nozzles

[Zippiot]

i want a really cheap but kinda reusable nozzle. i was thinking cement or sum kind of plaster, with a metal washer in the middle of the throat. and below it, some screws to help keep it within the motor. will this hold?

[Zippiot]

ok so i bought anchoring cement and copper pipe.

copper pipe has got to be sumwut reusable, more so than pvc

and the anchoring cement was chosen over regualr cause it expands as it hardens, rather than shrinks. this will help keep it in place, and with such a small amount used it cant possibly hurt the pipe...right?

hope it works

[Zippiot]

the anchoring cement works ok, but it cracks apart too easily. so this time i mixed in a bunch of chopped fiberglass to help hold it in one piece, for logner at least.

[Zippiot]

Will cement work in a pressed nozzle? In the palce of bentonite...
I have cement and it is a pain and an art getting the mix of water just right...so Maybe hammering the crap outta it might keep it still...

[BigtonyICU]

Pressing it won't work, yes it may stay together (if the moisture is high enough) but as soon as you light your engine it's just coing to erode (pretty much instantly).

I know this is not what this post is about but I had to say it...

Don't use coper for you cumbustion chamber... the maximum PSI rating for most coper tubing is 220 psi, in pvc it can go from 400-650 PSI

Coper cumbustion chamber = pipebomb

[Zippiot]

Yeah the moment that engine flew away I retired it...
Now I am making rolled paper tube motors, they work but I can't use common paper, as they tend to explode...
I have machined a metal nozzle, but it doesn't work well on a paper rocket, too heavy

[marksteamnz]

[.

Don't use coper for you cumbustion chamber... the maximum PSI rating for most coper tubing is 220 psi, in pvc it can go from 400-650 PSI

Come on!! It depends on the copper tubing diameter and wall thickness.
There are a ton of copper tubes out there running much higher pressures on and everyday basis

[Zippiot]

Actually the copper i used had a 550 psi rating...that beats pvc of the same id.

Something else I noticed, 1/2 inch pvc pipe is not 1/2 inch in any way shape or form...

Still looking for like a cash register paper roll, yes it has less yeild str than common printer paper, but I can make many more layers...
Well back to the topic, nozzles
I hate using cement b/c you gotta get everything just right...Prefferably I would like to find some good bentonite that I can press into place, kitty litter works I hear?

[Zippiot]

In a composite motor, will a graphite nozzle outlast a steel nozzle?

[Greg O'Bryant]

Zip;

Have you tried using paper grocery bags? I have made my engines out of these. Simply roll it up on a dowel with some wood glue or you could probably use epoxy. The big problem with this is that if you get glue on the dowel it can be hard to remove your tube, they take a while to dry, and last they tend to shrink just a little from the original diameter so you need to use a slightly smaller dowel to pack the propellant with. All else aside they do work. For the nozzles use the kitty litter mix with a little oil added so it packs good. The washer would be a good idea so the throat doesn't erode, but I wouldn't be planning on any of this as being reusable. So you're back to square one, you might as well use PVC for "single use" engines becuase it is cheap and you don't have to take the time to roll the cases. It may be worth it to brake down and buy a Dr. rocket case or something similar.
P.S. After reading the Nakka rocketry site I have decided to get back into this thing. Using his info for burn rates of catalyzed sucrose propellant and KN ratios I have calculated that an end burner may be a real possibilty with burn times that could be over three seconds. I just have to get my hands on a good ballance. Potassium nitrate is $22.00 for a 50 lb bag and I just bought an electric skillet for $5.00! I love sugar propellant! I know AP propellants have a higher impulse, but I think it would be hard to get the same impulse/dollar as you do with rocket candy!
good luck

[Zippiot]

I found that poster paper (my brothers science presentation) works extremely well. The stuff is as hard as wood when completely dry!! I just got a bunch of kitty litter and am having some trouble making a nozzle. Was I not supposed to grind it down before I use it?

My rocketry book says that cement and clay nozzles erode very rapidly with composites...but I still make sugar motors so I have a use for all the stuff.

At my not so local hobby shop, the man behind the counter showed me a 1 time use aerotech e sized motor that had a [drum roll] 30 second burn time!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

I find that unbelieveable...

I was going to try a cored endburner, similar to the estes black powder ones, just with candy fuel. The stuff burns slower than bp, so a larger core may be needed.

wont let me attatch a bmp so here is the link http://www.aerorocket.com/AeroIsp/AeroIsp2.gif

number 6 should be the cored endburner. The burn pattern is quick at first, then slows producing a regressive looking long lasting burn. May be useful for small rockets to get a little more distance off of em.

[hoxie08]

Well, i gotta say. THE best thing i have ever used for a rocket nozzle is Durham's Rock Hard Water Putty. No matter how wet or dry you get it, it wont shrink or expand. And in my experience, I have NEVER seen any erosion when used along with a steel washer. I have been building PVC engines for a few years now, and have built one that was 14" long and 1 1/2 diameter using this method, and Sugar(sucrose) propellant. worked great, REALLLLLLLY loud too. On second attempt with nice rocket however, it failed miserably...blew up at 50 feet and fragmented my rocket...i forgot to add some thermal protection so the front cap of the engine shattered, blowing into my rocket, i would suggest pouring some putty in the cap also, it keeps the heat from the plastic, and the putty crap is just what it says, rock hard and WILL NOT burn at all.

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okay, so the pic is crappy..but just kind of for the idea. The nozzle isnt really stepped, it would be directly from the hole drilled in the PVC cap, to the washer, just a straight line. I would suggest about 1" thick nozzle. The washer keeps the putty from eroding, even though i have tested it without the washer and it worked just fine, but it makes it easier to shape the nozzle, and hey, better safe then dead with fragments of pvc sticking in you eh? :shock: If anyone has any questions on any of this, email me hoxie08@yahoo.com and i'll try to get you some actual pics of what i'm talking about.

Hope this helps anyone![/u]

[hoxie08]

well the pic didnt turn out right :( sorry

[JetSet]

Nothing of my own to add.... but put the text art in code tags;

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[Zippiot]

I will definately grab some of that on my next trip to the hardware store, any idea if it works with composite propellant?

How long does it take to dry?