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.
Just want to share my technique of coil construction - maybe some of you would like to try it out: Part 1, overview:
Part 2, practice:
Here are the results:
The technique is good for coils wound with <1mm wires as those are easily bend.
The major problem for me now is the long setting epoxy - it is required to fill the coil and is hard to find: epoxy commonly available now is 5min ones. Any ideas where to find an hour-hardening type of epoxy?
I got 105 epoxy and 209 extra slow hardener. It cost me ~$100 - bottles are so big... In 10hr mix turns from liquid into sticky gel and it takes 2 days for the mix to harden. Did not tried on coils yet. This extremely slow curing and big bottles size dictate the new strategy: many coils in one day. Kinda have a few winding machines available, prepare the excessive amount of epoxy, and wind many coils one by one. In a next couple days you got all of them ready. Still, I would recommend 206 slow hardener instead of 209 - that one is just too slow, but I don't want to spend another $40.
BTW, maybe you have a question already arized "why not to wind coils directly on the barrel?". Because during the winding side pressure of the wire is big and not uniform: even if washers were aligned well, they may get repulsed causing barrel under the coil to bend into an arc. When I was practicing on-barrel winding in my early coilgun prototype, I stopped on 4th stage from 8 planned due to this issue causing barrel to get curvy. I still use homemade rolled paper-epoxy barrels which are not strong, but thin and non-conductive, and as far as they stay straight, they work perfect. Modular coils get into the barrel like beads.
Recently I found that steel washers I keep using at the ends of a coil support induction currents well enough to get repulsed from the coil. Even cut in a washer does not help a lot. So if you are using external iron make sure it is powdered iron or ferrite, otherwise some energy will be lost significantly reducing the benefit of using external iron.
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
Yandersen wrote ...
I got 105 epoxy and 209 extra slow hardener. It cost me ~$100 - bottles are so big... In 10hr mix turns from liquid into sticky gel and it takes 2 days for the mix to harden. Did not tried on coils yet.
Try heating it (putting the coils in a warm place) to cure it quicker. Around 80 degrees F should do it, read what it says in the instructions as far as temperature goes for further advice.
The beauty of this sytem is that you have plenty of time to work with it, at a cool temperature, then, when you are ready, you can increase temperature to cure it.
Maybe the 206 hardener would be better, but temperature is by far the biggest factor affecting curing times, especially with 'slow cure' hardeners.
EDIT: I looked at their website, it says 'cures in 6-8 hours @ 95F (35C)'.
"209 Extra Slow Hardenerâ„¢ is formulated for use with WEST SYSTEM Brand 105 Resin for general coating and bonding applications in extremely warm and/or humid conditions or when extended working time is desired at room temperature. Provides approximately twice the working time of 206 Slow Hardener. Forms a clear, amber-colored solid with good physical properties and moisture resistance for bonding and coating applications. Not intended for clear coating.
Pot life at 72°F (22°C): 40 to 50 minutes Pot life at 95°F (35°C): 15 to 20 minutes Cure to a solid state at 72°F (22°C): 20 to 24 hours Cure to a solid state at 95°F (35°C): 6 to 8 hours Cure to maximum strength at 72°F: 4 to 9 days Minimum recommended temperature: 70°F (21°C)"
Due to the plastic insulation around the coil I can't heat it up in the oven (common practice with 5min epoxies turning them into "glass" at 60C in 3min) - only when coil is taken out of the machine, but it can be done only when epoxy is hard. The mild temperatures are somewhat hard to keep for 8hr. Hm, what temperatures plastic can sustain without softening? Scotch tape? I can try making side rings out of the plexiglass and axial cylinder out of the plastic pen - if this will allow heating.
Update: video of coil winding process is added to the first post.
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
Yandersen wrote ...
Due to the plastic insulation around the coil I can't heat it up in the oven (common practice with 5min epoxies turning them into "glass" at 60C in 3min) - only when coil is taken out of the machine, but it can be done only when epoxy is hard. The mild temperatures are somewhat hard to keep for 8hr. Hm, what temperatures plastic can sustain without softening? Scotch tape? I can try making side rings out of the plexiglass and axial cylinder out of the plastic pen - if this will allow heating.
Update: video of coil winding process is added to the first post.
You could possibly try highly polished metal surfaces, eg electro-polished stainless steel, or aluminium. , however I'm not sure how successful this will be.
I can see that most of the plastics I can think of that epoxy doesn't stick to will soften at these temperatures, and also, that wax wouldn't be much use at these temperatures.
Does epoxy stick to the 'shiny' side of kitchen foil?
What about CD's? (I'm not sure what they're made of)
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
Yandersen wrote ...
Any smooth plastic would work. Any metal wouldn't (even if polished).
There are plenty of thermosetting plastics that epoxy will bond to. Metals need a rough surface to stick to epoxy, and they need to be clean. Any highly polished metal, especially if it is thin enough to be flexible, should be fairly easy to remove once it's cured. I used to own a business that specialized in producing stainless steel load bearing inserts for carbon fibre racing yachts. I'd need to etch the surface to get the epoxy to stick.
Ash, arguing like that we losing the point of discussion. Did you watched my second video? I couldn't get the nut off until I scraped epoxy out of the washer's edge. Metal was polished and it was easy to scrape epoxy from it, but still it was sticky enough to give me troubles. Scotch tape doesn't bond to epoxy at all. There is a set of materials which do bond to epoxy and some are don't. Just assuming your metal is nicely polished is not enough to be sure you will be able to get the coil out.
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.
Coil construction
