Rocket Tooling

[Aquarius]

I just tested my 12 mm ID with 100 mm long casing and 65 mm spindle, 5 mm coreburner today on a model rocket.

With my 70:20:10 meal + 10 % unmilled charcoal it lifted 66 grams of payload to a respectable height... on 10 grams of fuel.

My "motor on a stick" I lost sight of and it was never found.

 

On the 15 mm I have not done much on spindle length yet, I'll take off 10 mm and see how that works.

[moonshot]

Here is a pic of the tooling and motors I have built so far.

http://i107.photobucket.com/albums/m314/di.../Picture083.jpg

Along with my trusty dead blow ramming hammer. Hey I just got an idea! O.K here is the 15mm ID 130mm long motor with a header I designed.

http://i107.photobucket.com/albums/m314/di.../Picture084.jpg

I will load it up with some meal BP/ aluminum and BP/ iron filing pumped stars I have been messing around with and throw in a few cut TT stars. I'll name it Flaming Potpourri Even if it CATOS it will make a great show. And VOILA! It only took a few minutes to put it together since I had all the parts laying around.

http://i107.photobucket.com/albums/m314/di.../Picture086.jpg

http://i107.photobucket.com/albums/m314/di.../Picture085.jpg

I threw in some pieces of white and gold falling leaf fuse also. Total weight of the header is 70 grams. Total weight of the rocket 140 grams. I will shoot it tonight at a big birthday party I'm going to. I have some 1.4g stuff to shoot too.

Hey aquarius, do you live in the USA or overseas?

[Aquarius]

Moonshot: I live abroad...

 

My 15 mm endburner was a failure.

I didn't even leave my launchpole, just stood there and burned as a upside down fountain. Well well, I know they are hard to get right, so I'll make myself some nev tooling and try for a 3 mm nozzle instead.

 

My 15 mm ID coreburner took off all right, maybe the thrust was a tad short after I cut back on the corelength. But it flew! No CATO this time.

 

And my 12 mm ID coreburner lifted a dummy shell of 50 grams with no sweat. It had a small breakcharge to see if the delay was ok.

It was abit off, too short, so I'll probably use a spoulette for the real thing.

 

My fuel is ok, easy to make and with a lot of tail. I'll cut back in the added charcoal to get a little more thrust.

Not quite perfect yet. But getting there..

 

And since this thread is about tooling, I'll see if I get around to post some pictures of my setup as well..

[Aquarius]

My toolings for a 12 mm ID, 5 mm nozzle opening and 100 mm casing:

[lja]

Aquarius, I solved my "nicks and burrs" problem on the nozzles by getting rid of any sharp edges and giving them a good going over with 400 then 600 grit sand paper. A really light dusting of powdered graphite helped a lot also.

 

The bentonite likes to stick to the metal, any dry lubricant really makes a difference.

[invisibleworld]

I'm going to make rocket tooling in my shop class and was wondering how long i should make the fuse hole. I'm going to make a copy of this

http://www.firefox-fx.com/images/dscn2019.jpg

but my tubes are 2 inches long and have a 6mm diameter with a 2mm wall.

If you go to skylighter.com, firefox.com, wolterpyrotools.com, or cannonfuse.com and brouse around there sites, you can get a good look at some different types of rocket tooling. Everything from core and end burning black powder rockets to strobe and whistle rocket tooling. Skylighter will have a tutorial on how to ram the rockets. Some sites will even give you dimentions on building them. You will spend a lot of time getting the dimentions and the B/P formulas right for the different size diameter rocket tubing.One thing to remember, when you build your tooling,If you start out with a smaller nozzel opening (choke) and it explodes on take off, you can always drill a larger opening in the clay nozzel on the the rest from then on. But if you start out building your tooling with to large of a choke. You have to start all over building a new tool instead. Something I learned through trial and error.

[pyrotechnics.tk]

'm going to make rocket tooling in my shop class and was wondering how long i should make the fuse hole. I'm going to make a copy of this

http://www.firefox-fx.com/images/dscn2019.jpg

but my tubes are 2 inches long and have a 6mm diameter with a 2mm wall.

 

You can also try your nozzle and core dimensions first by drilling them, instead of making tooling.

[Mumbles]

Yes, or you could just make a set of tooling from standard dimensions and tweak your fuel to it.

[hst45]

Based on my "rocket envy" of the wonderful work of cplmac, I'm thinking of jumping on the whistle rocket bandwagon, but I don't want to spend much (any) money on tooling. I'm thinking of either 4 oz. or 1 lb. rockets since I have the tubes in inventory. I'm thinking of 70/30 perc/benz as a fuel since I have the chems. in inventory and I have 1/2" and 1/4" brass barstock in inventory as well.

 

My questions is, what would be your best advise on brazing together a toolset. Would a 3/4" I.D. rocket with a 1/2" core, or a 1/2" I.D. and a 1/ 4" core be acceptable, and if so, what would you recommend for a core length, and what would you advise for an overall tube length?

 

I would normally just cob something together and use my tried and true trial-and-error method, but as I understand it whistle rockets are right on the ragged edge of CATOing so a reasonable starting point would be appreciated.

 

Oh, and please for the love of God don't use the Metric system in response. I'm American (enter the sounds of Europeans booing), and all my tools are S.A.E.

 

Thanks in advance for your help and/or derision.

 

Edit 10/20/'07: A friend PM'd me the drawings. Thanks.

[pyro6314]

Why do you never see proper or even close to De laval nozzle geometries with rocket tooling. As such should you not have a much more gradual angle on the divergent part of the nozzle. I would have to guess there is a large performance loss.

 

On another note, what is the point of having a taper down the length of the spindle? Wouldn't a straight core work just as well as anything?

[jacob]

If you said what i think you said, it's because a flat nozzle won't direct the gases as well resulting in more burn-throughs and catos, it also adds needless weight. as far as the straight spindle, i'd like to know as well.

[pyro6314]

Thats exactly my point. Why wouldnt you want a more proper nozzle instead of a "flat" nozzle. (ie, a plug with a hole) The more gradual direction of gases within the motor would put less stress on the casing; especially at the near right angle where the nozzle starts. A conical profile on the divergent portion of the nozzle will in my knowledge greatly increase the useful effects of the passing gases as well.

 

My brain isnt working well right now but I am thinking there wont be much difference in weight between the two designs. The conical nozzles may even be lighter.

 

From alot of the pictures I see of rocket tooling there is barely a n angle on the convergent portion let alone the divergent portion.

[Mumbles]

Most commercial tooling I have used does in fact have angled convergent and divergent surfaces. I'm not sure about the angles, but I believe it is around 45 degrees on the interior, and 30 on the exterior. I agree that it would be adventageous to have conical nozzles.

 

As far as the tapered spindle, it's actually kind of simple. It's to allow the tooling to come out of the motor easier. The slight taper prevents it from becoming stuck. There is no preformance related issue as to why it is tapered.

[hst45]

As far as my rocketry is concerned, I'm not looking at perfection in the thrust-per-weight-of-grain, or in the absolute fastest or highest rocket possible. If you're looking to achieve optimum performance in these criteria I agree with you that the nozzle shapes could be optimized. For me, my rocket motors are a delivery system for a pyro header, so "good enough" is good enough. Rocketry for its own sake is a worthy endeavour and worth pursuing also but for me a 1 lb. endburner that will lift a 2" ball shell 300 feet is fine.

 

That being said I believe you're right, that a tapered nozzle would better utilize the thrust potential of the fuel, all other things being equal. As for the taper of the spindle, it serves both to facilitate the removal of the spindle from the core and to regulate the burn rate of the grain giving it a large impulse at launch. It's above my pay-grade, but the length, size and even the shape of the spindle is an art in it's self.

[jacob]

Ah, i must have misunderstood, yes a steep angle on the inside of the nozzel is better. my vocabulary must be lacking, by ''divergent'' do you mean ''outside of the nozzel'' and by ''convergent'' do you mean ''inside''? and yes there shouldn't be a noticeable difference in weight.

[pyro6314]

Yes Jacob, those are the terms I tend to use for the parts of the nozzle.

 

Just after I submitted the question about the spindle it dawned on why they did that. Answering my own questions now...

 

I think when I turn my rocket tooling I am going to give it a pretty gradual divergent angle, possibly around 15-20 degrees. For a KNO3/Sucrose propellant and say a 3/4 to 1" tube bore, what should be the dimensions of the core? Anyone have any tips on getting a good surface finish with carbide insert tooling. Im having a hell of a time with it.

 

Thx

[FrankRizzo]

The simple reason why most rocket tooling has a 45-degree taper is that it's an extremely easy angle to create on a lathe.

 

Here's a link to a great thread on UKR about nozzle geometry and the fluid dynamics of exhaust flow:

 

http://www.pyrosociety.org.uk/forum/index....rexpanded&st=15

[pyro6314]

45* angle is no easier or harder any other angle.

[FrankRizzo]

Between creating a conical profile with a form tool or using a standard cutter, the choice is obvious. Let me know how cutting that 15-20-degree angle works out.

 

As for the surface finish on aluminum, use a larger nose radius insert (1/32", not 1/64"), cut slightly above center to reduce chatter, and speed up the feed rate on the finish cut (.002"-.010" depth of cut).

[pyro6314]

For a 1" KNO3/Sucrose rocket how big should the nozzle bore be and how deep should the core be?

 

Thanks for the tips on machining, but I don't have much selection on tooling. Machining 1018 Cold Rolled has been hell for a surface finish but Im guessing its mainly cause I suck at choosing feed rates. I will look up on a table the proper feeds before I go messing around tonight.

 

As for the angle I was going to cut the spindle with the base in a live center then turn the compound to get the angle I want. Do what I need then cut it off with a hack saw (No parting tool or HSS blanks) and flip it to finish the tip of the spindle up.

[FrankRizzo]

Sorry, I don't do sugar rockets...they don't age well unless extreme measures are taken to keep them dry. jamesyawn.com was the best source of sugar rocket info last I read.

[pyro6314]

Over at Nakka Rocketry I found pretty much the exact size of engine Im building. Looks like the nozzle bore will be around 0.281" and he cores his casted grains right through.

 

http://www.nakka-rocketry.net/casting1.html - http://members.aol.com/ricnakk/engine3.html

 

When making the plungers is it really necessary to have progressively shorter flat plungers? And to cap the top do you just leave some space then after the grain is set slap some more nozzle mix (kitty litter) on top then press it solid?

[asilentbob]

Some people do that. Some hand drill (bit in hand) a passfire hole through the clay near the side of the tube (ie not centered) and then put some sort of header. Others don't bother with a top clay plug and just press in some delay mix of some kind before a little header of some kind. If these are your first rockets having a small amount of a flash composition, a couple stars, some flying fish / falling leaves fuse, etc as a header can help you figure out timing so you can start working on squeezing out a bit of glide time when the fuel is all burnt up and the rocket is just cruising up... then a shell near apogee for instance... However this will vary with total payload weight too...

 

Pressing in a very short increment of delay + aluminum as the last increment before a shell would go... on a rocket... but using a dummy shell of approximately the weight your shells have... can give a marker to help timing too.

[FrankRizzo]

Over at Nakka Rocketry I found pretty much the exact size of engine Im building. Looks like the nozzle bore will be around 0.281" and he cores his casted grains right through.

 

http://www.nakka-rocketry.net/casting1.html - http://members.aol.com/ricnakk/engine3.html

 

When making the plungers is it really necessary to have progressively shorter flat plungers? And to cap the top do you just leave some space then after the grain is set slap some more nozzle mix (kitty litter) on top then press it solid?

Good call, I had forgotten all about Nakka!

 

The reason for the progressively smaller rammers is they lessen the lever action on the tube as you get higher in the tube and lose the guiding support of the tube walls. Shorter rams give more stablity. Plus, they're cheaper as there's less total bar stock used.

[pyro6314]

I guess thats a good reason for the rammers. The reason I may have thought is so you can fit it all in a press. We did have a nice huge press but then I found out it wasnt ours and we were just borrowing it...for like 5 years. The guy came to pick it up so now Im trying to convince my dad to buy a nice smaller one for the shop.

 

asilentbob (A - Silent - Bob??? What about Jay?) Thanks for the advice on the cap/header. I may work my way to delays and headers but for now Im just gunna make some "lawn darts" and possibly reload them if they arent too bad. It would be cool to make some shells but I dont have the time considering I have too many other hobbies and things to do. Im gunna try and finish my ball mill today and possibly try turning some 1" tooling. And/or make some Poplar Charcoal and get some black powder grinding away.

 

Does anyone know if wheel weight lead is hard enough to be suitable for grinding media. I have already cast a tin full of 50 cal musket balls.