Sciencemadness Discussion Board

whistle mix problems

Practicaler - 13-11-2013 at 21:40

Hi everyone
Friend I used to make whistle mix with potassium chlorate and sodium benzoate in 7:3 but my rockets dont fly with it . They always burst out as bombs what could be the problem .

deltaH - 14-11-2013 at 02:07

What you are doing is very dangerous and illegal without a license. Be warned!

To show you just how dangerous this is, I quote from Wiki's article on 'whistle mix' and have taken the liberty of highlighting some text:

A typical whistle mix is made from 70% potassium perchlorate and 30% sodium benzoate, measured by weight. The fuel in most whistle compositions is a salt of an aromatic hydrocarbon. Compositions with chlorates and gallates were used historically, but have now been abandoned as prone to accidental ignition.
Whistle compositions tend to be particularly sensitive. To achieve the whistling behavior, the composition must be formed into a solid grain; it otherwise burns too rapidly and just explodes. The composition is typically compressed using an arbor or hydraulic press. Ramming with a mallet (which is acceptable for many other compositions) may result in an explosion.

[Edited on 14-11-2013 by deltaH]

woelen - 14-11-2013 at 03:07

Oops, I misread Practicaler's post. He uses chlorate instead of perchlorate :o
Chlorate-based compositions are extremely sensitive. This particular composition even is quite dangerous with perchlorate, but replacing perchlorate by chlorate is asking for lost hands or worse. Consider yourself lucky that you did not yet have an explosion while mixing the chemicals or preparing the device! I strongly suggest you to stop this endeavor for the time being and first read, study, read, study, and read.

hyfalcon - 14-11-2013 at 08:31

Go here:

Read EVERYTHING plus all the links on that page. Then you may have a better understanding just how dangerous this can be.

Gargamel - 14-11-2013 at 13:06


what you attempt is very dangerous when done improperly.

However, to help you, we need more information. What kind of equipment are you using?

What kind of pyro experience do you have, have you done rockets before?

Bert - 15-11-2013 at 10:46

Stop making whistle rockets or fuel until you understand the techniques involved... Look at the linked information mentioned in other responses as a start.

Give full details on your fuel mixing and loading procedure, size & geometry of the engines you are trying to make. You're obviously doing SOMETHING wrong- But a lot more details are needed to deduce WHAT.

chemrox - 15-11-2013 at 10:54

Fuel packing, engine design, tubing .. a good book on rocketry and another on pyrotechnics are indicated.

Fantasma4500 - 15-11-2013 at 11:56

what you need is to use perchlorate for safety, aswell as using a mechanical press that can give at least 2 tonnes of pressure at least for a small 50g engine

a vice might work, not sure tho.. but ramming is absolute no go and should be possible to find in the book of 'how to remove yourself'

Erbium_Iodine_Carbon - 15-11-2013 at 17:28

I've experimented a bit with perchlorate whistle and have had success with a vice. I was only ever able to make ground effects because I believe the tooling needs to be very exact in order to get a rocket that flies but doesn't blow up.

First of all, I used Skylighter's formula with 66% potassium perchlorate, 29% sodium salicylate, 1% iron oxide, and 4% mineral oil.

This might seem obvious, but you can't have any nozzle whatsoever or you will have an explosion every time (note that I haven't personally tested this). However, if you have no nozzle and no core, your rocket won't have enough thrust to fly. The trick is getting the right diameter and depth core which requires special tooling.

Vikascoder - 15-11-2013 at 21:59

please tell every detail about your rocket motor then only we can sort out your problem and watch this video may be it will help u in making fuel