tamaldas

Only in my opinion I find that for a round shell of reasonable fit in the tube 6 x the diameter is a fair length for a good clear and safe launch. Perhaps 8 x diameter if you need the maximum available height. There is a limit to the height achieved by small shells. For larger shells (over 10 inches) typical mortars seem to be shorter in proportion meaning that my 16" tube is only 6 feet deep which is about 4.5 Diameters high. Still It's your choice within the regulations for your country of residence. There may well be laws or approved codes of practise that actually lay down the precise measurements needed to comply with your local laws.

Thanks for the valuable information Arthur

Magnalium (MgAl) alloy seems to be included in every crackle formula in combination with CuO, lead tetroxide or bismuth subcarbonate/oxide.
Is there any particular reason for this? I mean, why can't either of the parent aluminium or magnesium metals be used instead of the MgAl alloy? Could a 50/50 mixture of fine magnesium and aluminium be used, or is it essential for it to be in alloy form?

The cracklig star formulae are basically thermite mixtures in which a metal oxide eg.Pb3O4,Sb2S3,Cu(ll)O orFe2O3 reacts with a reactive metal such as Mg or Al. In the reaction metal oxides break into their corresponding metals with explosion producing lots of heat called Thermite reaction. . CuO reacts readily with Al & Mg.Hence CuO is used in small amounts in the crackling formulae to start the initial reaction first to produce the heat, the heat evolved in the reaction further initiates decomposition of Pb3O4 or Sb2S3 which is present in a higher percentage in the composition. Thus MgAl is a must in crackling compositions.

Tamaldas, I apologise for hijacking your thread, but I can't help but reply to Arthur with a post of some links of some crazy skyrockets from Thailand...

http://www.youtube.c...feature=related

http://www.youtube.c...feature=related

http://www.youtube.c...feature=related

cato...

http://www.youtube.c...feature=related

Christ !!!!! they are really biggest ones! I wonder how they manage to ram fuel in those giants!

Tamaldas, I apologise for hijacking your thread, but I can't help but reply to Arthur with a post of some links of some crazy skyrockets from Thailand...

http://www.youtube.c...feature=related

http://www.youtube.c...feature=related

http://www.youtube.c...feature=related

cato...

http://www.youtube.c...feature=related

Christ !!!!! they are really bigger ones! I wonder how they manage to ram fuel in those giants!

Ti is pretty expensive as far as I am concerned and tricky to get hold of now also, especially cheap. Why dont you also try flake aluminium or just a course grade aluminium like 60 - 100 mesh etc?

I have tried AL fine flake but the flitter didnt come off, the whole thing burnt like a white flame. Flake Al worked well with another composition I have made NaNo3 : 37%
BaNo3 : 25% Al fineFlake :29% S : 3% dextrin : 6% Boric acid 2% soln tomake the star