Build Log: MFIC

Boom! The classic potato gun harnesses the combustion of flammable vapor. Show us your combustion spud gun and discuss fuels, ratios, safety, ignition systems, tools, and more.
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Blitz
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Wed Jul 24, 2013 5:49 pm

The pipe itself is rated to 250psi at 73 degrees F, actually, but the fittings I have do fit in that mid to high-100's range for max. operating pressure (It mostly depends on the design of the fitting, as some manufacturers designs the a bit differently than others that are inherently slightly stronger).
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jackssmirkingrevenge
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Thu Jul 25, 2013 2:12 am

Blitz wrote:You were very close - it's "MF in Charge". :)
That's how I would describe myself to my kids :D
hectmarr wrote:You have to make many weapons, because this field is long and short life
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Blitz
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Thu Jul 25, 2013 10:29 pm

That's how my dad described himself to me. Well, how he described my wife to me. :D

And, updates! Did some cutting of 6" long pieces to connect some of the fittings.

Image

Glued the fittings together to form what I guess could best be described as the receiver. :) Some fine gluing considering the sheer size of the pipe; holding it down to prevent it from coming back was a challenge and I actually had to sit on one piece.

Image

The completed piece. I should have cut the connecting pieces 1/4" shorter! Everything's bottomed out with each other though, which is important. I did not glue the chamber pipe yet.

Image[/img]
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Fri Jul 26, 2013 12:00 am

Bloody hell, that Nerf vortex really puts the size into perspective...
hectmarr wrote:You have to make many weapons, because this field is long and short life
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Blitz
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Fri Jul 26, 2013 12:10 am

:D I can ALMOST fit my head in the coupling.
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Blitz
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Fri Jul 26, 2013 12:57 am

Been batting around ideas for the breech; came across rain caps for vertical exhaust stacks.

http://www.grainger.com/Grainger/ANTHES ... aps-44Z135

I could reinforce that and implement a locking mechanism.
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Blitz
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Mon Jul 29, 2013 11:34 am

I should rename this to design log. :)

I'm currently working on the gun carriage. The goofy shape of an over-under cannon is making it a bit more difficult, still desiging that.
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Mon Jul 29, 2013 6:09 pm

So, I thought about creating an epoxy cast for a plug inside the 8" chamber, but I then found a polymer fabricator on Craigslist that had a bunch of engineering cut-off stock of varying materials. I e-mailed them and left a voicemail to see if their stock of UHMW was still available.
UHMW White 2 ¼ x 10 ½ x 12 (Quantity 1) $15.00 Each
UHMW White 1 ¾ x 11 ¾ x 12 (Quantity 1) $10.00 Each
UHMW White 1 ¾ x 10 ¼ x 12 (Quantity 1) $10.00 Each
I can just make a nice sturdy plug out of this. :)
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Mon Jul 29, 2013 10:49 pm

How are you planning on cutting a perfectly circular large disk of such thick and sturdy material? In the end it might be easier and cheaper to just cast the plug with epoxy, seeing as you're probably going to secure or at least seal the UHMW plug with epoxy anyway...
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Blitz
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Mon Jul 29, 2013 10:52 pm

Someone's going to do it for me.

And the whole point of doing this is having a more economical, non-permanent seal that would allow occasional access. If I wanted to seal that, I would have either ponied up for an end cap and just cement it on.

I'll be having bolts hold it in place.
Last edited by Blitz on Tue Jul 30, 2013 12:01 am, edited 1 time in total.
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Mon Jul 29, 2013 11:59 pm

Blitz wrote:I'm currently working on the gun carriage. The goofy shape of an over-under cannon is making it a bit more difficult, still desiging that.
Are you going to incorporate a recoil absorbing mechanism?
hectmarr wrote:You have to make many weapons, because this field is long and short life
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Blitz
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Tue Jul 30, 2013 12:13 am

jackssmirkingrevenge wrote:
Blitz wrote:I'm currently working on the gun carriage. The goofy shape of an over-under cannon is making it a bit more difficult, still desiging that.
Are you going to incorporate a recoil absorbing mechanism?
Yep! Even if I didn't really need one, I wanted one anyway. My math, if I did it correctly, showed there's around 88J of free recoil with a 5lb projectile. That's assuming a cannon with 180lbs of weight, though, and I think the actual gun isn't going to weigh as much. It shouldn't affect the numbers too much, though

And considering how much I suck at math, this could totally be off. I am making a nice cylinder that would be part of the carriage that'd attach to the cannon. The cylinder's coming along nicely and actually is quite easy to do, but haven't tackled how it attaches to the cannon yet. Not overly concerned yet; adding rails to allow attachment/free movement on a carriage is more important right now, and I've come up with some good ideas for that so far. Adding an attachment point to THAT would be quite easy depending how I want go about it.

Much of this cannon isn't about just getting something big done, it's a learning experience for me and trying out new things, incorporating new features that I haven't dealt with before.
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Tue Jul 30, 2013 3:36 am

Blitz wrote:Even if I didn't really need one, I wanted one anyway.
Oh you will need one ;)
hectmarr wrote:You have to make many weapons, because this field is long and short life
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Tue Jul 30, 2013 4:26 am

The cylinder's coming along nicely and actually is quite easy to do, but haven't tackled how it attaches to the cannon yet. Not overly concerned yet; adding rails to allow attachment/free movement on a carriage is more important right now, and I've come up with some good ideas for that so far.
Hope this helps...
CpTn_lAw wrote: :D "yay, me wanna make big multishot pnoob with 1000 psi foot pump compressor using diamond as main material. Do you think wet bread make good sealant? " :D
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Blitz
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Tue Jul 30, 2013 11:26 pm

wyz2285 wrote:Hope this helps...
How you used your air cylinder is similar to what I had in mind. Thanks for sharing that, though - purty hybrid!
jackssmirkingrevenge wrote:
Blitz wrote:Even if I didn't really need one, I wanted one anyway.
Oh you will need one ;)
Absolutely. :)
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