248 replies to this topic

[cplmac]

2lb whistle rocket with 3" C4 charcoal streamer crossette head

Rocket was little underpowered, crossette was broken a lot to hard.

[digger]

2lb whistle rocket with 3" C4 charcoal streamer crossette head

Rocket was little underpowered, crossette was broken a lot to hard.

Although it did not go high enough, it had a nice dense tail. I suppose a bit of tweeking and it will be soon up to your normal very high standards for rockets.

[dr thrust]

a beautiful tail! can we have preflight pics next time ,also may i ask what are the dims of your 2lb motor, only asking because ive just finished my first true 1lb,er measuring ten inch long, and to me thats a monster! i cant believe the weight of the thing! i guess a two lb'er would be 12 inches long, and so on,whats your thoughts on long motors?

Edited by chris m, 23 February 2008 - 10:31 PM.

[Mumbles]

Standard traditional 2lb whistle rockets have 6" long casings. The BP based 2lbs rockets are normally ~10". A true to form 1lb BP rocket is only 7.5" long. The pound thing is actually very outdated, and not really applicable to current rockets, nor even used correctly in most instances.

[richard2]

Digger,

If you don't mind me asking what are those tubes made from? They look very thin in order to withstand most bp rocket pressures and the yellow colouration is unusual.

Regards


Rich

[cplmac]

Chris I'll be doing another one of these in the next day or so, it will be a carbon copy of the one in the video so a pre-fire pic should be no problem. And what Mumbles said sounds right to me. Mine was actually just under 5 inches long because I wasn't reporting it.
That is some very nice tooling Digger. I kind of like the brass better than most of my tooling which is almost all aluminum except for the 6lb strobe which is polished stainless. I think the Aluminum stuff is a bit soft, I've sheered several spindles off the base plate, and I don't think it would have happened with bigger roll pins and brass/stainless tooling. That is some really nice tooling you have though. You couldn't pay me to use one of those clamshell sleeves though, I can't get past the image of pressing a hand grenade.

PS
That was a really nice batch of rockets, very consistent.

Edited by cplmac, 29 January 2008 - 07:01 AM.

[digger]

Chris I'll be doing another one of these in the next day or so, it will be a carbon copy of the one in the video so a pre-fire pic should be no problem. And what Mumbles said sounds right to me. Mine was actually just under 5 inches long because I wasn't reporting it.
That is some very nice tooling Digger. I kind of like the brass better than most of my tooling which is almost all aluminum except for the 6lb strobe which is polished stainless. I think the Aluminum stuff is a bit soft, I've sheered several spindles off the base plate, and I don't think it would have happened with bigger roll pins and brass/stainless tooling. That is some really nice tooling you have though. You couldn't pay me to use one of those clamshell sleeves though, I can't get past the image of pressing a hand grenade.

PS
That was a really nice batch of rockets, very consistent.

Thanks, the tooling is AluBronze as this is non sparking and is much harder than brass as you know. Yep it has crossed my mind about the clamshell sleave, however I have a hydraulic press that can be operated remotely so I should not be around if there is a problem, what do you use to support your casings?.

Digger,

If you don't mind me asking what are those tubes made from? They look very thin in order to withstand most bp rocket pressures and the yellow colouration is unusual.

Regards


Rich.

The tube in the picture is two layers of 160gm card, the outer layer bright yellow, the inner light yellow (it makes the wall look a little thinner than it is). These are hand rolled with a 75% PVA/Water glue giving a wall thickness of 2mm(and very hard).

Yep they do look very thin, however with my normal tooling they produce peek thrust of 2Kg - 2.2Kg, I have tested them with a narrower nozzle and seen 3Kg without them bursting. So they seem to be up to the job, the only CATO's I have had were when I was hand ramming the motors, and even then they were just blowing the nozzles out.

Digger

[cplmac]

3" whistle rocket with 21 pound dummy head

This rocket was 9'5"(3m) tall and weighed in at 35.7(16.3kg) pounds. The head is just dead weight, this rocket was just to test my motor to see if I can push a 12" shell. Good news, I can! This flight was a failure, but it showed that this motor does have the power to push the weight and it showed me a design flaw I would not have known about otherwise. It turns out I need a bulkhead to prevent the massive chamber pressure from blowing the delay out the top of the motor. I have 4" of delay on this motor, but as the core burns it becomes more powerful and the delay gets weaker, this caused the chamber pressure to eject the delay through the top of the motor. Tomorrow I will recover the remains and hopefully confirm this theory.

Pre-Fire Pic

Edited by cplmac, 03 February 2008 - 10:24 PM.

[cplmac]

I re-rendered it in a normal format this time, this one should work like normal.

3" whistle with 21 pound dummy head

[paul]

Wow, thats a massive rocket. I´ve got one question left: How much whistle powder is in that rocket?! About a kilo?!

[cplmac]

That rocket had 8.4 pounds of whistle fuel in it which is 3.8kg.
No I'm not on my knees, this rocket is 3 meters tall. The head was a 3 gallon plastic jug filled with 9 pounds of kitty litter and 2 pounds of sawdust with 10 pounds of water. I had to screw it onto the rocket motor to keep it securely attached and somewhat stable.

Edited by cplmac, 05 February 2008 - 07:58 AM.

[digger]

That rocket had 8.4 pounds of whistle fuel in it which is 3.8kg.
No I'm not on my knees, this rocket is 3 meters tall. The head was a 3 gallon plastic jug filled with 9 pounds of kitty litter and 2 pounds of sawdust with 10 pounds of water. I had to screw it onto the rocket motor to keep it securely attached and somewhat stable.

Bleedin eck that's a whopper.

I notice from the passfire thread that you drill the cores on these puppies. Does that make you sweat a bit?

[cplmac]

Not really, I press these motors with NO metal in them at all and operate the drill at a very slow RPM removing about a half inch of fuel at a time. I keep track of the bit temperature and go nice and slow, honestly the only time I'm really nervous is during the actual pressing of the motor.

[digger]

Not really, I press these motors with NO metal in them at all and operate the drill at a very slow RPM removing about a half inch of fuel at a time. I keep track of the bit temperature and go nice and slow, honestly the only time I'm really nervous is during the actual pressing of the motor.

Fair enough, do you drill them on a lathe? What pressure do you press these to?

I have an acquaintance (one of my dads squash buddies) who works for a defense company who over the years has worked on propellants for various missiles who has many stories to tell (the ones he can talk about) some regarding drilling experimental grains.

[cplmac]

I press these 3" motors at 3500psi loading pressure, which is to say 3500psi on the grain. It's less than half of the normal whistle pressure but the ceiling for what my press can handle. I actually deformed the press crossmember that the motor sits on when I pressed this last rocket. I core it out by hand with a drill and a paddle bit which takes a bit of finesse to get going.