A disturbing find

[zekester55]

I started back in August of '16, ordering a Thumler's AR-2, and some rough, as well as collecting some local smokey and white quartz from stream beds and the Appalachian Trail.  I've met with some success, and the AR-2 has been running continuously since that time.  I bought a set of two barrels for each of the four stages, so I'd never have an issue with cross-copmtamniation of grit.


This morning, when I checked on the  unit, it was in disarray.  The barrel closest to the pulley had walked off of the rollers, ridden up onto the pulley, and had 1/16 of an inch shaved off of the bottom of it before th unit hung, and the motor shut down (presumably on thermal overload).  The integrity of the barrel was not compromised (which would have been more of a mess), and it is still usable.  I have noticed over time that the barrels walk on the rollers towards the pulley.  I have taken the following steps, which have not changed this tendency:


- The unit is on a flat surface, checked with a level.  I have rotated the unit in place 180 degrees on the horizontal plane, and this does not change the tendency or direction of the barrels walking.

- The roller axles are well lubricated and have been for the whole time I have owned it.

- I tried removing the fee-rolling axle (the o0ne not attached to the motor via pulley) and swapping it around 180 degrees as well, with no effect.

I have noticed the the black spindles on the roller axles have developed and uneven surface over time, with slight grooves where the o-ring sits, and what appears to be some accumulated fused black rubber (wear from the barrels I am thinking) that causes lumps or rings on the spindles.  I have made an effort to clear these, but I am not a machinist, nr do i have a lathe, so i don't think this has made much difference.

I have the system up and running again after cleaning it all up and examining it, but watching it I can see that barrels walk all the way towards the pulley side of the spindles, and rub against the white nylon end-stop there.  I am confident that it is only a matter of time until this casualty occurs again.  Any recommendations or thoughts that any of you have would be welcome.

  

[notjustone]

could mount a small roller on that end to act as an end stop. my homemade tumbler has a chunks of plastic that my barrels hit and keep them from walking to close to the bearings.

[zekester55]

 
There are already end-stop rollers that came with the unit.  They are fixed in place, but do oscillate somewhat, which I think is desirable.  What I think is happening is that as the barrel rubs against this end-stop roller, friction causes the rubber to heat as well as abrade off.  This results in increased friction as the rubber heats and gums up.  Eventually I think it bound enough to jump the end-stop roller, when it then rode up against the pulley which, being metal, with a sharper edge, shaved the end off of it until it bound completely causing the motor to shut down. 

[notjustone]

Apr 30, 2017 10:51:47 GMT -5 zekester55 said:

 
There are already end-stop rollers that came with the unit.  They are fixed in place, but do oscillate somewhat, which I think is desirable.  What I think is happening is that as the barrel rubs against this end-stop roller, friction causes the rubber to heat as well as abrade off.  This results in increased friction as the rubber heats and gums up.  Eventually I think it bound enough to jump the end-stop roller, when it then rode up against the pulley which, being metal, with a sharper edge, shaved the end off of it until it bound completely causing the motor to shut down. 

theres a slot cut about halfway point of the rollers that engages in the metal frame. your rollers are to close cause they are not in right

[notjustone]

how yours are


how they should be


also your end stop rollers look to be to far in there should be some space otherwise gas buildup could bulge the end of the barrels and force the barrel to climb the stops. if you have both barrels on.


this an ar-12 but the concept is the same.

[jamesp]

my big homemade tumbler has 4 shafts. Runs up to 3-4 barrels on each set of shafts.
I mounted a set of end rollers on one side only intentionally. Tilted the whole machine until the the barrels always went downhill to the rollers.
Tilt is about 2 inches in 4 feet. Or 1/2" in 1 foot.

Try shimming it 1/4"

[youp50]

With the stamped sheet metal these tumblers are made of there is little can be done to stop them from rolling to the end with the rollers slightly further apart. The barrel will run to the widest gap.

Assembling your machine as designed will find the barrels rubbing on a wear washer as designed. There are several other interesting and valid solutions suggested.

As always James gets my mind rolling, does a 4% grade improve on tumbling action. Likely that I will never manage to find an effective way to measure it. Too much unmeasurable variation in the rocks being tumbled.

[zekester55]

@ notjuststone:  The picture I posted previously was a photo already hosted on the web; I did not have a photo hosting website account at that point.  My apologies., I am not great with this computer stuff.  Just created a Google account in order to post a YouTube video for you folks.  Ugh.  The nylon bushings with the slot have been correctly mounted in the sheet metal bracket as you so kindly indicated since I received the unit.


So I created a video to demonstrate the issue.  At JamesP's suggestion, I shimmed the unit (although I went to about 3/4").  Both barrels still move left, at the barrel on the left is rubbing on the end-stop within a minute and a half.  I also wonder about increased wear on the lid in this configuration.


Here's where to find the YouTube video: Thumler AR-2 Barrel Walk  

[georgeb138]

Thumblers recommended fix for the barrels jumping over the white "Stop washers" is very simple. Silicone lubricant on the washer and the barrel bottom. It worked for my AR-2.
They also recommend that the lids be facing each other.
I'm no expert. Just my 2 cents.

[zekester55]

Ok, I'll have to try some silicone lubricant. I've always put the lids facing one and other.

[spiceman]

I have the smaller version, one 3lb. Barrel. It was walking to the same end all the time and ridding up on the white collars. The size of the black rollers where different size from end to end. A piece of garden hose fits real nice and the size was now the same from end to end. No more walking. I also cleaned the shaft very good around the pulley and bushing ends. So one or both of fixes solved the problem.

[zekester55]

@ spaceman - So you covered the rollers and shaft between the white collars with a piece of garden hose? Can you post a photo?

[braat]

I just bought the AR-2 and have the same problem. I raised the end of the unit (motor end) 1.5 inches and while the barrels still climb up the shaft towards the motor there's minimal contact with the white roller stop...just enough to turn it. I can stop the white roller with my finger and there's no noticeable effect on anything so that's where it's set for now. If I raise the unit any further the barrels go to the other end. I can't adjust tilt height so the barrels ride in the middle of the rollers...it's either contacting one roller or the other. So I'll monitor for a couple weeks for barrel/roller contact wear and maybe try the silicon grease thing. Anyhow that's my "fix".

[zekester55]

I went back flat and added silicon grease this afternoon, will let you know how it goes after a few days.  While I know that rock grinding is a dirty business, I can't say i am happy with getting grease involved.  I'll be looking out for used Lortone units I think.

[spiceman]

I sent you a PM.

[jamesp]

Apr 30, 2017 13:50:08 GMT -5 youp50 said:

With the stamped sheet metal these tumblers are made of there is little can be done to stop them from rolling to the end with the rollers slightly further apart. The barrel will run to the widest gap.

Assembling your machine as designed will find the barrels rubbing on a wear washer as designed. There are several other interesting and valid solutions suggested.

As always James gets my mind rolling, does a 4% grade improve on tumbling action. Likely that I will never manage to find an effective way to measure it. Too much unmeasurable variation in the rocks being tumbled.

The 4% grade thing youp50....

Having built a couple of tiltable tumblers I found the tilt effects the grind.
Of course as the barrel approaches vertical all tumbling action approaches zero.
After about a 60 degree tilt from horizontal the rocks barely have a tumbling action at all.

I had to tilt this beast. It beat rocks up badly. Listen, it is rolling 55 pounds of 3/8" crushed glass. It does fine with smalls at horizontal position.



But with 1 to 2 inch rocks it becomes a rock damaging machine, sound is telling. The wedge shape around the edge was rough on rocks.



I may turn it into a Gatling gun tumbler. Weld some 20 inch long 6" pipes to the front of the round container.
Cap them with the 6 inch rubber cap you see in the video. Maybe 4-5 of them.
So it would be a bit like a Ferris Wheel.
The cap can be full opening size since it does not have to make contact with two shafts like a conventional tumbler.
For rolling larger rocks since they would fit thru the big opening.

[youp50]

May 3, 2017 21:05:09 GMT -5 jamesp said:

Apr 30, 2017 13:50:08 GMT -5 youp50 said:

With the stamped sheet metal these tumblers are made of there is little can be done to stop them from rolling to the end with the rollers slightly further apart. The barrel will run to the widest gap.

Assembling your machine as designed will find the barrels rubbing on a wear washer as designed. There are several other interesting and valid solutions suggested.

As always James gets my mind rolling, does a 4% grade improve on tumbling action. Likely that I will never manage to find an effective way to measure it. Too much unmeasurable variation in the rocks being tumbled.

The 4% grade thing youp50 ....

Having built a couple of tiltable tumblers I found the tilt effects the grind.
Of course as the barrel approaches vertical all tumbling action approaches zero.
After about a 60 degree tilt from horizontal the rocks barely have a tumbling action at all.

I had to tilt this beast. It beat rocks up badly. Listen, it is rolling 55 pounds of 3/8" crushed glass. It does fine with smalls at horizontal position.



But with 1 to 2 inch rocks it becomes a rock damaging machine, sound is telling. The wedge shape around the edge was rough on rocks.



I may turn it into a Gatling gun tumbler. Weld some 20 inch long 6" pipes to the front of the round container.
Cap them with the 6 inch rubber cap you see in the video. Maybe 4-5 of them.
So it would be a bit like a Ferris Wheel.
The cap can be full opening size since it does not have to make contact with two shafts like a conventional tumbler.
For rolling larger rocks since they would fit thru the big opening.

That's quite a gear box you have repurposed there.

That is a 'fire pit bowl'?

Its hard on rocks because they have so far to fall or because the drum is steel?  The steel drums could be lined with Devcon brand Flexane to cushion the fall.  I have done repair work at iron mine concentration plants.  The'tumblers' there are lined with iron based alloy wear plate, purpose being to pound the ore to powder.  Primary mills perhaps 50 ft in dia and pebble mills 16ft or so.

Have you ever baffled the interior of the barrels?  I am looking forward to settling into my new digs, planning a helix baffled full diameter opening tumbler drum.   The idea brought about by the tipping of the barrels.  Probably going to have to buy some jasper rough to compare smooth vs baffled barrel, then straight vs helix.  I will be cutting unistrut for the tumbler frame this week.

I think making a gatling gun tumbler may work.  If I were to do it, I think I would use 8 in sch 40 steel pipe and drill and tap four holes; two axially and two more axial ones 90 degrees radially for cap screw jam bolts.  Same principal could be accomplished with three pieces or angle iron.  Barrels could be 6 in sch 80 pvc then.  Full dia Fernco caps, more economical than glue caps, reducers, etc.

I am certain that I have no desire to get tangled in that machine.

[jamesp]

From a coarse grinding standpoint:

Probably the wedged steel surround and long fall as you mentioned youp50. You can fill the beast to 80% and get a much gentler action.
But the wedge reduces the amount of rocks at the top of the pile. Restricting the width of the avalanche within. And you can hear surges in the avalanche.
No doubt it is surging, the chain shows it clearly tightening and loosening, as does the sound. The surges are violent.
I am pretty sure that the most of the tumbling action in a rotary occurs in the top 30% of the rocks where the avalanche is occurring.
The lower rocks are experiencing little relative movement therefore can not be grinding.

Think about the avalanche at the top 30% of the rock pile.
Optimize the width and length of the avalanche. Gets technical.
A 50-60% full barrel gives the longest avalanche. That's a fact. You can't disprove that.(not in my eyes)
If you tumble obsidian with a 50-60% full barrel you will most likely bruise the heck out of it. Tough agates on the other hand can take much more abuse.
An alternative to reducing bruises in a 50-60% barrel is to run a protective slurry thickener.(that is what I do)

Is a longer 6" barrel at faster speed better than a shorter 8" barrel at slower speed both with equal volumes and equal surface speeds better ?
Real tough question. Most barrels are about as wide as they are tall or longer than their diameter. Yet some have a wider in diameter than they are long.
Not much data recorded on the tumbling performance of these dimensions. Rest assured one is better than the other.
I tend toward 6" and long at faster speed than 8" and short and slower. Having run those two sizes many times.

That rotating gun arrangement is no different than a standard rotary tumbler. Each pipe attached to the drum would be doing the same speed.
They would be traveling up and down in altitude by a couple of feet. About the only difference.
Lol, the fire pit shaped drum design was a serious failure for tumbling size rocks.
Plus the friction of a worm gear box eats more electricity. Chains and belts are dead efficient at transferring energy.

[zekester55]

Do any of you have suggestions for alternate commercially available barrels I could run on the AR-2, as opposed to the Thumper barrels?