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Post by pauls on Apr 7, 2018 21:01:27 GMT -5
I will just put this out there as an observation, I have no idea why it happens.
I recently decide my tumbler was just too slow, I had built it using pulleys I had scrounged so just went with the speed I got. It didn't worry me as I was also experimenting with different barrel sizes, I always noticed that while most folk here were talking about gas build up I was experiencing exactly the opposite, a negative pressure sucking in the lid. I finally decided an upgrade was in order so scrounged another larger pulley for the motor so now the barrel rotates at about 40RPM, all good but now I get gas pressure building up.
Same rocks (Agate), same slurry, same grit, same barrel, same rain water, all that's changed is the rotation speed. Why would it make a difference?
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Post by Drummond Island Rocks on Apr 7, 2018 21:35:03 GMT -5
You listed 40 as the barrel RPM but I did not see any reference to what the barrel diameter is. 40 RPM on a three pound lortone barrel and 40 RPM on a 12 pound lortone barrel are two completely different scenarios. That being said I have a homebuilt tumbler and several stock lortone units and the end of the barrel is sucked in at the end of a 7 week run most of the time. I have never had the gas build up others seem to have had even when running all obsidian. With obsidian I will say that the end of the barrels were not sucked in but rather flush (not bulging).
Stock Lortone 3 pound tumbler with a 4.5" diameter barrel 40-45 rpm Stock Lortone 12 pound tumbler with 6.75" diameter barrel 28-32 rpm
When I built my tumbler I pretty much trusted that Lortone is an expert and set my speed to match their units.
Chuck
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,159
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Post by jamesp on Apr 7, 2018 23:06:51 GMT -5
Gas build up on glass is much worse at 63 RPM verse 30 RPM. Must be simply a faster wear rate exposing more gas pockets. Agates ? Not sure.
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Post by pauls on Apr 8, 2018 0:00:42 GMT -5
Originally I was running a nearly 2 foot diameter barrel at about 19 RPM, much too heavy and a battle to keep it fed with grit and rocks, I downsized to a 13 inch dia barrel but left the speed the same. That's the barrel that I have now bumped up to 40 RPM. I read somewhere that the gas was Acetylene from the breakdown of the Silicon Carbide, I tried lighting it but nothing so unlikely to be Acetylene.
The price of electricity here is just stupid, I thought that by bumping the speed up I might get through first stage quicker, of coarse bigger pulley means greater load on the motor even if its for a shorter time, so it's possible my electricity bill wont change.
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,159
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Post by jamesp on Apr 8, 2018 5:44:24 GMT -5
2 foot barrel ! Hell, 13 inch barrel ! Those are some serious barrels dude.
I think there is 1000's of recipes for gas generation in a tumbler.
Rolling glass over and over I have learned that high gas is high wear. I have a habit of overfilling the barrel to avoid bruises on the glass. There is a narrow sweet spot where glass can be run at high speed without bruising(barrel fill at 80 to 85%) My rubber caps bulge when the barrel fill is correct and the glass is wearing rapidly. If I find the rubber cap is not bulging after 24 hours I remove material to get the perfect fill as it is hard to get it just right.
I do 63 RPM with 6.75", so 3.14 X 6.75 X 60 = 1271, you are 3.14 X 13 X 40 = 1632, 1632/1271 = 28% faster edge speed in your arrangement. Which is deceptive because I don't believe barrel size:rock wear is linear relationship.
A 13 inch barrel with surface speed of 1632 in/min(40 RPM) is in no way comparable to a 7 inch barrel with 1632 in/min(74 RPM) surface speed. For one reason volume is not a linear relationship. If you double the diameter you way more than double the volume and only half the speed.
7 X 12" long barrel = 461 cu. in. at say 50 RPM 14 X 12" long barrel = 1846 cu. in. would be 25 RPM with same speed shafts.
So doubling barrel diameter in this case means 1846/461 = exactly 4 times more rock but rolling at only 1/2 the RPM.
So all this is a bit of a side track but your 13 inch barrel at 40 RPM is a mean rock grinding machine. Lots of speed there, lots of splashing and turbulence within. Lots of high grinding forces. Ticket for gas... How long is this 13 inch barrel and how many pounds of rock does it hold ? Gotta be heavy !
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Wooferhound
Cave Dweller
Lortone QT66 and 3A
Member since December 2016
Posts: 1,423
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Post by Wooferhound on Apr 8, 2018 7:15:19 GMT -5
Yeah . . . I want to know more about the tumbler and barrels ?
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Post by pauls on Apr 10, 2018 1:13:22 GMT -5
The barrel is an old 20 pound propane tank, about 13 inches dia and about 13 inches long, so more or less a cubic foot. Loaded it's heavy, I really struggle to lift it. Rocks and silicon Carbide and slurry are a lot heavier than propane. I have been a bit camera shy since photobucket ate my photos. I just fired up a flickr account but its that long since I have posted a photo I am struggling, I have a photo of my tumbler on flickr. link
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Post by aDave on Apr 10, 2018 1:26:09 GMT -5
pauls ...I took the liberty of posting your photo for you. I've added some basic Flickr instructions below the photo. If you want your photos from Flickr to show up in your posts, instead of a link, follow these directions which I've posted for others before. ...with Flickr, you have the ability to copy and paste code that works in posting photos on this site. I'll make this as brief as I can.
Go to your photostream in Flickr and click on the photo you'd like to post here. When that photo loads as a single photo, you should see a series of symbols in the lower right corner of the screen. The curved arrow is what you are looking for.
Click on the curved arrow. After doing so, you should get a screen that says, "Share 1 photo to:". Select the BBCode tab. The code you see in the box is what you will copy and place in your post to show the photo. If you don't know, ctrl+c is copy, and ctrl+v is paste. After you've copied the BBCode, all you have to do is paste it directly in your post. Oh yeah, select "medium" as the size before you copy, as that attribute should be placed in the code you copy.When you place your BBCode directly in your post, no "image" tags are needed. For instance, this is what you would see if you copied and pasted the code from your photo: [url=https://flic.kr/p/25WQ9mL][img]https://farm1.staticflickr.com/820/41314603892_ba41594790_z.jpg[/img][/url] [url=https://flic.kr/p/25WQ9mL]tumbler[/url] by [url=https://www.flickr.com/photos/157435421@N07/]Paul Scott[/url], on Flickr With that code, it will show a clickable photo as well as information about your photostream next to said photo. If you don't want your stream and/or your name to show along with your photo, delete everything after the first [/url] which is at the end of the first line. You would be left with this, which shows only a clickable photo: [url=https://flic.kr/p/25WQ9mL][img]https://farm1.staticflickr.com/820/41314603892_ba41594790_z.jpg[/img][/url] These are instructions for working on a PC. I haven't posted photos from a mobile device. Hope this helps. Sorry for derailing the thread.
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Post by pauls on Apr 10, 2018 1:34:11 GMT -5
Thanks Dave, I need a bit of time playing with flickr I think.
For scale thats a six inch spanner on the floor.
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Post by aDave on Apr 10, 2018 1:54:49 GMT -5
Thanks Dave, I need a bit of time playing with flickr I think. For scale thats a six inch spanner on the floor. I added instructions above.
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Post by pauls on Apr 10, 2018 2:23:58 GMT -5
Thanks dave, no need to apologise for derailing the thread, it's only derailed if it's not relevant. I was looking for that BBcode, it was just well hidden.
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