Blaf

Well, my cores are at the most 10mm long and that's it. Usually I drill between 5mm to 10mm into the grain. This proved to work for me 100% with plastic counter-machine tubes that you can see in previous posts of mine. Of course, pressure would depend on burn rate of your meal too. I do granulate my meal before ramming...did you do it as well? Blaf

Congratulations Pirate! Welcome to the Club. CATO-s are unavoidable my friend so don't worry. Just keep fair distance from the launching site...and meanwhile, try to understand why things gone wrong. Crack in the rammed fuel (as you said) could cause blow as well as loosely rammed fuel...but from your report I presume fuel was compact and well rammed. Inner dia of the tube compared to nozzle dia shows no irregularities too. Fuel lenght should be no problem either...12cm is way too long for 11mm inner dia, though...for that tube dia should be around 50mm or so. The only variable causing tube walls rupture that come to my mind is wall thickness - in this particular case it should have been at least 3mm. And yes, too long core could cause pressure buildup so I make almost non existent core to my motors... Blaf

Ahhh, questons...my favourites. Yes, I first ram a piece of toilette paper in my tube, in approx 1cm depth looking from bottom side. The tube is then positioned upside-down so that bottom hole points upwards. Here we come to wood glue aplication. I pour two drops of it on rammed paper plug and spread it around tube walls...that's it. For exra strenght you can always fold a few inner layers of paper over the glue and leave it to dry. How long? Depends of how much glue you use...but I usually leave tubes to dry for two days... Blaf

Right, you can drill a shallow core, say 10mm, it can be narower than nozzle dia and fuse could be applied as you said, everything would work OK. I do wrap it with strip of tissue paper and just stick it into nozzle so that inner end of fuse touches composition. You can stick the fuse and then pour some meal slurry (little thicker than blackmatch mixture) around it as well. Of course, this has to be dried before use. But generally, my fountain nozzles are sealed by piece of Alu-foil after production and they wait to be "armed". Namely, I ram the nozzle plug first, drill a nozzle hole and then place round piece of double-folded Alu-foil on the inside part of nozzle plug. The hole is now closed and composition can be rammed in without spilling through it. Just before use I tear the foil with needle or toothpick and stick my fuse in. Blaf

Personally, I like your way of discarding unwanted KMNO4, he, he, he. Just keep on going that way Pirate....and don't get caught! Blaf

Pirate (and others), fountains are also pressed or rammed devices. If you leave your powder loose inside, even if you tap it against hard surface to settle the comp, it really means nothing and leaves too much space between comp particles which furtherly leads to inconsistent and erratic burn rate. It can even go BANG if the nozzle is too tight. In making fountains we're facing the same phenomenon called "flame propagation"...if particles are loose, burn rate of the comp is too high. Therefore, comps in fountains are always rammed (to slow down burn rate) just like in rocket motors. I do that using wooden dowel and hard rubber mallet and never had single problem. ¼ dia nozzle sounds good to me, though... Yes, I know, I had to post an image eons ago.... Blaf

Signet, you should ball-mill the fountain composition for an hour or so to make it work nicely. If the recipe calls for coarser metal or charcoal particles, they could be added after milling and mixed by screeening or diaper mixing. But ball-milling is no doubt essential for strong and rich fountain shower. Blaf

Hmmmm....Mighty Moderator...sounds good to me! Maybe I should change my username, he, he. Hay, just kidin'. Blaf

Pirate, you should start a KNO3 flash topic or so.....here we discuss KMNO4 flash only. This is just to keep this nice little forum tidy. And do not take this personally, OK? As for your Permanganate, I ball-mill it in small jar small with steel balls. Cofee grinder does the job done too. Pestle and mortar could be too messy...you know, little crystals jumping around and when your mother comes with wet mop your secret activity could be discovered. Blaf

Here are images you requested PGF. Upper die is made of wood as you can see but works OK. Recesses are cut with a tiny saw used by model makers and serve well too. Maybe, but just maybe, upper die could be made wider and inner angle of it could be even steeper so that collection of powder is more efficient. Wider die would prevent powder spills too. href> Here you can see detail where first 12 threaded yarns enter the lower die where they meet further 8 counterwound yarns. href> Hope this helps a bit PGF. Blaf

PGF, I'll do that but images will be posted from Zagreb since I go there tomorrow morning and will stay there for a week or so. I should remember to take photos when I come home this evening. Blaf

PGF, this is what I call nice little device. And what's the most important, it looks so harmless, he, he, he. I presume you use commercial miner fuse for this...looks like one with plastic waterproof coating. This is what Amers call M80 type of cracker, I mean regarding its outside shape. No doubt it goes off loudly... Blaf p.s. And welcome, of course. By the way, what kept you this long?

Congratulations and welcome to the club... Blaf

You shouldn't let NC/Graphite to form drop-looking tip. I make only one dip and slurry just barely connects two naked wires (makes thin bridge between them)...and no drop forms at all. You can play with slurry thickness so that you get consistent results. Blaf

Yes I have but with cardboard propellers. And they worked OK. This wooden propellers should be even more efficient and take devices even higher. We'll see... Blaf

No, glue has nothing to do with this. I moisten it with tap water. Or you can wrap it up with moistened tissue paper and leave it for ten minutes so that wood soaks the water up. Then you can remove paper and leave the stick in the jig to dry. Comprende? Blaf

Stijntje, of course I glue it....pay attention on text under the fourth image. Looking forward to see how your device looks like! Blaf

I remove just 1mm of the insulation and wind up wires as close as I can. The theory says that resistance is lower if terminals are closer and smaller surface is exposed. Of course, you should leave first coating to dry completely before application of meal slurry. At least that's the way I did... Blaf

No, I can fire it somewhere but can't make video clip for now. I'm waiting for my friend with digital camera and we'll make something. As for my images, I have an exclusive contract with Mr.Somebody to use fair portion of certain server...it's because I do it far more often than others. As for black borders, I don't know why would they have one at all. Wait, I recall now...when I was uploading my images on Imageshack server, they offered an option to resize image for use on forums or so....those undersized images used to have black borders. Maybe you talk about that, heh? Blaf

I know. You should hear when it goes off... Blaf

Yes, I can see the picture, rubber wings flapping the brass rod and thus producing vibrations. There's strong possibility that there would be too much vibration applied regardless on where those flaps hit the rod. Some sort of flow controll should be applied right at the exit hole of the funnel, sort of mechanical detector. Don't know yet how to build one but it would be nice to have it in action. As for that drive you mentioned, I think english version is Wormwheel or something, I know what you mean and if I ever come accross one I'll probably set it in somewhere. Blaf

If you simply tossed a few chunks of that charcoal into your milling drum, that's definitely wrong. Media could not mill it as you might expected...charcoal should have been crushed into much smaller particles and then put into millig drum. If you'd crushed it into powder and those round objects emerged from nowhere, something is terribly wrong with powder. Moisture or some sort of parafine soaked in chunks could have caused clumping. No other explanations come to my mind. Blaf

I don't think this is a good idea. Rockets usually have very strong thrust and speed up very quickly so any stabilizers mounted laterally would break for sure and fall off. Especially these sticks of light wood. Sorry for dissappointing you... Blaf

Sorry, nothing can be done in that regard for now... Blaf

You mean an explosion movie or...? Blaf