18 replies to this topic

[Frozentech]

OK... there are various tables of lift charge for shells, ways to calculate in advance approximate lift/height, etc. What is a good way to estimate lift charges for starmines ? I don't really want to use up powder on multiple tests.... specifically, using old festival ball mortars, and 3/8" cut stars. Any ideas ? I'm going to run a test tomorrow with 6 g of 10 mesh pulverone, fairly good powder and about 40 grams of stars. What are the odds running of getting a decent lift ? Place your bets gents.

[sizzle]

The method usually used for measuring lift for stars is to use a quarter of the amount of stars, for example, if you have 100g of stars, you would use 25g of Lift, although it is reccomended you use a tiny bit more, maybe 30g for 100g of stars.

[Pretty green flames]

1/4 is a general rule of thumb but as always it depends on the quality of your lift. I'd take 1 quater and experiment from there on until you get the best results.

[Maineiac]

I shot numerous 3" mines containing just stars and or a mix of stars and inserts at a club shoot in September. The weights varied from 250-300 grams each and all were lofted using 25-28gm of Goex 1F. None of these were short on lift so if you feel your lift powder is comparable to commercial I'd say to start at some amount less that 25%. 25 grams of powder seems a bit steep to me for 100 grams of stars. Again though as Pretty Green Flames said, all is dependant on the quality of your powder.
Mines I'd shot previously were 2" in diameter and loaded with 1/2 cup of .3125" diameter D1 glitter stars. Lift charge in these was limited to 10 grams and it was more than enough for these little effects. Weights were not taken on these unfortunately.

[sizzle]

Maineiac, I think (I'm too sure) that you're talking about a different device. Frozentech is talking about Star Mines which fire a burst of stars upwards from a tube of some description.

Edited by sizzle, 30 October 2005 - 01:52 PM.

[Maineiac]

Sizzle,
I am quite sure we are all on the same page here. While there are many variations in the construction of mines, they are all basically the same in function. Some throw stars in a tall column while others tend to make a nice short bushy burst. I often liken it to using different chokes in a shotgun. Tall colum=full choke; short and bushy=improved cylinder. Somewhere in the middle=modified.
Maybe my using the word "lift" threw you a bit? The only difference here is that unlike a shell being "lifted", in a mine the contents are "lifted" from the mortar. Hope that clears it up a bit.

[sizzle]

Sizzle,
I am quite sure we are all on the same page here. While there are many variations in the construction of mines, they are all basically the same in function. Some throw stars in a tall column while others tend to make a nice short bushy burst. I often liken it to using different chokes in a shotgun. Tall colum=full choke; short and bushy=improved cylinder. Somewhere in the middle=modified.
Maybe my using the word "lift" threw you a bit? The only difference here is that unlike a shell being "lifted", in a mine the contents are "lifted" from the mortar. Hope that clears it up a bit.

Sorry, yes I was under the impression when you started mentioning lift cups that you were talking about mortars, sorry for the mistake.

[Frozentech]

OK... there are various tables of lift charge for shells, ways to calculate in advance approximate lift/height, etc. What is a good way to estimate lift charges for starmines ? I don't really want to use up powder on multiple tests.... specifically, using old festival ball mortars, and 3/8" cut stars. Any ideas ? I'm going to run a test tomorrow with 6 g of 10 mesh pulverone, fairly good powder and about 40 grams of stars. What are the odds running of getting a decent lift ? Place your bets gents.

Well, after reading the various replies to my query, I went back and upped the lift to 10g for 40g of stars. Fired it last night, with mixed results. this batch of lift was much hotter than my previous efforts. The only change was that I switched from .5" lead media to 3/4" chunks of .75 in brass hex rod as media when it was milled. Same milling time ( just 2 hours ), same comp, same treatment ( 4% dextrin, dampened, sieved through 10 mesh and dried ).

I had two types of stars, Bleser Purple and a modified Silver Streamer, 3/8" cut. Made a mine canister up from toilet paper roll sized thin tube, with a cardboard disk over the 10g lift charge, the stars were mixed at random in the tube, with a bit of tissue over the top, and the top loosely rolled down over the opening.

It was much louder than expected ! I thought it cato'd for a second It looked like all the purple stars took fire, they lifted about 40-50 feet, but *none* of the streamers took fire. . I am going to try again with 6 grams of lift and heavier prime on the streamers. Also, hopefully this time, my video assistant won't miss it!

Edited by Frozentech, 31 October 2005 - 05:42 PM.

[Pieman]

I'm going to try my first starmine tonight. It was made following the tutorial from Dan Williams' site, only I'm using about 25g of chrysanthmum 8 stars (formula from Tom's IPP I think) and firing the bag in a 2" mortar. My friends going to bring his digital camera so hopefully I'll be able to film it. I was thinking about using about 5g of lift from my home made BP thats been riced through a 10mesh sieve, but I'll do a few tests to make sure the mortar holds first and to see if my BP can lift anything.

[JamesH]

I used 15g of 2FA black powder in my 2" mines and that was plenty.
You are going to need more than 5g to obtain a decent altitude.

Edited by JamesH, 23 November 2005 - 06:44 PM.

[Pieman]

I added some more BP to bring the total lift up to 11g. I was woried that if I added too much the mortar would break, it only had about 3mm thick walls. The whole thing worked fine I think, it all happened so fast and was alot more impressive than I was expecting (I'm not the most optimistic of people). Next time I try anything like this I'm goin to stand much further back. I think i was too close to get the whole effect.
I did managed to get the lift filmed but the camera man was as shoked as i was and so its quite hard to see the stars with the camera waving all over the place. Also the sound on camera doesn't come close to justifying the actual sound made!
The video:
http://savefile.com/...php?fid=8500897
(if your offended easily you may wish to turn the sound off, the cameraman wasn't fully prepared and is prone to swearing)

[Bub]

Erm, you might have too much lift in there .... they're not supposed to do that.

At least a couple of the stars lit too ..... cool commentry from the cameraman.

...Bub.

[Rhodri]

I don't think you've got a problem with your BP there Mr Pieman!

"Less is more"

[Pieman]

Alot more of the stars lit but went off the top of the camera screen, I think i'll try the age old 25% lift powder/star ratio next time. I set my avatar to be the first frame after the lift powder lit, it reminded me of the film independence day! I can't belive the mortar survived.

[Frozentech]

Alot more of the stars lit but went off the top of the camera screen, I think i'll try the age old 25% lift powder/star ratio next time. I set my avatar to be the first frame after the lift powder lit, it reminded me of the film independence day! I can't belive the mortar survived.

I would have to agree on the 25% lift estimate for starmines, and even then it might be on the upper end of the range The first mine I did I went with the 25% and it was so loud I thought I burst the mortar as well, and the white streamer stars blew blind, though the 20 grams of purples took fire and went quite high.