38 replies to this topic

[jermain]

You have this the wrong way round - a poorly consolidated fuel grain can lead to explosions due to voids/cracks in the grain, trying to lower the pressure by ramming lightly is not going to work.

Sorry that's not very clear or I am not understanding it properly, are you saying ramming results in more or less pressure inside the motor? At present I ram the composition quite hard and it keeps CATO'ing.

Thanks

[Mortartube]

Ramming SLOWS the burn. Loose powder burns faster owing to greater surface area.

Motors are commercially pressed on a hydraulic press. The smaller the motor the faster the propellant needs to burn. If you are getting Catos just add charcoal about 3% to 5% until you get the mix right. I make 16mm I.D endburners with straight BP milled and use a 3mm choke, they work fine, but if they are too fast just dilute the mix with extra charcoal as I say.

Those motors are pressed on a 1 ton arbor press.

Also ram/press your comp in at least 8 increments per motor to ensure it is all compact.

[Creepin_pyro]

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Edited by Creepin_pyro, 20 September 2011 - 04:45 PM.

[jermain]

Read the "A little on ramming." section here, some useful info I think. Also people often overlook nozzleless rockets, I think they're great and a good way of learning about rockets in general before moving onto nozzles and the inevitable CATOs.

http://www.angelfire...afts/dj002.html

hmmm, interesting reading, thanks for that!! He talks about using proper ramming equipment however and all I have is various pieces of cylindrical wood that i wrap paper round to make the rocket casings and then ofc ram using the saze diameter piece of wood. It's hard to ever be consistent! Oh well, I will keep trying!!!!

[starseeker]

I recast my lead by melting it in a baked bean (The type you open with a tin opener NOT the ringpull type as the lip left interferes with the pouring.) I heat the tin on a camping stove (having first deformed the tin a little to make a pouring spout.) Wear eye protection and gloves and do this outside. I use long nose pliers to lift the hot tin can.

I cast my media in home rolled card tubes that I'd rolled for rockets and I plugged one end with clay, just like making a choke. Tape one end, the just put the clay in and hammer it down with a drift.

Stand the card tubes in sand or earth and pour. When set, cut off the tubes with a knife.

Job done.

You can of course roll tubes to whatever length and diameter that best suits your needs.

obviously you will be wearing a respirator when smelting lead,you might otherwise in the future start forgeting what it was you started in the first place!

[Mortartube]

obviously you will be wearing a respirator when smelting lead,you might otherwise in the future start forgeting what it was you started in the first place!

I don't remember posting this. Lol.

Good advice.

[44RedHawk]

What is considered to be the best ball size for BP please ?
Marble size ?

I've had very good success with 1 - 1/4 inch (31.75mm) diameter ceramic ball (alumina) milling media running in a 15 lb capacity X one gallon rock tumbler/polisher/ball mill that I purchased on eBay. I run 6 lbs of media with 3 lbs of bp for three hours and the resulting milled powder is equal to commercial grade GOEX meal-D. I also use this milled bp for polverone and lift powder. To make commercial grade lift powder from home milled meal-D you'll need to add 5% dextrin, moisten with water to a clay like consistency then pound into a block, slice & dice with a cake knife to small granule size chips. -Enjoy

Edited by 44RedHawk, 19 August 2011 - 12:55 PM.

[michaelp]

Use the same chemical batch and mill for the same time, one batch with cylinder and the other with ball, while milling pop out and have a curry with a pint of cobra, which curry tasted better when milling with cylinder or ball.......? simples its also a test the wife would enjoy

[michaelp]

Why did my lovely wife have to be in when the four block bearings were delivered, .....could engineering companies please use wallis bags....

just waiting for my 1mtr length of 20mm s/steel bar rod