Blackthumb Posted January 15, 2014 Posted January 15, 2014 Anyone have success in duplicating commercial powder...grain hardness, burn rate, ?My powder is fast but still can't quite get the grain hardness to mimic commercial. Been makin' it for 30 years and still not happy....perfectionist on some things...
dan999ification Posted January 15, 2014 Posted January 15, 2014 Do you press and corn it? What binder if any? Dan.
Blackthumb Posted January 15, 2014 Author Posted January 15, 2014 I've tried every way...pressed w/dextrin and H2O......red gum and solvent. No better results.....burn rate is excellent...hardness of the grains is my issue....
LambentPyro Posted January 15, 2014 Posted January 15, 2014 (edited) I've tried every way...pressed w/dextrin and H2O......red gum and solvent. No better results.....burn rate is excellent...hardness of the grains is my issue....What is your method of testing the grain harndness? If it's because you're getting fines, you're always going to get fines, it's a matter of making BP. Also, where do you get your Dextrin? Red Gum is not an efficient binder, much better as a fuel instead. Edited January 17, 2014 by LambentPyro
dan999ification Posted January 15, 2014 Posted January 15, 2014 Press it harder at around 2g per cc you can cut your fingers with it. What are you doing with it that it needs to be that tough? Dan.
FlaMtnBkr Posted January 16, 2014 Posted January 16, 2014 What density are you pressing to? I believe 1.7 g per cc is the standard when coming which commercial powder is all corned (to my knowledge).
Blackthumb Posted January 16, 2014 Author Posted January 16, 2014 Dont have a gauge on my press....use a 6 ton bottle jack and give her all I have....
Mumbles Posted January 16, 2014 Posted January 16, 2014 It's still very easy to calculate density. It's just weight per volume.
Blackthumb Posted January 16, 2014 Author Posted January 16, 2014 You're right Mumbles...I simply forgot....I'll check...
Mumbles Posted January 16, 2014 Posted January 16, 2014 One of the things that might make you think that commercial BP is stronger is the fact that it's been tumbled. The process of coating BP with graphite involves tumbling in a drum, probably not unlike a ball mill. This both coats the surface, as well as breaks off any sharp edges. In a sense they just pre-break off all the fragile parts. After this you're left with much more seemingly resilient grains. If you don't do this with your powder, the process of handling and storing the material will probably chip off some edges and crack some sharp pieces off. This will increase the fines and dustiness, which might give the illusion that your powder isn't nearly as strong. In reality it's probably just fine, but you didn't knock off all the easy stuff yet.
Blackthumb Posted January 17, 2014 Author Posted January 17, 2014 I don't mind fines etc....can crush grains in my fingers... Here is what I'm working with........have 2 'pucks'...2" dia...3/4 and 1/23/4 wt 66g1/2 wt 47gMy calculations show a density of 23.1 and 29.93 using the formula wt/volIs this correct...used a 100 g sample of milled bp...added 5g dextrin, pressed with 6 ton bottle jack and still soft grains...way off the norm of 1.7 - 2.Suggestions?
FlaMtnBkr Posted January 17, 2014 Posted January 17, 2014 (edited) That is actually 1.7 g/cc for the 3/4" puck and a little more on the half. I don't think you converted to cc from cubic inches. Don't know why it wouldn't be hard. Should be rock hard at that pressure. You are using 75-15-10? What charcoal are you using out of curiosity? Edited January 17, 2014 by FlaMtnBkr
Mumbles Posted January 17, 2014 Posted January 17, 2014 Also, you don't make any mention of it, but you are wetting the BP before pressing, right? You need some water to activate the dextrin. If you're pressing dry, I could see it being pretty crumbly. You don't need much water really. With a decent press setup 4% water should be pretty good.
Nessalco Posted January 17, 2014 Posted January 17, 2014 I corn powder with 3% H2O and no dextrin. Grains come out rock hard. KO
Shadowcat1969 Posted January 17, 2014 Posted January 17, 2014 I actually usually use only about 2% water, I found at 4% I was getting a little bit seeping out the bottom of my pump and it was evaporating leaving KNO3 crystals behind. No binder. And I also use a 6 ton bottle jack/all thread homemade press. I also do pucks 3" in diameter by only 1/8" thick, using aluminum spacers I do 8 at once, giving 2" worth of pucks in one pressing. I find the thin pucks a LOT easier to corn when done. Once they have dried the grains are (to my fingers) as hard as commercial. I haven't done any real hardness testing, but they don't crumble or break down, it takes a mallet or such to crush them.
Blackthumb Posted January 17, 2014 Author Posted January 17, 2014 Yeah...forgot to convert to cc....Using pine charcoal...75/15/10, 5% dextrin, wetting with H2O...pressing, drying and I can crush the grains between my fingers.....
Bobosan Posted January 17, 2014 Posted January 17, 2014 Yeah...forgot to convert to cc....Using pine charcoal...75/15/10, 5% dextrin, wetting with H2O...pressing, drying and I can crush the grains between my fingers..... Interesting. Is the dextrin homemade?
Shadowcat1969 Posted January 18, 2014 Posted January 18, 2014 How long are you letting it dwell once you attain full pressing pressure? I like to let it sit for 5 minutes or so, then pump it a little more, if I can. Then let it sit at pressure for another 15 minutes. If you're not giving it dwell time, the powder can actually have some "spring back" in it. You can see this with comets sometimes, when they come out of the pump and crack or flake apart. That's the only thing I can think of, based on your comp and description of processing.
dan999ification Posted January 18, 2014 Posted January 18, 2014 Im a little confused, at that density it just cant be soft enough to easily crush.Could be the charcoal, I've had density issues with pine rocket fuel. Harder charcoals pack better. Do you let it dwell? The few pucks I made were left to sit for a while before removing from the die. Dan.
Blackthumb Posted January 18, 2014 Author Posted January 18, 2014 My last reply didn't post...think it must be the dwell time...am going to experiment more today and will post results here tonite...Thanks all...
Blackthumb Posted January 19, 2014 Author Posted January 19, 2014 Longer 'dwell' time helped quite a bit....now for some willow, paulownia, or balsa C....
FlaMtnBkr Posted January 22, 2014 Posted January 22, 2014 Balsa is very fluffy and probably a bit spongy/springy. I was actually wondering if that might be what you were using. With the dwell time it might work fine. But it might behave in a similar manner. I haven't tried it so just takin' a WAG.
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