Lift charge calculation

[memo]

 

I think you got the weight mixed up memo. Sulphurstan is talking about a 5 gram Comet.

 

@Sulphurstan

 

My standard comets are 17mmID (6-7) grams inserted into a 19mmID tube.

I used 1.7grams of hot home-made 4FA for lift. The comet went up approx. 25mtrs (80ft) - which was pretty much perfect for my glitter composition.

 

I'm not sure if there is a "rule of thumb", but Col on this forum helped me to work out Lift/Comet/Endplug etc. for my star gun - he may also have given advice on the amount of lift required. I tried to search for the post but couldn't find it.

 

Hope this helps in some way.

 

[EDIT]

 

Found the link: https://www.amateurpyro.com/forums/topic/10445-attempting-my-first-star-mine-questions/

No real info on the rule of thumb for lift, and I was using 1/4" cut stars in a 19mmID tube and since have moved on to comets. Still, there may be some worthwhile info.

 

Cheers.

 

yup, I started at the post above from 2015

[stix]

Yeah, considering that the original post was from 2013 and was about lifting shells I did wonder if I should have posted what I posted. But nevertheless, I guess in the end, Lift is Lift.

[Arthur]

Small inserts may have more lift than contents! my 16" shell weighed in at around 60lbs and went up with 3lbs of lift.

 

BUT as ever whatever you want to design is OK it's your design whether it breaks high or low, and often wow factor is directly opposed to safety!

[Mumbles]

I find the ounce per pound of 2FA rule of thumb really doesn't become applicable until you're approaching a pound of mass. Below that you'll need proportionally more. I'd suggest using a finer grade of BP than 2FA, and probably like 25% by mass with something like small single fire comets.

[Sulphurstan]

Yes, Mumbles, it is near of what Stix wrote (also around 25%), and I ll test that soon, once my N 1 comets are dry. Edited February 26, 2018 by Sulphurstan