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Fastest BP


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#16 alany

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Posted 29 March 2004 - 12:48 AM

This is the only reference I could find on the net in the past:

http://www.geocities...8/Benzolift.htm

I can't recall where I first heard about it, but as a simple lift replacement that is less dependant on the charcoal I found it pretty interesting. I've got a slightly different composition now:

http://www.vk2zay.ne...ition.php?id=23

It is still very much experimental as far as I am concerned.

#17 Yugen-biki

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Posted 29 March 2004 - 05:50 AM

I have not done anything BP related lately :rolleyes: . I have experimented with stars and dark comps. Some time this or next month I will stars milling C and S. And before next year I will have Price winning BP :P for my Not yet developed 4". :D

Edited by Yugen-biki, 29 March 2004 - 01:49 PM.


#18 Stuart

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Posted 29 March 2004 - 06:01 AM

http://www.ukrocketr...findpost&p=3869

Stick to the topic, I cant be bothered with a yellow powder argument

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#19 willd

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Posted 29 March 2004 - 01:50 PM

if it works without melting it might be ok

#20 adamw

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Posted 29 March 2004 - 07:46 PM

Yes it is said to work, but not as well. Anyway, we have discussed Yellow Powder before and we aren't going to go back to it.
75 : 15: 10... Enough said!

#21 thewildething

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Posted 31 March 2004 - 01:35 PM

Hi everyone,
Im not sure how relevant or helpful this will be but?? If you want to use the mortar and lift height testing methods I may just have an answer. What if you wanted to compare the ?power and efficiency? of your lift powder? One way of doing this would be firstly weighing your shell and getting the mass in Kg, putting it in the mortar with your lift charge, record how much lift you put in (in grams), then fire off your shell. Time how long it is from the initial ignition/ejection from the mortar tube until the shell hits the ground. Using the example below you could work out how powerful/efficient your powder is in joules of energy per gram.

Lets say, for example, your 4-inch shell weighed 0.5kg, and you used 15grams of lift to fire the shell, which remained airborne for 10 seconds, firstly what you want is the altitude the shell reached, using some projectile motion equations:

S= ut + (at^2)/2 where
S= displacement in metres(height)(what we want to find),
u = initial velocity, (which is zero so not needed in this case),
t = time, (time to reach flight apogee which in this example is 10 divided by 2 = 5seconds)
a = acceleration due to gravity(9.81metres per second per second)
so 5 Seconds + (9.81 * 5 Seconds squared) divided by 2 = S, which = 127.5 metres altitude, around 420 feet.

Then we need to find the ejection velocity (muzzle velocity) of the shell, found by using:
Velocity squared = 2 * a * s where
a = acceleration due to gravity(9.81metres per second per second)
s = distance, which is the height of the flight which is 127.5 metres so:
V^2 = 2 * 9.81 * 127.5 = 2491.74 so V = the square root of 2491.74 which = 49.9 metres per second muzzle velocity, which is 179.7 km per hour.

We can now work out the Kinetic energy of the shell in joules by using
Kinetic energy = half the mass of the shell multiplied by the muzzle velocity squared.
Which is 0.25kg * 49.9 *49.9 = 622.5 joules of energy transferred to the shell by the lift charge,
622.5 / 15 grams of lift =41.5 joules per gram of black powder.

This method works regardless of shell size and weight; it solely deduces the power and efficiency of 1 gram of powder. I hope I have explained it well enough for you understand, although most of you probably know methods like this anyway.

This ONLY holds true for vertical mortar projections, if you want to fire at various angles for range testing or whatever it?s a whole different ball game, let me know if you want any info on this.
I doubt this would help you to deduce the fastest bp but it would certainly allow you to compare power and efficiency of different compositions etc.


Let the efficiency tests begin!!
"Surf by day, set off so much pyro through the night that it seems like daylight, then go surfing again"

#22 Yugen-biki

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Posted 31 March 2004 - 03:06 PM

Nice post! Around here the "a = acceleration due to gravity" is 9,82 m/s*s.

At the moment and some time into the future I will not have any BP. I will start makeing some soon (soon = 1-2months).
A thought about BP: What are the reaction products? Probably ((ions) guessing...) CO2, CO, SO, SO2, K, NO2, NO, N2... Why I?m asking? When I look into my mortar after a fireing I find some white super fine dust cowering the walls and bottom. And nothing else! It seems to be very hydroscopic because after a short period of time the mortar walls is all wett. Is this K3(NO2)3 (or maby NO (monoxide))? Anyway they are easy to cleen :-) .

#23 Stuart

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Posted 31 March 2004 - 03:44 PM

You will also need the length of the mortar as the longer it is, the further it will go. Potassium Nitrite is KNO2. This may be whats on the walls of your mortar as group I nitrates (except lithium nitrate) decompose on heating to form their nitrites. I couldn't say for sure, I don't know how hygroscopic KNO2 is

Stuart

#24 PanMaster

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Posted 31 March 2004 - 07:09 PM

its K2CO3 of course, highly soluble, K2S possibly forms most of the smoke.
I doubt there will be KNO2 as will decompose at the high temp.
Where are the matches?

#25 Yugen-biki

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Posted 01 April 2004 - 12:23 PM

Thanks!

I don?t have Conkling?s book, but I had the chans too reade it once. In his book there were some interesting facts about BP and it?s reactions.

By the way the white powder taste very salty... Yes I could not resist to taste it to get a clue to what it was :rolleyes:

:D

Yes I know, but i figured KNO3, C and S would not add up to something poisones. I would never taste anything else, I can insure you. I?m curious buy not stupid.

Edited by Yugen-biki, 01 April 2004 - 05:55 PM.


#26 The_Djinn

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Posted 01 April 2004 - 02:48 PM

Yugen-biki and any other members, i would not recomend tasting left over residues or powders of any description. You were lucky this time but next time you may not be so fortunate.

Mark
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BPA L1 & L2

#27 Richard H

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Posted 01 April 2004 - 02:51 PM

Basic lab safety please people. Don't eat in the lab! The last thing you want is to shake some barium nitrate on your chips. :)

#28 Phoenix

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Posted 01 April 2004 - 05:50 PM

OK, I did it!

I got a stopwatch from eBay, and I've just done two tests of the mortar type that I described before. They were the same as the preliminary one I did a couple of weeks ago:

Mortar inside length: 180x25mm
Shell: 24.5x60mm, 20g
Charge: 1.5-2mm, 2g

In the first firing the shell was in the air for 4.87 seconds
In the second firing the shell was airborne for 4.66 seconds

This is significantly shorter than the time which I counted during the preliminary test, probably mostly due to my bad estimation of time then, but there were less fine particles in the gunpowder charge too, though the change of sieve sizes didn't seem to make that much difference.

I had expected/hoped that the times would be a little more consistent, but it was only two trials. I don't have much BP left and I'm out of fuse. In fact I'm nearly out of KNO3 but I'll have another go sometime soon. I suppose that since there are no other entries yet, I have the longest time - Woohoo! Care to join in, Panmaster?

#29 thewildething

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Posted 01 April 2004 - 09:35 PM

Hey Phoenix,
From the times you recorded I can tell you (roughly) that your shell reached a height of 58.1 metres (191 feet), and left your mortar at 33.8 metres per second (121kph) with a kinetic energy of 11.42 joules, giving your powder a value of 5.71 joules per gram.
This is only rough though because of a range of different factors that could affect this, seems that my theoretical powder in the example above was a bit too powerful for bp, although I may be wrong. :unsure:

Nice one phoenix.

Marcus.
"Surf by day, set off so much pyro through the night that it seems like daylight, then go surfing again"

#30 alany

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Posted 02 April 2004 - 03:37 AM

Blackpowder energy density is around 3 J/mg which is very low as most explosives go.

The muzzle energy you measure will be only a few percent at most of the chemical energy of the propellant because BP guns are very inefficient.

The ideal propellant brings the gun up to pressure instantly and keeps that pressure constant behind the projectile as it moves down the barrel ensuring the best use is made of the barrel length and bursting strength. That is very hard to achieve in practice, it requires a progressive burn (granulated BP is a regressive burner) but not one that will burst the gun.




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