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 #1253
Joined: Tue Jan 22 2008, 02:06PM
Location:
Posts: 39
Im in the beginning stages of my coil gun design, and I have a question on the barrel. I was planning on using a metal barrel, probably steel or brass, and I know about the eddie currents. My question is, when slotting the barrel do you slot all the way down the barrel? Or only where the coil is going? I have a link to two drawings explaining what I mean. I was planning on a 2 or 3 stage gun.
Eddy currents (and not eddie) that will be created are proportional to the magnetic field strength (actually to the magnetic field CHANGE) at the point that they will emerge. Away from the coil, the magnetic field will be significantly lower, so you don't need to slot the parts of the barrel that are at a reasonable distance from the coil - depending on your coil, current that feeds it etc. I would feel contempt with slotting beneath the coil and 3-4 cm before and after.
Caution though: the coil will aply a LARGE force on the projectile whenit enters (the coil) and this force MIGHT deform your barrel easily, if it is slotted. Imagine that it will squeeze the barrel, like holding it in your fist, but with a lot more force. This deformation might lead to blocking of the projectile.
Steel is ferromagnetic, so DON'T use it as a barrel, as some energy will be lost in magnetising it.
I have worked with TEFLON (PTFE, polytetrafluorethylene) barrels with a lot better success, remember that teflon has the minimum friction of almost all solids, no eddy currents, and no magnetisation. Only problem is that if the diameter of the bore is large, it might crush under the coil - but if it is small, e.g. 6mm inside, 10mm outside you have no problem, at least with amateur coils and fields.
Registered Member #1253
Joined: Tue Jan 22 2008, 02:06PM
Location:
Posts: 39
Thanks, that helped alot. I think im going to stick with the brass for the time being, if that ends up not working well I may switch over to the Teflon.
I have a small question for you though: how are you going to slot the brass tube?
I understand that if it is of a large diameter, e.q.2-3cm then it could be done easier, still it troubles me. If you have any good ideas, glad to hear them!
Registered Member #1513
Joined: Sat May 31 2008, 12:08PM
Location: Russia Klin
Posts: 48
I done this using angle grinder for 5 minutes you could do this with more accuracy. you also will need to clear agnails from internal side of a barrel.
Here you can see partly-sloted barrel
[Edit: Maximum 400 pixels and hotlinking random sites is rarely a good idea.]
Yea I also considered a dremel or angle grinder, but I couldnt think of a way to get decent accuracy, and im not sure how the fibres in my carbon fibre barrel would react to the method of removing the material....
Registered Member #1253
Joined: Tue Jan 22 2008, 02:06PM
Location:
Posts: 39
Im going to use a mill, probably use a 1/16" (1.59mm) end mill to slot the piece. For now im going to use Aluminum, had some readily available, but im ordering the brass as I type this. If only I could find my freaking calipers so I can make up a drawing!!!!
I'm going to slot it tomorrow, Il post up some pictures!
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.
Barrel Questions
