couple simple questions- ok 3 questions

[Merlin]

I am just starting on rockets so I am pretty ignorant. I thought about using 75/15/10 but my instructions called for a different formulation ratio which I suspect is weaker.

I have been making 4 oz BP rockets 1/2 ID by 5" with nozzles. Are the nozzleless type more powerful in terms of lifting? What is the next size up? Can anyone suggest tooling and what type of tubes to use with the tooling? My current tooling is aluminum and I bent the spindle attempting to press and the tube crushed as well so I straightened the spindle and am hand ramming but thinking of moving up a bit in size to lift a small payload of display effects. Seems to me the spindles would be better if stainless steel.

[mikeee]

Merlin,

 

Next sizes up are 8OZ (5/8"), 1# (3/4"), 2# (7/8"), 3# (1"), 4# (1-1/4"), 6# (1-1/2")

It helps to use a tube support when ramming and pressing motors.

A quality tube support will keep the tube vertical and aligned with the spindle.

When the spindle or tube gets off center you will bend the spindle while ramming and pressing.

Quality motor tubes also help when ramming and pressing motors. (NEPT)

Brass spindles work well with most fuels and are easy to polish smooth.

Stainless is a stronger material which will work for a spindle but takes longer to machine.

Aluminum can be treated with a chemical process that applies a hard tempered slick finish.

Stainless can also be treated with a chemical process that applies a slick finish.

You can also apply a release agent on any type of spindle to ease removal.

There are several tools available that help in removing spindles from pressed motors.

Wolter Tools, FireSmith Tools and Caleb Tools all make quality rocket tooling.

[Arthur]

Very small rockets use 75/15/10 mix milled as per BP then rammed into the tube. As the rocket tube gets bigger then you need to use a slower powder.

You can change the mixture and/or change the process or both BUT look up some respected reference books for a starting point. If it's too fast a fuel then it will go bang if it's too slow then performance will be impaired. Lancaster's book has some information.

 

Alterations to the mix include added nitrate, charcoal and sometimes sulphur to vary the mix and vary the degree of incorporation of the fuel powder. Consider making a fuel that only has 20% of the mill time that your good BP would take.

 

Above all work logically and TAKE NOTES! you will make several attempts before one works as you want, you need then to know exactly how you made that particular powder.

 

Bigger rockets do need a weaker powder or they turn into big bangers and make a mess and get you noticed for all the wrong reasons, better to leave a smoke trail in the sky rather than a big hole in the ground.

Edited June 8, 2015 by Arthur

[Arthur]

Fully polished hard steel makes the most robust tooling but costs the most, so most people use an aluminium alloy for cheap machining costs (time). IF you develop a liking for one size then have that tool made in hard steel but be prepared to PAY for it, Hard stainless is better but more expensive!

 

Waxing the spindle can ease removal, waxing the tube interior can ease ramming/pressing so that the powder compresses before the tube collapses.

[GMetcalf]

Another option for larger motors is standard Black Powder but screen mixed rather than mill mixed. Have all your ingredients at least 100 mesh size and screen together a few times through an 80 mesh screen (maybe even a 100 mesh screen). You'll intimately mix it enough for it to work well but not so much it'll blow up on you.

 

You could also consider adding some Atomised Aluminium as a phlegmatiser (such as in the 'RP' Propellant). The Aluminium takes some of the energy from the mix to burn and this makes it less likely to explode (or at least that's the theory).

 

In terms of lifting power, a nozzle will win out because it'll maintain a high pressure for longer during flight (hence more thrust). Not to say that a good nozzleless rocket doesn't have lifting power - you can lift plenty with a good powerful rocket. Whistle for example is nozzleless and can lift plenty. I'm not fully versed in rocket science though, but I'm sure someone who knows the maths will gladly explain!

[Arthur]

Small motors can be made from commercial 7FA just rammed into a tube over a core. larger motors need to have slower powder so some commercial powder and some ingredients just screened will work, as the motors get bigger the slowest mix possible is needed and this is usually simply screened ingredients. Sometimes the mix is slowed by the addition of more fine charcoal just to move the mix away from it's stoichiometric ratio.

[Arthur]

PS there is a vid on youtube of a three inch bore whistle rocket lifting a 12" shell into the sky! An estate agent would use the stick for something else!

[schroedinger]

The comp you prob. Read about is 6/3/1? This get normally only milled for about 15 min or more common just screened. It is designed to work with normal bp spindles.

In nozzleless rockets hot bp is common.

 

From point of lifting ability the nozzleless is stronger.

 

One recent development is the use of waxed spindles, where i read about hot bp used in a 19 mm rocket with nozzle. If you get those to work, you will have the highest lifting force possible with bp.

 

The design with the slow fuel will give you a slow ascend, whereas the hot fuel gives a fast and agressive ascend.

[Merlin]

The comp you prob. Read about is 6/3/1? This get normally only milled for about 15 min or more common just screened. It is designed to work with normal bp spindles.

In nozzleless rockets hot bp is common.

 

From point of lifting ability the nozzleless is stronger.

 

One recent development is the use of waxed spindles, where i read about hot bp used in a 19 mm rocket with nozzle. If you get those to work, you will have the highest lifting force possible with bp.

 

The design with the slow fuel will give you a slow ascend, whereas the hot fuel gives a fast and agressive ascend.

Actually it was 55% nitrate with the C being composed of commercial airfloat and 80 mesh and 10 S. The first one I launched had a small report heading and it flew well but didnt really get to the altitude I thought it should. I am making 1/2" or 4 ounce rockets from this so I am thinking of increasing the nitrate to 75%. Next I will make 5/8 or 8 oz rockets and will start off with less nitrate. At least this is what I am thinking considering some BP rockets are much larger than these my thought is these small ones need a hotter BP. I have made up some 75% nitrate BP and granulated it with a 10 mesh screen using lacquer thinner and mineral oil but have not assembled anything with it yet. I am using clay nozzles.