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Unread postAuthor: mobile chernobyl » Sun Feb 12, 2012 2:00 am

MrCrowley wrote:
    One shot
    One day
    Two days
    Three days
    Four days



I'll wager on the following - giving you the benefit of the doubt! :wink:
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Unread postAuthor: MrCrowley » Sun Feb 12, 2012 2:04 am

My friend is taking his small car instead of his Dad's SUV so Mjollnir will not be accompanying me on this trip, only the smaller hybrid.

Think we're going up again later this month though and my friend should have the SUV if we're taking the boat with us for fishing.
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Unread postAuthor: MrCrowley » Wed Feb 15, 2012 11:25 pm

Back.

Remember that tiny bulge I found near the breach of my copper barrel? Yeah, it got a little bigger. So, are we calling this DDT or just the consequence of using copper tubing at pressures above what they're intended for? The projectile for the shot in question at a 10x mix was a 42g fishing sinker with a loose-ish fit in the barrel so had a foam sabot accompanying it.

I had previously got in to the habit of avoiding holding the barrel of this hybrid and the new chamber configuration made sure my hand was well clear. It was the loudest shot by far that I've ever heard from this cannon (probably due to the report exiting at the side instead of pointed away from me) and I fell over on my ass (probably from shock) from a kneeling stance for a measly ~1000ft/lbs of muzzle energy.

There is a video, doesn't show a whole lot but it'll be up some time this week I assume.

Edit:
jackssmirkingrevenge wrote:We've had this conversation before, the sabot is most likely breaking up inside the barrel. What of those compressed foil sabots I had recommended ;)

I actually found some sabot after a particular shot. There were two large pieces that would combine to make 90% of the sabot, so I don't think the foam is too bad until I find something better to use.
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Unread postAuthor: warhead052 » Wed Feb 15, 2012 11:29 pm

Told you it would burst. :D
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Unread postAuthor: jackssmirkingrevenge » Thu Feb 16, 2012 1:13 am

MrCrowley wrote:So, are we calling this DDT or just the consequence of using copper tubing at pressures above what they're intended for?


No, just a shít sabot resulting in the projectile bouncing around the barrel like a golfball in a drainpipe ;)

Once you weakened it, it was only a matter of time...
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Unread postAuthor: MrCrowley » Thu Feb 16, 2012 1:19 am

jackssmirkingrevenge wrote:No, just a shít sabot resulting in the projectile bouncing around the barrel like a golfball in a drainpipe ;)
If it hadn't been a fishing sinker (the diameter of the barrel) that was fired on this fateful shot, I may have taken you seriously :D

Oh and the reason I suspect DDT is because of the large bulge associated with the tear as I'm not sure that the tearing would have weakened the copper enough to allow it to bulge out as a consequence of the tearing.
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Unread postAuthor: jackssmirkingrevenge » Thu Feb 16, 2012 1:22 am

MrCrowley wrote:If it hadn't been a fishing sinker (the diameter of the barrel) that was fired on this fateful shot, I may have taken you seriously :D


It's the chain of events:

1. golfball/drainpipe incident weakens barrel

2. Massive lead projectile with its associated high inertia accelerates slowly causing pressure buildup in the barrel

3. pressure finds weakened spot, ruptures barrel
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Unread postAuthor: MrCrowley » Thu Feb 16, 2012 1:25 am

Does it make a difference I had fired leak sinkers twice before at 10x mixes? Granted, the other mixes could have been a little bit less powerful for whatever reason but wouldn't the barrel continue to show signs of possible failure in the form of larger bulges forming?
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Unread postAuthor: jackssmirkingrevenge » Thu Feb 16, 2012 1:30 am

Had you checked that the projectile could slide smoothly down the barrel before firing? It could be that previous shots deformed the barrel profile in a way not really visible but to the extent that for the last shot, the projectile temporarily jammed in the affected area causing an abnormally high pressure buildup behind it.

Worth pointing out that the failure mode of copper is very forgiving, many other materials in the same circumstances would have had you picking shrapnel out of your hand...
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Unread postAuthor: MrCrowley » Thu Feb 16, 2012 1:32 am

Yeah I checked for jams, I even had a problem where the sinkers were falling straight through the barrel and out the bottom. The sabots put a stop to this though.
jackssmirkingrevenge wrote:Worth pointing out that the failure mode of copper is very forgiving, many other materials in the same circumstances would have had you picking shrapnel out of your hand...

Indeed, I was aware of these characteristics hence me continuing to use the barrel after seeing the small bulge last week.
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Unread postAuthor: jackssmirkingrevenge » Thu Feb 16, 2012 6:20 am

on an unrelated note, cloud bbmg on memebase :) http://senorgif.memebase.com/2012/02/15 ... chine-gun/

source is a video by a none-too-prolific spudfiles member: http://www.spudfiles.com/forums/bbq-lig ... 22823.html

[youtube]http://www.youtube.com/watch?v=r_8wRpgvhyg[/youtube]
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Unread postAuthor: POLAND_SPUD » Thu Feb 16, 2012 8:00 am

damn
that's nice.... nice and simple
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Unread postAuthor: Fnord » Thu Feb 16, 2012 10:57 pm

ITWOST, Fnord has an eff'in paint bucket.
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bucket.JPG
Cost was zero dollars, but I got lucky on the fiber blanket. That's a cut-up propane tank in there.
A cheapo blow torch powers the thing.
I'll be attempting a 5-gallon version when I find a metal bucket of the correct size.
block.JPG
Rough cast.
Mold was made in two halves from plaster of paris. I did not secure it together well enough the first time and ended up with a big puddle of molten aluminum in my garage. So technically the mold lasted two castings.
blocksanded.JPG
Finished stock material.
I was aiming for 1" wide, ended up up at 0.99, and 0.97 after sanding. Slight shrinkage near the back, but I'm not using that part anyway.
This was a BTB inspired venture to further my work on another BTB inspired venture.
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Unread postAuthor: killerbanjo » Tue Feb 21, 2012 3:24 pm

[youtube]http://www.youtube.com/watch?v=gTC63YSa1-k[/youtube]
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Unread postAuthor: jackssmirkingrevenge » Tue Feb 21, 2012 4:04 pm

Good old British engineering, liberally sprinkled with innocent inuendo like coming on one's face while working with a guy called Dick :D
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