248 replies to this topic

[seymour]

I don't think there is any problem with resurrecting an old thread.

Sometimes people answer a question on a thread from years ago, often with the person who asked the question not being a regular anymore. That's always a little funny!

As for lighting the rockets with, or without quickmatch, I think you have demonstrated that it's not always going to make much of a difference, but at other times, it certainly does!

One factor that certainly affects it, is the rocket size. With smaller rockets, you are not going to get such a significant difference. With my 27mm ID (only slightly bigger than '3lb' rockets) coreburners I've found that if you light them with just visco, they burn fairly gently before taking off, often for over a second! With quickmatch, they are right up to power straight away, and they take off with no delay.

Your point about fuel is right on the mark, and I think that's the other main factor. I am indeed using 60/30/10 (with quite long cores) and it certainly is a factor in the leisurely takeoff if not lit with QM.

I can understand what you are saying about 60/30/10 being slow, but I like it that way. You can still lift respectable payloads by lengthening the core, and all that extra charcoal goes straight in to improving that fantastic spark trail!

[shadowpyro]

Haha good to hear!

Ahh I see, I guess i'll have a play around with a few more composition ratios when i get round to it!

Perhaps i'll stick with the quickmatch method, I always get the "oh crud....its not gonna lift off...everyone run!" moment when it's abit slow on takeoff.

Cheers for the reply

[dr thrust]

agreed my non quick match fused 3lb er's are slow on the take off sitting around for a second or so, burning up fuel, fusing definitely makes a difference on larger motors

[vaslop2005]

I have been working on my BP rockets also, (recently stepping up to the 1", or 3 pounder) but I'm using my own tools, that are made around my rocket fuel (60-30-10 +1% vaseline) and have found that the cores for the larger rockets are amazingly short, 70mm long for a 1" rocket!, any more and then it CATO's.

I was quite surprised that some people here seem to use such a fast fuel with such a long core, what dimensions and fuels does everyone use?

And ive found that when experimenting with fuels, that having a set 10% of sulfer, and 1% vaseline (to help reduce dust) and then adjust the ratio of KNO3 and AF charcoal, if that helps...

[dr thrust]

if you click back a page you'll see my 3lb ( 7" core) urbanski fueled motors, vaselines ok but i think it slows down the initial take off, and you loose most of the charcoal tail

[shadowpyro]

Just made a batch of that BP but with 70:30:10. I see what you mean about it being messy...

Will hopefully control the burn a little, as these bamboo sticks have a tendency to make the flights a little spiralled.

Edited by shadowpyro, 04 August 2010 - 06:40 PM.

[vaslop2005]

if you click back a page you'll see my 3lb ( 7" core) urbanski fueled motors, vaselines ok but i think it slows down the initial take off, and you loose most of the charcoal tail

I used to not use Vaseline, and that was fine, but I just feel a bit more comfortable with the added waterproofing (I know that this is almost non-existent) and a better bound fuel grain. but i'm happy with my rockets at the moment. they are very powerful, and i have spent maybe 1 year or more working on my own tools and dimensions.
I just find it surprising that with such a long core your rockets don't explode.
Mine have a nozzle 1/3 the ID of the rocket, but are yours the standard 1/2 ID.

[Vic]

Hey Guys,

Was just reading into the whole using a QM for fusing so that ignition starts at the core of the engine, rather than the nozzle end. (If that makes sense).

Was wondering if there's actually any marked different between those two, as i was doing some testing earliar with using just visco or with QM to the engine core. Composition ratio used was 70:30:10 (hot! but the 60:30:10 was too slow, so i opted to add more KNO3), made with pine charcoal, milled for 30min for even mixing, though all components had already been pre-milled.

Both engines seemed to fly to a good height, with a very fast ascent! So I personally didnt notice any particular difference, although I would suspect that the flame front would spread in similar ways up from the nozzel or down from the core?

Perhaps It'll be more noticeable with a slow comp like 60:30:10 (or weingarts 55:30:10)? Has anyone had a play with this?

Cheers

Edit: Also just realised I've just ressurected a year old thread, but didn't want to start a new thread on something thats possibly so trivial!

You didn't say the size of the rockets you are testing or the type of tooling you are using so cannot say too much about your ratios.
If you use plain old black match and push it to the top of the core it will act like quick match and the flame front will light the whole core very quickly.

[dr thrust]

I used to not use Vaseline, and that was fine, but I just feel a bit more comfortable with the added waterproofing (I know that this is almost non-existent) and a better bound fuel grain. but i'm happy with my rockets at the moment. they are very powerful, and i have spent maybe 1 year or more working on my own tools and dimensions.
I just find it surprising that with such a long core your rockets don't explode.
Mine have a nozzle 1/3 the ID of the rocket, but are yours the standard 1/2 ID.

thats easy i have a 20ton press, a cool bp fuel, 1/3 id, the 1/2 id is for whistle motors and fast nozzle-less motors

[vaslop2005]

thats easy i have a 20ton press, a cool bp fuel, 1/3 id, the 1/2 id is for whistle motors and fast nozzle-less motors

Thats unbeleivable! I wouldnt have thought that would even work (I'm sure your telling the truth though ), is it possible to get a video of a gram or so of the fuel burning? my 60-30-10 is very leisurely when in a pile, but has some real kick in the motor (with a 70mm core)...

[rocketpro]

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Edited by rocketpro, 06 August 2010 - 09:24 AM.

[dr thrust]

Thats unbeleivable! I wouldnt have thought that would even work (I'm sure your telling the truth though ), is it possible to get a video of a gram or so of the fuel burning? my 60-30-10 is very leisurely when in a pile, but has some real kick in the motor (with a 70mm core)...

i see, i think your fuel is to fast, for a 3lb,er, why not try one of the urbanski, propellants,60/25/15( very high sulphur content), or the 58/33/9 both riced with 2-3% vaseline.
i have used these with success with an inch shorter than normal 3lb'er with 7 inch core.( my full size 3lb'ers catoed lol
for my 1 lb'er my favorite bp propellant is from an old brock book i have ,13/7/2, i use this when im emulating 1940's/50's period "standard" rockets in a vain attempt to recreate motor performance of the time ( i need a life lol
do you have a press?

[vaslop2005]

i see, i think your fuel is to fast, for a 3lb,er, why not try one of the urbanski, propellants,60/25/15( very high sulphur content), or the 58/33/9 both riced with 2-3% vaseline.
i have used these with success with an inch shorter than normal 3lb'er with 7 inch core.( my full size 3lb'ers catoed lol
for my 1 lb'er my favorite bp propellant is from an old brock book i have ,13/7/2, i use this when im emulating 1940's/50's period "standard" rockets in a vain attempt to recreate motor performance of the time ( i need a life lol
do you have a press?

I do, but its not up to much, (1.5 ton) i will soon upgrade it to maybe 4 or 6 ton, I'm also lacking any kind of gauge, which is a huge annoyance (and I'm stuggling to find a cheap way of making/buying one, in the same style as walters tools)

also I've noticed that large amounts of vaseline (above 2%) seem to produce a chuffing effect, is this a problem? also, i quite like the effect of a short core, but it does mean that a can only use my home-made tools.

just as a reference, what size shells do your 3lbers lift?

[shadowpyro]

You didn't say the size of the rockets you are testing or the type of tooling you are using so cannot say too much about your ratios.
If you use plain old black match and push it to the top of the core it will act like quick match and the flame front will light the whole core very quickly.

Ahhh sorry forgot!

I was using Greg Boyd's 4Oz core rocket tool set, which is 1/2" ID engine.

As a side note, I've had a try with that fuel using the vaseline, using my standard 70:30:10 (pine, hot!). Dissolving the vaseline first in paint stripper (Petroleum distillates i believe these days), then mixing into the dry powder. I did not rice this mixture, but simply spread it out in thin layers on kraft.
It took a LONG time to dry, although perhaps that was because of the bit of cold wet weather we've had recently.
I noticed that ramming it was alot easier, and dust was almost non existant. Probably because the comp now had some colligative (sp?) properties.

I used a 30g payload mounted on a 4oz engine, balanced using a bamboo cane.
Also made a second engine without payload.
Comparatively the rocket without payload seemed rather out of control (spiralled flight), whereas the payloaded was straight and controlled. This is probably because i was using a hot composition.

All in all, the only obviously difference would be the ease of ramming. I would presume as OP suggested, the comp would be resistant to moisture.

I would also link some videos, except my camera decided to die on me 2 seconds into the first test...my bad

Edit: Just for sake of completeness, the stars used were meal + Al (30micron, flake) + 1% Boric acid, bound with gum accaroides/alcohol. Primed with meal BP.

Edited by shadowpyro, 07 August 2010 - 01:24 AM.

[alany]

The secret I find with larger BP motors is to use more granular charcoal for increasing fractions of to total charcoal content of the propellant as the size increases.