knackers

the mesh size of your MgAl is all important for crackling, if anyone has any test results for the grades please make youself known.

Hi phill, i cannot post results for multiple grades but can post results for the 100--200# size MgAl using the following formula, from pyro guide. Btw, my tube was a little long as this was a test for christmas, it was 200mm long but got a bit of build up towards the end......

'Dragon eggs' star (Crackling star)
Source: rec.pyrotechnics. Composition from "The best of AFN III"[12], page 121
Comments: Sometimes, Bi2O3 is used instead of Pb3O4. The composition is extremely sensitive, both to friction and impact. It is also quite poisonous and explosive. Gloves and an air mask must be worn at all times when handling this mixture since the mixture contains the very toxic Pb3O4.
Preparation: Add lacquer untill the thickness is like wood putty. Pass the mix through a screen and dry it to make 1mm squares. These will explode with a sharp crack shortly after lighting and can be used as star cores.

Pb3O4.............................................81.8
Magnalium (50/50, 100-200 Mesh)...................9.1
Copper(II)oxide...................................9.1
Nitrocellulose lacquer binder.....................10% by volume

crackling fountain

No worrys a_bab, I am very interested in your results, , I havn't loaded a payload onto these motors because my mortar launched shells were / are working very good and after rocket testing it was less time consuming to bang a lift cup on the bottom of a shell than a rocket motor, i have launched a few shells on rocket motors but they were big motors ( 150mm long x 38mm ID with a 12mm core, 100mm long ) fueled with Bp and they sent my shells into the stratosphere almost ( you almost needed binoculars to see them ).
Yes i am from oz

Oh, thank you so much knackers.

I'll try to put here some thoughts I have.

People like cplmac with their high performance rockets go for very strong NEPT tubes, which are supposedly the best. Even with these tubes they can have issues, as they use lots of pressing force. Not a good sleve=split in the wall. They press these nozzle-less very hard, with long cores, but these rockets will do tricks such as a 1" rocket would lift 1-2 kg to 500 meters or more with no effort.

On the other hand you just proved that is perfectly possible to fly a whistle with the "crappiest" tube around (spiral, thin walls, gap between the spirals, AND recycled paper). Moreover, the fact that you pressed with no sleves makes for more wonder from me.

Anyway, you've been VERY helpfull. I really appreciate this.

There are just few more things I need to clear up:

1.A spindle drawing (or dimensions)
2.Did you try to attach a payload to these 1" rockets? What would be the maximum lift power?
3.How much fuel? How many increments?

Thank you knackers in advance.

My pleasure a_bab,
I've read often about NEPT and would love some but expensive to buy due to int' shipping costs. I have made about 15 of these rockets and split the tube once and have had zero cato's, i do have an identical spindle except the taper is about 1--2 degrees off parrallel ( just enough to release the motor easily ) and it works great too but not quite as much power as the pic below.
My motor specs are :- Total weight of motor ( one i just weighed ) = 94.5g.......70.7g fuel.... card tube = 18.8g... Bulk head = 5g ( 5mm thick )
I press 1x diameter increments ( a full 1.5 t-spoon) until the fuel is about 1/4" from the top then press in bentonite just shy from the top, The delay is 20mm.
I have never attached a payload to these so can't speculate of the lift potential but, they are very powerful.


Those 10" rockets Thrusty, Man they are huge ! They must take ages to press, are they difficult to get off the spindle ? One could use them as a baton to keep law and order
Are they nozzless Bp motors ?

Edit :- not long ago i saw some 1/4" ID plastic insert caps, they looked to be about 2" long and yellow by colour, ( used for report inserts with 1/4" time fuse ) Could somebody please point me in the right direction to get some ? Thanks

a_bab, Yes the tooling is my avatar, I'm sorry but i don't know if the tubes are virgin or recycled, i got them from here bits and pieces (although he is still in the process of builing his site back up due to a hacker in his old site). The spiral joint is 1mm wide with the paper laying 1 full turn. I don't have a gauge on my press but its a 4 ton press and i press it to the point where its probably on the verge of splitting ( i don't use a sleave ) i just cosollidate it untill its very firm,( by the feel of my press i would hazard a guess at about the 1 ton mark, afaik the tubes are not made any stronger ( they look like all of my other tubes) but you could always wrapp a few turns around them to make them stronger.
If i could get 5mm+ walled tubes and at a decent price i would but, these are what is available to me and at a reasonable price
4'' long
1'' ID
3mm wall


i hope this has helped you some what even a little bit

The fosters you guys get in the uk is not the same fosters we get here in au, ours is crap ! you guys get Crown larger in a fosters can, ( thats a nice beer )
I'm drinking a nice cold steinlarger from NZ