Rocket tooling dimensions ??

[tim2985]

Anyone know what core tool thickness length and tapered end diameter is for a 7 1/2 inch long 3/4 ID is ?? I used normal 75 15 10 mix and the wall thickness is 3mm. I made my own tool approximating the dimensions from screen shots and I think the nozzle at 10mm is too big - also the tapered end (4mm) to core plug is 5 1/2 inches Any help appreciated My first three rockets all blew up on a test bench outside

[DavidF]

The search function turned this up. 75-15-10 is not usually used in nozzled BP rockets, especially if hand rammed. Ball milled 75-15-10 is used in nozzleless BP rockets though. As a screen-mixed powder, it's usually too strong for nozzled, too weak for nozzleless. 

[Arthur]

Rocket fuels start off like BP but then diverge. Fast fuels go in small rockets and have a short core. Fuels can start with BP then get slowed with unincorporated ingredients mixed in. Lancaster's book contains several formulae for fuel for assorted sizes of rockets, also some of the means of slowing the powder. YES made and rammed BP will explode in a 3/4" rocket case, when you mix fast BP with (say) +20% of charcoal and +50% 20 mesh nitre then it may burn more like you hoped.

[tim2985]

Thanks for that very helpful - I will read Lancaster's book.

Did you mean add +20% charcoal and +50 % Nitrate meshed into the BP ?

Edited Thursday at 04:59 AM by tim2985

[Arthur]

Yes! That's one way I've seen noted of reducing the speed of burn without adding inerts. Probably every rocket factory has their own formulations, and formulations for small rockets will be different from those for big rockets. Either you take BP and slow it down til it works or yoou take raw ingredients and add BP til it works.

Consider that a "stick" of BP burns in milli seconds but the same amount of rocket fuel needs to be controlled to burn in half to five seconds.

[Arthur]

Remember that a "tube full of BP" can be a rocket, a driver (for a wheel) or a fountain. The skill is to have a safe compound to make something do what you want.