, so this design can generate a very large force but only over a short distance. The solenoid coil has a much lower gradient but can produce a force over the full length of the coil. If you use a low inductance coil the short pulse will produce a force but the pulse will be over before the armature has moved much, force x distance = kinetic energy so the efficiency will be low. If you use a high inductance coil the long pulse will produce virtually no force at all.
This site is powered by e107, which is released under the GNU GPL License. All work on this site, except where otherwise noted, is licensed under a Creative Commons Attribution-ShareAlike 2.5 License. By submitting any information to this site, you agree that anything submitted will be so licensed. Please read our Disclaimer and Policies page for information on your rights and responsibilities regarding this site.
Fuel Rod Cannon (coilgun)
