My First BP Rocket

[ollie1016]

This is the first one I've ever done and if failed miserably. http://youtu.be/OOLgg59_DDs

 

Tube Diameter: ID= 25mm (1") OD = 30mm A solid Kraft paper tube parrel wound and glued with PVA.

 

Fuel:

60:30:10, milled for 6 hours in a Chicago Rock rumbler with 5LBS of .5" lead media.

 

Core: 8mm core going 3/4 way into the fuel grain. (Hand drilled out with drill bit)

 

Nozzle: Bentonite clay powder, 1" thick, the exhaust hole as 10mm wide.

 

Rammers: 1" wooden dowel, and a rubber mallet,

 

Stick: 4ft section of bamboo, about 5mm, was almost balanced.

 

I recovered the rocket casing ( after cutting my hand open on a barbed wide fence). The nozzle and top stopper had both completely blown out.

 

Just thought I'd try get some content out, and if anyone has any tips or tricks I'd love to hear them!

 

- Ollie

Edited August 18, 2013 by ollie1016

[Bobosan]

Try ramming with a deadblow hammer or leather mallet on a hard surface.

[pyrokid]

I second the advice about getting a good mallet. They make a world of difference. I’d also invest in a nice aluminum rammer.

 

In my experience with BP rockets, screened 6-3-1 has done the job. I have found no need to mill it. It seems to me that unmilled fuel will be slightly slower, which would help you avoid blowing out the top plug. I granulate my fuel without a binder. I feel that it is easier to compact.

 

I would advise against drilling out the core on such a large motor. Since you used a wood rammer and a rubber mallet, it doesn’t sound like you achieved a solid fuel grain, and drilling out the core would only exacerbate this problem.

Edited August 18, 2013 by pyrokid

[pyroman2498]

My rockets do the same thing, and mine are nozzleLess. I recommend adding some mineral oil to the powder for easier ramming

[kpknd]

I think 6 hours is a bit much, I only go 1 hour with my fuel. Sound like your fuel is too hot, or the grain is not solid enugh wich can leave small voids in the propellant and cause a CATO. Get a leather mallet and aluminum or nylon rammer.

[Mumbles]

Another thing that can help to keep the nozzle in is to recess it into the tube, instead of making it flush with the end of the tube. When you ram a plug or nozzle, the walls will expand slightly. Having bare tube both above and below this can help hold it in place. Some others will also use grog to give the plugs more grip, but this can mar tooling, and potentially cause issues when trying to drill.

 

I suspect the milling made the fuel too hot. 6:3:1 is normally just screened or lightly milled as others have stated.

[VikingPyrotechnics]

I mill my 6-3-1 for severall hours, and had never a CATO or blowthrough with this fuel?!

I think you have to ramm it harder. Like the other guys said, go and get a dead blow hammer!

In my early days, i have made some very nice motors with it

[WonderBoy]

I would like to know a bit more before making any recommendations.

 

Core: 8mm core going 3/4 way into the fuel grain. (Hand drilled out with drill bit)

 

How long was your core? 8mm is a bit more narrow than "standard" for a 25mm ID coreburner.

What size increments are you using?

What weight and type of mallet?

Did the tube show bulges on the outside from ramming?

How thick was your bulkhead("top stopper")?

 

6-3-1 is pretty tame, so it may work well with the more narrow core and nozzle. Btw, why is your nozzle opening larger than your core?

 

 

WB

[ollie1016]

I would like to know a bit more before making any recommendations.

 

 

 

How long was your core? 8mm is a bit more narrow than "standard" for a 25mm ID coreburner.

What size increments are you using?

What weight and type of mallet?

Did the tube show bulges on the outside from ramming?

How thick was your bulkhead("top stopper")?

 

6-3-1 is pretty tame, so it may work well with the more narrow core and nozzle. Btw, why is your nozzle opening larger than your core?

 

 

WB

 

The core was 3 3/4" long.

1 teaspoon increments.

Rubber mallet. It's about 2lbs ish?

 

The nozzle did, but the fuel grain didn't.

 

Top stopper was, 10g of bentonite clay.

 

Bigger nozzle, less pressure? So should be less chance of a Cato! But not in my case!

 

[Mumbles]

Considering that your rocket, and thus core, is half as long as normal core burners of this size are, that should further tame it. I'd recommend a bigger hammer. Also ensure that the nozzle and bulkhead are around 1ID thick each.

 

Out of curiosity, what sort of charcoal are you using? Using something quite reactive might also be an issue.

[Col]

The rubber mallet wouldnt consolidate the grain as well as a heavy mallet or deadblow hammer. The relatively high charcoal content of the 6-3-1 will make it harder to get a solid grain. Give it more ummph.

my 2c

Edited August 21, 2013 by Col

[ollie1016]

Considering that your rocket, and thus core, is half as long as normal core burners of this size are, that should further tame it. I'd recommend a bigger hammer. Also ensure that the nozzle and bulkhead are around 1ID thick each.

 

Out of curiosity, what sort of charcoal are you using? Using something quite reactive might also be an issue.

 

I really just need to buy some 1lbs rocket tooling, just haven't got the extra cash at the moment. I'm found to try get dead blow hammer. Unfortunately I've only got wooden rammers for the moment.

 

I will bulk up the nozzle and bulkhead a lot more next time. I used just straight bentonite. I've heard of using a mix of grog, Bentonite, sand and PVA? What are your thoughts on that?

 

In using home cooked pine charcoal. I only use pine for BP. I pre mill it for 4 hours before I make my BP. The fuel is probably far too hot!

 

Here is my first end burner. There was no bulk head because if run out of bentonite. Basically just a massive 25mm spolette! http://youtu.be/T3WoWk7l2bg

[karliWadt]

I've found personally although im reiterating what other members have said that more compacting helps! I was even advised to use dextrin as a binder (without much success admittedly) I've gone into the realms of hybrid fuel and LOX-Methane now but BP and Rocket candy are still my bread and butter. If you open an estes engine you'll see just how compacted that BP is. Although very few of us have access to the same level of equipment estes has on hand!

[FlaMtnBkr]

If you are out of clay you can use cheap kitty litter that has been milled to dust. A couple percent of mineral oil will help it consolidate.

 

Also, a 1" motor is going to be harder to ram by hand than a smaller rocket. Any imperfection in the BP grain will cause it to blow. Smaller motors are easier to learn on as that is a 3 lb motor. I would probably try to learn on a 4 oz 1/2" rocket.

[karliWadt]

I've found using a modified version of the screw mechanism of an engineering vice can compact BP well. Assuming of course your tubes can handle it. You can create a great deal of pressure with a vice (yeah i know im a girl so can't hit as hard with a mallet) but it works for me

[Monster90ash]

If it held together that thing would of taken off with a crack. Like the guys and gals say im guessing your grain was too fine or you didnt ram the fuel hard enough.....nice effort but

[WonderBoy]

As was mentioned earlier, I would recommend a larger mallet. For 1" ID motors I use a 4lb dead blow mallet and give each increment about 8 solid blows, it can give your shoulder quite a workout..

 

If you are out of clay you can use cheap kitty litter that has been milled to dust. A couple percent of mineral oil will help it consolidate.

 

I like to use unmilled kitty litter +3% oil. I have cut a tube open after ramming the nozzle and the grains of the kitty litter really bite into the case walls.

 

Also, Mumbles mentioned recessing your nozzle in the tube, do you do this, or is your nozzle pressed flush with the end of the tube?

 

 

WB

[ollie1016]

As was mentioned earlier, I would recommend a larger mallet. For 1" ID motors I use a 4lb dead blow mallet and give each increment about 8 solid blows, it can give your shoulder quite a workout..

 

 

 

I like to use unmilled kitty litter +3% oil. I have cut a tube open after ramming the nozzle and the grains of the kitty litter really bite into the case walls.

 

Also, Mumbles mentioned recessing your nozzle in the tube, do you do this, or is your nozzle pressed flush with the end of the tube?

 

 

WB

 

I do need a bigger hammer, the next hammer size up after my 2lbs one is a 14lbs sledge hammer!

 

For this rocket I used blended cat litter. I normally use the cat litter granules that don't pass through my 20# screen. Between 2-4mm ish. I've never tried adding mineral oil, I'll add some next time.

 

For the next few months, I am going to have to leave pyrotechnics on the back burner. As my education takes priority now. It's great to get so much useful and friendly information from the forum.

 

Ollie