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 #1329
Joined: Mon Feb 18 2008, 07:31PM
Location: Harwinton Connecticut
Posts: 53
Hello Folks,
Today I started building a disc launcher. The coil is made of #12 wire and is the size of a CD rom disc in diameter. It is only 1 wire thick at this point. The hole in the center is 3/8" in diameter. The gorilla glue is almost done curing.
I spent a while on youtube and here looking at other folk's launchers. Here is the question:
Why did I not see, or perhaps I missed it, that anyone has mounted their launcher onto a steel backing, for the bottom side?? Would that not concentrate the magnetic field on the topside of the disc and increase the efficiency? Also give the coil a nice firm launching pad? PauLC W1VLF
Registered Member #75
Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711
The reason is that a steel backing would lead to massive eddy current losses. Furthermore, depending on the pulse you deliver to the coil, the steel backing would probably be repelled from the coil and launch the coil itself into the air! What people do is to place a steel rod through the center hole, which has to be laminated to avoid eddy currents, and this seems to help only in low power designs.
What you could do (and this has not been tried AFAIK) is to use a backing of ferrite ceramic, possibly a disk shaped ferrite magnet from an old speaker or from a microwave magnetron. Stick a ferrite rod through the center hole for added field focusing.
Registered Member #1329
Joined: Mon Feb 18 2008, 07:31PM
Location: Harwinton Connecticut
Posts: 53
Hello Dr Shark, Yes... I forgot about the Eddy currents... I always thought that Eddy currents were only generated in Non-ferrous materials. YThe other thing that made me think of this idea was that some folks have used ferrous pipe around thier coilguns to improve efficiency.
Registered Member #75
Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711
If by stacking you mean putting several layers of winding in series or parallel, yes, people have done that. This way you can tweak your coil for more inductance (layers connected in series) or less resistance (layers in parallel). If you are somehow hinting at an arrangement with several stages of acceleration, thats kinda impossible to do since the disk would have to pass through all the subsequent coils.
Registered Member #1329
Joined: Mon Feb 18 2008, 07:31PM
Location: Harwinton Connecticut
Posts: 53
Thanks again Shark, and yes I was thinking about the former. Also I would assume that the field increases with additional layers of coil? If they are phased correctly??
Ijust launched my first aluminum disc!!! WOW I was not ready for that Havinf fun PaulC W1VLF
Registered Member #158
Joined: Sun Feb 12 2006, 09:53PM
Location: Central Ohio
Posts: 282
Depends on how the coils are connected. If they are wound in parallel the layers basically act as heavier wire, the number of turns stays the same. You should get a stronger pulse due to lesser resistance. I've wound a coil this way, two layers, and did get increased performance using the identical setup with single layer coil. Good luck with your project, disc launchers are a lot of fun (and of course be safe .
Registered Member #179
Joined: Thu Feb 16 2006, 02:08AM
Location: Hagerstown, Maryland - Close to Prime Outlets
Posts: 287
More layers are good to a point...I found my 3-layer coil was less efficient than my two layer designs. I usually parallel the layers. I think the distance from the bottom layer to the projectile on top results in large magnetism losses.
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.
Disc launcher questions
.
