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Registered Member #3888
Joined: Sun May 15 2011, 09:50PM
Location: Erie, PA
Posts: 649
so i was drawing up a design while bored in class for a 12 rail (6 per side) railgun. 2 rails would be in contact with the projectile and thus need to be replaceable. the remaining rails would be fixed and provide added field augmentation. the magnetic forces between the augmenting rails and the cross connections at the ends would be attractive, so a sturdy insulator would have to be used between them.
____ ____ |_|_| |_|_| |_|_||_|_| |_|_| |_|_|
that's the layout, with the innermost and center rails being the ones in contact with the projectile. I've got the crossing connections laid out in a simple and efficient way.
So i was wondering.. why haven't i seen this done more often in railgun designs? Is the added resistance and inductance a major problem vs. the single rail design? If i ever do build a prototype, it will just be a small scale version maybe 10" long with .125" square copper bars.
Registered Member #2939
Joined: Fri Jun 25 2010, 04:25AM
Location:
Posts: 615
Funny, I had a similar idea a long time ago. Thinking about it now it may be that there is nothing to gain. Since the force is I x H (basically), if you consider that you have a fixed amount of energy available then more turns on the "inductor" means lower current, though you get more H for your current. Result, I think, is either the same or worse than the 'single turn' scenario.
Adding permanent magnets to enhance the field is probably more useful.
Still thinking, if there is no difference due to the h up = I down, there may be some system advantages, such as lower peak current in the caps, less field in the wires from caps to rails, longer current pulse time etc.
Registered Member #3888
Joined: Sun May 15 2011, 09:50PM
Location: Erie, PA
Posts: 649
well if you can get the same force into the projectile while sending less current through it, then that is definitely a gain since the rails would erode less. That's the main problem i always think about when it comes to railguns, and why i haven't built anything larger than a classroom demo version. well if i happen across some suitable copper or aluminum square bar then i'll try it out.
Registered Member #2939
Joined: Fri Jun 25 2010, 04:25AM
Location:
Posts: 615
Got curious and did a quick excel spread sheet. Simple force calc, using constant energy, constant size and varying turns. Force stays constant, I varies as 1/ SQRT(turns). I did not account for increased turns resistance, but this is probably dominated by energy source impedance.
Registered Member #3411
Joined: Sat Nov 13 2010, 08:25PM
Location:
Posts: 33
While I dont have a paper name on the ready, I believe Ive read a similar setup made by russian scientists. They used a stack of 5 pair of rails, insulated with teflon (i think). The armature was built the same, 5 conducting pieces with teflon spacers between. The single railgun-circuits (rail-armature-rail) are then connected in series. Effiency is supposed to be much higher than normal railguns.
Registered Member #3888
Joined: Sun May 15 2011, 09:50PM
Location: Erie, PA
Posts: 649
I imagine making each projectile as a stack of insulated layers of conductor would be a pain. I was just thinking a single rail in contact with the projectile, while the other 10 provide field augmentation.
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multirail augmented railgun
