20 replies to this topic

[mike_smith919]

Hi all,

This is my first post, i have been interested in fireworks since i was about 12. I usually buy lots of fireworks for bonfire night, but over the last few months have started experimenting with home made ones.

Now onto my problem, i have been trying to make a rocket since reading the 'Rockets with headers' thread.

I am using wrapping paper wrapped 3-4mm round a 10mm former, 10cm long, rammed with 60:30:10 (hand ground (pestle & Mortar)) + 10% coarser charcoal added after grinding. nozzle is 1.5cm thick and 4mm hole hand drilled 3/4 of the way through the composition and the stick is 6mm dowel 40cm long(The rocket balances behind the nozzle.

I am getting pressure (the smoke and sparks are shooting out the bottom) but its not lifting.

Is this a design flaw or is my propellant no good?

Cheers,

Mike.

[marble]

Everything sounds fine, I suspect that your fuel is suspect

How does it burn openly? I would try removing the +10% charcoal and trying again.

The stick isn't being held down by anything is it?

Other than that it should either take off or CATO.

Edited by marble, 20 April 2008 - 03:35 PM.

[cplmac]

It sounds to me like there are a couple of problems. First thing I would choke the motor out a little more and drop the nozzle and core down from 4mm to 3mm. Second, that fuel is going to have a hard time lifting a rocket. Start with a 75/15/10 fuel and no additives. If you can make this strong enough to lift your rocket then you can start adding more fuel to it. A mortar and pestle is not going to give you very good BP but it will probably do for the 75/15/10 fuel. If that still doesn't get you off the ground (it should) I would add some water to the mix when you mortar and pestle it and make sure to grind it up for a lot longer than you think is necessary. Good luck!

[Arthur Brown]

75/25/10 is the best place to start. Ground as fine as you can in a m&p. Probably time your next attempt. a small rocket usually burns for two seconds. If your burns for longer then there is a powder speed problem.

Far better to build UP to a flying rocket than try to recover from a CATO with nothing but shrapnel to show for it.

[cplmac]

Any rockets burn time depends entirely on the amount of delay in the motor. It isn't always easy to tell when a rocket changes gears from core to delay, especially with BP rockets.

[digger]

Any rockets burn time depends entirely on the amount of delay in the motor. It isn't always easy to tell when a rocket changes gears from core to delay, especially with BP rockets.

I agree, so I add titanium to the cored area plus a depth above the core equal to the inner radius and additional charcoal to the delay area so it is very apparent when as you say it changes gear. I have to press and not ram them though due to the titanium.

[Arthur Brown]

If you get a burn time in the order of 1.5 - 2 seconds then useful thrust is possible. If you get a silly long time (say over 3 seconds) then the powder is too slow and the thrust will likely not be enough to lift the motor and stick. If you get a time less than a second, run!

[digger]

If you get a burn time in the order of 1.5 - 2 seconds then useful thrust is possible. If you get a silly long time (say over 3 seconds) then the powder is too slow and the thrust will likely not be enough to lift the motor and stick. If you get a time less than a second, run!

You can always test them on digital kitchen scales, thats what I did when I wanted to know how much weight I could lift with them. Motor upside down, in a holder, video camera on a tripod then review the video frame by frame to work out the thrust in Newton seconds (ish).

[icarus]

6mm dowel is a heavy stick i would use the thin green split cane sticks from a garden centre or b&q .I agree 4mm too big a nozzle hole3mm better. If you are struggling for bp then vk2zay,s website gives full info of a superb small rocket, the case can be rolled with pva glue. Barbecue charcoal is good enough, . and the coarse Al powder from a grp supplier is good enough .The tinyest rocket is the amazing 5c candy rocket by teleflight corporation a KNO3 sugar and sulphur fuel that tends to cato in larger motors

[mike_smith919]

Hi all,

Cheers for the input, i have built a ball mill and am trying to make a press, hopefully i can make some faster BP now.

I Have a large bag of 8mm stainless steel BB's Laying about will these be any good for milling media or are they going to spark?

Mike.

[marble]

They make for great milling media but unless you know the grade (I'm told 316 is ok) you cannot use them for making BP, they will be great for everything else though.

Edited by marble, 23 April 2008 - 08:23 AM.

[portfire]

They make for great milling media but unless you know the grade (I'm told 316 is ok) you cannot use them for making BP, they will be great for everything else though.

Indeed,I'd be weary of using those for BP. Ceramic or lead (the latter been the best choice) media are your best options. You can find lead ball at fishing stores, or shooters shops that deal in muskets,for the lead shot. If your in the UK you could try here
http://www.freewebs.com/cooperman435/

Great service

Also, building a press is always a good idea,but not really needed for standard BP rockets.Only if your adding metals like Ti, and other metals which will make the comp sensitive, then a press is needed, AND make sure you fit a blast sheild!!!

If your just using standard BP then you can just ram your rockets.I do,from 10-19mm ID rockets. It's faster aswel, BUT again think 'SAFETY FIRST', and ware appropriate PPE.

Dean

[mike_smith919]

Hi all,

Update.

I got my first rocket to fly today. yay! 'twas a 5cm long, 10mmID, 3mm core with some 75:15:10 pestle & mortar BP. flew about 20feet into the air.

Cheers for all your help, Now to get them higher.

While im here I cant find the milling media on cooperman's site. also Im having pully troubles on my ball mill, i need a 5mm ID , 10cm OD pully, Any ideas?

Edited by mike_smith919, 23 April 2008 - 06:52 PM.

[portfire]

Hi all,

Update.

I got my first rocket to fly today. yay! 'twas a 5cm long, 10mmID, 3mm core with some 75:15:10 pestle & mortar BP. flew about 20feet into the air.

Cheers for all your help, Now to get them higher.

While im here I cant find the milling media on cooperman's site. also Im having pully troubles on my ball mill, i need a 5mm ID , 10cm OD pully, Any ideas?

Great stuff, glad you got them working.Now get them consistant, and you can start putting headers on them

http://www.freewebs....rsalehidden.htm

Can't help with the pulley, sorry

Dean

[seymour]

If you have a hole saw (if that is the name, the drill attachment that lets you cut out circular wooden disks) you can make a plywood one. Get one bit with a 10cm OD and two more with slightly larger OD's for on either side of it. Glue them together, and there you have it.