Lift charge, how much?

[MrB]

If you lift a 6" shell with 100 kilos of BP, then, assuming it survives the launch, i'd assume it's going to make a very nice burst somewhere near on of the geostationary satellites... I'm exagerating, slightly, and you, of course, made a typo. :- )

 

But even so, 100kilo of BP is always better then the alternatives.

B!

[Arthur]

With 160g of lift it was way too high so 100 or 75g would have been better. Yes typo, I can't get 100kg of BP in a six inch tube.

[schroedinger]

With 160g of lift it was way too high so 100 or 75g would have been better. Yes typo, I can't get 100kg of BP in a six inch tube.

Wellmwhy's that 0? Just make it a km long

[match]

Wat is better for lift powder to press your bp into a puck or just granulate I use commercial airfloat charcoal I mill my bp around 5hrs with 50Cal. Lead media

[match]

Wat is better for lift powder to press your bp into a puck or just granulate I use commercial airfloat charcoal I mill my bp around 5hrs with 50Cal. Lead media

[schroedinger]

Pressing into pucks gives much better results.

[Jakenbake]

Pressing into pucks gives much better results.

I would say more consistent results. Not necessarily faster.

[schroedinger]

I would say more consistent results. Not necessarily faster.

Well specially with lift consistency is key, also not to forget about the fact that corned bp is much more compact then riced stuff.

[enanthate]

The shell I just built is gonna break BIG and loud. I want it to get up there because the stars will hang for a bit. I do not think 14% the weight is overkill. My 2F is great but not the best.If you look at the above vid that shell was 18%.

14% is alot though.. Recommended lift for a 6" is 8% of the shell's weight. I use about 10% myself just to be sure it goes up there, but then it really goes up there...

Your BP might be a bit slow though. If 14% works for you, then by all means, go for it.

[pyroMIKE]

14% is alot though.. Recommended lift for a 6" is 8% of the shell's weight. I use about 10% myself just to be sure it goes up there, but then it really goes up there...

Your BP might be a bit slow though. If 14% works for you, then by all means, go for it.

Yep look up at the vid a few posts up.That was my 6 inch with 18% shells weight. The OD was loose in the gun on that one and that was another reason I used so much.My bp is a bit slow also(when I say a bit, I mean a small notch below fast BP). Also that was 2F. Also what is a good gap between the shell OD and gun ID?

Edited November 1, 2014 by pyroMIKE

[Arthur]

A shell should glide slowly down it's tube as the air escapes from below it, with BP based break adding pasting paper will make the fit better and the eventual break bigger and harder. small shells usually need pushing gently down their tube.

[enanthate]

Yep look up at the vid a few posts up.That was my 6 inch with 18% shells weight. The OD was loose in the gun on that one and that was another reason I used so much.My bp is a bit slow also(when I say a bit, I mean a small notch below fast BP). Also that was 2F. Also what is a good gap between the shell OD and gun ID?

Yes, you mentioned the 18%. Nice shell btw, the reports sounds really good

Regarding the gap, on my 4" I have about 7-8mm total gap. This is probably too much by the book, but I get a good height anyway, so doesn't really matter to me. The mortar and shell casings comes from the same website.

You SHOULD have a gap between the shell and mortar, I'm just not sure exactly how much. There is a formula, maybe some1 else can update you on that (or Google it). Personally I figured it's not a big deal, so I dont mind the gap.

To make a guess for your 6", I recon a ~5mm total gap should be good.

[Arthur]

There is a formula for the gap in Shimitzu's book. Rule of my thumb 1mm total gap for each inch of shell diameter - a gap but not a lot.

[Mumbles]

Another relatively easy rule of thumb is 5% gap. Conveniently, this corresponds to a circumfrence of about 3x the nominal diameter. IE, you want a 12" circumference shell (3.82" OD) for a 4" mortar.

[CrashLanding]

If a shell is tight in the mortar, the pressure has more time to build up and the report is much louder. Form my limited experience, if a gap is a bit too much, it doesn't seem to make a difference. Perhaps the hot gasses don't have time to go around the shell through a small gap.

[dynomike1]

That was a good looking shell. What were the inserts made of? I was thinking i read somewhere that a 1/8" total clearance would be about right. That would be a 1/16 on either side.

Edited November 4, 2016 by dynomike1

[Wiley]

I've had long cylinders that had to be stuffed into their tubes. They lifted fine with hot screen-granulated 2FA. I've also had single break cylinders that fit sloppily in their mortars, yet they still lifted fine because I used finer, hot 3FA. Those were all 6.26% of the shell weight (ounce-per-pound). Trying to lift light single breaks with coarse 2FA doesn't work well, even when more is used, so I now lift them all with the finer 3FA. I'd imagine spherical shells would behave more like those single break cylinders, at least until they start getting relatively large in diameter.