15 replies to this topic

[nickpatts]

Hi, after reading matts page on his rockets i decided to give it a go,all seemed well until launch time, after fuse ignited rocket i got a slight spray then a very slow take off and flight, any tips nozzle size,propellant,core depth.

some info

tubes 100mm lenght,16.5mm OD,12.5 ID, 4.5mm nozzle size with a core depth of 70mm.

using standard bp + 5% dextrin ball milled for a couple of hours.



Nick

[Pyromaster2003]

ah, so it did take off then? why did you add dextrin to your BP propellant?i always add around 5 grams extra charcoal to every 50g meal. the nozzel size was a bit too small aswel i think, i use a 1.5-2 nozzel size depending on weather i add a payload ad how much it weighs. cores fine. try again the way i described and im sure it will shoot up like stink:)

o and btw hwo do you compress it?im not sure which is the best way but i use a ram and malet to realy ram the propellant in, the bottom of my tubes always crease i ram it so hard!

Edited by Pyromaster2003, 31 August 2003 - 07:57 PM.

[nickpatts]

yeah it took off but very slow and did'nt get too high,nozzle size i'll make smaller then will try a 2-3mm, i added dextrin and misted the bp slightly so it was'nt messy when i rammed the comp into the tube and compacted well,yes i used a ram and mallet,ive got my car jack but have'nt had time to build a frame for it yet.

will give it a go tommorow and report back

thanks

Nick

[Pyromaster2003]

no, sorry my bad, i didnt explain well enough, i meant 1.5-2 cm nozzel not mm.*remember to add more charcoal instead(or with, if you prefer, dextrin)

Edited by Pyromaster2003, 31 August 2003 - 08:39 PM.

[nickpatts]

?? how fat are your rocket then to have a 1.5-2cm nozzle hole,are we on the same lines here? are you talking about nozzle size as in depth?,as mines about 1.5 already,im talking about the nozzle core hole,surely a small nhole will give me more pressure?.

Nick

[Pyromaster2003]

ahh sorry my bad again, i thought you where talking about the nozzel length, not the hole. my tubes are 12mm ID and a 4mm hole. right, it must be the BP propellant then, add more C and se how they fly, and maybe no water vapour.

[Matt]

12mm rockets are best off with 3mm holes. All the rest of your rocket sounds great. One thing, unless you already do it is to ram increments no larger than the ID of the tube. So lets say your ramming propellant in your 12mm tube, you put in a 3cm deep increment and ram it, it sould end up about 12mm ( with any luck ) naturally you will need to do a fair bit of tweaking with your rockets. That little tip there is possibly the best peice of advise I had ever been given, it jacked my rockets performance right up! I also apologise for the rocket vid on my site. It was easily the crappest one i have ever filmed but i still put it on there, stupid me.

-Matt

[maxman]

I've been testing 12mm id rockets 80mm in length with kn03/sugar/sul 63/27/10 using a 3.175mm exhaust hole and a core length of about 46mm into the grain 52mm in total length as 6mm was the depth of my nozzel, primed with meal powder up the core. However the take of has been very slow maybe a second or two but still very good hight gained. Tonight Imade one with a thicker nozzel about 12-15mm but it ejected its end plug, the same as my next size up which is 19mm id x80mm with 3.9mm hole 5/32.These rockets have been flying with a 6-8mm thick nozzle but very slow take off and sometimes poor hight so i made the nozzle to the thickness of the tube 19mm and that one blew up to.

I seem to be able to make them go with a slow take off ok but if i try to use a faster powder and a shorter core they still explode, so sticking with the sugar mix or a comp that burns at that rate (i have a charcoal mix too) can anyone sugest what migt be happening or give me some other dimensions to try?

Ihave been working to the spec on this link to which i have the missing jpegs for the dimensions http://huizen.dds.nl..._rocket_EN.html

many thanks

[Matt]

Priming isnt necesary. If you prime with a propellant like that you may end up degrading the grain by giving it moisture. As we all know that propellant is quite hygroscopic so you dont want to give it water to absorb, unless ofcourse your priming with BP in alchohol or NC laquer in which case i dont think the grain would be able to hold that kinda moisture. Let me know if ive missed something, I love to help..... if I can. Oh yea, I made another one of my fanned fountain and micro mine peices, Lets just call 'em my little cakes. I still cant get over how nice they look

-Matt

[mrpyromx]

i made a nice fountain tonight, only 3" long 12mm ID w/a 4mm nozzel, home made BP and super fine german al. it shot sparks and flame about 10 to 15 feet up for about 20 seconds.

by the way i used about 1/2 a teaspoon of the aluminum, couldnt tell you the weight cause i was just trying it out.

Edited by mrpyromx, 02 September 2003 - 02:21 PM.

[Pyromaster2003]

nice one, good idea iv never realy thought of putting super fine Al in with the BP, iv always used a courser 250 which is pretty good for white and orange sparks when some chunk charcoal is added. will give the super fine Al one a try tonight.10 - 15 feet

[Pyromaster2003]

btw how are your rockets coming on Nick?

[Pyromaster2003]

any success Nick........?

[nickpatts]

badley would be the word, mainly down to ignition,my black match aint small and reliable enough,saturday night had two rockets explode due to black match getting stuck and too much pressure built up and sunday nite thinner black match failed to ignite rocket eg went out,finding it really hard to get a 3mm id to ignite with current fusing.

Edited by nickpatts, 07 September 2003 - 10:08 PM.

[Pyromaster2003]

try using a 4 mm hole, thats what i use, while this size hasnt made the rockets find the altitude my 3mm rockets did, non have exploded and all work perfectly. what propellant was used?

Edited by Pyromaster2003, 08 September 2003 - 06:12 AM.