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Homemade solenoid

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Homemade solenoid

Unread postAuthor: AlphaOmega » Wed Sep 16, 2009 10:27 am

Hello all this is my very first post on here I have been doing a lot of reading just this is my first post. I have drawn much inspiration since I have joined and have been reading the posts. I think i have finally decided to start designing my first pneumatic. I have a good idea of where to start but I have a question regarding solenoids. I do not have anything drawn up yet but I was wondering if anyone here has ever used a solenoid to replace a hammer valve? From what I have gathered so far using solenoids has somewhat become obsolete due to the slow opening time. So my idea is to make a custom solenoid in my dc electronics class at ITT tech. The idea I have been toying with would consist of a custom solenoid, don't have the parameters yet(size of core, core material, what gauge wire and how many winds yet) My question is has anyone ever tried to make a capacitor bank to dump a high current into the solenoid? Such as a coilgun would use. I'm not the sharpest knife in the drawer but I think it might work so if anyone here is good with this sort of thing any help would be greatly appreciated. Also if this helps I would like to build a semi-auto pcp air gun similar to the FX-Monsoon. Most would be crafted from billet 6061-T6 aluminum and would have a operating pressure of 3000-4000 psi and would like to get somewhere close to the .25 caliber range. Sorry if this message is jumbled but any help would be greatly appreciated.

-AlphaOmega
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Unread postAuthor: boyntonstu » Wed Sep 16, 2009 10:49 am

How about using a powerful, fast acting, long stroke solenoid to compress the air?
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Unread postAuthor: jackssmirkingrevenge » Wed Sep 16, 2009 11:03 am

Using a capacitor powered solenoid to knock a valve open is the concept behind the Harper Wolf pistol and many Daystate rifles, using so called"Capacitor Discharge Technology", more details here

I have a Daystate Mk.3 in my collection that uses this system. Oh, and I have a Monsoon too :D
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Unread postAuthor: AlphaOmega » Wed Sep 16, 2009 11:03 am

My goal is to have an over under pcp air gun. based on the fx-monsoon. I was hoping to replace the hammer valve with a solenoid build from scratch that way I can build it to my specs. My question is does anyone think that if i used a capacitor bank to dump the electricity through the solenoid it would sufficiently increase the opening speed? I was also thinking that i could harness the excess air by drilling x amount of holes in the barrel and having that escape through the shroud operating a gas ram for recocking. If this were to work it would be fairly easy to design a switch fire board. Well maybe not fairly easy but mos-def doable. Another plus of this design would be that if the firing valve were electronically actuated then a bull-pup design would be much easier with an electronic trigger than having a long mechanical rod to actuate the sear. Well it makes sense in my head. Any thought or ideas or criticism are welcomed with open arms. Once again all parts will be rated for a minimum of 3000 psi operating pressure. My goal is a high pressure multi-shot pcp air gun with an electronic trigger I figure if I am going to build it I mise as well do it while i can get help in school.

Thanks for all the help -AlphaOmega
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Unread postAuthor: jackssmirkingrevenge » Wed Sep 16, 2009 11:13 am

My question is does anyone think that if i used a capacitor bank to dump the electricity through the solenoid it would sufficiently increase the opening speed?


Are you going to start off with a commercial PCP and convert it or build it from scratch? As well as the valve, you have to think about rotating the magazine. The Monsoon does it using the air blast from each shot, but it doesn't have to be a rotary mag, if you're using spherical projectiles there are much simpler variations that would not need external power.
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Unread postAuthor: AlphaOmega » Wed Sep 16, 2009 11:14 am

Ty for the reply jack. That is basically exactly what I would like to do but I would like to completely replace the poppet valve and hammer with a solenoid. Instead of a solenoid operating a poppet I would like to use a custom push solenoid that pulses to open that valve that is normally closed by a spring and the pressure in the tank. Not sure if it would work otherwise would have probably already have been done. The attractive part about this is power could easily be adjusted by the current running through the solenoid and/or the solenoids valve time. Hope I am making sense

Thanks again Jackssmirkingrevenge

-Alpha Omega

I will hope to build this all from scratch. The magazine seems to be the trickiest part for me at the moment. Maybe I can design a spring feed clip that will reside in the butt of the bull-pup design. We shall see.

Edited by jrrdw.
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Unread postAuthor: jackssmirkingrevenge » Wed Sep 16, 2009 11:20 am

Instead of a solenoid operating a poppet I would like to use a custom push solenoid that pulses to open that valve that is normally closed by a spring and the pressure in the tank.


Isn't that saying the same thing? A poppet is a valve that is normally closed by a spring and the pressure in the tank ;)

What calibre and ammunition do you have in mind?
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Unread postAuthor: AlphaOmega » Wed Sep 16, 2009 11:25 am

I suppose you are right about the poppet valve. I would hope to be using standard .25 caliber lead or alloy pellets. Or possibly something custom cast. Nothing is set in stone yet I am here to ask the pros opinions. I have been messing with ggdt here and there to get a vague idea of all the dimensions. My ultimate goal is to have her shoot around 1200-1500 fps I know its far fetched but I think it is obtainable. I am sure a whole lot of trial and error will be in place but with my determination and the help of the cannon gods here I think it it can be done once again thank you for the help.

-AlphaOmega

The gun will also use a bolt that is operated by the gas ram to chamber the next projectile. Not sure if I mentioned that before. And the air from the chamber will flow through the bolt to fire the pellet. Somewhat as the design paintball guns.

Edited by jrrdw.
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Unread postAuthor: jackssmirkingrevenge » Wed Sep 16, 2009 11:40 am

It's certainly an ambitious project to build from scratch. You'd have to make something like the hammer valve that pilots Gippeto's masterpiece but operated by a solenoid instead of a hammer. As to the reloading system, I would make something simple like the blow-forward valve but you'd need heavy duty construction if you're operating at 3,000 psi...
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Unread postAuthor: Technician1002 » Wed Sep 16, 2009 11:56 am

There are many issues with trying to create a fast electric solenoid. Lets cover a few. Some solutions are mentioned but without details.

1. Inductance. A coil of wire is an inductor that will resist step changes in current. A high voltage to force the issue is a solution. To prevent the current from rising too far over time, a capacitor that discharges over the same time make a nice fast risetime in the coil. As you add turns to increase the power, you also add resistance and inductance that in turn slow it down.

2. Mass. The mechanical parts need to be iron and large enough to have enough force to be useful. Here again bigger make stronger so hopefully faster, but bigger is a larger mass to accelerate. Yuck, no easy answer. Again a higher voltage and bigger cap will throw more impulse energy into getting it moving.

3. Hysteresis. What the heck is that? When you throw a strong magnetic field on a piece of iron, it becomes magnetized. To reverse or neutralize the magnetism, a reversed field is needed. The difference between the fields that will change the magnetism in the iron is the hysteresis curve. This is an energy loss resulting in heat in the core. Used to your advantage, this is how a magnetic stripe is written on a credit card or data recorded on your hard drive.

4 Eddy Current. Again, what?? A changing magnetic field in the presence of a conductor (iron conducts electricity.. surprise) it will induce a current into the conductor. The current in the conductor meets resistance and this heats the conductor and uses energy. It saps power from your intended motion. The higher the frequency the higher the loss. Um.. didn't we want a fast solenoid? Yes. so this is BAD. The solution is to break up the iron into smaller parts separated by insulation. In low frequency transformers a laminated core is used where the thin strips are varnished to stop eddy current from robbing power and heating the core. High frequency switching power supplies use powdered iron in an epoxy core. The problem with that is now the core is brittle and can be shattered with a hammer, or fast operation of a solenoid. This provides the design engineer a design challenge. how to make it strong and yet not lose power to energy robbing eddy currents.

5 Core saturation. Remember the hysteresis curve above? Iron has a property that in a strong magnetic field, it can't increase magnetism any more. In the case of the inductance above that limits inrush current by inductance, at saturation, the inductance vanishes and current can run away. It also means that increased current does not provide a stronger pull on the solenoid. Didn't we want a strong solenoid to provide high impulse force to move the mass quickly? Could this limit our peak speed? More headaches for the design engineer.

In short. I don't envy your design challenge. Let me know how it works out. :D For starter, study car fuel injectors. They have all the problems mentioned and their engineers got them to work. It may be worth tearing a few apart to study construction, material selection, and drivers. Then you may have an idea on how to scale it up. Modifying one for higher flow may be a solution to the fast electric pilot. They are designed to operate at moderate pressure and high speed. Flow for a hammer valve replacement is an issue with them. :(
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Unread postAuthor: AlphaOmega » Wed Sep 16, 2009 12:14 pm

Thanks technician that is a lot to take in thankfully my dc electronics teacher is willing to help with the design of this aforementioned solenoid. I may just take your advice and disassemble a fuel injector or 2. I have also came across a solenoid calculator or 2 just have to remember where. I know for this being my first pneumatic anything it will be very tough and involve more math than I would like but I firmly believe the end product if operational as expected would be an amazing piece of home brewed artillery. I will keep everyone posted and hopefully draw up a design or two.

Thanks Again for being smarter than me :o

-AlphaOmega
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Unread postAuthor: Technician1002 » Wed Sep 16, 2009 12:42 pm

AlphaOmega wrote:Thanks technician that is a lot to take in thankfully my dc electronics teacher is willing to help with the design of this aforementioned solenoid. I may just take your advice and disassemble a fuel injector or 2. I have also came across a solenoid calculator or 2 just have to remember where. I know for this being my first pneumatic anything it will be very tough and involve more math than I would like but I firmly believe the end product if operational as expected would be an amazing piece of home brewed artillery. I will keep everyone posted and hopefully draw up a design or two.

Thanks Again for being smarter than me :o

-AlphaOmega


If you got it working and into the innovative contest, you would have won my vote because I understand the issues of making a solenoid with high flow, high speed and high pressure. My hats off to you if you are successful.
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Unread postAuthor: spudamine » Wed Sep 16, 2009 1:40 pm

I made some solenoids last year http://www.spudfiles.com/forums/5-shot-hybrid-repeater-t17181.html
They weren't for a main valve so performance wasn't a big issue but they weren't bad, I couldn't hold on to the armature when turning on the coil and they were fast.
construction was quite tricky, I wanted the armature as close to the coils as possible so wrapped some PTFE tape around it and wrapped the wire straight on with high temp epoxy between each layer, worked a treat after curing and removing the PTFE.
I had the same idea as you when I was doing this, also thought it would be quite fun to use a big solenoid with a blade attached inside a chamber to rupture a burst disk, however never got a chance to do anything with either of these ideas.
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Unread postAuthor: AlphaOmega » Wed Sep 16, 2009 5:00 pm

so another ? Is there a certain metal that the coil should be wrapped around? Once again any help would be appreciated
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Unread postAuthor: POLAND_SPUD » Wed Sep 16, 2009 5:12 pm

also thought it would be quite fun to use a big solenoid with a blade attached inside a chamber to rupture a burst disk
use an air cylinder... that will work better
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