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4" Rocket Nozzle

Posted: Mon Feb 11, 2013 6:33 pm
by Dave_C
Ok, It is done!

This one is a 4" rocket nozzle, made for a rocket motor that burns "sugar fuel".

It is about 6.371" in length & has a .900" throat.

I made this one to put on the shelf as a keepsake. Although it is made to spec, it will never see flight time.

Thanks to all who helped with the boring advice.

Dave C.

Re: 4" Rocket Nozzle

Posted: Mon Feb 11, 2013 6:54 pm
by wsippola
That's very nice! Looks like that would take a fair bit of work. Great finish too,


Re: 4" Rocket Nozzle

Posted: Mon Feb 11, 2013 7:01 pm
by GlennW
Beautiful, Dave.

Re: 4" Rocket Nozzle

Posted: Mon Feb 11, 2013 7:26 pm
by hammermill
but did you build a second for some flight time???

Re: 4" Rocket Nozzle

Posted: Mon Feb 11, 2013 7:28 pm
by warmstrong1955
Nice work!

So..... you building more? I was kinda lookin' forward to seein' the whole enchilada...


Re: 4" Rocket Nozzle

Posted: Mon Feb 11, 2013 8:03 pm
by Dave_C

I guess I kinda mucked up the "not going to fly" comment. I have made several of these over the years for some guys in the Iowa Amerature Rocket Association. They were made for high power rocketry and needed FAA permitts to launch.

I made the whole motors for them. Even made the fuel grain molds and test stands for testing thrust and chamber pressure.

What I was getting at is I made this one for myself to put on the shelf. All the others that I have made got shipped to someone else and I wanted one just for show.

This is the largest of the Nozzles made to so far. The smallest was a 1.5".

They are fun to make but take quite a bit of time because a lot of the cutting is done with the compound! This 4" nozzle took about 7 hours to cut. (4 sessions of after work play time)

The stock 3.75" OD blank weighed 20-lbs, the nozzle weight is about 2-lbs so you remove about 80% of the material.

The secret is having a very accurate drawing to work from. You have to do the inside cuts first and then the OD's. The inside is real easy if you can cut accurate angles. IF you can't, you won't be able to cut the outer walls to match. Since the outlet cone walls are only .100 thick, you have to get them straight. The throat area has .150 walls and the convergent end is .200 thick because of the heat.

This may be the last one I do. My guys in Iowa have gone quite for a long while now. No one has launched anything for about 2 years.

Dave C.

Re: 4" Rocket Nozzle

Posted: Sat Aug 17, 2013 7:47 am
by Mike Walsh
Very nice work! Did you know there are other fliers that make their own propellant as well? I don't know if you might be interested in a different market. PM me if you would be, as I might be able to direct you to a new way to contact those guys.


Re: 4" Rocket Nozzle

Posted: Sat Aug 17, 2013 6:42 pm
by Dave_C

I saw your post on your level 3 cert. Congrats!

As far as making nozzles, it took about 5 hours to machine that nozzle and most hobbiest won't pay me $50.00 an hour to make parts. Most have some way to get it for little cost. Can't blame them, just can't support my tool habit without some decent cash flow.

Good luck on your future launches!

Dave C.

Re: 4" Rocket Nozzle

Posted: Sun Aug 25, 2013 7:07 pm
by RSG
That's really cool DrDavo, I was just at the Smithsonian in Washington looking at all the rocket exhibits. I've always been intrigued with rocket engines and had a desire to build them even as a kid. Never did of course but someday.

Re: 4" Rocket Nozzle

Posted: Mon Sep 09, 2013 9:34 am
by Andypullen
Nice work Dave...

Here is a rocket engine I made as part of a student project at work. It was in the design phase for 2 years with 2 different designers working on it. It's liquid fueled. Alcohol and oxygen, just like the German V-2. The main body is 5" diameter. The inside of the neck is about 1 3/4"-2"....I don't have the drawing handy.

The nozzle was made on a HAAS TL-3 cnc toolroom lathe. The program used to program it was GibbsCAM.

The combustion chamber was a short length of steel tubing welded onto the nozzle. I had to drill .020" diameter holes around the periphery of the nozzle for film cooling on a 30 degree down angle. That was fun....Rotary table on the Bridgeport with the head tilted to the correct angle with the sensitive drill chuck. I only broke 1 drill bit. I had to chase a Navy Commander away while I was doing the small holes....He didn't like getting yelled at, but, oh well.

The injector at the top of the motor was also fun. All the fuel and oxidizer holes had to be carefully drilled so there wouldn't be any break throughs which could cause an explosion. Originally, it was submitted for outside quotes, but all the prospective vendors quoted it at $4500+. I silver soldered the fuel and LOX fittings onto the rings and there was no leakage.

It was taken to California last spring and static tested. It wasn't a complete success. The injector may not be designed correctly as it was burning rich and not producing the designed thrust. We are working on it this winter and hopefully will get that worked out and we'll try it again.

Andy Pullen

Re: 4" Rocket Nozzle

Posted: Fri Aug 29, 2014 8:29 pm
by tcbetka
Sort of resurrecting an old thread, but just wanted to say that's a gorgeous nozzle Dave. I am getting into things like that myself--although I am just getting started. I am in the process of building my first high-powered rocket now (to get certified with), but that won't have such a nozzle. I haven't used a metal lathe in 20 years, so there's a learning curve to come up again there as well. In a past life I was a licensed aircraft mechanic, so I have some of that training to fall back on--along with several basic engineering courses and a WHOLE bunch of information on high-powered model rocketry (and R-candy fuel) from the likes of Richard Nakka and Jimmy Yawn. Those guys are really on their game about this stuff.

Anyway, I hope you see this post--and thanks for taking the time to post some of the details of the machining process of those nozzles you've built. Very impressive stuff there indeed.


Re: 4" Rocket Nozzle

Posted: Sat Aug 30, 2014 8:13 am
by Dave_C

Yes I saw the thread and thanks for the feedback! Good luck on your rocket endeavors. Drop me a message if you want to talk about machining nozzles. They can be a pain to figure out if you've never done one.

Dave C.