BP rocket problems

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jonarthur33
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BP rocket problems

Post by jonarthur33 »

Unfortunately I did not know any better and got a cheap 3/4 rocket tool set off Ebay.
I have tested it again tonight and even waxing the tubes changing to a slower charcoal using 60-30-10 still getting CATOS firstly the rammer is 3.2 mm less than the ID of tubes secondly the end is flat the spindle is 5 mm at Base tapering to 3.5 mm at the top and is 80 mm long and brass. I'm at a loss what to do tried an even shorter motor tube of 3/4 by 4 inches and that was a loud ground salute any help please.
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Lloyd
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Re: BP rocket problems

Post by Lloyd »

Jonathan,

Early pyrotechnic tools were quite crude in dimensions, yet, they made good rockets with them.

Try 'dialing down' the power of your rocket fuel. Add (say) another 10%-20% charcoal (of the original amount) over what you're using now, and see how that fares.
If you're using 20%, try 22% or even 25%.

Lloyd
"Pyro for Fun and Profit for More Than Sixty Years"
jonarthur33
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Re: BP rocket problems

Post by jonarthur33 »

Thanks Lloyd will add some oil too as I'm hand ramming.
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Lloyd
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Re: BP rocket problems

Post by Lloyd »

Jon,
If you're hand-ramming, one thing I can suggest is to reduce the size of your increments. Without very predictable compression from 'lift to lift', you may be getting soft-spots. Reducing your increments to 1/2 tube-id per lift (compacted) may help with that.

Lloyd
"Pyro for Fun and Profit for More Than Sixty Years"
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Pyro-Gear
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Re: BP rocket problems

Post by Pyro-Gear »

I have to say the tooling leaves a lot to be desired, however, I have pigeon motors from China that do run a 5mm nozzle but the core is very short around 20mm.

I have seen a picture of the tooling and noticed it uses a nylon rammer, now in my opinion that is bad practice as you need to transfer the energy from the hammer blow to the grain so I suspect the majority of energy has been lost, a little like ramming with a rubber mallet on a rubber mat!

One option you have is to swap out the rammer for an aluminium one , just to add if the spindle is 80mm long then your tube length should be around 110mm so not a true 1 pound motor.
jonarthur33
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Re: BP rocket problems

Post by jonarthur33 »

Thanks again Lloyd and Ken. As you know ken I'm getting a proper 15 mm ID set from you next month.

I did manage to get a 1/2 BP end burner up last night. I have found 15 ways that tooling won't work but it's like a challenge now plus I have a load of waxed 3/4 inch ID tubes to use up.
jonarthur33
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Re: BP rocket problems

Post by jonarthur33 »

So what size should the nozzle hole be ideally. Is there a formula also for an end burner?
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Pyro-Gear
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Re: BP rocket problems

Post by Pyro-Gear »

For a true 1 pound motor around 9.5 to 10mm, my 15mm set runs a 7.5mm nozzle, a short ¾ end burner should be ok on a 5mm nozzle.

Jon have you thought about trying the motor nozzle less you should try it.
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Lloyd
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Re: BP rocket problems

Post by Lloyd »

Jon,
For all of our nozzled products, we make a modified DeLaval-style nozzle, with both convergent and divergent cones of different angles.

We use - universally, but for one product - a 33% nozzle diameter, and 'tune' the fuel package to make best use of that size. That one 'quick-shot' model uses a 50% nozzle i.d..

For our purposes, it's not for the goal of "getting out as much gas as possible in the shortest time", but for getting a high velocity to carry sparks the furthest distance. When used for rockets, the thrust is always 'adequate' -- but I wouldn't call them spectacular, only reliable.

Lloyd
"Pyro for Fun and Profit for More Than Sixty Years"
jonarthur33
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Re: BP rocket problems

Post by jonarthur33 »

Thanks again Ken and Lloyd, I have actually made up four variations to try out tonight one is nozzle less one is rammed and re-cored to 8mm and stepped down to 5mm. One must work its beyond a joke now. I'm thinking of taking the spindle off and converting it to end burner.
jonarthur33
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Re: BP rocket problems

Post by jonarthur33 »

To low powered now, I added 20 % extra charcoal two went up in a semi circle one hit a neighbours house. Normally test at Epsom downs but it too busy there at the moment.
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Pyro-Gear
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Re: BP rocket problems

Post by Pyro-Gear »

Jon chop the spindle down to 30mm and use it as an end burner.

Good news is I was up till 3 am last night in the workshop 15mm rocket tool is made and the upgraded helicopter tooling
jonarthur33
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Re: BP rocket problems

Post by jonarthur33 »

Thanks Ken I will chop the spindle down. That's good news looking forward to getting that set. :D
sambo
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Re: BP rocket problems

Post by sambo »

jonarthur33 wrote:To low powered now, I added 20 % extra charcoal two went up in a semi circle one hit a neighbours house. Normally test at Epsom downs but it too busy there at the moment.
yep, that aint no fun. When I first ventured into rockets I bought a crappy homemade set off a Greek guy who goes by the name of pyrogeorge. He seemed like a decent bloke but he ripped me off really and sold me a large bore aluminium tooling set with completely off choke and spindle measurements. Let's just say I had the same problem, with a motor that burned for something like 20 seconds in total !

If you've got a set from Ken then you can trust it will work and not only that but it will perform well. I'd wait until you get his tooling myself or at least, like you say, have a large test area.

Good luck !
jonarthur33
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Re: BP rocket problems

Post by jonarthur33 »

Thanks Sambo,

I've cut the spindle down to 30 mm long for endburners. Going to test 3 motors tonight on a large isolated field near me.
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