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Barrel Questions

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LAN_403

Doubl3 Helix

Thu Jul 23 2009, 03:16AM

Registered Member #1548 Joined: Mon Jun 16 2008, 09:22PM
Location: Ohio
Posts: 61

I would imagine that one could use a reciprocating saw with the tube clamped firmly in place. Maybe not, i'm not a coil gun expert by any stretch of the imagination, but I personally don't see why something like that wouldn't work.

Barry

Thu Jul 23 2009, 05:27AM

Registered Member #90 Joined: Thu Feb 09 2006, 02:44PM
Location: Seattle, Washington
Posts: 301

kromsson wrote ...

... you don't need to slot the parts of the barrel that are at a reasonable distance from the coil ...

I suggest that a reasonable distance is to extend the slot about twice the coil's inside diameter away from the coil's opening. This will ensure the magnetic field is much less than 1% of its peak strength.

Example: Suppose your coil has 10mm inside diameter. In other words, the firing tube's outside diameter is 10mm. So ... make sure the slot extends at least 2cm beyond both ends of the coil.

Cheers, Barry
Sex on the TV is fine ... as long as you don't fall off.

kromsson

Thu Jul 23 2009, 06:00AM

Registered Member #1444 Joined: Tue Apr 15 2008, 06:55AM
Location:
Posts: 20

Im going to use a mill to slot the piece

This would obvious be the best solution, however you should be careful to not deform the barrel at the points the barrel is clamped in the mill. Especially if you use aluminum, which is quite soft metal. Please inform us of the results!

using angle grinder

Well, only if you have a large diameter barrel, and a very thin disc for your grinder - and very delicate hands!

carbon fibre barrel

I am very curious about this. I think that the carbon fiber has VERY LARGE tensile strength, but when the field is squeezing it inside the coil (when firing that is) I believe it might deform a lot, as this material is very elastic. Please show results!

PYLEMET-mk2

Thu Jul 23 2009, 11:03AM

Registered Member #1513 Joined: Sat May 31 2008, 12:08PM
Location: Russia Klin
Posts: 48

wrote ...
Well, only if you have a large diameter barrel, and a very thin disc for your grinder - and very delicate hands!

barrel on a photo has diameter 8/10mm. I used 1mm disc. If you fix barrel in vice, it is quite easy to slot it by a angle grinder

wrote ...
I am very curious about this. I think that the carbon fiber has VERY LARGE tensile strength, but when the field is squeezing it inside the coil (when firing that is) I believe it might deform a lot, as this material is very elastic. Please show results!

you're not right. I used carbon fibre barrel in my coilgun and its works properly
742760

kromsson

Thu Jul 23 2009, 12:01PM

Registered Member #1444 Joined: Tue Apr 15 2008, 06:55AM
Location:
Posts: 20

carbon fibre barrel in my coilgun and its works properly

I'm sorry, I did't write what I meant in full.
When you have a full cylindrical section, like a normal barrel, its shape is such that it will be able to bear great forces from the field, even for soft materials.

But if you slot it, THEN it is VERY easy to deform under squeezing pressure!

So, I'm sure that a full carbon fiber barrel will work fine under the normal stress, but if you slot it, THEN it will deform very easily, even if you squeeze it with your hand!

H~Tank~V

Fri Jul 24 2009, 02:35AM

Registered Member #1253 Joined: Tue Jan 22 2008, 02:06PM
Location:
Posts: 39

Ok, so after a day at work I finally got to slot and drill my barrel. I made this one out of Aluminum, its all I had. I used a 1/8" end mill to cut the slot, and a #31(0.20) drill to drill the holes. Unfortunately my machining skills are lacking at the moment, but my boss mentioned that next time with the brass barrel I should use a slitting saw, which will make better cuts in the tube. The 1/8" endmill tends to chatter allot, so its kind of hard to get a perfect slot, but its pretty good.

Last pic is of a projectile I made.

Oh and the washers are just pushed on, nothing holding them in place at the moment!

kromsson

Fri Jul 24 2009, 04:44AM

Registered Member #1444 Joined: Tue Apr 15 2008, 06:55AM
Location:
Posts: 20

Beautiful machining work. If the slots were thinner, it would be perfect.

PYLEMET-mk2

Fri Jul 24 2009, 09:07AM

Registered Member #1513 Joined: Sat May 31 2008, 12:08PM
Location: Russia Klin
Posts: 48

wrote ...
But if you slot it,

why I might slot it? Carbon is bad conductor, and its no need to slot it

big5824

Fri Jul 24 2009, 10:47AM

Registered Member #1687 Joined: Tue Sept 09 2008, 08:47PM
Location: UK, Darlington
Posts: 240

Im slotting my carbon fibre one primarely so my photogates function, but carbon fibre is a conductor (although a bad one), so there will be some eddy currents present. Also yes im aware it could deform easily, so im only making each cut around 6cm long, hopefully this will leave enough support to prevent it from compressing. Although now i think about it, i am putting a layer of epoxy on each coil layer as i go, so the coils may not compress at all.

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