Advice on 1lb BP Cato.

[TheMetalKing]

I'll start by saying hello, I'm James.

I've lerked for a minute here, but I've been in pyro a number of years, but rocketry is a recent adventure.

 

Anyhow:

A video would probably be best for everyone, my video did not come out as I hoped. So let's not try to dissect a very poor quality video.

 

I've started exparementing with 1lb skylighter BP tooling. I previously messed with 1lb cohete tooling from Woody. Although I prefer what Caleb makes over pretty much everyone else, the skylighter set was gifted to me free of charge from another pyro.

This morning I did my first test fire of one, with a pretty cool Cato. Not what i was hopping.

 

The Cato was a very prompt burn off of the rocket on my test stand. It vented off through the top of the rocket.

 

Fuel used is currently the fastest I could produce, and many here will make mine look slow.

( it's still slow enough to require a nozzle).

75/15/10 willow charcoal based black powder.

I'm using a 1ton arbor for the pressing, and in this case didnt use a top bulkhead, nozzle was 1 tube width.

 

From the test I did this morning it left me with three conclusions.

1: My fuel is too hot for this tooling.

2: A top bulkhead is required.

3: I should avoid lighting from the top of the core.

 

Any advice or thoughts on the matter would be appreciated.

-J Luck.

Edited June 30, 2022 by TheMetalKing

[Guernica]

I'd try one without a nozzle & see what happens... it might not be so much that your fuel is too hot for the tooling, just too hot for a nozzle.

 

I'm not sure I'm following when you say the CATO vented off through the top. Doesn't a CATO happen too fast to even see the mechanism of failure? For whatever it's worth, I've never used a bulkhead, (the delay section is the de facto bulkhead) and it's never been a problem. Also, are you pressing damp (1-2% moisture in the fuel)?

[FrankRizzo]

A bulkhead is usually a good idea, but those type of failures are usually a result of the casing expanding and ejecting the fuel grain. Using a tube support when loading your fuel can help if you're not already using one. A support allows the fuel to compress the walls of the tube and pre-expand the tube so there's not much additional elasticity.

 

If you don't have a support, waxing the tube interior and using a clay bulkhead should help. The wax slightly inhibits the outside wall of the fuel grain so when your tube balloons a bit, fire won't propagate up the sides of the grain and make it CATO.

Edited June 30, 2022 by FrankRizzo

[Arthur]

Your conclusions could each be a part of the problem. Many people use a bulkhead or press a delay comp there, Lancaster directly states the mix of (commercial) BP with added fuels -a ratio that changes as the diameter. The whole point of a rocket is the thrust from the whole surface burn up the core.

 

As with everything pyro the method is at least as important as the mixture.

[TheMetalKing]

I'd try one without a nozzle & see what happens... it might not be so much that your fuel is too hot for the tooling, just too hot for a nozzle.

 

I'm not sure I'm following when you say the CATO vented off through the top. Doesn't a CATO happen too fast to even see the mechanism of failure? For whatever it's worth, I've never used a bulkhead, (the delay section is the de facto bulkhead) and it's never been a problem. Also, are you pressing damp (1-2% moisture in the fuel)?

Tube and nozzel survived the blow out, it vented straight upward blowing through the delay section.

Which now that I've had 24hr to think likely also could have been too little of delay.

 

I'm pressing at 2% moisture.

[Arthur]

If the power came out of the top then there is the problem! Add more fuel or add a clay plug -either would hold the pressure in for more normal flight

[Uarbor]

I have been doing nothing but making one pound rockets for a year now. I am using Universal tooling though. 75 15 10 Willow is very hot for for the nozzle size you are using. My main question would be are you dampening the propellant before ramming it? I had the same problem you are having quite a bit whenever I was hand ramming. Once I got my press it only happened once in awhile. Now that I have Caleb's bulkhead forming tool which leaves a pass fire so you don't have to drill I no longer have this problem. I think you're going to have a difficult time with an arbor press unless you use a bulkhead depending on how hard you're able to pull down on that handle. And I would assume with that tooling your powder is a bit hot. But that is easy to fix by adding a bit of charcoal five or 10%. Dampening the propellant with one or two percent water gives you much greater compaction And there is no need to dry them out after they will fly just as well or better with that moisture level. I am also a huge believer in waxing of the tubes. I use a shotgun swab from my 12 gauge. Just be careful not to overdo it all you need is a thin layer. The other advantage of the bulkhead former is you can make fountains with it. I was using a homemade tube support but when I finally broke down and bought a real one things went much smoother. A good tube support and also protect your spindle from getting bent because there is much less chance of the tooling getting out of whack or kicking out. Also the type of tubes you might be using could be a problem. Do not use those thick pulpy tubes which appear stronger when you look at them but actually they compress on the inside when you press powder in them. Edited July 1, 2022 by Uarbor