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Rocket Drawings and Design


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#1 chemicalwazi

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Posted 05 August 2004 - 01:42 PM

Hello again folks!

This is a drawing of a recent rocket

I am using Rhodri's formula 61:34:8 and then adding 20% 75:15:10 for the fuel
(Thanks for that one)

Overall with stick this weighs 75g.
I've only launched one, which went up to about 60-70ft quite quickly but then slowed, turned 180, and headed back down with the still motor burning reasonably fast.

Could someone give me advice on how to modify to achieve more height and fully utilise the motor?

Is it a good idea to make one with an entirely hollow core ie:full length?

A bit of advice would be much appreciated :D

Cheers

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#2 chemicalwazi

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Posted 05 August 2004 - 01:45 PM

Sorry, i put this in the wrong section :blink:
"The Saltpeter is the Soule, the Sulphur the Life, and the Coales the Body of it"

#3 Phoenix

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Posted 05 August 2004 - 05:35 PM

There is too much solid propellant above the core, which doesn't produce nearly as much thrust as the cored portion. The cored bit burns, and gets the rocket up in the air, but the uncored bit doesn't have enough thrust to keep it there. One quick and easy solution is to put less uncored propellant on top of the cored portion, so that the payload will be ignited before it tips over. This way the rocket would go to your estimated 60-70 feet, then discharge the payload.

Another option would be to use the same length of propellant, but increase the core length to achieve a shorter delay (since that is a reason for the uncored section - to allow the rocket to slow a little before the stars discharge). However, this may result in the rockets blowing up, and you might need to use a slower burning propellant. This method would probably increase the height the rockets reach over your current 60-70 feet. With either of the above, I would probably reduce the delay section to a little uner half its current length.

Alternatively, you could try to reduce the mass of the rocket until the uncored portion can confortably carry it after the cored bit has finished burning, in which case the rockets would ascend higher than they do at present.

[EDIT] Oops... sorry, I didn't realise you'd relocated the topic to a better area until after I made this post, as I'm in the habit of reading topics bottom to top of the list.

Edited by Phoenix, 05 August 2004 - 05:44 PM.


#4 Arthur Brown

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Posted 05 August 2004 - 06:45 PM

Solid propellant burns on the exposed surface. As your propellant burns it exhausts the cored - fast burning part, and only has the slower burning solid part to burn, perhaps too slowly to lift the payload.

The core in large rockets is sometimes star shaped. This means that the thrust/time relationship can be controlled and the initial burn produces usable thrust sooner after ignition.
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#5 chemicalwazi

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Posted 06 August 2004 - 06:51 AM

Thanks for your help

Longer core test this weekend, I will post the result :)

Cheers
"The Saltpeter is the Soule, the Sulphur the Life, and the Coales the Body of it"

#6 The_Djinn

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Posted 06 August 2004 - 10:44 AM

Just a run through on my experience / inexperience of rockets. I am using 3/4" ID x 7 1/2" long tube with a core starting at 6mm dia tapering to 3mm dia and is 5" long. I have used the standard BP mix and have copacted in 3/4" increments by hand (no press). Only issue I have to date with this is once the fuse burns down and the rocket launches.... that is the last I see of the dam things as they tend to fly out of sight (straight up).
This weekend I will be placing a 3" dia payload which I hope will burst within seeing distance.
I have no doubt over the rockets ability to lift the payload as my initial test on the motor was to place it inverted in the ground a bit like a fountain.. I had to dig nearly 2' down to recover the tube.

Mark

PS RichardH.. you think UKRA would pass this as a hybrid motor ? :rolleyes:
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#7 chemicalwazi

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Posted 06 August 2004 - 10:59 AM

Hi The_Djinn

Just a quick question or two
Do you load your rockets wet, with alc or water, or dry?

Presumably you are using tooling to get the 6-3mm taper?
"The Saltpeter is the Soule, the Sulphur the Life, and the Coales the Body of it"

#8 The_Djinn

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Posted 06 August 2004 - 05:38 PM

I am using a dry mix although I will try a wet mix soon.
Yes, I am using tooling which is from Greg Boyd.. not sure of the web site but it will show up on a search of the forum.

Mark
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#9 alany

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Posted 07 August 2004 - 03:11 AM

I could have sworn I posted in this thread two nights ago, where did my post go?

Anyway, I basically said what Phoenix did, just in my usual more verbose manner.

#10 chemicalwazi

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Posted 08 August 2004 - 04:03 PM

Tested 118mm rocket last night with full length core and reached approx 150ft.
But also tested a 88mm rocket, 12mm i/d filled with 75:15:10 black powder and went at least 200ft. superb! These are only my estimates on height but i was impressed!
Ive only been making wheels, rats and fountains before this so last night was pretty cool. :D

Thanks All!
"The Saltpeter is the Soule, the Sulphur the Life, and the Coales the Body of it"

#11 Rhodri

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Posted 09 August 2004 - 10:44 AM

Good result chemicalwazi! So you are now a competent rocketeer!

:)

(Alany, please excuse me - it was I who deleted the posts - yours and mine included. I attempted to do some housekeeping and messed it up :( )

Oh well!

:blush:
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#12 maxman

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Posted 26 August 2004 - 10:53 AM

Hi The_Djinn, you said you were using tooling from Greg Boyd, I also have his 1lb spindle set. Are we using the same tooling as mine starts at 10mm and tapers down to 6mm at the top. I've only tried one so far and have three more ready to go. I have been using 60.30.10 green mix but will be trying 70/30 meal/coarse charcoal on one of the others.

chemicalwazi, I thik the drawing you showed would work well with straight meal or meal and 10% C as I have had great success with a rocket of similar dimensions recently.

#13 The_Djinn

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Posted 26 August 2004 - 01:14 PM

Yeh, that sounds about the same.. +/- 10mm to +/- 6mm.
Think I found out why it went like a bat out of hell, I used my perc BP and not the KNO3 bp which may have made it a bit more energetic. Also my perc BP had been milled a while longer so a better performer overall.

Mark

ps: Anyone used pyrodex in place of BP for anything ?
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#14 chemicalwazi

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Posted 26 August 2004 - 07:32 PM

Yeh, that sounds about the same.. +/- 10mm to +/- 6mm.
Think I found out why it went like a bat out of hell, I used my perc BP and not the KNO3 bp which may have made it a bit more energetic. Also my perc BP had been milled a while longer so a better performer overall.

Mark

ps: Anyone used pyrodex in place of BP for anything ?

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Hi Mark

Could i ask the formula for your Perc BP?

Be nice to try against my standard BP. I also have just been given a Ball Mill and my 11mm lead shot has just arrived. Cant wait to give it a go :rolleyes:

Thanks maxman, that's another one for the test.

Paul
"The Saltpeter is the Soule, the Sulphur the Life, and the Coales the Body of it"




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