ball milling question

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Andibates
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ball milling question

Post by Andibates »

hi guys
i have been some looking around at diffrent methods of making black powder

i have looked through quite a few sites there seems to be alot of differing milling times

how long do you guys mill your powder for ?
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Lloyd
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Re: ball milling question

Post by Lloyd »

Andi,
There's no such THING as a "definite time" for milling BP, unless ALL the parameters are controlled.

EVERTHING about milling varies the time. The speed, the media, the size of the media, the diameter of the jar, the loading factors.... man! ALL of it causes variations.

Now... if everything is PERFECT, there are amateur pyros who swear that one hour of milling (from raw materials) is enough to produce the BEST BP you can home-mill.

There are others of us go mill for longer... but there are drawbacks to that, too.

So... In all... there IS NO DEFINITE TIME for milling BP. It's all in the setup, and the target use.

LLoyd
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Pyro-Gear
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Re: ball milling question

Post by Pyro-Gear »

Andi, Lloyd is absolutely correct.

Years ago most guys in the UK would be using stone polishing tumblers like the Beech or Evans, it was not uncommon to read posts on other forums stating that they milled for up to 3 days! Now to me that’s crazy and risky.

When we ran tests on various charcoals some time back using my own mill the maxim time we milled for was six hours after that the powder did not improve one iota with further milling.

Given a descent charcoal like willow white pine and poplar I can make good lift in around an hour and a half.
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Re: ball milling question

Post by Andibates »

I was just curious as I was reading the different black powder comps
On the sky lighter page and he's says to mill the powder for 4 hours and on another site
For the same comp and method it says mill for 6 hours
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Re: ball milling question

Post by richardh08 »

I was going to make the same points as Ken did, but he beat me to it. Despite Lloyd's insightful study of the milling process, it is by no means an exact science. Most recommended milling times in the literature are arrived at by rule of thumb. They should be viewed as guidelines rather than prescriptive values.

When we did our milling tests (using one of Ken's mills, with his recommended media and 100g of mix) we found, in addition to all the factors Lloyd mentions, that the type of charcoal made a huge difference. To reach the point where there was no further improvement in performance (measured as the powder's burn speed) some charcoals needed to be milled for no more than one and a half to two hours, while others took five hours or more.
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Re: ball milling question

Post by Andibates »

i will be getting a mill from ken in the very near future and i buy my charcoal from ken as well i was thinking about doing my own tests when i get it
test it in half hour increments just to see what the diffrence is of till i find what i need/am happy with
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Another ball milling question.

Post by Alchemist »

A while ago, I purchased two of Ken's mills for making BP with the intention of using one solely for milling potassium nitrate and the other solely for charcoal. The two milled components would then be screen mixed with sulphur to complete the composition. I chose to go down this route, rather than mill everything together, for increased safety due to the fact that I don't have a lot of space and neighbours close by. I was also influenced strongly by David Foster's paper "A Comparison of milling media and Preparation Methods for Black powder" that shows that effective BP can be made by such a route.


before staring out, I read quite a few posts and other articles and interpolated the data to come up with what I thought would be a reasonable start point and used a mixture of 21mm, 17mm and 10mm hardened lead media to give a volume of about 36% of the mill jar. I used slightly less than 25% of the jar volume as potassium nitrate and that came to about 200g and the same volume of #4 mesh willow charcoal which came to about 35g. I decided to run the nitrate for 2 1/2 hours and the charcoal for 4 hours.


On opening the mill at the end of the run, I found that the nitrate was very grey in colour, think of the colour they paint warships and you'll be pretty close! Now, I'd read that contamination of BP from the milling media does occur but, to me, it looked like a lot of contamination rather than just a bit. In an effort to find out if this was due to the media being new and not used before, I washed the mill out and after drying ran two lots of 200g of sugar as a cheap disposable substance. The first run gave a similar result to the nitrate run with the sugar being, visually, the same colour as the nitrate. The second run produced material that looked white and significantly better than the previous run. I had accurately weighed the washed and dried media before the mill run and re-weighed it after washing and drying again. From these weights, I calculated that the level of contamination in the sugar was 0.23% which was not insignificant but did not seem to be too bad. Encouraged, I washed and dried the mill again and re-loaded it with potassium nitrate but again found a very grey material when I opened it up after the run. Having washed, dried and re-weighed the media, I calculated the level of contamination at 1.56%, which seems a lot.

Having said that, combustion rate tests show that the final BP mixed from this nitrate is very fast and, I'm reliably informed. is as fast as commercial material so the apparent high level of contamination doesn't seem to affect performance. I'm in the process of corning it at the moment.


My question really is whether or not anyone has any idea of what sort of contamination levels to expect when milling BP and whether people think that my measured level is high?
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Re: ball milling question

Post by Boophoenix »

I’ve not tested this so take my input as just an opinion. I do think your contamination factor is high. I do believe Lloyd has stated that varied media sizes can grind each other down. This may be a contributing factor. I would also think the smaller of the three media’s you listed would do more work that the others especially with charcoal. Maybe not so with the nitrate.

Since you are single component milling I’d almost certainly look to stainless media. Keeping in mind and I say this everytime I mention stainless milling media that it is just spark resistant not spark proof. I facilitated some of the stainless in use in the US and felt this a proper warning. I’ve not heard of any instances of accidents with stainless, but do know of a few pyros who moved away from it for three component milling. However I know more who went the other way too.

Dave’s efforts in researching processes are pretty valuable. We discuss ideas and principles fairly regularly when we’re not side tracked talking about other topics. He has found some very interesting ways to manipulate the process to reach his goals.
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Re: ball milling question

Post by Pyro-Gear »

I have to agree with Brad on the use of stainless media for single component milling, I was lucky enough to be gifted some stainless media from brad and I have to say the stuff is awesome, I have used it to mill various chemicals in my mill and it works fantastic.
Mixed size media is not ideal Lloyd has covered this before and I am sure he will explain why.
Your levels of contamination seem to be high but if the BP works then that’s a bonus.

In the UK there is a lot of grades of lead it works through codes so what you have is questionable.
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Re: ball milling question

Post by Alchemist »

Thanks for your comments guys, much appreciated.

Yes, I could switch to ceramic or stainless steel media but the real question is "do I really need to"? My point being that I'm only aware of the degree of contamination because I chose to mill the components individually. if I'd gone down the conventional route and milled all three components together, I wouldn't have known that the nitrate component was grey because of the presence of charcoal.


I have no interest, at the present time in milling potassium nitrate for anything other than BP so the real question is whether or not my levels of contamination are high or not.

I certainly accept your views that mixed size media may not be ideal but, from my reading, it's not uncommon and I've seen a number of articles using such a mix.


As regards the comment on the lead being "questionable", I can only say that I purchased it from two suppliers who I've dealt with many times before and who I would consider to be reputable. Both suppliers were aware of my interest in pyro and, indeed, claim that the media is suitable for milling BP. In addition, one supplier was aware of my intention to mill the BP components separately.
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Re: ball milling question

Post by Pyro-Gear »

Ok so did the vendor who supplied the media give you the lead code?
Even with antimony hardened lead, you’re going to get some contamination, in answer to your question (is my contamination level high) then 1.5% is on the high side.
To answer the question about your lead code then it is code 4 pretty hard, that’s what Tim supplies ;)
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Re: ball milling question

Post by Alchemist »

Thanks for that Ken but I really would like to quantify where I am in relation to normal contamination levels and where I need to be. Can you steer me towards some published data on this topic?

I'm not going to name names in terms of my suppliers on a public forum, all I will say is that neither supplier quoted a lead code at the time of my placing the orders.
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Re: ball milling question

Post by Boophoenix »

Another thing to consider is you are burning up your media. Allthough slowly.

My first lead media I got here in the US was from the now passed away Leadballs. After a good 30hours of milling in a 5.28 liter milling jar the molding nipples where still on the media.

You’re not sacrificing anything really with the contamination that I’ve found any info on unless your levels are high enough to cause a adverse reaction. If it ain’t broke and doesn’t concern you continue forward. Personally I didn’t like the discoloration so I moved to stainless for that reason alone.

I then found I really liked using it. So much so I started a collection of stainless media. The below photo is the majority of my stainless collection. Ranging in sizes from 5/16 to 1.25 inches most of which if not all is 302 and 304 stainless some of which has tolerances in the range of +/-0.00002in if I’m recalling correctly. Ken has one of the toleranced boxes and may can confirm that from the label if he kept the box ( I may have one to many zeros in there ).
10813713-9540-461A-BDFC-EE44DE11EC7C.jpeg
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Re: ball milling question

Post by Pyro-Gear »

+/-0.00002in is correct Brad, those balls are precision made and I can only assume they were for a high end bearing manufacturer.
I have been using mine to mill 4# charcoal over the last few days and I am getting air float in 10 minutes or less, what I really like is how easy they are to clean just shake them over a screen and there as bright as they went in the mill.
The box, well that has now been reused and is in France.
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Re: ball milling question

Post by Boophoenix »

Glad you’re getting good use out of them! I should warn ya from experiance and an almost cussing I almost got once. Don’t drop them. They’re a PITA to recover from the floor.

I’m a lot more comfortable swapping chems when using stainless too after a quick cleaning. Even though my lead is hardened I can’t help but thing it’s a little porous and might have residual chems imbedded into it. I also don’t like that it oxidizes if not used for a while. So I loaned my lead out with my large upgraded mill to keep the media all nice and shiny, lol
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Re: ball milling question

Post by Alchemist »

Thanks a lot for your answer, Brad, I'm particularly encouraged by the fact that you've seen grey potassium nitrate too. It suggests that the levels of contamination you had are probably not too far away from mine given that the greyness isn't apparent at a level of about 0.25% contamination. Of course, we can't compare the shade of grey so we can't be sure. I take your point about wearing away the media as well but the figures tell me that I lost just 0.09% of the media on my last run so it's going to last a long time at that rate of attrition.

I intend to do some more work using media of the same size, just to see if that is the root cause of the contamination levels I've seen and for the sake of interest.

Stainless steel media doesn't seem to be that easy to come by over here, on the basis of a cursory search, but I intend further searching just to see what I can find. Otherwise, I'm inclined to say that despite my grey nitrate the resulting BP seems to be good enough for anything I want to do with it so I'll probably live with it. In any case, I'm looking for consistency of performance from it rather than the most power that I can get.
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Re: ball milling question

Post by Lloyd »

Alchemist,
Bradley didn't steer you wrong concerning the use of mixed sizes of media. ALL the major makers of ball mills recommend against it due to the fact that the larger media tends to 'mill' the smaller media, along with the material being ground.

You might only suffer a 0.02% loss in the same run, using all-same-size media particles.

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Re: ball milling question

Post by Boophoenix »

DaveF did some investigating on the lead contamination. They were quick and simple tests as a recall. I’ll see if I can find the other info or get him to add a comment or two.
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Re: ball milling question

Post by Alchemist »

Thanks for the replies guys, much appreciated.

I didn't think for one minute that you were misleading me on mixed media sizes, Bradley, and I apologise if I gave you that impression. I was just commenting on some of the stuff that I've read over the last couple of months or so and I can see that the larger media could grind the smaller.

Of course, I'd be delighted to get any info that anybody has on the subject but, just for my own interest, I'll do some tests of my own with single sized media.


Just out of curiosity, what size of stainless media would you recommend for a PG mill for milling potassium nitrate and charcoal separately? can the same size be used for both or is there a "best size" for each component?
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Re: ball milling question

Post by Pyro-Gear »

Media size is 5/16- 7.9375mm, jar load just media 2.5 kilos that takes it just under half full.
Potassium nitrate used was nitro Paris granular for my tests, run time was 20 minutes to achieve air float.
If you use this media you may notice that the jar gets a little warm but nothing to worry about.
Using this media for single component milling has for me produced some remarkable results.
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Re: ball milling question

Post by Boophoenix »

I never thought you were disputing. I tend to ask questions and challenge responses a little and then go find out Lloyd was right and I was wrong fairly often. Actually probably every time so far, but I’m not ready to surrender just yet :lol:

I stumbled onto a stash of 5/16 years ago by accident. I ordered everything the vendor had at the time. I’ve used it almost exclusively since unless I was testing another size.

In my personal opinion and I say that as it’s just an opinion because I’ve not tested to find out. I believe 8-13mm or 5/16-1/2 inch media to be best. I’d aim for the mid range in there probably. The KNO3 may would appreciate a little more weight to the media if milling time is a concern.

The smaller media is awesome all the way up till when you’re separating it or spill it.

DaveF did some experiments and he’s pretty good with those and sharing. From the best I can recall there was no major differences that stood out in the range above. So what ever you can find and are comfortable with the price of would serve you well.
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Re: ball milling question

Post by Dave F »

Alchemist, first off, thanks for the interest in my recent article. Please excuse me if I suggest that you may be missing a major point. Your concern seems to be focused on the potassium nitrate contamination. What about the much greater contamination of the charcoal component? In the article, I concluded that milling complete black powder with hardened lead spheres gave fairly insignificant contamination, and produced the most powerful black powder of the six types tested. Conversely, the charcoal that was milled by itself with the same lead media gave the least powerful powder in the group. The lead contamination of the charcoal was very significant, at a whopping 4%!

If you plan to do single component milling, it's the milling of the charcoal that is going to bite you, not the milling of the potassium nitrate. The reason for this is the fluffiness and lack of density of charcoal, compared to potassium nitrate. The media falls right through the aerated charcoal, and beats itself down pretty quick.

One thing that is in your favor is the fact that you are using a Pyro-Gear mill and jar. It is quite small, compared to the setup I used in my tests. One thing that I don't hear people talk about much in regard to ball mills is 'fall'. A larger diameter mill jar has more fall. It will mill more efficiently, but it will also wear the media faster- which is only a serious issue with the charcoal, as I pointed out.

I have produced excellent screen-mixed black powder with the Pyro-Gear mill. I use stainless steel media exclusively. If I were you, I would not bother with ceramic. It is the least efficient media I've worked with. I fill my jars just over half full with media. I like the 5/16" media best for charcoal, and the 1/2" media best for the potassium nitrate. The reason why is because the nitrate may clump more easily when smaller media is used. The smaller media mills it well though, as long as it's quite dry. The smaller media grinds the charcoal a little better than the larger size, which I've proven in a different round of tests, but the difference isn't a deal breaker. Since I have both, I use both. If I had to choose one size or the other for all my chemical milling needs, I think I would have to go with the larger size, because it has greater versatility.

The fastest black powder I have ever made was made with the 5/16" 'peas' I got from Bradley. The charcoal was pre-milled for 4 hours, and the complete mixture was milled for another 4 hours. Bradley will be all over me if I don't mention the possible sparking potential of the stainless steel media, when milling complete black powder. I no longer have a need to do 3 component milling, but I do it occasionally for testing purposes. If it is true that the S.S. media could spark, it seems logical to me that the likelihood would go down with smaller media, and with smaller jar diameter.
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Re: ball milling question

Post by Alchemist »

My sincere thanks to the three of you that posted such detailed answers to my questions over the weekend. The info is just what I was looking for and has given me cause to pause in my activities.


Dave, you were absolutely right to redirect me towards the contamination issue with the charcoal, I guess I'd put it to the back of my mind whilst focussing on the more visually obvious problem of grey nitrate. I re-read your paper this morning and see where you're coming from. In the light of that re-read, I think that the work I'd planned to do would be a waste of raw materials so that's on hold at least for now.


My first thoughts were that I'd got a lot to think about before proceeding but maybe there isn't really much because it's a no-brainer. The good thing is that, despite the contamination, I seem to have prepared some good BP so that'll last me for a while so there's no rush to change but, for me, stainless looks to be the best way to go.


Thanks again.
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Re: ball milling question

Post by sambo »

Dave and Alchemist, the question I have been wondering, now that I'm also a convert to single component milling is should we be evolving from ball mills altogether. I've mentioned previously about air micronisers ( or jet mills ) - although in the case of charcoal which is quite soft a rotary impact mill might be better. Dave, I'm wondering have you tried a rotary impact mill for your charcoal? this would of course in Alchemist's case obviate the need to use lead at all!
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Re: ball milling question

Post by Dave F »

Sambo, no I haven't tried anything for my charcoal but ball milling. I've just tried to get the most I can out of that process, and that's kept me busy thus far :)
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Re: ball milling question

Post by Alchemist »

That's an interesting question Sambo, as you will have gathered, I'm fairly new to this so I certainly haven't tried anything like that for BP components. I do have some experience of rotary hammer mills though from the time when I had to work for a living. My experience though is limited to milling relatively hard and brittle materials so I'm not sure if it would translate to the soft versions of these mills for milling charcoal. I think that such a mill would have to be very soft with relatively low rpm. I do know that the harder faster ones are not very good with soft materials.

One thing to keep in mind though is, of course, that mixtures of charcoal and air can produce a dust explosion in the same way that many other organic powders (and metals for that matter) can too. There must be a very slight risk in ball milling charcoal with steel but, since it's been done for a while without incident, I imagine the risk is very small. However, a rotary hammer mill would be a very different animal and may increase the risk.
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Re: ball milling question

Post by Dave F »

https://patents.google.com/patent/US3660546A/en

Hey guys, this might answer a few questions for you. It's way outside anything I would ever consider, but certainly an interesting read.
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Re: ball milling question

Post by sambo »

Interesting Dave, wasn't quite what I was thinking but in my research, I came across the use of Jet Mills in the production of match head composition. I could potentially gain access to a jet mill and conduct some tests, I'm told it will pulverize match composition to a fine tomato paste type consistency within seconds.
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Re: ball milling question

Post by Alchemist »

As you say Dave, "an interesting read". I came across a reference to jet mills in another paper I was reading on BP but didn't really appreciate what they were and hadn't got around to looking them up. At least I now have an appreciation of them but they're way above what I want to do at the moment . Especially given that my requirements are pretty small for now. Thanks anyway.
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Re: ball milling question

Post by Alchemist »

Well, I don't seem to be able to paste the attached document into the forum in its entirety so please have a look at the attachment if you want to see my results on milling BP with stainless.
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Re: ball milling question

Post by Pyro-Gear »

PDF works fine thanks for the information.
Cut and paste won’t work as we are the cheap seats.
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Re: ball milling question

Post by Boophoenix »

Just skimmed threw and saved for a later read but looks interesting. Thanks for sharing. There can never be to much research in this area
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Re: ball milling question

Post by Lloyd »

Yep! Interesting. I'd never have guessed that shorter milling time would produce faster powder!

My supposition must be that retaining some of the 'cellular' structure of the charcoal is beneficial.

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Re: ball milling question

Post by Alchemist »

"Cheap seats" Ken, blimey it's been quite a few years since I heard that phrase!


Yes Lloyd, I too would have thought that longer milling times would produce the faster powder, after all, there are many published papers that come to such a conclusion at least until a plateau area is reached. Personally, I'm a bit reluctant to conclude that shorter milling times are better simply because the differences in all the results are so small. I prefer to think that maybe I have a particularly efficient mill set-up, quite by chance, and so a short milling time is all that's needed to get onto the plateau shown in other work. Maybe there's a parallel here with Ken's comment that he can get air float charcoal in just 10 minutes milling with his set-up.
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Re: ball milling question

Post by Lloyd »

Thank you! That was a reasonable response. I was afraid you'd stick to the idea that "shorter is better". But "quicker to the plateau" is a perfect answer!

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Re: ball milling question

Post by Boophoenix »

Alchemist, have you considered doing another round with a different charcoal? I think it would be interesting to compare this using an inferior charcoal like pine.

I sent a copy to DaveF and we debated back and fourth for some time from both angles. We do this with lots of things to learn more and gain the advantage of the others input and direction of looking at things. Don’t get me wrong I find it quite interesting, but for the sake of value you have to look for the flaw in the test if there may be one. I admire the effort and the sharing and hope you understand the reasoning behind the scrutiny. I think it may have been Lloyd that said that “ if anything of value is learned you have to ram it down people’s throats “ .

I’d also be interested in more details that you wouldn’t think to mention in a test. Like was this a one day project or multiple day?
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Re: ball milling question

Post by Alchemist »

Alchemist, have you considered doing another round with a different charcoal? I think it would be interesting to compare this using an inferior charcoal like pine.
No, I hadn't thought of that so far Brad but, yes it's a very interesting idea. At the moment, I only have willow charcoal in lump form, everything else is air float so I wouldn't be able to reproduce the original method just at the moment. However, I can certainly get other charcoals in lump form and I'll think about adding some to my next order.

I'm very happy (and accustomed) to discussing my results with others so, please don't worry about expressing your views, it's all part of learning.

As for the details you asked for, it was a two day event. On the first day I milled the materials and made up the BP samples. On the second day I rammed the tubes with the BP and fired them. Of course, there was also the third day spent analysing the results :) !
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Re: ball milling question

Post by Boophoenix »

Thank ya for the info. I had wondered if the samples made that have been prepped over more than one day if that may have accounted for the spike. Apparently that isn’t the case.

I do hope ya continue down the path, just be careful of the rabbit hole. I fell into the hole and have spent a couple of years now gathering things for a research project into charcoals and still going. I’m much closer though.
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