When to go public / ask for support | Coilgun | crowd funding

Discussion in 'Off Topic' started by DerAlbi, Apr 8, 2017.

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  1. DerAlbi

    DerAlbi Junior Member

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    Hi guys,
    I am a young engineer from Germany and in the past 4 years I invested a lot of my time in developing a Coilgun. A Coilgun is basically an electric motor. It uses coils/inductors to create a magnetic field which attracts a ferromagnetic projectile to accelerate it. I kind of think it would fit in this forum.
    Sorry that I have to blast you with a wall of text but I think my final question needs some context.

    State of the Art: There are a lot of Coilguns out there – most of them displayed on Youtube by hobbyists. Before you search yourself, let me summarize: the most viewed coilguns are the pretty ones. Most showoffs are made by shooting glass, cellphones, whatever.. basically everything that would break if you let it drop from a table :-D OK - some are penetrating thin aluminum cans.. the projectile energies reach up to ~20J.

    Now some technical stuff: Being an electric motor a Coilgun converts electrical energy (stored in capacitors) into kinetic energy. This energy conversion has of course an efficiency because there is also heat as a byproduct. Here is the catch: The typical Coilgun design you find on youtube reaches around 1% - 3% efficiency. Pathetic, isnt it. This is why most titles say “xxx kJ-Coilgun” which is mostly a reference to the electrical energy stored in the gun. This of course is pure click bait, because 1% of 1kJ electrical energy is still just 10J in the projectile.
    Now keep in mind that 1J of electrical energy can be stored in 1g of component weight in current capacitor technology. So if you want higher projectile energies – lets say 100J – then you need to store an insane amount of energy which comes in capacitors which weigh so much, the whole device is basically unusable. Also there is the issue of “the more powerful the motor/coilgun has, the more copper is involved” and copper is heavy too.

    So here is what I did: After some of research, tests and experiments I came up with a Coilgun design that is far superior to the hobbyist designs. I can reach up to 40% efficiency which changes the whole game. With 40% efficiency you can build a 100J (kinetic!) Coilgun and would only need 250J = 250g worth of capacitors. Actually I can sacrifice the efficiency and make coils not from copper wire but aluminum wire which has 30% more losses, but just 1/3 of the weight! Still lets say 20% efficiency only requires a capacitor bank of ~600J. Manageable.
    So in conclusion what I can offer based on this:
    - 100J – 120J projectile energy (100m/s muzzle speed)
    - rifle form factor (80cm – 90cm long)
    - 5.5kg overall mass (still heavy but thats why its such a leap forward – I reached a manageable weight with all the improvements.)
    - 2 shots per second (if you want that… [I dont really care])
    - should be classified as toy in Germany (using a special rail design as projectile guidance) The gun has no “barrel” in a legal sense.
    - it will cost 1700€ retail. (sry!)
    - its as silent as it gets. The projectile inevitable pushes some air out of the gun but thats about it.
    - it shoots (L)40mm x (dia)10mm iron dowel pins which are readily available and should mostly be reusable if not deformed. The flight characteristics are currently unknown but I suspect its not too bad.

    Also as electrical device there are a lot of security issues. I actually mean it in a good way. Its easy to incorporate a fingerprint sensor for turn on (family safety), accelerometers to disable the gun while free-falling or when impacting the gun (getting slapped by a supervisor?) and much more stuff. (No, I wont include Bluetooth for remote shooting – I actually will do everything to prevent this scenario, sorry)

    I really think there could be a marked for it even with the hefty price tag. Its not only a technical curiosity, it also has some elegance and ease of use. There is also the technical aspect for some interested people since I can give access to the coil timings in the firmware.

    I am currently developing a prototype which will show the technical achievements of the engineering I did. Its only a 20J gun, but in pistol form (26cm long) which will incorporate all proof of concepts of a bigger gun (its really just a thing of scaling stuff up in the end[whick makes a lot of stuff actually easier]). This prototype must then be evaluated by the German authorities to make it an official toy gun ;-) Then I need to actually scale it up. This small prototype should be finished around 1 year from now, I am around half way done.

    So here I talk money: its sooooo expensive! Expensive in two ways actually: first of all its actually expensive then I only work for 24h a week to have sufficient time for the project – thus cutting my salary quite a bit. In the last year alone I made 3k€ minus to get things done. The obvious solution is crowd funding – but I suck at marketing.

    See, my problem is: I am an engineer. I made an extremely cool electrical design which most people will never understand, appreciate or even care about. Its primarily visual coolness that sells! I currently only can sell a design scheme, nothing else. I am extremely hesitant to advertise the half finished idea because I do not want to be one of the crowd funding parasites who made a few renderings and promises curing world hunger and become a millionaire – even that would be easier :-D
    I am currently not ready to ask for support because I dont even know how the final gun will look like. How can I promise anything as long as its not done – I can promise electrical specs of course, but as said thats not what people care about.
    Yet, I need the support. Not only financial but I also need people that keep asking me for progress to keep up my motivation. I would even like to stream my engineering sessions to be honest. Doing everything by your own gets lonely at times.
    Man, I would even like to go so far and go full time on this gun. My current job at the university is a huge source of depression – seeing the education system fail student for student and being part of this system where no one can fail to become a PhD is just ridicules – I dont value that title anymore so why bother..

    There is also a lack of crowd funding sites available for stuff like guns (terms of service restriction)… I searched a lot of platforms but I didnt find anything that gave even a bit of security to the funders. The best I found is gofundme.com but I dont expect much publicity there to be honest.
    My crowd funding goals would be either to finish the current small prototype or to develop the big 100J version. For 100 guns I would need around >150k€ and 2 – 3 years of time to get it absolutely right. I also need community input to make it attractive for the user

    So now lets formulate my actual question:
    - When to go public with the project? (When the prototype is done? Now? When the final look stands?)
    - How to be trustworthy for crowd funding? (Should I share concept work which is not related to the finished product to give people an impression of progress?) Can I somehow show off the things I learned and the abilities I have that qualify me for this project without having an annoying bragging factor attached?

    Also please ask any open question – technical or personal, I try to answer.
    I can also show what I have actually done so far – just for now its enough text. Apologies to everyone who actually read it.
     
  2. onnod

    onnod Im from Holland, isnt that weird?

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    It sounds really cool for sure! As a design student, I've discussed a lot about crowd funding and the possible dangers like plagiarism through a funding campaign, etc.

    I personally would like to see a working prototype if I were to crowdfund. I would be more hesistant to fund something purely based on drawings (I think some sites even require prototypes.) The most Important question for you is right now a different one though. Would crowdfunding really be the best source of funds for you? Would a coilgun (especially an effective one) be the thing for the public right now? I think there are big big companies etc jumping around for such improvements. Look there maybe?

    So, I would wait with going public until you have a working prototype. About bragging factor, I'm kinda "oiled up" now so I don't have a clue sorry.
     

  3. Will

    Will Thread Hijacker

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    Im no scientist, just a dumb pipefitter. However, I do know that the US has recently abandoned the idea of coilguns/railguns as a viable means of weaponry. Very curious to see what secrets you have developed, that they failed to examine.
     
  4. DerAlbi

    DerAlbi Junior Member

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    Many thanks for reading this!
    Well the truth is kind of disappointing i guess. I havent done any magic. The problem is that the Coilgun community itself is stuck. Its for most people a fun hobby project which leads to many amateurs and beginners to play with the topic. A lot of them then teach their findings to others which leads to a lot of misconceptions and wrong ideas about how the stuff works. I really just tried to get every single aspect right. Thats it. :rolleyes:

    Afaik railguns are deployed on some battle ships in the US. However there is a big difference between railguns and coilguns. Railguns are easily scale-able to very high power and make most sense at high powers while coilguns become quickly unmanageable. As you can see even (in my eyes) maxed out coilgun-technology has just crossbow-like projectile specs which is kind of pathetic. It will never be a weapon of war in my eyes which is totally fine for me. Specially projectile speed is a very limiting factor so its really really hard to get to supersonic speeds. Its actually easier to accelerate a very fat projectile to low speed as a small projectile to high speed - my trade off here is 100m/s with a 24g projectile which is - as said - crossbow-like.
    The direct competition to crossbows is also what made me choose this forum. :)

    This is a good question. The problem with a company is that it sounds like a lot a one time buy out which, until its not 7 figures, seems like a bad deal. I do think that i would greatly benefit from the established distribution system but not much else.
    What i extremely like about a community driven design is is the idea of feedback while developing. Feature requests and so on can assure a really nice product in the end. Its kind of an equivalent to the "early access"-idea which is flooding the gaming scene right now.
    My problem is basically that i never held or even shot a gun in my life - so input would be greatly appreciated and needed.
    You know.. companies.. it just feels a lot like they would just suck up my IP and all my years of development climaxes in a "well thanks, but now **** off".

    You can see my case design for the small prototype which is currently optimized for 3D-printing. Its kind of ugly but its also a proof of concept for me: a bigger gun has inherently much more space for electronics - a butstock alone has more room for electronics than this design provides.
    The question is for example if people will understand this fact, or if i should avoid the technical challenge, make a bigger case that people will more likely appreciate visually. However from a technical standpoint this case is more impressive - but with marketing in mind, ugliness is a show stopper.

    Btw: this image is more pleasing than the real case. Imagine the orange/green thing (acceleration-coils) repeating 8x in the forward direction, then add a hood around it. Suddenly the whole front of the thing becomes very box-like. Ugly.
     

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    Last edited: Apr 9, 2017
  5. JoergS

    JoergS Administrator

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    Well, if you can build a prototype that delivers the performance you have described and still is portable, then that is the key to your funding. I would not recommend using crowd funding, except if all else fails. You need to partner up with a company that has access to the market at some point anyway, so you might as well use their money for the funding. After all, if your prototype works the next step is making a product out of it. I am sure that several successful German companies would jump on a chance like that.

    But the working prototype must exist. This is what you must do first. If the prototype is ready, feel free to contact me. I can certainly put you in touch with the industry and also feature you on my channel (when the time is right).
     
  6. DerAlbi

    DerAlbi Junior Member

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    Well i will start loosing weight for the camera then :-D
    But in all seriousness, i would appreciate the opportunity, i just want to clarify that the small prototype will not have the full performance, just 20J (40m/s) and will not feature aluminium coils which makes it very heavy (2.5kg) for its form factor. Its all i need currently for the BKA to inspect the general barrel design. Its also all i need to again verify my math.
    A big prototype will cost in excess of 30k€ (mainly because there is a minimum order quantity for aluminium wire). This is nothing i will even try as long as the legal status is not clear.

    But its interesting that you would point me towards a company too. Do you know how those deals work?
    I really would not like to just give my IP away or to become a regular employee. And even a profit based salary feels not right, because it adds cost to the customer. A coilgun is something really expensive, adding cost due to greed kills the product. And even if this was the way to go, it will stay a niche product due to price - so profit based salary will never pay me back my years of development. :(
    Given the amount of people who are capable of developing such a gun, i just feel like i should be able to make a living out of it. A good living, if you know what i mean.:eek:
     
  7. JoergS

    JoergS Administrator

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    1700 € retail is no problem with that kind of performance. In my store, we sell both the ball shooting STS crossbow (1400 €) and the Verminator arrow airgun (1700 € in the package). They sell quicker than we can get them in. Plenty of Germans that dearly love powerful guns and have the cash - but no gun permit. But keep in mind the margins and the VAT. In order to offer it for 1700, you have to be able to make it for 800. 600 would be better in case you want a big piece of the cake for you.

    It is too early for a BKA assessment. You need to be much closer to a real product for that. The final product will be so much different that the assessment for the prototype will be worthless. Plus, it took four years to get the assessment for the "Verminator" arrow shooting airgun... you don't want to wait that long. If you give the BKA such ample warnings, they will try to delay the assessment until the next gun law overhaul - then your product is finished.

    In fact the Verminator assessment clearly states that if a gun has no tubular barrel (that gives the projectile a "certain amount of guidance") and it is NOT powered by muscle energy, then it is unregulated. You can really transfer that over to your project. Rails aren't tubular barrels. Otherwise crossbows would be guns.

    There are many ways how to structure deals between inventors and companies. I would recommend a mix - a modest salary during the development stage (you have to eat, after all - even if on a diet :) ), then a bonus when the product is released and a percentage of the sales, maybe with a guaranteed minimum per year. In exchange you would have to issue exclusive marketing rights for as long as the product is actively and properly advertised, produced and sold. If the company stops the line, then the rights fall back to you. But that is irrelevant really as you only have one shot - the next version of the gun law will close the loophole and your weapon will require a full permit.
     
  8. DerAlbi

    DerAlbi Junior Member

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    My comment: :)

    Well, i dont think so. The most defining thing about the barrel will stay the same. A bigger gun will change nothing in that regard, except the acceleration path will be ~5x longer for 5x more energy. My hope was, if you get the underlying principle aknowledged as a toy, you wouldnt even bother to ask for the bigger gun if the defining feature remains unchanged.
    I attach a photo of the current design idea below. The problem here is that, if you look into the "barrel" you see a tubular design because the coils (not shown!) wrap around the projectile. They however do never ever touch it (it would be a problem if they did!).
    I am pretty sure i am on the save side of things with this design (which is btw a technical demand, its not done to circumvent the law) however you know how they are.. they pull some argument out of their behinds that a 0.5mm air gap between the "tubular" coils and projectile is pretty equivalent to "touching" or "guiding" the projectile or whatever... and suddenly the fun is over depending how ridicules they want to argue -.- So i'd rather hand them over a pathetic weak version of the same thing to reduce resistance a bit.
    Its quite possible that i am way too naive here.

    It sounds a lot if you were screwed over. One should have the right to withhold taxes for the time period.:mad:
    So you wouldnt bother with the BKA? Is that your conclusion? Sounds kind of risky.

    Agreed, but how to pay for material and machines? Those are the most expenses :rolleyes:
     

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  9. JoergS

    JoergS Administrator

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    The answer is yes, I would not bother with the BKA for now. I would apply for a BKA assessment right before market entry. If handled by a company that has a gunsmith license (all big companies in the industry have one), then there is no danger during the development. They will also have specialized lawyers that can issue legal opinions, plus most likely push the BKA hard for a quick assessment.

    It goes without saying that material, machines and proper personnel must be provided by the company. But you MUST make a convincing prototype. Maybe they would give you a few thousand for doing that, in advance, to see if the idea is viable.
     
  10. DerAlbi

    DerAlbi Junior Member

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    Well many thanks for your input. I will try my best with the small prototype. It wont be pretty, but very functional :rolleyes:
    As said, it will take me another year in my current work-situation.
    I have solved all electrical issues and all of the mechanical issues in separate tests, but i didnt assemble a complete device yet and i dont have any firmware... The prototype will mainly answer the open question about projectile behavior :eek: It should be chaotic/unstable, but the chaotic behavior should be delayed very much. Its the only thing thats just theory/gut-feeling/hope for now. I had a stationary proof of concept with 50J some years ago but i never could shoot far enough in my room :D
     
    Last edited: Apr 9, 2017
  11. JonS

    JonS New Member

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    I don't even know what a coil gun is or how exactly it works, but what I can say is that you have some CAD skills!
     
  12. DerAlbi

    DerAlbi Junior Member

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    Thanks a lot for your compliments :) I think you would regret saying it if you knew how long that took - specially to get it printing correctly..
    Anyway... think about a coilgun as a smart electromagnet.
    If you have some iron and a magnet on a table, there is a distance when you start to move/attract the iron. This in it self is a kind of projectile acceleration.
    Now additionally pull the magnet away so the projectile never catches up with the magnet.. the iron will accelerate as long as the magnetic field stays in front of the projectile!
    A coilgun creates an equally moving magnetic field by pushing current through an array of inductors with some very precise timing (i am talking µs-precision to stay ahead of the projectile) and some extreme amount of current (multiple 100 Amps)

    Anyway here is a preview of the thing:
     

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  13. Belargo

    Belargo Mad Scientist

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    Very interesting!
    I've got some questions too:

    1) If going from copper to aluminium wire means you have to deal with 30% more resistance, why don't you increase the wire diameter to make up for those losses? Sure, you won't save as much weight. But a bit more wire should be cheaper than more capacitors to make up for the losses, right ?

    2) Is it really necessary to make the prototype with the aluminium wire? Can't you use copper on that one and switch to aluminium once that one is working?

    3) Regarding flight stability of the projectile, do you think it would help to make them top heavy like crossbow bolts, by attaching a length of light material (wood, plastic) to a ferromagnetic head? Or maybe some fins like these airgun darts:

    [​IMG]


    By the way, I don't think your pistol prototype is ugly. It has a kind of no nonsense Sci Fi look to it, just what I would expect from a high power Gauss pistol :cool:
     
  14. DerAlbi

    DerAlbi Junior Member

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    Aww those questions are complicated to answer!" Thanks for numbering though :D

    1) To have highest efficiency in a coilgun you have to decide for a fixed coil shape that works best for your system. The performance of a coil is measured by the ratio of inductance achieved over wire resistance (time constant = L/R). This is usually optimal in a so called "Brooks Coil" where the cross section of the coil is a square and the outer diameter is 3x the inner diameter of the coil.
    This gives you quite some constraints and the idea of having different coil shapes quickly makes no sense anymore.
    If you have a fixed coil shape the only thing changing wire diameter does is to increase or decrease the number of turns that fit in the given volume thus changing inductance. This is crucial for having good performance however. The first few acceleration stages have very thin wire (like 0.3mm) and an extremely high inductance - this makes the current rise slowly in the coils which is totally fine, since the projectile is so slow to reach the optimum point of highest pull force. In contrast later coils have really thick wires (1.3mm) to reach 800 Amps in just 50µs or so which only works with low inductance. The cool thing is that no matter what you do the energy loss in a fixed volume coil is constant, since the lower inductance is achieved with lower resistance (constant L/R!) and thus can tolerate the higher current.
    The one thing i will do is to go from round wire to square wire, which may increase conductor density to make up for some losses. But in general adding some capacitors more is no big deal - they are aluminum based too and my efficiency is high enough that i dont need as many in the first place :D

    2) The small prototype will be based on copper coils. The bigger gun wont. The point here is that you cant just exchange the coils when you built the thing. The lower efficiency has consequences for the capacitor bank and switching devices and the system must fit together perfectly. There is also the issue of weight in a bigger gun. If the acceleration path alone is already at 6kg the gun will suffer from a whole lot of stiffness problems that arent there when the overall mass of the coils is just 1.5kg. Remember that I somehow have to stabilize the gun and i do not have a tubular barrel which would give some stiffness to begin with.

    3) If it would help is not so much an issue to be honest - i am sure everything would help that is better than a standalone iron dowel pin.. Its more a matter of feasibility. The dowel pins are mass production stuff made to DIN or ISO standard which should be available world wide with reliable dimensions (extremely important).
    I also need access to both ends of the projectile as resetting the magnetic "memory" of the projectile from possible previous shots is important to have a predictable acceleration behavior.
    However my current thinking is that it might not be so important to have flight stabilization. A 100m/s gun does not have a huge effective range. So if you can delay the onset of chaotic flight behavior it should be good enough. See, chaotic behavior is nothing more than the strong dependence on initial conditions of an actually predicable behavior. Luckily the acceleration of the projectile is an extremely clean process so the initial conditions like parasitic momentum should be minimized.
    To back up what i say just think about the following: there is a difference if you hold a pencil dangling by its tip or if you try to balance it on it end on your finger. The first situation is stable (pulling with 1 g [9.81m/s²]), the latter is unstable [pushing with 1 g].
    The good thing in a coilgun is that the projectile is sucked with a pull force at the tip which is the inherent stable situation just like the dangling pencil.
    So problems that occur due to some (asymmetric) "pushing from behind" like in crossbows or slingshots for example will not happen.
     
  15. Austin

    Austin Administrator

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    I would wait till you had a working prototype myself. People want to see what they are investing in.

    That being said, make sure you get patents if you can. You don't want people Stealing your ideas.
     
  16. Belargo

    Belargo Mad Scientist

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    to 1) and 2): Ah, I see... I had the feeling that this is a "non-trivial" problem ;)
    I agree, sounds like there is no way around aluminium coils.

    to 3)
    My reckoning is, people who can, for example, afford a high end crossbow will also buy good bolts for it.
    So I think it would be a problem if you sold them precision coil gun bolts instead of sending them off to the hardware store to buy some standard iron dowels. ;)
    As for degaussing the dowel, how about a small tapped hole in the front and back? That way there is access, and as a added bonus the user can change smashed tail fins or blunt tips like with throwing darts.
     
  17. DerAlbi

    DerAlbi Junior Member

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    Patents are quite controversal.. not only that they cost a fortune, but they also cost insanely much to legally defend them. I do not think that this is any option for me. Also there is the issue that i didnt do any magic-- so what to protect? hmmh.

    to 3)
    I think the fundamental difference between a coilgun and a cross bow is apart the obvious also the shooting behavior. With a crossbow its part of the deal to cock the crossbow, put your projectile in place and so on - its much more physical with all the touching and sticking in if you know what i mean :rolleyes:.
    A coilgun however is a brute force machine in that regard. Depending on how fast the mechanics allow a reload and how fast the electronics can recharge the capacitors its just click, click, click. There is no emotional attachment to the projectiles, so i think they become more objectified. A coilgun gives you in contrast a satisfying/annoying? reload noise when the stepper motors do their job, a nice whining noise known from a photo-flash and a satisfying silent poof when shot.
    The is also the issue if "the wealthy" would bother to reuse the projectiles. A coilgun is in some regard a precision instrument. Dirt on the projectile is a big no go and will lead to aborted shots. Tolerances in order of 25µm have to be met. Not much fun cleaning them if you shot in a pile of dirt. Luckily steel dowel pins can come hardened and deformation or surface damage is unlikely if you shoot an adequate target. However there is still the issue of recovery: if you go the save way and shoot something soft (avoiding reflection in your face), getting the projectiles out is a big pain in the butt because they cant be gripped like crossbow bolts.
    Any dependence on the projectile would add a whole lot of inconvenience.. People would not only be dependent on me for continued support.. its also a whole additional product to manufacture for me.
    I think going for a mass product at this point is just the safe route.. however this has to be reevaluated until the actual flight behavior is known.

    Degaussing is automatically done during reload, no worries there - as for the rest: again the problem here is the necessary precision.. Exchangeable tips are a source of tolerance and in a coilgun for a successful shot the projectile position during the shot must be known with sub-mm-precision. I opted against optical sensors because they are big, can become dirty and may need maintenance - my alternative sensors however dont give a good signal if the tip (or the end) of the projectile is not reasonable blunt. Both sides of the projectile are used for position/velocity/acceleration detection. Its very intolerant to shape and weight changes :(
     
    Last edited: Apr 11, 2017
  18. Belargo

    Belargo Mad Scientist

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    Seems like this is one of those cases where the devil is in the details.
    Well, the availability of high quality prefabricated ammo in the form of those dowels surely isn't a bad thing.

    Pardon me if this is another stupid question, my physics knowledge is a bit rusty, but do you think it is possible to make the projectile also spin like a bullet while it's accelerated by the coils?
    Or maybe spin it up with a little motor-and-contact-wheel-assembly before it enters the coils...
     
  19. DerAlbi

    DerAlbi Junior Member

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    Hmmh. This is a question that has been asked before and its still not answered - at least to my knowledge and its by no means stupid but rather interesting to discuss.
    First of all one has to discuss the mechanism: i agree with your proposal that an electric motor would be the way to go. Having a guidance system in place that gives the projectile spin during acceleration is not going to happen. The friction is way too high - which in a conventional gun is totally fine as this builds up pressure, but in a coilgun it just killing the little efficiency it has.
    My thoughts about this are again precision related. I think a rotating projectile inside the rails would be comparable to a worn out bushing - if the fit isnt tight (which it isnt!), its not going to be pretty - it will result in wobble or chaotic movement as the rotating projectile collides with the rails...
    So my guess is that it will actually worsen the projectile behavior in some way because the rotating motion is feeding unknown initial conditions into the system.
    Another thing is a reliable and practical solution, but this is nothing i will even touch until i know the problem is actually real.
    I know it sounds frustrating and very wrong from an engineering point of view, but "fingers crossed". You catch me on the one and only thing i am uncomfortable to make any predictions on.
     
    Last edited: Apr 12, 2017
  20. seppman

    seppman Folding-Ladder Expert

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    Hmm. No? I have just read an article about the Zumwalt Class Destroyer a while ago that lead me here:

    http://www.thedrive.com/the-war-zone/8594/watch-the-u-s-navy-test-fire-its-much-touted-railgun


    It has just been testen some weeks ago.