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 Post subject: BP Research
PostPosted: Fri Feb 05, 2016 9:46 pm 
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Now that our latest BP article has been published in the February 2016 issue of AFN, I believe it’s time to move the discussion out of the R&D section and into a publicly accessible area. Rather than just move existing topics, with all their side-lines and diversions, I thought I’d make a new thread, starting with a review of all the information we have gathered over the last year or two. In addition to our latest findings, this posting brings together information that has previously appeared in a range of different topics in this forum.

The first investigation was into a single charcoal, and introduces some of the techniques used in all subsequent trials: http://www.pyrobin.com/files/CharcoalTrial.pdf. It showed that the charcoal in question reached a peak in performance after about 5 hours of milling. There was also an indication that the rise in performance was linear, when plotted against the logarithm of the milling time.

The second investigation made similar measurements on twenty one different charcoals: http://www.pyrobin.com/files/An%20Investigation%20of%20the%20Influence%20of%20Charcoal%20on%20BP.pdf. It showed that all the charcoals reached a plateau of performance, but at a milling duration that differed from charcoal to charcoal. In all cases the rise was a reasonably linear function of the logarithm of the milling time. Comparing the burn rate performances of the different charcoals (in a 75:15:10 composition) showed that there was a dependence on the measured ash content. The performance also correlated well with charcoal density, indicating that less dense charcoals tend to have better performance, as measured by their burn rate.

A third set of tests extended the data on the same set of charcoals to include some ballistic data: http://www.pyrobin.com/files/BallisticPerformanceOfBP.pdf. The results confirmed that the best performance came from charcoals with around seven percent ash content and showed that there was a broad correspondence between burn speed and ballistic performance.

Another document: http://www.pyrobin.com/files/Milling%20BP.pdf, contains a few thoughts on the nature of the milling process and shows that a very simple physical model is compatible with the results of the earlier trials. The derivation of the relationships involves a bit of mathematics, but gives a couple of interesting results. The first is that arranging the samples in the order of the parameters that come out of the analysis seems, more or less, to group them by the type of wood from which the charcoals were made. The second is that one of the other parameters (which characterises how quickly the milling process progresses) is very strongly correlated with the measured densities of the charcoals.

Our latest studies, published in the December 2015 and February 2016 issues of AFN, start to look at the way the properties of BP vary with changes in the percentage of charcoal in the mix. To avoid any possible copyright issues, I’ll just summarise the more significant results.
We looked at six different charcoals and measured how the burn rate varied with changes in the amount of charcoal in the mix. A typical result is shown in the following diagram.
Attachment:
BP01Pic.png

Despite the fact that the charcoals had ash contents that varied between 3 and 18 percent, all six samples showed a peak burn rate at a composition that contained between 20 and 23 percent charcoal, which is very different from the accepted ‘ideal’ fifteen percent for a standard BP. There was no detectable correlation between the measured ash content and the amount of charcoal that gave the maximum burn rate.

Measurements of the ballistic properties of 70:20:10 mixtures indicate that the increased burn rate does not necessarily correspond to better ballistic behaviour; some showed an improvement but others were worse.

A really surprising result was the apparent strong correlation between the percentage improvement in burn rate and the charcoal density, as shown in the following graph (comparing 70:20:10 and 75:15:10 formulations).
Attachment:
BP02Pic.png


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 Post subject: Re: BP Research
PostPosted: Fri Feb 05, 2016 9:53 pm 
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Hmmm...

Richard, I must study your results in greater detail. I _think_ I see a relationship between ballistic performance and the quantity of sulfur, but I'm not convinced that I'm correct, yet. <G>

LLoyd

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 Post subject: Re: BP Research
PostPosted: Fri Feb 05, 2016 11:32 pm 
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What troubles me is that the stoichiometry of the reaction will vary with the density of the charcoal; I would have expected a relationship between apparent density and burn speed to follow a cube-square law. If the mass of sulphur and of KNO3 are kept constant yet the charcoal component is measured by volume and samples are matched with charcoal volumes yielding a <comparable> fuel mass (although of course they wouldn't be identical) I wonder what bearing this would have on the burn speed.

Similarly if you control for "fuel mass" as above and press the samples to equal density does the effect disappear ?


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 Post subject: Re: BP Research
PostPosted: Sat Feb 06, 2016 1:00 am 
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i always visualize charcoal as a sponge. There is the size of the holes, the regularity in the size of holes and the thickness and regularity of the size of the cell walls. Milling squeezes the sulfur and nitrate into the holes. Too thick of holes and it burns slow too thin of walls and the charcoal cell structure crumbles also slowing burning.

Tom


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 Post subject: Re: BP Research
PostPosted: Sat Feb 06, 2016 2:26 am 
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Sambo, I've ponders very similar to that. For adding materials by weight and a hardwood charcoal that has a high density would it maybe be leaning out the charcoal content compared to things like Paulowinia that is pretty darn light.

I've got so many curiosities on charcoal I'm just now starting to find some literatures that indicates a few may even have some merit. Hopefully I can get a good plan together for my tests while I finish up getting equipment together.


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 Post subject: Re: BP Research
PostPosted: Sun Feb 07, 2016 12:49 pm 
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Tom Schroeder wrote:
i always visualize charcoal as a sponge. There is the size of the holes, the regularity in the size of holes and the thickness and regularity of the size of the cell walls. Milling squeezes the sulfur and nitrate into the holes. Too thick of holes and it burns slow too thin of walls and the charcoal cell structure crumbles also slowing burning.

Tom


Exactly the way I see it Tom, one thing I have found is the straighter the wood grain and the faster growing the tree is the better the charcoal.
One wood that stands out is Albesia wood so far to date myself and Richard have never found a more reactive charcoal.


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 Post subject: Re: BP Research
PostPosted: Tue Feb 09, 2016 9:03 pm 
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For the moment, I've given up on trying to apply theory. I've been surprised a little too often about by unexpected results. All I (we) can do is continue making measurements and hope that something sensible will emerge.

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 Post subject: Re: BP Research
PostPosted: Thu Feb 11, 2016 9:15 pm 
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Just for sh**s and giggles... https://www.youtube.com/watch?v=8wW5KR1pDxs and https://www.youtube.com/watch?v=P5iJZjw8k40

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 Post subject: Re: BP Research
PostPosted: Fri Feb 12, 2016 9:14 pm 
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Yep,

have watched most of his channel - they are all really good. He does 2 other great vids. One on heavy water which he makes with solar powered electrolysis and another one on nitroglycerin !


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 Post subject: Re: BP Research
PostPosted: Tue Dec 12, 2017 1:37 pm 
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Jw does the moisture content of the wood used have any effect on the cooked charcoal.


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 Post subject: Re: BP Research
PostPosted: Tue Dec 12, 2017 2:13 pm 
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Jonarthur, I wouldn't think there would be much other than the variable of actual cooking.

Cooking via TLUD trying to keep a burn or good cook could be tricky with green wood.

A retort cook may could benefit, but the nature of how it is designed negated that to a degree. My thinking there would be more moisture would mean more preasure, but since we vent the cooking chamber this never really builds up. If we regulated the venting off of the preasure may could open the pores or keep them from contracting some under the cooking process. If that would effect anything would have to be tested some day, but my simple mind says it would ever so slightly. Would you be able to notice the variable in everyday use, probably not.


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