5 replies to this topic

[cooperman435]

Hi

OK then I have a few questions so Ill put them all here with a number so please say which question (s) you are advising me on. Thanks

my materials are:

KN3O (98% Pure)
lumpwood charcoal (BBQ Stuff run through coffee grinder)
Sulphur

24mm ID by 3mm wall thicknes cardboard tube
fire clay mixed with dried builders sand for nozzles

Ive made my own brass spindle and ramming bars on the lathe and am using a rubber mallet to ram the rockets contents as advised on this site

my first engines were all definately mismatched dimentions (ie too small nozzles (7mm) with too long cores (100mm)) they all popped the top out or the nozzle. Strangely though 1 did fire perfectly but the bp was made using an estimation as I didnt have scales at the time! it did have a beautiful trail of burning charcoal particles behind it so I assume I put in a large amount of charcoal?

Im hoping to make a slightly longer burning engine by continuing using a 7mm nozzle to aid power production

With 60 30 10 bp which is not milled just measured and ground in a bowl till fine and smoothly mixed (thery being that more charcoal and a more "meal" mix will be slower burning)

an engine with 15mm deep nozzle, 7mm opening, 70mm propelant with a core running into the propelant 50mm just went CATO! It did light and thrust for 2 maybe 2.5 seconds before popping the top off the engine. After retreval of the casing the nozzle has opened to 8mm (I expected more) and the tube has survived unscathed.

With what must be relitavely slow burning propellant I was suprised the engine CATOed Im thinking that as the core burns the increased ID of the propelant means increased surface area and therefore more gas production which simply gets too much for one end of the top of the engine.

Question 1

Would you expect making the charcoal proportion higher to slow down the burn rate further to allow the engine to finish its burn? This would also have the benifit of making the engine burn longer in total and produce more engines per measure gram of KN3O

Question 2

I have made a mix of 50 40 10 but when I test burn a sample there is a large amount of slurry left over which I assume is unburnt charcoal. It could simply be that as it burns slower it doesnt "throw" out the unburnt solids and allows them to stick together? Will this cause a problem to the nozzle as it apeared "sticky" when hot but when cold was easly crushable inbetween my fingers but lumpy?

Question 3

Does anyone have any advise on endburners? Im thinking that with a 24mm ID tube that Id need a 6mm (1/4 according to the other posts) nozzle and solid packed propellant? Im thinking that the nozzle would have to be made of something suitable to sustain the longer burn time too.
This sounds too easy so what am I missing?
If this IS correct then I assume that simply the length of the propellant would determine the thrust time?

Question 4

This is about dextrin......
Has anyone else found that when using dextrin that things take much longer to dry? Does dextrin affect the burn rate of BP if so to what degree with what %? Im reluctant to use it for this because of my experiences of it slowing down the rate of drying but would this be a way of slowing the burn rate instead of charcoal?


Any answers or advise will be greatly apreciated including others past experiences that will aid me.




As a thanks I will happily give people the instructions for an incredibly good method I have made for production of E Matches that so far with over 200 set off not a single misfire. There relatively quick and easy to make and look very profesional.

Thank everyone

Edited by cooperman435, 01 December 2006 - 08:58 PM.

[RegimentalPyro]

I'll try and answer some of your questions.

It is undoubtably true that adding more charcoal will slow the burn down. This will make your engines more efficient in their use of KNO3 as you expected.

I have had good results by making a fast mix [60:30:10 milled for 2 hours] and a slow mix [60:30:10 just mixed well - unmilled]. The fast mix tends to pop the nozzles, so I slow it down by adding some of the slow mix in various ratios [eg 3 fast : 1 slow, 1 fast : 1 slow etc....]

Popping nozzles can also be remedied by adding some small pottery shards to the nozzle clay. When rammed the shards "bite" into the tube walls and give a much stronger nozzle.

The addition of 5% dextrin to the comp doesn't really alter the burn time that much, although it might slow things down a *little*. I don't actually use it that much in rockets though. If rammed properly into a good strong tube, with measured increments [no more than 1xID at a time], a binder is not usually needed.

Hope this helps.

[aquarius]

I had some trouble getting my motors right, perhaps not all the same but similar. I made my own spindle and rammers, and used both kittylitter and bentonite for nozzle and endcap. I use 70:20:10 with 10 % coarse lump charcoal. Works fine and gives a good tail and fair thrust. By altering the length og the spindle I get different thrust/burn rates.

My biggest problem was not nozzle or endcap failure, but shredding of the casing. Now I use the trusted maillafolder-paper, approx 5 mm thick and it works very well. If your endcaps blow out, increase the length og the rammed clay.

As mentioned here before, use millgram scales and never change more than one thing at a time!!

As an example, start with a standard ( 60:30:10) mix, and a fixed nozzle. Alter the length of the spindle and find a safe and working design. And as mentioned before by Alan Yates and others, there are two CATO-catergories: Nozzle/endcap and tube failure...

[TzaRocket]

This is my first 2 step rocket and i dont know how to clasifie it:CATO or good flight


Here is the link to the video:2 step rocket

[newtoolsmith]

I think, that was a good catoed flight!

[karlfoxman]

Me and Wazi made some 2 stage coreburners, they flew great! Both went to about 250 seet and turned horizontal then fired the second motor and went across about 400 feet very quickly. We always fire in very open places with no one and nothing to damage. Its a great pyro fix and takes about 10mins to build. I always use my mixture I have tried and tested. It never fails me and is able to lift 4" ball shells to good heights! I spent a few weeks getting the mixture right and the ball mill time correct, now I have a mixture that is on the tip of cato and I get massive thrust from them and lovely tails. For the delay I love making the glitter tails and it adds a nice end to the burn before the break opens. I did find that a too thin end plug or a hole in the plug that is too big makes the rockets fail.