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 #2906
Joined: Sun Jun 06 2010, 02:20AM
Location: Dresden, Germany
Posts: 727
Interesting concept. I like the light trap solution! Its a bit big for 10J ouput energy but that comes with the efficiency - which is suprisingly high for your arrangement to be honest
Maybe you could add a video of a longer distance shot.. you projectiles should be very stable! It would also be interesting how consistent your output energy is. (Measure multiple shots)
mkF means MikroFarad = "µF" mcHn for MicroHenry = "µH" Russians...
Big flaw: Your circuit diagram is missing diodes in parallel to your capacitors to avoid reverse polarity. Since you use electrolytics you will destroy them in a very short time!
Anyway... nice to see something finished Kind of. The Diodes are really worrying.
Registered Member #57984
Joined: Thu Nov 19 2015, 09:44AM
Location:
Posts: 58
Big flaw: Your circuit diagram is missing diodes in parallel to your capacitors to avoid reverse polarity. Since you use electrolytics you will destroy them in a very short time!
That is only simplified animation, not diagram. Reverse diodes are of course installed (P600J). As for long distance shots - going to do this. Accuracy testing shows that approximately 50 m may be reached with my bow target.
Registered Member #2906
Joined: Sun Jun 06 2010, 02:20AM
Location: Dresden, Germany
Posts: 727
I am relaxed then Did you get this gouping by aiming with your hand or did you put it in a vice? Either way i find this quite good for 1sec flight time. I had bigger problems in my design with inconsistencies due to projectile premagnetisation and sensor noise. But thats caused by my tendency to overcomplicate things
Registered Member #57984
Joined: Thu Nov 19 2015, 09:44AM
Location:
Posts: 58
The accelerator was fixed (not in vice, just with some heavy objects like books etc :) Alas, the ditance in test was only 10 m, so the accuracy is quite poor - probably because of flexibility of the arrows. Anyway, there is a lot to improve.
Registered Member #58215
Joined: Wed Dec 30 2015, 11:27AM
Location: Boise, Idaho
Posts: 65
Wanting to reply to this actually is what got me to finally make an account and not just lurk. If you can get the timing down for it- You should add an additional piece of iron/steel at the other end of the crosbow. It does not have to be the same weight as the nose to imbalance flight, (same diameter, but shorter to take advantage of flux?) but doing this will essentially double the number of stages your gun has. Not to mention, when the rear end of the projectile comes through, your projectile is already sped up so you don't get the horrible inefficiency of the first stage for it. I think it is dedinitely worth looking into.
For stability, you should add flexible fins that wrap around the rear of the shaft(trim the plastic before second piece of iron if you do add another piece and put fins there. Once dart leaves the barrel, the fins will pop out and help stabilize it.
Registered Member #57984
Joined: Thu Nov 19 2015, 09:44AM
Location:
Posts: 58
You should add an additional piece of iron/steel at the other end of the crosbow. It does not have to be the same weight as the nose to imbalance flight, (same diameter, but shorter to take advantage of flux?) but doing this will essentially double the number of stages your gun has. Not to mention, when the rear end of the projectile comes through, your projectile is already sped up so you don't get the horrible inefficiency of the first stage for it. I think it is dedinitely worth looking into.
I thought about such constructions. But calculation shows that any heavy object on rear end of the arrow will definitely disbalance it (even a short one). Another thing is that my coilgun is SCR-driven and has single cap battery per stage, so the stage can work only once.
For stability, you should add flexible fins that wrap around the rear of the shaft(trim the plastic before second piece of iron if you do add another piece and put fins there. Once dart leaves the barrel, the fins will pop out and help stabilize it.
Can't imagine this. To unwrap after the shot and sustain airflow the fins must have high rigidity, but such fins will damage inner surface of the barrel and it will fastly loose its transparency, and also they must make high friction during acceleration (if I understand your idea).
Nontheless, I must say that you rise important question. In fact I think the projectile's construction is the only problem which interferes commercialy avaliable coilguns to be produced. Neither low speed nor efficiency.
Registered Member #2906
Joined: Sun Jun 06 2010, 02:20AM
Location: Dresden, Germany
Posts: 727
In fact I think the projectile's construction is the only problem which interferes commercialy avaliable coilguns to be produced. Neither low speed nor efficiency.
Bold statement. Let me explain why i think otherwise: 1) If you buy a gun you want raw kinetic energy. You want to feel the primitve manly powers, kickback and you want to have reasonable accuracy and precission for competetive behavior. Normal guns provide those features. Even crossbows. But coilguns? Everything below 20..30J is basically no fun to shoot. You say "yes it is" but think about customers who are not allready biased by the great self-made technology... And dont just think about Youtube videos where you shoot glass or anything that shatters easily. People will be disapointed as soon as they shoot anything that does not have an inherent spectacular effect when beeing hit. Even 100m/s is quite disapointing over a short distance because you notice the lag between shot and impact. Its no match to a supersonic bullet. 2) To provide usefull projectile energy you have to provide even more electrical energy. Thats directly related to efficiency. Every electrically stored joule will add weight (1g.. 2g) This adds up to quite a heavy machine adding the copper coils and batterys and a reasonable (>500W) cap-charger. No one wants a gun that fires once every 10sec. It is frustrating to use. No fun. The waiting time is basically the same as when microsoft office starts up. You allways want it to "just work allready!!!!" 3) To be on the marked you need customers which will decide to use a coilgun over any alternative. The price point of an electronic gun will allways be high in contrast to its output power. You need to convice. Noone who can buy a regular gun (eg in USA) will decide for a coilgun or will recommend it further. A normal handgun is way cheaper and has 5..20x the kinetic energy and supersonic and easy-to-buy projectiles. just think about with who/what you are competing. A commercial design can not only rely on a niche market. The prototype costs for the casing and everything alone demands a quite high number of guns to be sold just to compensate for your development costs. And you need to sell it at a way higher price than you can build it to live. 4) to reach alternative customers outside of the USA (which have more restrictive gun laws, thus nicer police and less gun related deaths) you need to be inside the legal system and you need to be able to sell your guns without the need to registration or licencing - a coilgun is not worth such effort. It basically needs to be free and 18+ but must be forbidden to carry it in public and that has implications on how to build your gun to go around legal definitions. There is quite a lot engineering involved in that alone. 5) You need a community that can play with the gun.. you need firmware to customize your gun, the acceleration profile (create more kickback stimulation, or a smoother acceleration profile or what not.. you also need security features.. what happes if you drop the gun? What happes when it rains? What happens when somebody puts a wrong projectile in... you are responsible for every engineering fault - and no offence - i like your design, its a nice idea, well built, but not the best show-off if you want to convince professionals about your engineering skills. 6) It must be reliable. It must work out of the box for thousands of shots. Even when dirty. Just think about your Light-traps alone... what if they get blocked by dust or someone uses graphite dust to lubricate the barrel. You need propper heat management for rapid fire, a solid reloading mechanism and a solution when it finally still jams. 7) Design for Manufacturing. DFM does need special considerations. If you want a reliable production process you have to take special precautions to make assembly as efficient and easy as possible. every complicated solution is basically no solution. Just rethink your build-process... was there anything that was not as easy to assemble as you wished it was? How to change it without compromising weight, volume or output power?
I could go on but as a conclusion: you need to rethink your statement from a customers view. A view of someone who is not allready biased by the technology. If you neglect thats a coilgun what is left over a crossbow? Higher price? Less performance? Heavier? Yes, maybe higher fireing rate. But everythin else? The energy density of any coilgun is just pathetic.
I am playing with the same idea... even with my design i am currently humble about the future of such endeavour. However i provide security, high output power (~120J), low weight (5.5kg) and a usefull formfactor (85cm long rifle). But high price (1.5k€).
I dont think with a more inefficient design you will be able to be get even close to this (even you might not need to get close to this). There is quite a lot of bulky stuff you need in any coilgun of any size. So a bigger gun is acutally better because the longer acceleration path provides more room for electronics. you can not build a smaller and proportional weaker and proportional cheaper coilgun. The formfactor just will not give you the volume for everything. (Battery, battery/cap-charger and stuff)
Projectile design: you must basically rely on having no design at all. The best is to use a world wide available standard projectile format. Anything else will leave any customer dependend on your continous production. Would you spend money on a product where you are dependend on a maybe soon failed start-up company? Never ever.
I hope i gave you an insight in what i am thinking about.... how would you do it? Do you think what i say is overcomplicated salesman-talk or do you think that basically anything on the market will make a nice bussiness? I honestly dont think so. But i wish it was true...
Registered Member #58215
Joined: Wed Dec 30 2015, 11:27AM
Location: Boise, Idaho
Posts: 65
_Eugen_ wrote ...
I thought about such constructions. But calculation shows that any heavy object on rear end of the arrow will definitely disbalance it (even a short one). Another thing is that my coilgun is SCR-driven and has single cap battery per stage, so the stage can work only once.
Can't imagine this. To unwrap after the shot and sustain airflow the fins must have high rigidity, but such fins will damage inner surface of the barrel and it will fastly loose its transparency, and also they must make high friction during acceleration (if I understand your idea).
Nontheless, I must say that you rise important question. In fact I think the projectile's construction is the only problem which interferes commercialy avaliable coilguns to be produced. Neither low speed nor efficiency.
Is projectile balance not more important than simply the presence of another heavy object in the rear? so a little lighter on the front, and add more onto the back? You wouldn't need to add more SCRs to the design, but it would introduce more capacitors and more complexity. It's just the thought I had, seems you have looked into it.
They really wouldn't. Even adding a simple streamer to the rear of a long projectile will stabilize it if it is moving fast enough- the fins could be fairly flimsy plastic (think the plasticy paper?) , with not much force pushing them to the outside of the barrel and they would still unfurl once they left. Even this small force would eventually scratch the barrel, I suppose, but it would take a lot of shots. Again, just an idea if the dart is tumbling in flight.
Registered Member #57984
Joined: Thu Nov 19 2015, 09:44AM
Location:
Posts: 58
to DerAlbi: I think you do really have tendency to overcomplicate things :) I just wanted to say that stabilization of projectile is the problem with little attention payed for (relatively to speed, power, efficiency etc). One may build a coilgun with >100 m/s and 100 J in projectile, but it worths nothing without stabilization. As for your list of statements: 1), 2) - it is up to the customer, I think. Many crossbows have <100 m/s and loading time is more than 10 sec - nevertheless they are spead goods. Moreover, I do suppose that some coilgun models avaliable in Internet could be commercilally attractive provided they had stabilized shots (and nicer design) (although I don't pretend on it with my EM-3 - I just put it into a suitable case, although 90% gaussers in Internet don't even think about it). 3) - I suggest it is unfair to compete coilguns with conventional firearms. Their opponents might have been pneumatics, bows and crossbows. 4) - 7) The problems you are writing about are true but they concern future times, when the coilguns (if created) will be produced by hundreds and thousands. We decidedly cannot foresee all troubles especially about reliability - they can be revealed only in mass production and exploitation. But some questions can (and must ) be anticipated now. For example we can forbid for user to apply graphite dust by manuals :) As for law limitations - that is not our business, I think. Although you are right that coilguns are in "law vacuum" now, but I rely that these problems will be solved essentially. I see my own challenge to produce a sample with "interesting" characteristics (including as good design as it is possible for hobbyst) - all other tasks are not my deal. I absolutely agree with you that even in our test models we must try to ensure water-proof and electrically safe design.
Projectile design: you must basically rely on having no design at all. The best is to use a world wide available standard projectile format. Anything else will leave any customer dependend on your continous production. Would you spend money on a product where you are dependend on a maybe soon failed start-up company? Never ever.
I didn't meet "world wide available standard projectile format" for coilguns - may be some examples? The only thing I can imagine is standard steel balls (sold for crossbows and slingshots) - I have projected some systems for such a projectile, but my latest calculations show that it will be dispersed very strongly because of the gap between the barrel and projectile, which is inherent to coilguns. Sorry for my short answers, but I think this detailed discussion is somehow out of place in this thread :).
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 EM-3 ("Electric bow")
