Page 96 of 165

Posted: Sun Feb 12, 2012 2:00 am
by mobile chernobyl
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:

Posted: Sun Feb 12, 2012 2:04 am
by MrCrowley
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.

Posted: Wed Feb 15, 2012 11:25 pm
by MrCrowley
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.

Posted: Wed Feb 15, 2012 11:29 pm
by warhead052
Told you it would burst. :D

Posted: Thu Feb 16, 2012 1:13 am
by jackssmirkingrevenge
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...

Posted: Thu Feb 16, 2012 1:19 am
by MrCrowley
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.

Posted: Thu Feb 16, 2012 1:22 am
by jackssmirkingrevenge
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

Posted: Thu Feb 16, 2012 1:25 am
by MrCrowley
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?

Posted: Thu Feb 16, 2012 1:30 am
by jackssmirkingrevenge
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...

Posted: Thu Feb 16, 2012 1:32 am
by MrCrowley
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.

Posted: Thu Feb 16, 2012 6:20 am
by jackssmirkingrevenge
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][/youtube]

Posted: Thu Feb 16, 2012 8:00 am
by POLAND_SPUD
damn
that's nice.... nice and simple

Posted: Thu Feb 16, 2012 10:57 pm
by Fnord
ITWOST, Fnord has an eff'in paint bucket.

Posted: Tue Feb 21, 2012 3:24 pm
by killerbanjo
[youtube][/youtube]

Posted: Tue Feb 21, 2012 4:04 pm
by jackssmirkingrevenge
Good old British engineering, liberally sprinkled with innocent inuendo like coming on one's face while working with a guy called Dick :D