22 replies to this topic

[Wyvern]

I have just moved onto making rockets from a few happy years working with mines and fountains.
so i bought both 4 ounce and 1lb sizes from Greg at Pyrotooling, the 4 ounce dont work too badly although they are a bit slow taking off but the 1lb ones just blow straight away. im rolling my own tubes using 70g kraft pasted with 50:50 pva glue / water rolled to about 2.5-3mm walls.
The bp im using is standard 75:15:10 ball milled for 1 hour and i am hand ramming them.

if anyone has any idea please let me know.

Edited by Wyvern, 15 January 2007 - 09:46 AM.

[Frozentech]

I have just moved onto making rockets from a few happy years working with mines and fountains.
so i bought both 4 ounce and 1lb sizes from Greg at Pyrotooling, the 4 ounce dont work too badly although they are a bit slow taking off but the 1lb ones just blow straight away. im rolling my own tubes using 70g kraft pasted with 50:50 pva glue / water rolled to about 2.5-3mm walls.
The bp im using is standard 75:15:10 ball milled for 1 hour and i am hand ramming them.

if anyone has any idea please let me know.

Sure... you are using way too hot of a BP fuel comp for a 1# rocket. The larger the rocket, the slower your BP needs to be. A good 1# rocket can be made with green mix ( screened a few times, no ball milling ) even.
I use a variation of the Degn 1# comp in mine. 67 KNO3, 23 C ( split 50/50 airfloat and 60 mesh ), 10 S. I add 7% mixed firefly aluminum for a nice tail, but 5-7% of most any metal will work ( don't ram it with FeTi or Ti in there though )

[Wyvern]

Sure... you are using way too hot of a BP fuel comp for a 1# rocket. The larger the rocket, the slower your BP needs to be. A good 1# rocket can be made with green mix ( screened a few times, no ball milling ) even.
I use a variation of the Degn 1# comp in mine. 67 KNO3, 23 C ( split 50/50 airfloat and 60 mesh ), 10 S. I add 7% mixed firefly aluminum for a nice tail, but 5-7% of most any metal will work ( don't ram it with FeTi or Ti in there though )

Ahh, that makes more sense but i will need to mill the bp as my KNO3 is of rather a large mesh size and my willow charcoal ranges from airfloat to about 40 mesh, what ill do is mill it with 50% of the charcoal in there and add the other 50% afterwards, i dont have ant Ti but i have got some alu that i use in fountains which should work nicely to make a tail.

[Wyvern]

Well even if the rocket blew at least the veline blue came out very nicely

[Wyvern]

Time to Catalogue the latest attempt, Still a cato :, i used the mix of bp you recommended but still no joy i might have to make it even slower burning, heres the video anyway

http://video.google....542286456751770

[Caramanos2000]

May i suggest less Ti and dont put a live payload in until you know its works as not to waste any mix.

[Wyvern]

I only put 5% Ti in and even with no additive they still blow, it seems to me the tubes cant stand up to the preassure. Yeah i agree with the payload idea,

[Mortartube]

Thicker tubes would be good. 4 - 5mm wall thickness. Slow down your mix. Take the mix you were using and add 10% by weight of airfloat charcoal. If it's too slow add less charcoal next time, if too fast (i.e they still cato) add more until you have fine tuned your mixture.

[Yugen-biki]

I agree with the previous posts that the fuel needs more C. But a problem I came across when experimenting with 1lb fuel was the fuel particle size. If more coal is added the fuel is more difficult to press solid (no change in milling time). If it is to lose it will CATO even with the "right fuel ratio". The problem is solved by milling finer, but this makes the fuel more powerfull. I use 6:3:1 with 5h ball milling, but keep in mid that i use a different tool, ballmill, initial chemical particle size etc..
I would just want to say that keep in mind that the fuel ratio might not be the only reason they CATO. Tube thickness and fuel characteristics may effect the results.

[maxman]

I had the same cato problem years ago. Even very slow fuel I thought was too fast. The problem in my case was the tubes! When the preasure built up either it loosened the nozzle or end plug or just plain split the tube.

How hard are your tubes? can you crush or deform them by pressing between your fingers the open end? if so they prob aren't strong enough! Is it the tube ripping or the plugs blowing out? describe how you make the plugs and maybe upload a vid of some of your fuel burning in a loose pile for us too see the burn rate.

[Wyvern]

The tubes are pretty hard they dont even flex when i pinch them between my fingers, and i dont think its the plugs as the tubes usualy end up in a thousand pieces around the launch site.
ill try to get a fuel burning video done at the weekend

[BrightStar]

The type of charcoal is also important - yet another variable.... When making endburners, I found the difference between hard wood charcoal and willow was a stationary smoke b**b, and an instant CATO.

Frozentech, for your split 50/50 airfloat and 60 mesh C in the greenmix, are you using hard or softwood?

pyrotooling.com seems to be offline at the moment but there is a good page there on how to make BP core-burners, including some fuel mixes.

[leosedf]

I have the same problem, my tubes are very strong parallel ones. For fuel i have used unmilled, milled, hardwood and softwood charcoal. I even used 3% linseed oil for my fuel. They keep catoing or sometimes produce a small upside down fountain.
Some of them tend to lift of the ground for a few meters and then cato, others just cato instantly.
I am sure that my nozzles are very good with minimum corrosion.

[Wyvern]

The type of charcoal is also important - yet another variable.... When making endburners, I found the difference between hard wood charcoal and willow was a stationary smoke b**b, and an instant CATO.

Frozentech, for your split 50/50 airfloat and 60 mesh C in the greenmix, are you using hard or softwood?

pyrotooling.com seems to be offline at the moment but there is a good page there on how to make BP core-burners, including some fuel mixes.

hmm, the type of charcoal might well be what is making the difference, i use 100% willow od which i mill 50% of the total amount with the KNO3 and S and add the other 50% ranging from airfloat to 60 mesh afterwards.

[karlfoxman]

See this link, this fuel is perfect and always works. Mill for 60mins first and they will fly!

Here