8 replies to this topic

[Give_me_APCP]

I have recently decided to try some rocket designs, but have been faced with the problem of a pourable nozzle substance.

I regularly work with high-power experiental rocket motors, but the nozzle designs I use are graphite and/or a very hard grade of phenolic which is black. These sorts of nozzles are not efficient obviously in firework designs as they are too costly, and also are non-castable materials.

I tried testing the erosion rate of a filled epoxy, and man was that a mistake. It turned epoxy into goo immediately under the heat, but I figured it would have happened without some sort of high-temp filler in the epoxy.

For my firework rocket motor designs (which haven't worked due to no efficient nozzle materials), I cut rings into the inside of the case end for the nozzle to lock into, then I insert a paper plug about 20mm deep. I fill the end with the nozzle material and drill the proper convergence/divergence cones with a countersink bit.

It is a straightforward method so far and would work excellent if the nozzle material I use could hold up to the heat.

Is it possible to get some recommendations from you guys on pourable nozzle substances?

The material needs to be able to withstand very high pressures, 400-600psi, so I would assume this would not permit the use of clay due to its brittleness, but maybe I am wrong.

Thanks a lot.

[Electron]

For my pvc rockets i use quick set cement(sets in 10mins), i have heard of similar products like pourstone. It comes as a powder that you mix with water to a paste or slurry consistency and sets rock hard. Erosion is minimal if any, with a KNO3/Sucrose propellant anyway. You should visit the Inverse Engineering website for more info on simple efficiant nozzles.

[Darkstar]

Is it possible to get some recommendations from you guys on pourable nozzle substances?

The material needs to be able to withstand very high pressures, 400-600psi, so I would assume this would not permit the use of clay due to its brittleness, but maybe I am wrong.

Thanks a lot.

Phenolic *is* castable if you use the component parts, but I think epoxy would
be easier - you need to add a refractory component to make it sufficiently heat
resistant, however.

The cast nozzles I used on my 3 inch "Clarke's Giant Steel Fountain" PGI competition
entries were made from a combination of high compressive strength plaster, "ciment
fondu" - a high alumina casting cement (or "secar 71") and 30 mesh fireclay grog.

This will need a masonry drill to bore out, if you cast solid as I did on my gerbs - and
carbide files to shape the nozzle. It's hard!

[Give_me_APCP]

For my pvc rockets i use quick set cement(sets in 10mins), i have heard of similar products like pourstone. It comes as a powder that you mix with water to a paste or slurry consistency and sets rock hard. Erosion is minimal if any, with a KNO3/Sucrose propellant anyway. You should visit the Inverse Engineering website for more info on simple efficiant nozzles.

Excellent, after posting I did manage to find out that the stuff should easily hold the pressure, provided it is secured well.

I am going to grab some of the quick set and see just how well it holds up for me, sure as heck can't be as bad as epoxy!

I will visit the site recommended as well, thanks.

[Give_me_APCP]

Phenolic *is* castable if you use the component parts, but I think epoxy would
be easier - you need to add a refractory component to make it sufficiently heat
resistant, however.

The cast nozzles I used on my 3 inch "Clarke's Giant Steel Fountain" PGI competition
entries were made from a combination of high compressive strength plaster, "ciment
fondu" - a high alumina casting cement (or "secar 71") and 30 mesh fireclay grog.

This will need a masonry drill to bore out, if you cast solid as I did on my gerbs - and
carbide files to shape the nozzle. It's hard!

I am interested in a method which could yield something slightly erosive like phenolic, but honestly I am unsure of just how exactly phenolic is produced. I believe a nozzle manufacturer which produces it does it under a few tons of pressure I was told.

What might be a refractory component able to hold up to the heat when used in an epoxy? The way I thought of it, is that even if there was a bunch of something else in the mix, the epoxy breaks down at such a low temp that every molecule of epoxy around the refractory component would turn soft, thus reducing strength until it is spitting chunks. Or am I simply testing this with the wrong type of epoxy? I am using a common fiberglass epoxy not really intended for any high heats.

[Bluehawk]

For my BP rockets I found that sanded tile grout works amazingly well...just dampen lightly and either hammer ram it or use an arbor press...the nozzle dries like cement and erosion is negligible! It's not pourable but it's an alternative.

[damocov]

For the last month or so I've been making converging-divergin nozzles out of milliput putty and using an icing nozzle to form the cones.

I score a groove on hte inside of my tube,
put the milliput in and ram it slightly,
use a 2mm drill to put a pilot hole throug ht putty by hand then from each side press the piping nozzle into the milliput to make the cone shaped cavities. (put the nozzle on the end of a pencil to do the inside one)

I've reused hte tubes 3-4 times each and it seems to be the cardboard tube that burns away before the nozle erodes too much.

[Give_me_APCP]

For the last month or so I've been making converging-divergin nozzles out of milliput putty and using an icing nozzle to form the cones.

I score a groove on hte inside of my tube,
put the milliput in and ram it slightly,
use a 2mm drill to put a pilot hole throug ht putty by hand then from each side press the piping nozzle into the milliput to make the cone shaped cavities. (put the nozzle on the end of a pencil to do the inside one)

I've reused hte tubes 3-4 times each and it seems to be the cardboard tube that burns away before the nozle erodes too much.

That's an excellent idea. I have currently just been using large drill bits as well as countersink bits to do my not-so-optimal cones with. Optimal convergence is roughly 45 degrees, while optimal divergence is in the 15-20 degree area with higher pressure motors. Mine are usually around 45 degree exits, so definitely not as efficient a design, but a little better than having just a hole.

With both conv/divg angles set properly, as well as correct exit cone hole diameter, as much as 10-25% efficiency and impulse can be gained as opposed to using just a hole in clay. More so with high psi motors than lower.

[icarus]

fire cement seems promising its cheap and withstands high temps im using kn03/sugar cast pellet dropped into a homemade tube with lining paper and cooking foil layers rolled together with sodium silicate as glue/hardener/ fireproofer i dry the nozzles with a heat gun or oven on 160 c without fuel pellet in