20 replies to this topic

[TritonPyro]

Hi all, I am trying to come up with a recipe for a delay in a rocket header. Nothing too exotic! I have the usual chemicals and such, so a reply from someone would be gratefully received.

[barnsley-mark]

Delay composition #1
Source: Kirk-Otthmer technical encyclopedia[8], chapter 'Explosives and Propellants'. Comments: Heat of reaction: 2.010 kJ/g; Gas volume: 13 cm3/g; Ignition temperature: 450°C; impact sensitivity test: 12 % of TNT.
Preparation:
Barium chromate...................................90 Boron.............................................10
Delay composition #2
Source: Kirk-Otthmer technical encyclopedia[8], chapter 'Explosives and Propellants'. Comments: Heat of reaction: 2.081 kJ/g; Gas volume: 12 cm3/g; Ignition temperature: 485°C; impact sensitivity test: 23 % of TNT.
Preparation:
Barium chromate...................................60 Zirconium-nickel alloy............................26 Potassium perchlorate.............................14

[Deano 1]

Delay composition #1
Source: Kirk-Otthmer technical encyclopedia[8], chapter 'Explosives and Propellants'. Comments: Heat of reaction: 2.010 kJ/g; Gas volume: 13 cm3/g; Ignition temperature: 450°C; impact sensitivity test: 12 % of TNT.
Preparation:
Barium chromate...................................90 Boron.............................................10
Delay composition #2
Source: Kirk-Otthmer technical encyclopedia[8], chapter 'Explosives and Propellants'. Comments: Heat of reaction: 2.081 kJ/g; Gas volume: 12 cm3/g; Ignition temperature: 485°C; impact sensitivity test: 23 % of TNT.
Preparation:
Barium chromate...................................60 Zirconium-nickel alloy............................26 Potassium perchlorate.............................14

He said "not too exotic" Mark

[dave]

whats wrong with a length of time fuse / safety fuse ?

 

simples

 

dave

[TritonPyro]

Nothing...........but that was not the question.

[portfire]

Hi TritonPyro and welcome on board. Would a slow burning black powder mix rammed, pressed on top of the fuel grain not suit your needs?

[TritonPyro]

Thanks port fire, I have a very successful bp pressed rocket motor that I wanted now to fire some stars. That sounds good although I guess.the mix for the delay would be a lot different. What would you suggest? Thanks for the reply.

[portfire]

It doesn't have to be anything more than the same fuel used for the grain. In my 1lb's I use to ram an extra 3/4" after the top of the spindle, you would have to dial this in to suit your fuel. I've seen a lot of folks use star comps as a delay charge to good effect, such as D1 glitter, Chrysanthemum #6 or meal powder + metal such as Titanium (pressed, obviously!) Timings and powder charge can be worked out using short tubes the same ID as your motors (think spoulette) and the powder charge adjusted to your needs..  

Edited by portfire, 17 January 2013 - 09:19 PM.

[Richard H]

Why not simply try a pressed (end-burning) sulphur-rich black powder composition above the fuel grain element that will burn slowly and readily ignite any payload effects? This technique is used extensively to produce the delay element (and a good amount of tracking smoke in daylight) in model rocket engine (Estes) motors.

[TritonPyro]

Thank you. It has given me some thoughts for the delay for the motor. Thinking of using effect fuse pieces and a report for the header. I live in a tiny place and have no space or room to make stars ( although I would love to )!

[dr thrust]

You can have such a thing as too much delay,lol when I first started out making motors and headers , and i did the same as portfire suggested using the same propellant as the main core, for the delay a charge of 12/18 mm in depth above the spindle then a " passfire " hole through the bentonite clay bulkhead( even the thickness of this can effect timing ).
then igniting a visco fuse for the heading the dam thing may already be on he floor! or to far away to see the effect, I tweaked my timing by using fast visco fuse, you don't really want to be waiting more than few seconds after the propellant has depleted

Edited by dr thrust, 17 January 2013 - 11:34 PM.

[TritonPyro]

I wonder if a cm of time fuse bedded in the bulkhead would work? The thick Chinese type?

[dr thrust]

Every option is Worth investigation , it's this that makes amateur pyrotechnical experimentation so fascinating , I do know one method of Chinese delay through dissection of a motor a mixture of hard granules of bentonite and bp pressed together to form a fast and easy to manufacture ( no pass fire hole ) combined clay bulkhead and delay.
http://www.pyrosocie...2?hl=dissection

Edited by dr thrust, 17 January 2013 - 10:59 PM.

[TritonPyro]

That is a very interesting option. Thanks!

[dr thrust]

Kitty litter may be one sorce of the granules , glad to help( well all love helping ) Check out my vids something for everybody