Idea for a coil gun
Gregary Boyles, Wed Apr 08 2015, 03:31PMI was reading about how air core coils are very inefficient at transferring energy from the current to the projectile.
And I saw some one had crudely stacked some E-pieces from large transformer, drilled a hole through the stack to insert the tube and then put the windings around the stack.
I was thinking, surely a better way to do it it would be to get an iron core from a toroidal transformer, put the windings through the toroid and then stick the tube through the hole in the toroid.
As it happens I found a discarded electrical device that contained such a toroidal transformer. I am removing the windings and will tuck the core away for future use.
Does any one have any thoughts about the pros and cons making a coil gun via this method?
Also I had some thoughts about the projectile and about eddy currents decreasing the efficiency of the transfer of magnetic energy to kinetic energy.
What if you were to araldite a series of steel washers (I know soft iron is the best material but it might be hard to come by washers made of iron rather than steel) together and then put this assembly in a bullet shaped mold and fill it with liquid epoxy.
The principle would be the same as using a laminated iron core in a transformer to minimise the eddy currents.
Does any one have any further thoughts about this?
Re: Idea for a coil gun
Skynet, Wed Apr 08 2015, 04:10PM
I´ve made some simulations in FEMM. It helps to better magnetic induction but bigger coil inductance negatively affects the switching speed.
Skynet, Wed Apr 08 2015, 04:10PM
I´ve made some simulations in FEMM. It helps to better magnetic induction but bigger coil inductance negatively affects the switching speed.
Re: Idea for a coil gun
Gregary Boyles, Wed Apr 08 2015, 04:20PM
I assume you mean that the magnetic field cannot build quickly enough with an iron core to generate the acceleration for the projectile.
Perhaps a large ferrite core would be better, as they are meant for high frequency operation.
The rectangular cores out of TV flyback transformers spring to mind - I have several of those stashed away.
I could make a multi-stage gun in that case.
Gregary Boyles, Wed Apr 08 2015, 04:20PM
I assume you mean that the magnetic field cannot build quickly enough with an iron core to generate the acceleration for the projectile.
Perhaps a large ferrite core would be better, as they are meant for high frequency operation.
The rectangular cores out of TV flyback transformers spring to mind - I have several of those stashed away.
I could make a multi-stage gun in that case.
Re: Idea for a coil gun
DerAlbi, Thu Apr 09 2015, 09:12AM
All that external iron does is to change the shape of the force vs projectileposition F(x). This leads sometimes to better efficiency in primitive Coilguns, however thats only due to better timing where the Integral( F(x)*I(x) ) is larger at the end. But thats nothing you can generalize. What you can say is that air cores are not the best thing for SCR-switched coilguns... but air coils transfer energy quite happily if used correctly.
As Skynet said correctly the larger indurctance reduces switching speed. Thats why you will end up with less turns for the same original inductance. Less turns means less resistance which is interpreted by people that it must result in higher efficiency. What they dont see is the picture that Skynet posted: the actual positions where the projectile is accelerated becomes actually shorter because the field extrends less. Less distance means shorter traveltime and less energy transfer. That means in the end youve got less resisitve losses, but also lower energy transfer. It basically results in the same efficiency.
Efficiency is not controlled by the coil, but the timing.
DerAlbi, Thu Apr 09 2015, 09:12AM
I was reading about how air core coils are very inefficient at transferring energy from the current to the projectile.You are a victim of people who think they know much, but dont. This wrong selfreflection leads to a lot of guys doing tutorials without actual background knowledge. You can watch a lot of those guys on youtube.
All that external iron does is to change the shape of the force vs projectileposition F(x). This leads sometimes to better efficiency in primitive Coilguns, however thats only due to better timing where the Integral( F(x)*I(x) ) is larger at the end. But thats nothing you can generalize. What you can say is that air cores are not the best thing for SCR-switched coilguns... but air coils transfer energy quite happily if used correctly.
As Skynet said correctly the larger indurctance reduces switching speed. Thats why you will end up with less turns for the same original inductance. Less turns means less resistance which is interpreted by people that it must result in higher efficiency. What they dont see is the picture that Skynet posted: the actual positions where the projectile is accelerated becomes actually shorter because the field extrends less. Less distance means shorter traveltime and less energy transfer. That means in the end youve got less resisitve losses, but also lower energy transfer. It basically results in the same efficiency.
Efficiency is not controlled by the coil, but the timing.
Also I had some thoughts about the projectile and about eddy currents decreasing the efficiency of the transfer of magnetic energy to kinetic energy.Thats a useless thought. What makes a coilgun efficient is complex circuits, but not avoided eddy-currents. Ive got 30%eff with a solid projectile. Where all those tricks people do leas maybe to the increase from 2% eff to 4%eff... thats kind of not worth the effort at all (from my point of view).
Perhaps a large ferrite core would be better, as they are meant for high frequency operation.Now its getting pathetic. Ferrite saturates so early that it will just be like air. You just add weight and complexity without gaining anything.
as they are meant for high frequency operation.DUUUUUUDE STOP IT! a coilgun is NOT a high frequency device. You getting completely esotheric here, thats not helpfull at all. If you say its high frequency, then pleas proofe it first. Tell me a actual frquency you expect and why you expect this frequency and then why this would be too high for normal iron...
Re: Idea for a coil gun
Gregary Boyles, Thu Apr 09 2015, 10:04AM
Ferrite cores....
My understanding is that they are designed for switch mode power supplies that operate efficiently with kHz frequency DC.
But Iron cores are better suited to low frequency AC.
In a coil gun the coil is energized within milliseconds or microseconds....hence my assumption that ferrite cores might be better.
But I will take your word for it that a core of any sort is not necessary.....it was just a thought.
I will fix the primary coil of my iron toroid, re-wind the secondary and use it as a transformer instead.
Gregary Boyles, Thu Apr 09 2015, 10:04AM
Ferrite cores....
My understanding is that they are designed for switch mode power supplies that operate efficiently with kHz frequency DC.
But Iron cores are better suited to low frequency AC.
In a coil gun the coil is energized within milliseconds or microseconds....hence my assumption that ferrite cores might be better.
But I will take your word for it that a core of any sort is not necessary.....it was just a thought.
I will fix the primary coil of my iron toroid, re-wind the secondary and use it as a transformer instead.
Re: Idea for a coil gun
DerAlbi, Thu Apr 09 2015, 11:03AM
But dont take me wrong: if you plan a SCR-Design Coilgun, externail iron can do something. Its just not generally true, that iron improves the energy transfer of an aircore-inductor.
I just corrected such wrong generalized stuff because it causes wrong thinking and understanding of coilguns. Efficiency is all about the right timing.
DerAlbi, Thu Apr 09 2015, 11:03AM
within millisecondsis acutally realistic... now: 1ms is 1kHz. multiple milliseconds is lower than 500Hz. Ferrites:
with kHz frequency
But dont take me wrong: if you plan a SCR-Design Coilgun, externail iron can do something. Its just not generally true, that iron improves the energy transfer of an aircore-inductor.
I just corrected such wrong generalized stuff because it causes wrong thinking and understanding of coilguns. Efficiency is all about the right timing.
Re: Idea for a coil gun
Skynet, Thu Apr 09 2015, 05:55PM
Here is bachelor's thesis from my university dealing with magnetic shielding/effiency.
Skynet, Thu Apr 09 2015, 05:55PM
Here is bachelor's thesis from my university dealing with magnetic shielding/effiency.
https://www.vutbr.cz/www_base/ zav_prace_soubor_verejne.php?file_id=88073
Re: Idea for a coil gun
DerAlbi, Thu Apr 09 2015, 08:35PM
Well i would say that your reasoning and evaluation is far from complete, but i can agree with
8.3.3. "Results shows mostly an insignificant difference"
What did you get for this experiment-outcome-presentation-style-work ?
DerAlbi, Thu Apr 09 2015, 08:35PM
Well i would say that your reasoning and evaluation is far from complete, but i can agree with
8.3.3. "Results shows mostly an insignificant difference"
What did you get for this experiment-outcome-presentation-style-work ?
Re: Idea for a coil gun
Skynet, Thu Apr 09 2015, 08:58PM
I find out that for achieving major changes in efficiency is useless to experiment with projectile materials or coil shielding. And in my project, I focus on precise switching control
Skynet, Thu Apr 09 2015, 08:58PM
I find out that for achieving major changes in efficiency is useless to experiment with projectile materials or coil shielding. And in my project, I focus on precise switching control
Re: Idea for a coil gun
DerAlbi, Thu Apr 09 2015, 09:01PM
..and thats perfectly right! Halfbridges rock like hell.
DerAlbi, Thu Apr 09 2015, 09:01PM
..and thats perfectly right! Halfbridges rock like hell.
Re: Idea for a coil gun
Signification, Fri Apr 10 2015, 05:57AM
I have several bags of iron filings from my TC'ing time. I wanted to experiment with various iron-core inductor parameters (for filters) based on hollow wire-wrapped plastic tubes filled with various iron configurations. I had Ultra-fine to coarse iron filings, iron shavings, BB's, a tube full of coat-hanger segments, and a solid iron rod. I even remember a couple of high-power toroids in the batch.
--BUT, getting to the point, -Gregary- mentioned something about araldite'ing' filings (I had to look up the word--anyone using this?) into, IIRC, coilgun projectiles that wouldn't saturate too fast and have reduced Eddy current effects.
I would like to try this. I have the aforementioned iron fillings and experience with 'resin work'. My goal would be to create an easily reproducible sturdy projectile that would not saturate too fast in a powerful B-Field produced by a high-current coilgun coil.
Signification, Fri Apr 10 2015, 05:57AM
I have several bags of iron filings from my TC'ing time. I wanted to experiment with various iron-core inductor parameters (for filters) based on hollow wire-wrapped plastic tubes filled with various iron configurations. I had Ultra-fine to coarse iron filings, iron shavings, BB's, a tube full of coat-hanger segments, and a solid iron rod. I even remember a couple of high-power toroids in the batch.
--BUT, getting to the point, -Gregary- mentioned something about araldite'ing' filings (I had to look up the word--anyone using this?) into, IIRC, coilgun projectiles that wouldn't saturate too fast and have reduced Eddy current effects.
I would like to try this. I have the aforementioned iron fillings and experience with 'resin work'. My goal would be to create an easily reproducible sturdy projectile that would not saturate too fast in a powerful B-Field produced by a high-current coilgun coil.
Re: Idea for a coil gun
Gregary Boyles, Fri Apr 10 2015, 08:00AM
Had not thought of just mixing iron filings with the liquid epoxy and molding the mixture.
It would be no doubt more convenient that frigging around with steel washers, and iron filings would be soft iron rather than inefficient steel.
Assuming one can find a convenient and cheap source of soft iron filings or course.
Gregary Boyles, Fri Apr 10 2015, 08:00AM
Signification wrote ...
I have several bags of iron filings from my TC'ing time. I wanted to experiment with various iron-core inductor parameters (for filters) based on hollow wire-wrapped plastic tubes filled with various iron configurations. I had Ultra-fine to coarse iron filings, iron shavings, BB's, a tube full of coat-hanger segments, and a solid iron rod. I even remember a couple of high-power toroids in the batch.
--BUT, getting to the point, -Gregary- mentioned something about araldite'ing' filings (I had to look up the word--anyone using this?) into, IIRC, coilgun projectiles that wouldn't saturate too fast and have reduced Eddy current effects.
I would like to try this. I have the aforementioned iron fillings and experience with 'resin work'. My goal would be to create an easily reproducible sturdy projectile that would not saturate too fast in a powerful B-Field produced by a high-current coilgun coil.
I have several bags of iron filings from my TC'ing time. I wanted to experiment with various iron-core inductor parameters (for filters) based on hollow wire-wrapped plastic tubes filled with various iron configurations. I had Ultra-fine to coarse iron filings, iron shavings, BB's, a tube full of coat-hanger segments, and a solid iron rod. I even remember a couple of high-power toroids in the batch.
--BUT, getting to the point, -Gregary- mentioned something about araldite'ing' filings (I had to look up the word--anyone using this?) into, IIRC, coilgun projectiles that wouldn't saturate too fast and have reduced Eddy current effects.
I would like to try this. I have the aforementioned iron fillings and experience with 'resin work'. My goal would be to create an easily reproducible sturdy projectile that would not saturate too fast in a powerful B-Field produced by a high-current coilgun coil.
Had not thought of just mixing iron filings with the liquid epoxy and molding the mixture.
It would be no doubt more convenient that frigging around with steel washers, and iron filings would be soft iron rather than inefficient steel.
Assuming one can find a convenient and cheap source of soft iron filings or course.
Re: Idea for a coil gun
Gregary Boyles, Fri Apr 10 2015, 08:05AM
What if you were to have a series of iron or ferrite toroids butting up against each other and get the timing of switching on one after the other just right?
The issue of constricted magnetic fields and reduced force over distance might be neutralised and the increased magnetic field strength from the core might realise an increase in energy transfer efficeincy due to the stronger magnetic fields.
Gregary Boyles, Fri Apr 10 2015, 08:05AM
What if you were to have a series of iron or ferrite toroids butting up against each other and get the timing of switching on one after the other just right?
The issue of constricted magnetic fields and reduced force over distance might be neutralised and the increased magnetic field strength from the core might realise an increase in energy transfer efficeincy due to the stronger magnetic fields.
Re: Idea for a coil gun
DerAlbi, Fri Apr 10 2015, 09:17AM
I have done that before. The results just suck. I tried a homemade toroid from resin and ironpowder with particle sizes of 90µm and 500µm and a mixture of both.
The Attrached photo shows the quality of my achievement (90µm): no air inside, very high material content. I used acetone to make the resin thinner and a small vibrator (yes,....) to shake the mixture and make all the particles really dense.
The result is: µr = 4.
I talked to a guy who actually makes ferrite/ironpowder-cores for a living (should have dione that before failure
): it seems to have something to do with the size of the particles - the smaller they get, the less effective µr they have. Additionally, since they are isolated by resin the mass is magnetically not really a whole thing but really porous... thats why ironpowder-cores are done via chemical isolation (the particles are coated with a metaloxide) and then pressed together mith multiple 10s of tons of force and heated up.
My conclusion is: save your time. Yes you will make something thats really hard to saturate, but thats only because of the low µr
Even professional made Ironpowder cores have only a fraction of the solid irons µr.
Maybe bigger particles will have an advantage, but they have then allready the problem of eddy-currents. Remember: transformer-sheets are 0.5mm in thickness... and thats good for 50Hz. so i dont see much point in having particles >500µm in a coulgun configuration where frequecies are in the hunrets of Hertz.
DerAlbi, Fri Apr 10 2015, 09:17AM
I have done that before. The results just suck. I tried a homemade toroid from resin and ironpowder with particle sizes of 90µm and 500µm and a mixture of both.
The Attrached photo shows the quality of my achievement (90µm): no air inside, very high material content. I used acetone to make the resin thinner and a small vibrator (yes,....) to shake the mixture and make all the particles really dense.
The result is: µr = 4.
I talked to a guy who actually makes ferrite/ironpowder-cores for a living (should have dione that before failure
): it seems to have something to do with the size of the particles - the smaller they get, the less effective µr they have. Additionally, since they are isolated by resin the mass is magnetically not really a whole thing but really porous... thats why ironpowder-cores are done via chemical isolation (the particles are coated with a metaloxide) and then pressed together mith multiple 10s of tons of force and heated up. My conclusion is: save your time. Yes you will make something thats really hard to saturate, but thats only because of the low µr
Even professional made Ironpowder cores have only a fraction of the solid irons µr.Maybe bigger particles will have an advantage, but they have then allready the problem of eddy-currents. Remember: transformer-sheets are 0.5mm in thickness... and thats good for 50Hz. so i dont see much point in having particles >500µm in a coulgun configuration where frequecies are in the hunrets of Hertz.
Re: Idea for a coil gun
Signification, Fri Apr 10 2015, 10:15AM
@ Gregary, Have you seen this?
Also the powered iron (last time I checked) was plentiful and cheap. I once successfully extracted the iron out of a box of 'corn flakes'! After putting them in a blender with water. I got the powered iron out with Neo magnets after the blending was done. It had the texture of baby powder! It was a very small amount--but the finest I have ever seen. So next, I tried the same thing with iron tablets (Ferrous Sulfate), a dietary supplement, with no luck. But I hardly put much effort into it. The powered iron I have out now has been sitting around for years--but I will ask my friend where he got it. What could it hurt to try??
Signification, Fri Apr 10 2015, 10:15AM
@ Gregary, Have you seen this?
Also the powered iron (last time I checked) was plentiful and cheap. I once successfully extracted the iron out of a box of 'corn flakes'! After putting them in a blender with water. I got the powered iron out with Neo magnets after the blending was done. It had the texture of baby powder! It was a very small amount--but the finest I have ever seen. So next, I tried the same thing with iron tablets (Ferrous Sulfate), a dietary supplement, with no luck. But I hardly put much effort into it. The powered iron I have out now has been sitting around for years--but I will ask my friend where he got it. What could it hurt to try??
Re: Idea for a coil gun
DerAlbi, Fri Apr 10 2015, 10:34AM
You get Iron-powder from ebay in various particle sizes. Just make sure its not iron-oxide. I am sure the supply will be even better using ebay.COM, instead of ebay.DE (in my case).. But yeah.. it doesnt hurt to try of course, but it hurts to be disapointed and waste time for something that has no chance of success. I just felt like i could share my results...
success would be.. dependable on what you actually want
for me µr=4 (and for coilgun applications in general) is pretty useless.
DerAlbi, Fri Apr 10 2015, 10:34AM
You get Iron-powder from ebay in various particle sizes. Just make sure its not iron-oxide. I am sure the supply will be even better using ebay.COM, instead of ebay.DE (in my case).. But yeah.. it doesnt hurt to try of course, but it hurts to be disapointed and waste time for something that has no chance of success.
I just felt like i could share my results... success would be.. dependable on what you actually want
for me µr=4 (and for coilgun applications in general) is pretty useless.Re: Idea for a coil gun
Ash Small, Fri Apr 10 2015, 10:37AM
My understanding regarding soft iron and ferrite and frequency is that the iron gets hotter than the ferrite at the same frequency, so soft iron isn't used for high frequencies BUT we are not talking about frequency in a CG, we're talking about period.
t's one shot, then a gap, then another shot. A frequency of less than one Hz, isn't it?.....you can't fire it fast enough for 'frequency' to be a problem
Ash Small, Fri Apr 10 2015, 10:37AM
My understanding regarding soft iron and ferrite and frequency is that the iron gets hotter than the ferrite at the same frequency, so soft iron isn't used for high frequencies BUT we are not talking about frequency in a CG, we're talking about period.
t's one shot, then a gap, then another shot. A frequency of less than one Hz, isn't it?.....you can't fire it fast enough for 'frequency' to be a problem
Re: Idea for a coil gun
DerAlbi, Fri Apr 10 2015, 10:44AM
Ash, you are wrong in your simplification.
Consider a repeted shot every 10s interval. Now take the 10s current-wafevorm. Sure, it is mostly 0, but there is a peak at the beginning of the period. Now Take a fourier-transform of such a period. You will find, to represent the result you will need quite some amount of higher frequency-components. These higher freuqencies are present inside the core material. No way around it.
So even a short pulse every 10s contains kHz-Frequency spectrum.
Your way of thinking implies that a solid transformer core is loss-free, if its turened on only once a year for just a minute. Thats just wrong. During this minute it will be extremely loss, even the switchign period is 1 year. You need to consider all frequencys that the core has to withstand, not just the largest fundamental period.
DerAlbi, Fri Apr 10 2015, 10:44AM
Ash, you are wrong in your simplification.
Consider a repeted shot every 10s interval. Now take the 10s current-wafevorm. Sure, it is mostly 0, but there is a peak at the beginning of the period. Now Take a fourier-transform of such a period. You will find, to represent the result you will need quite some amount of higher frequency-components. These higher freuqencies are present inside the core material. No way around it.
So even a short pulse every 10s contains kHz-Frequency spectrum.
Your way of thinking implies that a solid transformer core is loss-free, if its turened on only once a year for just a minute. Thats just wrong. During this minute it will be extremely loss, even the switchign period is 1 year. You need to consider all frequencys that the core has to withstand, not just the largest fundamental period.
Re: Idea for a coil gun
Ash Small, Fri Apr 10 2015, 11:07AM
I'm aware there will still be iron losses, hysteresis and eddy currents, but if the eddy currents are minimized using iron powder or whatever, you just have hysteresis losses.
Can you expand on these 'kHz frequencies'?....I was under the impression that the capacitance and inductance 'define' the 'fundamental period', especially if fast diodes are used to prevent ringing.
Ash Small, Fri Apr 10 2015, 11:07AM
I'm aware there will still be iron losses, hysteresis and eddy currents, but if the eddy currents are minimized using iron powder or whatever, you just have hysteresis losses.
Can you expand on these 'kHz frequencies'?....I was under the impression that the capacitance and inductance 'define' the 'fundamental period', especially if fast diodes are used to prevent ringing.
Re: Idea for a coil gun
DerAlbi, Fri Apr 10 2015, 11:24AM
Maybe its just a missunderstanding... i saw you aguing that the frequency is low (like i pointed out above below 1kHz) using the short frequency as reference period.
What you said now, that the period is defined by RLC, is much more agreeable
DerAlbi, Fri Apr 10 2015, 11:24AM
Maybe its just a missunderstanding... i saw you aguing that the frequency is low (like i pointed out above below 1kHz) using the short frequency as reference period.
What you said now, that the period is defined by RLC, is much more agreeable
Re: Idea for a coil gun
Ash Small, Fri Apr 10 2015, 11:28AM
I assume there may be some losses from stray capacitance and leakage inductance, but this can be minimized through the usual procedures.
Ash Small, Fri Apr 10 2015, 11:28AM
I assume there may be some losses from stray capacitance and leakage inductance, but this can be minimized through the usual procedures.
Re: Idea for a coil gun
Gregary Boyles, Fri Apr 10 2015, 12:31PM
Have you guys seen that cool coil gun, on youtube, that fires the US copper alloy pennies from a magazine? A coil machine gun.
I believe that not magnetic metals are fired from a coil gun by induction.
It is very well done.
Gregary Boyles, Fri Apr 10 2015, 12:31PM
Have you guys seen that cool coil gun, on youtube, that fires the US copper alloy pennies from a magazine? A coil machine gun.
I believe that not magnetic metals are fired from a coil gun by induction.
It is very well done.
Re: Idea for a coil gun
DerAlbi, Fri Apr 10 2015, 12:40PM
i would use a rubber band instead. that could shoot 10 coins at once with more power
DerAlbi, Fri Apr 10 2015, 12:40PM
i would use a rubber band instead. that could shoot 10 coins at once with more power
Re: Idea for a coil gun
Signification, Fri Apr 10 2015, 01:14PM
Yes, "It doesn't hurt to try" I agree with you there. AND, as you say: to be disappointed may hurt, but that's how the learning and experience process works--Don't let it beat you just because you stumbled and it hurt a tiny bit. One NEEDS this if he is serious about learning, feeling, and creating new/unique methods in the application! Believe me, they are right there. {voice of experience } However you are dead-wrong calling this a waste of time and stating that there is no chance of success. If nothing else, other worthwhile discoveries will emerge--most likely new EPA-forum related processes that can grow exponentially for your process. For now put aside that "ur=4" bump, DON'T give up, and MOVE on. If you are are really serious and have the drive, it is amazing what will emerge! You CAN and SHOULD share your results--they are most welcome and will not go overlooked.
Signification, Fri Apr 10 2015, 01:14PM
DerAlbi wrote ...
You get Iron-powder from ebay in various particle sizes. Just make sure its not iron-oxide. I am sure the supply will be even better using ebay.COM, instead of ebay.DE (in my case).. But yeah.. it doesnt hurt to try of course, but it hurts to be disapointed and waste time for something that has no chance of success. I just felt like i could share my results...
success would be.. dependable on what you actually want for me µr=4 (and for coilgun applications in general) is pretty useless.
You get Iron-powder from ebay in various particle sizes. Just make sure its not iron-oxide. I am sure the supply will be even better using ebay.COM, instead of ebay.DE (in my case).. But yeah.. it doesnt hurt to try of course, but it hurts to be disapointed and waste time for something that has no chance of success.
I just felt like i could share my results... success would be.. dependable on what you actually want
for me µr=4 (and for coilgun applications in general) is pretty useless.Yes, "It doesn't hurt to try" I agree with you there. AND, as you say: to be disappointed may hurt, but that's how the learning and experience process works--Don't let it beat you just because you stumbled and it hurt a tiny bit. One NEEDS this if he is serious about learning, feeling, and creating new/unique methods in the application! Believe me, they are right there. {voice of experience
} However you are dead-wrong calling this a waste of time and stating that there is no chance of success. If nothing else, other worthwhile discoveries will emerge--most likely new EPA-forum related processes that can grow exponentially for your process. For now put aside that "ur=4" bump, DON'T give up, and MOVE on. If you are are really serious and have the drive, it is amazing what will emerge! You CAN and SHOULD share your results--they are most welcome and will not go overlooked.Re: Idea for a coil gun
DerAlbi, Fri Apr 10 2015, 02:10PM
Hmmh. But when you learn from failure that physics dictates the failure then there cant emerge much from anyone else, since the pricipal is prooven wrong;-) I see no one who got better than µr = 10 and even this result is extremely doubtfull. (since the measurement is not that easy)
If it was so easy with resing and ironpowder, then more people would do it. And industry would for sure not rely on a technique which involves extremely expensive casts that withstand the pressures and forces involved in makeing iron-powder-cores.
In the end.. if these experiments take away your time and money which you could have spent to build maybe an IGBT-halfbridge... i just strongly advise against following dead ends.
DerAlbi, Fri Apr 10 2015, 02:10PM
Hmmh. But when you learn from failure that physics dictates the failure then there cant emerge much from anyone else, since the pricipal is prooven wrong;-) I see no one who got better than µr = 10 and even this result is extremely doubtfull. (since the measurement is not that easy)
If it was so easy with resing and ironpowder, then more people would do it. And industry would for sure not rely on a technique which involves extremely expensive casts that withstand the pressures and forces involved in makeing iron-powder-cores.
In the end.. if these experiments take away your time and money which you could have spent to build maybe an IGBT-halfbridge... i just strongly advise against following dead ends.
Re: Idea for a coil gun
Ash Small, Fri Apr 10 2015, 02:54PM
You could use commercial iron powder cores and grind them to shape, you can even stick them together with epoxy (araldite).
Ash Small, Fri Apr 10 2015, 02:54PM
You could use commercial iron powder cores and grind them to shape, you can even stick them together with epoxy (araldite).
Re: Idea for a coil gun
Gregary Boyles, Fri Apr 10 2015, 05:00PM
Well it is cool if your only about having a bit of fun with the concept rather than to trying to produce a device that can penetrate plate steel or what ever.
Gregary Boyles, Fri Apr 10 2015, 05:00PM
DerAlbi wrote ...
i would use a rubber band instead. that could shoot 10 coins at once with more power
i would use a rubber band instead. that could shoot 10 coins at once with more power
Well it is cool if your only about having a bit of fun with the concept rather than to trying to produce a device that can penetrate plate steel or what ever.
Re: Idea for a coil gun
BigBad, Sat Apr 11 2015, 07:54PM
Edit: even if you get this to work, the projectile if it is ferrous it is magnetised by the acceleration process and will be attracted laterally to the magnetic bore, and your projectile pretty much definitely will jam.
edit2:
BigBad, Sat Apr 11 2015, 07:54PM
Gregary Boyles wrote ...
I was reading about how air core coils are very inefficient at transferring energy from the current to the projectile.
They're inefficient at low speeds, but at high speeds they become very efficient. Most people never get anywhere near fast enough.I was reading about how air core coils are very inefficient at transferring energy from the current to the projectile.
Edit: even if you get this to work, the projectile if it is ferrous it is magnetised by the acceleration process and will be attracted laterally to the magnetic bore, and your projectile pretty much definitely will jam.
edit2:
Gregary Boyles wrote ...
Have you guys seen that cool coil gun, on youtube, that fires the US copper alloy pennies from a magazine? A coil machine gun.
I believe that not magnetic metals are fired from a coil gun by induction.
It is very well done.
Have you guys seen that cool coil gun, on youtube, that fires the US copper alloy pennies from a magazine? A coil machine gun.
I believe that not magnetic metals are fired from a coil gun by induction.
It is very well done.
Re: Idea for a coil gun
Gregary Boyles, Sun Apr 12 2015, 02:30AM
What would you guys consider is the minimum voltage for one of these?
I have been considering one that charges at 30-40V using 50V electrolytic capacitors which are easy to come by in discarded hifiis etc
Or one that charges at 100V or so using the 400V capacitors from tv circuit boards.
Or are these types of capacitors unsuited for a coil gun?
Gregary Boyles, Sun Apr 12 2015, 02:30AM
What would you guys consider is the minimum voltage for one of these?
I have been considering one that charges at 30-40V using 50V electrolytic capacitors which are easy to come by in discarded hifiis etc
Or one that charges at 100V or so using the 400V capacitors from tv circuit boards.
Or are these types of capacitors unsuited for a coil gun?
Re: Idea for a coil gun
DerAlbi, Sun Apr 12 2015, 09:39AM
That really depends on what you want.. if you try
DerAlbi, Sun Apr 12 2015, 09:39AM
That really depends on what you want.. if you try
having a bit of fun with the concept rather than to trying to produce a device that can penetrate plate steel or what everthen a batterypack and a mosfet will do fine.
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