253 replies to this topic

[Damp Squib]

hehe, whipped up 8g of sulphurless balsa BP, just put it through a sive a few times, didn't mill it.
the 8g had a volume of about 1/2 a pint, and burnt incredably fast! a line of it was gone faster than i could see, and burning 2g in a pile dazzled me from 10m away.

very nice, especially if you don't have a ball mill but need to make something fast.

only bad thing is, balsa wood is expensive as hell.

First post here I'l just get stuck in ,I just whipped up a batch of balsa charcoal 344g "2-2litre coffee cans full"of balsa produced 80g of charcoal which takes up around a litre of space mixed with nitrate 80\20 no sulfur just pestle and mortar for 15 mins,the result was quite shocking a 12 inch trail burned in under half a second with bright white flash and quite a roar,I dont think I wanna put the stuff in my ball mill ,the addition of iron oxide and sulphur and a few hours ball milling would make this stuff quite frightning

With regards to the milling time slowing down burn rate have you considered contamination from the mill container and media?try measuring your barrel and media before and after with a micrometer

[completebeginner]

I never really thought of adding a catalyst to my bp does it really improve the burn speed?

[Damp Squib]

I never really thought of adding a catalyst to my bp does it really improve the burn speed?

ATM I have four oxides to test red,yellow,black and red synthetic. My interest is purely for small pressed rocket motors in particular end burners for model rocketry,so far I have only tried yellow iron oxide in a simple train burn test test using the balsa charcoal and a 1% addition of oxide,I'll be honest the yellow iron oxide performed a little slower than the 80\20 but I'm sure this was down to the amount of milling done in the pestle and mortar as each keeps getting noticably faster with every added minute of milling,I'll have to do a more detailed and controlled test for anything worth recording

Most metal oxides catalyse high temperature reactions,the big question I suppose is how much will they catalyse black powder,you may find this page interesting,its what put me on to the idea of catalysts in rocket motors years ago, only now am I in the position to test them out

http://www.nakka-roc...net/oxidex.html

[MFX]

I wouldn?t like to search a huuuuge area to determine how far a little white ball went.... I?d like to see the place where you could do such tests without the risk of harming any people or something.

How about having a standard tube and standard ball. Mount the tube on a piezioelectric sensor on a solid surface (concrete) and fire your mass into the air. The recoil will cause a signal from the sensor which should be proportional to the amount of force your BP generated. The sharpness of the signal should also give an idea of the burn speed.

Martin.

[Damp Squib]

Heres a video of some bp I made mixed 80\20 in a pestle and mortar using balsa charcoal,the charcoal was milled for 3 hours before mixing with the nitrate,then it was dry pressed to around 2gcm3 and broken into peices

http://www.zippyvide...03193280486/bp/

Edited by Damp Squib, 18 January 2006 - 11:26 PM.

[F?bio]

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[RegimentalPyro]

Longerfuse Dampsquib. Longer fuse! Once more to make it stick *LONGER FUSE*

You were far too close to that. Also filming and lighting at the same time is NOT recommended.

On the BP front - Seems to be a good fast powder. Have you tried lifting anything with it yet?

[fishy1]

First post here I'l just get stuck in ,I just whipped up a batch of balsa charcoal 344g "2-2litre coffee cans full"of balsa produced 80g of charcoal which takes up around a litre of space mixed with nitrate 80\20 no sulfur just pestle and mortar for 15 mins,the result was quite shocking a 12 inch trail burned in under half a second with bright white flash and quite a roar,I dont think I wanna put the stuff in my ball mill ,the addition of iron oxide and sulphur and a few hours ball milling would make this stuff quite frightning

With regards to the milling time slowing down burn rate have you considered contamination from the mill container and media?try measuring your barrel and media before and after with a micrometer

in my experience with balsa BP, adding sulphur seems to slow it down.

[Squib]

in my experience with balsa BP, adding sulphur seems to slow it down.

Where's the best place to get balsa - model airplane shops are going to be
expensive and I dont remember ever seeing a balsa lumber yard!
What else do people use it for apart from models?


Squib

[fishy1]

Where's the best place to get balsa - model airplane shops are going to be
expensive and I dont remember ever seeing a balsa lumber yard!
What else do people use it for apart from models?
Squib

ATMO, i'm looking to get a couple of kilos of offcuts from ebay,

[Damp Squib]

Longerfuse Dampsquib. Longer fuse! Once more to make it stick *LONGER FUSE*

You were far too close to that. Also filming and lighting at the same time is NOT recommended.

On the BP front - Seems to be a good fast powder. Have you tried lifting anything with it yet?

I'm the safety king I wasnt that close its just the way it seems on camera,my camera also adjusts for the low light levels making the flash look much larger than it actually was,I'd already electrically ignited a few trains so had a good idea how close I could be,point taken though I'm a fuse scrouge

No I'm only interested in rocketry I made this batch just out of interest,I might try though just for sciences sake give you an idea of how good it is,you cant tell from the clip because the paper gave off smoke,but the powder is practically smokeless,I have a clip of a chinese triangle fire cracker I made just for fun with 1gram in,I folded the triangle 8 times so the wall thickness is 4 sheets of medium weight white paper,its a little out of focus but you can clearly see theres no smoke,you guys dont like noisemakers though so I aint sure if I should post it,it too has a short fuse my bro wanted to light it so it doesnt matter,muhahaha ,THIS IS A JOKE! ,the fuse was my version of chinese cracker fuse it jumped a portion of the fuse

le me know if I can post it RegimentalPyro

On the balsa front it was bought from a model shop in a 'balsa bundle' about a pound in weight for ?5 a little on the harsh side considering I only got around 120g of charcoal,twas worth it too me I want a fast clean burning powder for parachute ejection,the sulphur in standard black powder leaves your airframe smelling of eggs for about a year

[Damp Squib]

fishy I too have made few test batches with sulphur and it also seemed to slow it down for me could be a number of reasons though,I think ball milling is a must when you add sulphur and my batches only got 30 mins in the pestle and mortar,sulphur doesnt seem to crumble easily into fine powder like the charcoal and nitrate,always seems to mix like a slightly wet powder to me even when dried out completely and wont incorporate itself into the mix as readily

[RegimentalPyro]

...you guys dont like noisemakers though so I aint sure if I should post it,it too has a short fuse my bro wanted to light it so it doesnt matter,muhahaha ,THIS IS A JOKE! ,the fuse was my version of chinese cracker fuse it jumped a portion of the fuse

le me know if I can post it RegimentalPyro

Course you can. It's not that I don't like noisemakers. It's just that some people tend to obsess on them a bit. BP bangers are certainly a valid part of the pyrotechnician repertoire. Feel free to post [in an appropriate forum of course!]

Please *don't* skimp on fuse though - It's just not worth it.....10 secs minimum is a good rule of unburned thumb.

[alany]

I've got a "standardised" burn-rate testing method that is pretty easy to replicate and seems to offer a useful metric. I've mentioned this in another thread, but here are the details in a more appropriate thread...

It isn't actually using the composition as a propellant, it purely measures its regression rate. From experence different classes of compositions *can not* be compared, but within the same family (e.g. BP) the results are very good predictors of performance in devices. Unlike grain powder trail tests it isn't very sensitive to variations of the test equipment. It is also very easy to implement, safe and quiet compared to projectile methods.

OK, I am being selfish, but I'd like to talk as many people into doing the same test so there is a good sample of numbers to compare with.

The setup is very simple and takes longer to describe than actually do:

1) Aquire a 2" long tube, 1/4" ID (50mm x 6.4 mm ID). (e.g. buy one from pyrotube.com or cannonfuse.com, or roll your own).
2) Weigh tube as accurately as you can.
3) Charge meal powder into tube for a length of approximately 1".
4) Measure the empty space in the tube to calculate the actual powder column length.
5) Weigh tube again, calculate the density from the mass and length of the powder column.
6) Secure vertically in a test stand, empty half up, and ignite with blackmatch.
7) Video test and recover burn-time from the audio or video with software (or a stop watch).
8) Calculate burn rate by dividing column length by burn time. (I express the result in mm/s).

Steps 2 and 5 are not manditory. I don't use the density to normalise the results, but it is of help im making your own tests repeatable. Most people who have tried this achieve about 1.4 to 1.7 g/cc with hand-ramming in about 5 increments. The rate is sensitive to density, but much less than you would at first think, especially for BP.

Step 3 and 4 can be combined into using a marked rammer and extra care. In practice though I've been using the measurement method because it is faster when you have to prepare many tubes for comparison. It does normalise the results fairly well, with good repeatability.

I can do step 7 if you are having problems. Doing so also means I'll be creating the same systematic errors which may be valuable.

If you are going to do this please include:

a) Composition (especially Charcoal type, etc)
Preparation details

Knowing how many mm/s your BP does is quite valuable for comparing batches. Of course if you want to ram spoulettes all the guess work is gone, just do the math, mark your rammer and charge away.

[pyrotrev]

I've got a "standardised" burn-rate testing method that is pretty easy to replicate and seems to offer a useful metric.
It isn't actually using the composition as a propellant, it purely measures its regression rate. From experence different classes of compositions *can not* be compared, but within the same family (e.g. BP) the results are very good predictors of performance in devices. Unlike grain powder trail tests it isn't very sensitive to variations of the test equipment. It is also very easy to implement, safe and quiet compared to projectile methods.

This is a good point, especially since the challenge was to produce the "fastest BP". A ballistic test doesn't necessarily measure the burning speed, but the rate of release of energy; hence a powder that burns more slowly but produces more gas, could perform as well as a fast burning one when it comes to listing. Lancaster mentions as "standard column test" that sounds like it works on the same principle as Alany's test.