Questions on Rockets

[WSM]

W,

 

How shall we interpret the 1 ID in height? Throat, overall distance between the convergence and divergence, any clay in the tube? The reason I ask is that I have a tooling set made for porcelain nozzles (kaolin) that uses a standard bell shaped nozzle with a long convergence of 1 ID. These nozzles are pressed wet, air dried and fired at 2700° F and are used for APCP rockets instead of using milled graphite nozzles. The overall length in a 3# rocket motor is 2.5" so one ID would be way to short and a full ID for the throat would be too long.

 

Consider if you will the spindle. At which point does the spindle start to become aggressively tapered compared to the base width? The Universal hybrid tooling has a consistent taper of 1-1/2° from divergence end to spindle tip, a full ID of throat length decreases the nozzle a full 1/32" on my set and I would lose a full increment of fuel on the spindle.

 

-D

 

Hi D,

 

I usually measure from the top (or start of the convergence) to the bottom (or end of the divergence) for traditional core-burn BP rockets. If your goal is high performance model rocketry utilizing a DeLaval nozzle, I'd modify that specification to fit the appropriate height of that nozzle design (try 2x the ID in total height and a maximum nozzle throat heigth of 1/4x the ID). These are rough estimates but a good starting point, I think.

 

WSM

[dagabu]

... maximum nozzle throat height of 1/4x the ID.

 

WSM

 

I like a little more throat then that but if it works, why fix it?

 

I tried one of my porcelain nozzles epoxied into a NEPT tube last year with R-candy and it flew wonderfully, the problem was the amount of work it took.

 

-D

[WSM]

I like a little more throat then that but if it works, why fix it?

 

I tried one of my porcelain nozzles epoxied into a NEPT tube last year with R-candy and it flew wonderfully, the problem was the amount of work it took.

 

-D

 

Hi D,

 

The amount of work? I bet!!! Just try turning graphite! What a glorious mess, and if it gets into the motor of the lathe...BRZZzzzapP!

That's all she wrote.

 

Have you tried pressing the fireclay, graphite and boiled linseed oil nozzle mix? It comes out like a turned graphite nozzle with hardly the mess. If you try it don't forget to let the linseed oil air polymerize before use (takes about three to four weeks but worth the wait). I'm told this mix sticks to the casing better than anything and resists erosion physically and chemically.

 

WSM

[Algenco]

Have you tried pressing the fireclay, graphite and boiled linseed oil nozzle mix? It comes out like a turned graphite nozzle with hardly the mess. If you try it don't forget to let the linseed oil air polymerize before use (takes about three to four weeks but worth the wait). I'm told this mix sticks to the casing better than anything and resists erosion physically and chemically.

 

 

 

now you've got me interested, how do you do it?

[dagabu]

Hi D,

 

The amount of work? I bet!!! Just try turning graphite! What a glorious mess, and if it gets into the motor of the lathe...BRZZzzzapP!

That's all she wrote.

 

Have you tried pressing the fireclay, graphite and boiled linseed oil nozzle mix? It comes out like a turned graphite nozzle with hardly the mess. If you try it don't forget to let the linseed oil air polymerize before use (takes about three to four weeks but worth the wait). I'm told this mix sticks to the casing better than anything and resists erosion physically and chemically.

 

WSM

 

LOL! Yes, I am on my third motor, I had tooling cut for me to make the convergence and divergence and milled the belt by hand. I was using a shop vac to pull the dust away and it zapped so I got a HEPA filter for the replacement... ZAP! I ended up using an air vac and a HEPA vacuum bag (totally rigged) to draw the dust off but it still created enough dust to arc the windings.

 

That was years ago, haven't done HP since the BATF put APCP on the explosives list.

 

Hmmm, can you give up the formula? I would love to try that.

 

-D

[WSM]

Hmmm, can you give up the formula? I would love to try that.

 

-D

 

The information below is borrowed from the March 2005 PGI Bulletin with permission from the author:

 

Graphite Nozzle Mix

55 fireclay

35 graphite powder

10 boiled linseed oil

+40 campstove fuel

 

First sieve the clay and graphite powders together into a stainless bowl. Next mix the linseed oil with four times it's weight of hexane (Coleman fuel or white gas). Mix the dissolved oil into the clay/graphite mixture; this should be done outdoors, in the shade and away from any source of ignition. Mix thoroughly with gloved hands and spread it out to dry on a non-stick tray to dry.

 

To speed the drying time (usually 3-4 weeks if air dried), a few drops to a 1/2 cap full of Japan Drier (available from the paint section of a hardware store) added to the linseed oil/stove fuel mixture before mixing with the dry ingredients, will speed the drying time to about three or four days!

 

This mixture, after the linseed oil polymerizes, goes plastic under pressure and flows around the clay and graphite grains and into the tube fibers to bond everything together, PLUS the graphite helps prevent chemical reduction of the oxides in the clay by the products of combustion from the propellant.

 

 

This mixture smells funny but works and resists erosion very well.

 

WSM

[WSM]

That was years ago, haven't done HP since the BATF put APCP on the explosives list.

-D

 

D,

 

Haven't you heard? The BATFE backed off on APCP when they lost the court case several months ago. Look it up, it's true!!!

 

WSM

[dagabu]

Sounds slippery too! Thanks, I will try it next spring, we are getting snow in the next few days and I have to put off warm weather things for a while

[WSM]

Sounds slippery too! Thanks, I will try it next spring, we are getting snow in the next few days and I have to put off warm weather things for a while

 

 

Yes it is a little slippery, but that's a plus when it's time to remove the rocket from the spindle.

 

Regarding the clay; I'm losing interest in bentonite powder and leaning toward fireclay. Bentonite has an affinity for water and will absorb enough to cause swelling and narrowing the nozzle throat just from the atmosphere. I've had success using Lincoln 60 and Hawthorne Bond. Fireclay is used for making firebricks which find service in lining fireplaces and kilns. With wax or oil (drying oils like Linseed or Tung) added it really resists erosion.

 

The graphite helps by resisting thermal and chemical erosion. Graphite is very inert. It's used in nuclear cores and in molds for thermite, as well as rocket nozzles and crucibles for metal casting. I've seen rocket nozzle throat inserts made of graphite virtually untouched after firing which eroded the surrounding metal badly (in amateur metal rockets firing zinc/sulfur; 13lbs/0.2sec).

 

With the weather turning cold it sounds like a perfect time to light an outdoor fireplace and fire off a few rockets (isn't that what they do in England?!).

 

WSM

[dagabu]

The nozzle thing is a lot like like the BP question, black match question, etc. Ask 10 pyros and get 11 different answers.

 

It may be you, it may be Lloyd, it may be Dukey or Jim that gave me the Kaolin, graphite, hawthorne and bentonite recipe some time ago but I found that it scratched my spindles at high pressures. Bentinite has been very gentle and I bring the proper reamer with me to the shoot site just for that reason of tight nozzles.

 

BTW- My catalog says that Lincoln 60 is a mix.

 

15 Hawthorn fireclay

10 Lincoln fireclay

40 Goldart

15 Ball clay

10 Silica

7 Feldspar

3 Redart

8 Grog or Sand

[WSM]

The nozzle thing is a lot like like the BP question, black match question, etc. Ask 10 pyros and get 11 different answers.

 

It may be you, it may be Lloyd, it may be Dukey or Jim that gave me the Kaolin, graphite, hawthorne and bentonite recipe some time ago but I found that it scratched my spindles at high pressures. Bentinite has been very gentle and I bring the proper reamer with me to the shoot site just for that reason of tight nozzles.

 

BTW- My catalog says that Lincoln 60 is a mix.

 

15 Hawthorn fireclay

10 Lincoln fireclay

40 Goldart

15 Ball clay

10 Silica

7 Feldspar

3 Redart

8 Grog or Sand

 

Well I didn't know that !

This changes things then. I'll stick to the Hawthorne Bond. Thanks D.

 

WSM

[mjc092]

hello all! this is my first post to this forum! i am unable to create a new topic, so i am going to post my question under this topic. So i am new to making BP rockets and am having some trouble. Ok so I have been trying to make 3/4 inch PVC BP rockets ranging from 4inchs to 6 inchs. My nozzles are from rock hard wood putty and do not blow out. I currently am working with two types of BP, one batch is CIA method BP, and another batch is just coffee grinder BP. Both mixes are created with the standard ratio of 75/15/10. i have made around 13+ motors that have all exploded "CATO", the nozzles and end caps do not blow out, the rockets have just been exploding the second the fuse hits the powder!! I have tried end-burner and cored rockets, with the nozzles and cores being drilled with a 1/8, or 5/32 drill bit. I have read thru this site and cannot seem to find an answer to my problem. Does anyone have any hints for me?

 

 

[pyrokid]

hello all! this is my first post to this forum! i am unable to create a new topic, so i am going to post my question under this topic. So i am new to making BP rockets and am having some trouble. Ok so I have been trying to make 3/4 inch PVC BP rockets ranging from 4inchs to 6 inchs. My nozzles are from rock hard wood putty and do not blow out. I currently am working with two types of BP, one batch is CIA method BP, and another batch is just coffee grinder BP. Both mixes are created with the standard ratio of 75/15/10. i have made around 13+ motors that have all exploded "CATO", the nozzles and end caps do not blow out, the rockets have just been exploding the second the fuse hits the powder!! I have tried end-burner and cored rockets, with the nozzles and cores being drilled with a 1/8, or 5/32 drill bit. I have read thru this site and cannot seem to find an answer to my problem. Does anyone have any hints for me?

 

 

 

 

Well, I would strongly advise against using pvc for the casing, Paper works just as well in my expierence. Also, You really shouldn't grind complete comps in a coffee grinder.

 

As for your rocket problem, I would guess that they don't have enough compaction on the fuel grain. Small cracks or loose powder will build up too much pressure for the tube to handle.

 

Also, most bp fuel formulas fall somewhat near to the 6:3:1 ratio, your bp may be too hot for the motors. This could be causing the cato's too.

 

Hope I was of some help.

[dagabu]

Well, I would strongly advise against using pvc for the casing, Paper works just as well in my expierence. Also, You really shouldn't grind complete comps in a coffee grinder.

 

As for your rocket problem, I would guess that they don't have enough compaction on the fuel grain. Small cracks or loose powder will build up too much pressure for the tube to handle.

 

Also, most bp fuel formulas fall somewhat near to the 6:3:1 ratio, your bp may be too hot for the motors. This could be causing the cato's too.

 

Hope I was of some help.

 

Nice pyrokid! I think you hit the nail on the head.

[mjc092]

Nice pyrokid! I think you hit the nail on the head.

[/quote

 

ok cool thank you for the bp mix ratio and the help. I am going to try that to make up a new batch of bp and try it out. What about the nozzle

drill bit? Do you think I should keep using the same size or use a different size? Do hand rolled kraft paper tubes really work as well as PVC?

[Mumbles]

Your nozzles are way too small. I'd start around 1/3 ID, 1/4", and go from there.

 

The suitability of hand rolled tubes is entirely dependent upon how well you roll them. Regardless they're much safer and ecologically friendly. You should definitely use them. You can purchase high quality tubes for pretty decent prices too.

 

http://www.hobbyhorse.com/pyro_tubes.shtml

[Col]

On 19mm id x 110mm motor, i drill a 5mm core by hand until it reaches 15mm below the top clay bulkhead, then redrill just the clay nozzle with an 8mm bit. There are better ways to do it but i launched 16 rockets with these cores using 60/30/10 and 75/15/10 fuel last weekend and they all flew well enough. The tubes were handrolled too

[mjc092]

Awesome thank you for the help! When you say 1/3 or 1/4" what do you mean by that? Is that the drill bit size? And is there a formula or ratio to find the size of a nozzle based on the size of the ID of the rocket tube? Just to throw it out there are these rocket motors taped to a stick considered fireworks?

[Col]

25-33% of the tube inside diameter which is 5mm- 7mm for a 19mm tube.

The fuel makes quite a difference, i get 1.2kg peak thrust from cool 60/30/10 and upto 3.5kg from hot fuel 75/15/10. The cool fuel carries my 135g rocket/header/stick to a decent height.

Cool fuel test

[dagabu]

Awesome thank you for the help! When you say 1/3 or 1/4" what do you mean by that? Is that the drill bit size? And is there a formula or ratio to find the size of a nozzle based on the size of the ID of the rocket tube? Just to throw it out there are these rocket motors taped to a stick considered fireworks?

 

Regretfully, there is no real proven ratio since I have seen rockets fly with a 25% nozzle and up to a 100% nozzle (nozzleless).

 

As far the second part, if you live in the USA, if you make almost anything pyrotechnical, it is fireworks and is 1.3g automatically since the CSPC has not tested it. Sorry:blush:

[mjc092]

I started using 1/2 inch pvc which greatly reduces the amount of BP i have been using everyday. I found a nozzle of 4mm will get my BP 1/2inch PVC end burner rocket up about 4 feet in the air. So now i have not had any explosions in the past few days, just fountains and 2 rockets that went up a few feet. The hardest thing is trying to find a place to launch the rockets.

 

 

 

 

[dagabu]

I started using 1/2 inch pvc which greatly reduces the amount of BP i have been using everyday. I found a nozzle of 4mm will get my BP 1/2inch PVC end burner rocket up about 4 feet in the air. So now i have not had any explosions in the past few days, just fountains and 2 rockets that went up a few feet. The hardest thing is trying to find a place to launch the rockets.

 

MJC,

 

You will find that there is very little support for the use of PVC here. The reality is that PVC fractures into shards and they do cause injury. Frankly, if your rockets are only going 4', then its time to ask a few questions, roll some tubes, and get those babies flying!!

 

best of luck with the rockets

[mjc092]

Hey all, ok so Im going to try to roll some tubes but I need some help. I just made 4 tubes out of brown paper bags, as I was rolling the strips of paper around a 5/8inch dowel I coated the paper in elmers glue and finished the tubes when the walls were about 4 mill. When dried I used wood putty to make a plug, but once I started to ram the bp the tubes were bending above the cap. So I junked them. Can anyone help me on making some good solid tubes? And can I continue to use wood putty with paper tubes or should I switch to kitty litter nozzles etc? I know that no one here wants to hear this but I did get 2 of my 1/2 inch PVC end burners with a nozzle drilled with a 5/32 bit, up to about 20 feet! Also I'm thinking about just buying some metal rocket tools where should I go for some cheap end burner tools? Maybe even just the base because I can continue to ram the rockets with a wooden dowel.

[Mumbles]

I think you will find that good quality tooling comes at a price. I suppose you could get some of those cheap chinese tooling sets, but those don't have a taper or angled nozzles. Both of which you will want for any decent rockets. If you think good tooling is too expensive for you, the other thing you may want to look into is taper pins. The angled nozzles can be made from wooden dowels and a file and sandpaper.

 

I'm not sure if you meant what you said about the tubes. You said 4 mill (mil?) which is .004" thick. That would be one layer or less of most papers. You'll probably want to roll the tubes to around 1/16" to 1/8" or more. For brown paper bags, like grocery bags, you'll need around 20" strips for 1/16", 43" for 1/8", and 70" for 3/16"

 

20 feet still isn't very impressive. If you can't hit a few hundred feet, you really haven't succeeded yet.

[dagabu]

MJC,

 

If you are talking millimeters, you have it about right BUT you may have two problems that are really common when hand rolling tubes.

 

1. Make sure you pre-glue your paper.

I do this by taking the advice from a fellow pyro and dilute Titebond ll wood glue 50/50 with water, spray or brush your paper on both sides and let dry. Spray or bush a lite coat on to the dried paper and roll it up.

 

2. Use a board to compact the paper.

Use a flat board at least 150% wider then your tube and 12-18" long, place it over your rolled tube and press while rolling the tube away from the end of the paper, you will know immediately if you are going the wrong way as the tube will unroll. Do this until ALL of the excess glue and water are expelled and the tube shows NO gaps at all between the sheets.

 

Make sure you use something to break the bond of the glue with your rolling dowel since this method will tighten the paper significantly. Also, stop with the wood putty, its expensive and a waste. Use the cheapest kitty litter you can find, break it up a little in a zip lock, put a tea spoon in the dried tube and give it 15-20 smacks. Don't pound too hard, the idea is to compact, not burst the tube.