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Post by captbob on Oct 27, 2015 0:40:34 GMT -5
Personally... I wouldn't bolt your bearings down until you make the barrels. The picture you posted several posts above just shows a piece of PVC resting on the shafts. Your finished barrels will have end caps which will make the outside diameter of the barrels bigger than just the PVC alone - won't they?
You may need to have the shafts spaced differently with the finished barrels than how you have them with the PVC alone. I haven't made a homemade tumbler (yet) so I haven't sat down and done all the math, but it would seem that the O.D. of the barrel would change the RPM. (?)
Maybe someone that has been there, done that could chime in on whether the barrel diameter makes a big difference on shaft placement.
I would also hold off on mounting the motor until you get the belt that you are going to use - unless you are using an adjustable belt.
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Intheswamp
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Post by Intheswamp on Oct 27, 2015 7:07:37 GMT -5
From my (very) basic understanding, the deeper the barrels ride between the rollers the better traction they get. There is a semi-limited amount of space below the rollers, though. The side pieces of 2x6 lumber that the bearings rest on will limit how far below the rollers that the barrels can ride. I've planned things on a 6" span, this would allow two sets of rollers to be installed, but there's enough room to fudge wider if I decided to, so that's really not an issue. I've been using 7.27" OD for the 6" barrels...data on the fittings from Home Depot...the ones that I will be getting from a commercial plumbing supplier my indeed be different (but I wouldn't think a lot different).
Someone (sorry, can't remember who it was but thanks for the info!) stated that the span between rollers should be around 75% of barrel diameter...this comes to just under 5-1/2"....Jim suggests a wide span for more "pinching" of the barrel for better traction. My compromise was to go with six inches. Chuck, on the other hand has some rollers spaced at 4"(I think) and his tumblers work well with 4" and larger barrels. I believe Chuck's tumbler is in a protected environment, though, where dew/wetness isn't an issue on the rollers. Mine will most likely be in a protected area but may end up being under an open shed. I really like the fact that Chuck can use 4" barrels on his tumbler, but the added traction of a wider span (more pinch) appeals to me, too.
As for the barrel diameter affecting RPMs...it does. But, once you get one size of barrel "dialed in" to your desired optimal speed then when you use other sizes of barrels it automatically turns those barrels at an equally optimal speed. A larger barrel will turn slower (which is good)...a smaller barrel will turn faster (again, good). The distance that the surface layer of rocks tumbles should be constant (speed determined by rock hardness)...a 4" barrel (simply speaking) would have to turn twice as fast as an 8" barrel to result in the same distance covered by tumbling rocks in the same period of time...referred to as surface feet per minute(SFPM).
Using Chuck's pulley calculator... 1140rpm motor, 2"/9" pulleys, 3/4" drive shaft: 4" barrel turns at 47.50rpm = 15.83sfpm 8" barrel turns at 23.75rpm = 15.83sfpm ...in that minute of time the surface layer of rocks in each barrel travels the same distance.
The adjustable belts are appealing, but the plain-jane cogged belts are a lot cheaper. I figure I will get the motor positioned in what I deem it's permanent position then calculate the size of belt. That should get me pretty close and I can then adjust motor location bolt holes and inch or so in either direction if I need to and still preserve the ability to use the adjustment slots on the motor mount.
Good feedback, Bob. Thanks!
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Intheswamp
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Post by Intheswamp on Oct 29, 2015 10:12:27 GMT -5
Well, my 4" barrels are still bugging me. They might be handy for small batches of special rock or when I simply don't have enough rock to run in the big 6" barrels. So, I'm still pondering over shaft spacing. I have been planning on spacing the shafts six inches apart. Today I moved them 1/2" closer (to 5-1/2" spacing) and set a piece of 4" coupling on them. There's probably less than 1/4" on each side of the coupling hanging over the top of each shaft. Here are a couple of images with the 4" coupling sitting on the shafts with a 5-1/2" spacing. I should have gotten a shot looking more straight down one shaft to show the coupling overhang a bit better...maybe I'll get one later. Anyhow, do you think this will be narrow enough to hold the 4" barrels securely? As well as the Shoe-Goo is working inside the pvc barrel holding the rubber inner tube in place I might could glue some rubber to the outside of the 4" barrels for added traction *and* to make them a touch larger in diameter... IMG_7351a (Custom) by Intheswamp, on Flickr IMG_7347a (Custom) by Intheswamp, on Flickr
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Intheswamp
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Post by Intheswamp on Oct 29, 2015 10:14:11 GMT -5
...and another question is: Will I give up much traction with the 6" barrels by narrowing the spacing by 1/2"?
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Post by captbob on Oct 29, 2015 10:24:02 GMT -5
Wow that looks to be sitting awfully low. Again, I haven't built one, so maybe it's just fine. just seems the resistance sitting that low would be quite high. The motor is probably enough overkill for the job that it will work, but I think it will have to work harder than it would were the barrels higher. May not matter. I like your strip of rubber using the Shoe-Goo adhesive on the coupling idea. But I like to over design things. jamesp can probably answer these issues better has he has made these PVC tumblers.
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Post by captbob on Oct 29, 2015 10:29:48 GMT -5
Just went out and measured my Thumler's. The 15 lb barrel is just over 9" in diameter, and they sit less than an inch below the roller shafts.
Someone with more physics knowledge can probably better explain the downside to sitting so low in the shafts.
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Intheswamp
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Post by Intheswamp on Oct 29, 2015 10:59:24 GMT -5
Bob, I'm curious about how far apart the rollers are spaced and also the shaft diameter.
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Post by captbob on Oct 29, 2015 11:21:13 GMT -5
The shafts are thin, between 1/4 and 3/8 inches. But, they have rubber hose sections on them where the barrel sits. The rubber hose is a shade over 5/8". The rubber hose to rubber hose space is a shade under 5 1/2" Bad picture so you understand (hopefully) what I'm talking about -
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Intheswamp
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Post by Intheswamp on Oct 29, 2015 11:20:58 GMT -5
Here's a different view from the side that might be a better shot of how far below the shaft the coupling is riding... IMG_7350a (Custom) by Intheswamp, on Flickr
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Post by captbob on Oct 29, 2015 11:30:46 GMT -5
On a Thumler's 3 lb barrel, the barrel is roughly 5" wide where it meets the shafts - and the shaft spacing (rubber hose to rubber hose) is only (roughly) 3.5" The coupling you show on the last page is less than 5" across isn't it? Just thinking your shafts are kinda wide for the small barrels you plan. NONE of my store bought barrels sit that low. Again, big motor may make that irreverent. James needs to chime in on his shaft spacing if he hasn't already. I'm too lazy to go find pictures of his machines! ETA: I would look at his build to see if his bearings are offset for the shafts to be closer. ooooooh.... jamesp!
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Intheswamp
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Post by Intheswamp on Oct 29, 2015 11:51:50 GMT -5
The shafts are thin, between 1/4 and 3/8 inches. But, they have rubber hose sections on them where the barrel sits. The rubber hose is a shade over 5/8". The rubber hose to rubber hose space is a shade under 5 1/2" Bad picture so you understand (hopefully) what I'm talking about - That was a great picture! Explained things quiet well! To be sure we're comparing apples to apples...the spacing (5-1/2") that you mentioned...is that between rollers or center-to-center? I'm measuring mine center-to-center. Actual space between the shafts inside-facing surfaces would be around 4-3/4"...the actual "gap", I guess I could say. Jim, has stated before that it's better for the barrels to sit lower for better traction. Now, *how much* lower, that's an unknown...for now. That coupling in the images measures 5-1/8" which is the final OD of the pvc 4" barrels. With my crude Jethro ciphering ...I come up with .1875" of coupling overhanging the shafts....about 3/16" on either side. So, I think the rollers will hold the 4" barrel securely at this spacing, but as you've mentioned, will the pinching affect be too much in this case.
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Intheswamp
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Post by Intheswamp on Oct 29, 2015 11:53:03 GMT -5
ETA: I would look at his build to see if his bearings are offset for the shafts to be closer. ooooooh.... jamesp! I think most of his builds have the bearings end-on-end.
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Post by captbob on Oct 29, 2015 12:13:17 GMT -5
The 5 1/2" was rubber to rubber. Center to center would be more. Maybe the sitting lower, on bare shafts, for better traction is a good thing when using PVC, maybe even necessary! Just overthinking things - as usual! proceed...
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jamesp
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Post by jamesp on Oct 29, 2015 12:19:10 GMT -5
I would put set screws to outside Ed, probably keep them cleaner out there. No need to file flat spot for set screw landing.
On the end away from the big pulley trap the bearings. Two to outside, two to inside. that traps the shaft, as does the set screws.
I suggested the shaft collar clamps because on occasion pillar blocks have fussy eccentric locks.
The table is your preference/space allowance. Adding another set of shafts, hmmm, that depends on how much Ed wants to tumble. If you build it with the box design you can add to it. Not sure about other designs. You have plenty of shaft length, that will help to add an end pulley on the side away from the motor drive. You may have to move the outboard bearings on the original shafts inward to expose more shaft for the take off drive pulley to the new shafts.
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jamesp
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Post by jamesp on Oct 29, 2015 12:24:43 GMT -5
Building it for 4 inch barrels is probably an issue. I would stick with 6 inch as we started with.
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Intheswamp
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Post by Intheswamp on Oct 29, 2015 12:26:36 GMT -5
I'm roughly calculaing your center-to-center distance is around 6-1/8" going by the data I have. That's roughly what I was planning on to begin with, though my barrels would be almost 2" smaller in diameter than your 15# barrels and sit a good bit deeper between the rollers.
If the 5-1/2" spacing is too wide for the 4" barrels (5-1/8" OD)and will pinch them too much then I'll spread it back out to 6" spacing. Kinda waiting on Jim's input till I make a decision. Chuck mentioned running some barrels at a narrow spacing working good for him...I think I'll go back and refresh myself on what he said.
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Post by captbob on Oct 29, 2015 12:26:54 GMT -5
On the end away from the big pulley trap the bearings. Two to outside, two to inside. that traps the shaft, as does the set screws. < font = eyes glazed over >
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jamesp
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Post by jamesp on Oct 29, 2015 12:27:15 GMT -5
This arrangement perfect for future shaft addition. Upper right hand corner shaft is longer and hanging out past 2 X 6. Perfect to mount take off drive pulley for another set of shafts. To keep Bob's eyes from glazing over LOL mount the split collars on each side of the two bearings on the right as positioned in photo. Looks like the pillar blocks are going to hit together if you do not offset them for 4 inch barrels. The 4 inch PVC is an issue. But we started this project off with 6 inch barrels... Excellent box. Lookin good Ed. Because the shafts are offset, it pushed the upper right shaft out to the right offering a place to mount the take off pulley for the second set of shafts if wanted. So do not cut off that extra length at upper right corner. As far as pursuing 4 inch barrels confusion and shaft spacing issues will continue I believe. Kind apples and oranges.... Me, I would leave those 2 X 6's sticking out and mount a 'roll off table' area so you can simply roll the barrels off the shaft and onto a landing. Got a 'roll off' table on one set of shafts and not the other. Like the roll off table.
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jamesp
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Post by jamesp on Oct 29, 2015 12:51:38 GMT -5
See roll off table on left shafts. But not one on the right shafts. The long barrel on the right weigh 45 pounds when loaded. i.e. heavy Never measured how many pounds of rocks it holds, but it is a hoss.
Yes, PVC barrel may have 20 pounds of rocks, add weight of PVC barrel alone with water and the whole thing gets heavy.
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Post by captbob on Oct 29, 2015 13:13:49 GMT -5
Sorry, still lost here. Maybe you covered this earlier?
What does "trap the bearing" mean? What are the split collars for?
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