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 #4318
Joined: Sun Jan 08 2012, 02:11AM
Location:
Posts: 3
So this is my second coilgun that I have built, this one is much larger than my first, using up to four 450V, 2400microfarad capacitors (243J each). It has a 1/2" PVC barrel, while the projectile is a 3mm wide, 21mm long bolt. The coil is 3 inches long. We are hitting a speed limit of 70MPH (30m/s), as it seems when we go from 2 capacitors to four capacitors, the increase is not substantial. We are using 10 gauge wire, a nice SCR and 12 gauge magnetic wire for the coil. Did we overlook something, or are we just overloading the wires and need to turn down the joules???
ANY post is WELL appreciated, thanks for any time you give me.
Registered Member #1451
Joined: Wed Apr 23 2008, 03:48AM
Location: Boulder, Co
Posts: 661
You need to tune your coil for the added capacitance. It sounds like you might be getting some slight suckback, so remove some turns. As you remove them the velocity should increase. Go until it peaks!
Registered Member #4318
Joined: Sun Jan 08 2012, 02:11AM
Location:
Posts: 3
Suckback? would moving the projectile backwards from the barrel help? It's for a science fair project, so I'm trying to keep everything as constant as possible
Registered Member #1451
Joined: Wed Apr 23 2008, 03:48AM
Location: Boulder, Co
Posts: 661
As far as efficiency goes, you need to remove turns. The pulse is too long with the extra capacitance. The magnetic field doesn't die completely out by the time the projectile reaches half way so some of it actually slows it down inside the coil.
Moving the projectile might help, but as long as you are changing that variable, why not change the coil? If nothing else, you can change it to verify the strange behavior of power not increasing when you add the extra caps.
Registered Member #3888
Joined: Sun May 15 2011, 09:50PM
Location: Erie, PA
Posts: 649
For my class room demo coilguns i just move the projectile back from the coil if there's noticeable suckback. It makes for an interesting point to mention and leads to a discussion on the design considerations that would go into optimizing the initial conditions. So for a science fair project I wouldn't bother with changing the coil unless you want it to be the best it can be. If you do decide to remove coil turns before or after the science fair then be cautious: the increased current sometimes causes wires or connections to explode (although very unlikely with your wire sizes)
Registered Member #4318
Joined: Sun Jan 08 2012, 02:11AM
Location:
Posts: 3
You sir just described my entire science fair project, optimizing the initial position based on the energy of the capacitors in Joules. Well thanks all, I have my data.:-D
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.
Coilgun question
