# Ball mill has hit a snag



## bswartzwelder (Jan 8, 2012)

I recently started to build a ball mill for crushing IC chips. My son had a discarded 30 gallong air compressor setup which had died. I cut the top and bottom out of the air storage tank and got a nice cylinder to start the project. The inside diameter is 17 7/8 inches so I bought 3 pieces of 3/16 inch thick plate steel 17 7/8 inches square to fabricate the ends. Tack welded all three plates together and painted with red steel dye for the layout portion. The bottom plate will be solid. The plate on the other end will be a circular donut about 1 1/2 inches wide. I will drill 12 holes (evenly spaced) on a circle 3/4 inch from the outside of the donut. I will then weld 12 3/8 inch bolts in the holes so they protrude towards the outside of the finished drum. The outside removable plate will have 12 evenly spaced 1/2 inch holes that will allign with the protruding bolts. Twelve nuts will secure the top in place when the unit is running. There will be a sheet rubber gasket between the donut ring and the outer front cover to seal everything.

As I said, I welded the three 3/16 inch thick plates together so I coould cut them all at once and they would all be the same. Never thought about having to cut an almost 18 inch diameter circle which is 9/16 inch thick. Could not cut them with a jig or saber saw. Sawzall barely cut through them. Got out the Porta Band and went to town. Got almost halfway around the circle when the porta band died. Found out it had plastic gears on the inside of the drive hub. Plastic gears will not take the pounding that metal gears will, so the gears are now somewhat toothless. Will have to wait until Monday to order replacement parts and then wait for their arrival. This will give me time to come up with a metod to drive the barrel. Need about 46 RPM. Have been thinking along the lines of a belt (or maybe two) which go around the drum as a method of spinning it. Will still need a motor and some more pulley speed reduction to get it down to 46 RPM or slower.

I would like to put 4 "catchers" on the inside of the drum every 90 degrees around. They will catch the "balls" and help take them to the top of the rotation where they will let them drop. Dropping from the top of the rotation should give the best crushing action but it will make it noisy. I may have to build an enclosure lined with fiberglass insulation on the inside to help deaden the noise. The enclosure would roll around on casters. Anybody with any other ideas, please feel free to share them.


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## Harold_V (Jan 8, 2012)

Nothing wrong with using a belt around the OD to drive the drum. I did that with my ball mill with excellent results. I also used a variable pulley to fine tune the speed. The belt for the drum is readily visible in the attached photo. 

Lose the idea of putting anything inside to lift the balls. If it's necessary, you're running the ball mill at the wrong speed, and nothing you do will make it more efficient. Run it at the proper speed and it does exactly what is required--it carries the charge and balls to the apex of the upper curve, at which time they fall to the bottom of the drum. Anything you add in the way of lifters offers the possibility of protecting the charge from proper action. 

Running the ball mill to fast or too slow is not a good idea. If the charge does not drop at the appropriate time, or if it simply slides along the drum, you'll break down the charge only by attrition. That's correspondingly as hard on the ball mill as it is the charge and balls. 

Harold


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## glorycloud (Jan 8, 2012)

Nice ball mill Harold. What did you primarily use it for?
What materials did you process through it?


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## Anonymous (Jan 8, 2012)

Harold_V said:


> Lose the idea of putting anything inside to lift the balls. If it's necessary, you're running the ball mill at the wrong speed, and nothing you do will make it more efficient. Run it at the proper speed and it does exactly what is required--it carries the charge and balls to the apex of the upper curve, at which time they fall to the bottom of the drum. Anything you add in the way of lifters offers the possibility of protecting the charge from proper action.
> 
> Running the ball mill to fast or too slow is not a good idea. If the charge does not drop at the appropriate time, or if it simply slides along the drum, you'll break down the charge only by attrition. That's correspondingly as hard on the ball mill as it is the charge and balls.
> 
> Harold


bswartzwelder,
The ball mill that I built was a beast.Just over 22 inches in diameter,1/4 steel,with huge slugs,pucks,and balls. I used a lifter bar in my ball mill,and it works pretty well.It is raised off of the drum to allow the material to remain at the bottom,while the media was being lifted to drop point.Once finished,I ran it with cover off,and fine tuned the "drop point" by lowering my lifter bar,until the media dropped on to the "sweet spot".The reason I chose to do it this way,was because,once my mill was finished,I was limited to a number of sheaves to adjust the speed,and I was unaware of what an adjustable sheave was.I love my ball mill,because I designed it,cut almost every piece of metal myself,and built the entire thing.It is my pride and joy,but............from an industry standpoint,it is as slow as mollasses running uphill.Utilizing the exact same setup,but switching to variable sheaves,I could literally grind 10 times the material,in any given amount of time.
The main problem with using a lifter bar is this,with every rotation of the drum,the media is lifted and dropped only one time.When _not_ using a lifter bar,and using the rotational force to lift the media,and material to an apex,everything is being lifted and dropped constantly.Nothing is ever sitting idle at the bottom of the drum,waiting to be raised by the lifter bar.Also,using a lifter bar ONLY works when the drum is turning slower than a non-lifter drum.In the words of GSP "Go for the gusto" use variable speed sheave,and lose the lifter bar.
Here's a list of them on ebay 
http://www.ebay.com/sch/i.html?_nkw=variable+sheave&_sacat=0&LH_BIN=1&_sop=10&_odkw=variable+speed+pulley&_osacat=0&_trksid=p3286.c0.m270.l1313


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## rusty (Jan 8, 2012)

My mill is now 3 years old, uses a lifter bar. 

The job currently under way, the mill is abrading silver contacts loose from the buss bars.


I'm with Harold on this lose the idea.

[youtube]http://www.youtube.com/watch?v=IaDd34paaQU&list=UUisCclhYzYd2NOSEm1AyTdg&index=1&feature=plcp[/youtube]


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## jack_burton (Jan 9, 2012)

Rusty- what kind of motor is this?


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## ericrm (Jan 9, 2012)

what size of ball is the best to use?is the bigger the better or is there a magic size ball who doest the trick like one or 2 inch ball?


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## Anonymous (Jan 9, 2012)

ericrm said:


> what size of ball is the best to use?


It depends on what you want to accomplish.Sometimes you have to try different media,and watch the results.


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## Smack (Jan 9, 2012)

Rusty, looks like yours could go about 3x as fast.


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## bswartzwelder (Jan 9, 2012)

Unfortunately, I already had the lifter bars installed when I made the post. They are simple 3/16 inch thick by 2 inches wide pieces of plate steel and unfortunately they were welded full length to the barrel on both sides. I will continue with the design from here. If I have to remove them in the future, I'll think of a way either cutting or grinding. The part to fix the band saw was ordered today and might be here in time for the weekend. I'll keep everyone informed. I may just cut an end cover out of plexiglas so that I can fine tune the speed. I found an equation for the critical speed and it said that typically ball mills run at 65% to 75% of the actual calculated critical speed. For mine, that would work out to 46 RPM. Thanks Harold, for the idea of the variable speed pulley. I'll order one soon.


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## Harold_V (Jan 10, 2012)

glorycloud said:


> Nice ball mill Harold. What did you primarily use it for?
> What materials did you process through it?


The ball mill was built to run a specific product, which, in this case, was a complex gold ore that assayed over 300 ounces/ton. I received the ore crushed to ½"-. 

The ball mill is (was) a continuous feed---so ore was constantly introduced, along with lime, and water. How much water was introduced dictated how long the material spent in the mill. A set of classifier bars in the discharge prevented anything of size from being ejected, then the discharge was classified twice. First time was at the top, where small nuggets were trapped on a coarse screen, then again at the bottom of the chute, where a fine screen trapped finer gold and tiny bits that were not crushed fine. Very little had to be returned to the mill, simply be controlling the water rate. 

The ball mill was a resounding success, and contained no lifters. There's a formula for calculating proper operating speeds for a ball mill. If the formula is observed, as in my case, a ball mill is far more efficient. 

Harold


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## Harold_V (Jan 10, 2012)

ericrm said:


> what size of ball is the best to use?is the bigger the better or is there a magic size ball who doest the trick like one or 2 inch ball?


Size of the ball will be dictated by the size of the charge. What you'll quickly come to understand is that if the balls are too small, they don't crush. They will, however, slowly abrade the pieces until they're to a critical size, at which time they'll fracture and be crushed fine. That's not a very good way to operate a ball mill. 

My mill had a varied size charge of balls and rods. I had balls up to 2" in size, and everything down to about 3/4". All were just commercial balls, from ball mills, but well used. Many of them start life as large as 6" in diameter, but are slowly abraded. 

I also ran a large number of rollers from large bearings. They varied in size, too, but not greatly. About 7/8" diameter by about 1½" long to 3/4" diameter and an inch long. 

The charge was adequate for the feed, in my case, but I added a couple large pieces of ore (hadn't been crushed), which remained in the mill for several hours (make that a few days). Again, once down to a particular size, they were rapidly eliminated, but the process getting them worn down was very slow. It is for that reason I suggest that a ball mill be made to operate at the proper speed. They're way too noisy to be allowed to run unnecessarily. I could not be in the same room with the ball mill without ear protection when it was operating. 

Harold


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## glorycloud (Jan 10, 2012)

300 Oz of Au per ton = NICE!

Thanks for sharing Harold! 8)


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## ericrm (Jan 10, 2012)

thank you harold for the answer ,steel ball are realy expensive so knowing will save me much needed money


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## rusty (Jan 10, 2012)

ericrm said:


> thank you harold for the answer ,steel ball are realy expensive so knowing will save me much needed money



Only Harold could tell us how many pounds of balls it took to make his mill functional, I'm guessing no less than 200 lbs. The drum would have been at least half full.


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## ericrm (Jan 10, 2012)

if it realy take that much ball ,i think i will look to find some cheaper ball,
do you think that a steel tube(full)cut in section could do the trick?


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## rusty (Jan 10, 2012)

ericrm said:


> if it realy take that much ball ,i think i will look to find some cheaper ball,
> do you think that a steel tube(full)cut in section could do the trick?



This is why we amateurs use a lifer bar, it allows us to use less balls to achieve the same goal.

When your refining on a toll basis your working against the clock, we have the luxury of ownership.

Owning a continuous feed ball mill would be the ultimate toy, with the amount of feedstock I acquire in one years time this is exactly what a mill like Harold's would be just another toy in my shop. I could not justify having a continuous fed mill like this over my lowly mill with a lifter bar and a half dozen balls.

My mill may not grind the same pounds per hour that Harold's mill would have, for example if I load 60 lbs of IC's into my mill at 5:00 PM you can bet there is nothing left of those chips come morning other than a very finely milled powder.

Harold's mill in the same time period may have milled 400 lbs and I may have well over estimated on the amount.


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## kuma (Jan 10, 2012)

Hi all , how are tricks?
I hope all is well! :mrgreen: 



Harold_V said:


> Lose the idea of putting anything inside to lift the balls. If it's necessary, you're running the ball mill at the wrong speed, and nothing you do will make it more efficient. Run it at the proper speed and it does exactly what is required--it carries the charge and balls to the apex of the upper curve, at which time they fall to the bottom of the drum. Anything you add in the way of lifters offers the possibility of protecting the charge from proper action.



Giggles! Just when you think that you have something sussed in your mind , ........ :shock: 
Once again Harold , thank you for the heads up! 
Wishing you all the best and sending my kindest regards ,
Chris :mrgreen:


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## Harold_V (Jan 11, 2012)

rusty said:


> ericrm said:
> 
> 
> > thank you harold for the answer ,steel ball are realy expensive so knowing will save me much needed money
> ...


By weight, no, as I never weighed the charge, but I kept the ball level slightly below the bottom trunnion of the right hand end of the mill. The entire assembly was tilted downhill to the right, with the discharge trunnion smaller in size than the intake trunnion. I would estimate the drum was probably 40% full at the most. 

I was fortunate to have a used equipment dealer near me when I built the ball mill. They had a small assortment of well used balls. I do not recall the price, but they were affordable. They are nothing more than castings, often with traces of the runner still attached. Doesn't matter, not for the purpose. 

Harold


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## Harold_V (Jan 11, 2012)

glorycloud said:


> 300 Oz of Au per ton = NICE!
> 
> Thanks for sharing Harold! 8)


Nice, it was! The gentleman that owned the ore gave me several samples, some of which would likely assay well over 1,000 ounces/ton. I posted pictures of them some time ago. One of the samples is sawn---exposing a large percentage of the surface as gold. 

Remember---this was an ore--not a concentrate. He informed me that he could have purchased some that assayed over 600 ounces/ton. I processed for him only one time. He was quite old then. Indications were that he had purchased the ore from miners that were (my assumption) high-grading from the mine where they worked. I was given very little in the way of information, aside from the fact that the ore came from Colorado, sold from a residence in Grand Junction. 

Harold


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## Harold_V (Jan 11, 2012)

ericrm said:


> if it realy take that much ball ,i think i will look to find some cheaper ball,
> do you think that a steel tube(full)cut in section could do the trick?


You're not thinking clearly. Think of a ball mill as a hammer and anvil. If you strike pieces with a light hammer, they may or may not break. Using tubing lowers sectional density, so it, too, may not strike with enough force to do the crushing. You are better served with pieces that weigh a great deal. 

There are other devices that can work. Rod mills, for example, where lengths of steel are used in place of balls. 

I'm not a physicist, but consider that the longer an item falls, the faster it falls, so distance can be a substitute for larger balls. That would be a consideration if one were to think of a large ball mill, but for small objects and home use, I'd still consider simply using the proper sized ball, and running the mill at the appropriate speed. Remember, you only have to do it right once, assuming you build a robust mill---and you're most unlikely to wear out the balls unless you operate for years on end. 

Doing it wrong can be the source of considerable frustration, taking pleasure out of the project. That's how it works for me, anyway. YMMV.

Harold


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## butcher (Jan 11, 2012)

Took me a while to figure out this modern language these young people use nowadays 
:lol: 
YMMV translation my guess is your mileage may vary. 

Trailer hitch balls (ball cut off, large ball bearings, large steel rods cut to almost ball size, big heavy stainless steel would be a nice find, check out your local scrap yard they may have something laying around? 

A gearbox and DC motor can easily be run off of an Alternating current source with a bridge rectifier (to convert AC to DC), a light dimmer, variac, or even a transformer (which secondary could be tapped), can be used to adjust the speed, (with the gear box the speed is reduced and the motor would not need to be as large) if you do not have one in your garage check the junk yard while your there looking for ball mill materials. The motor, gearbox, bridge rectifier, light dimmer, variac or transformer would all have to be sized to the load.


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## Harold_V (Jan 11, 2012)

butcher said:


> Took me a while to figure out this modern language these young people use nowadays
> :lol:
> YMMV translation my guess is your mileage may vary.


Correct, and a violation of my own rules, where no one should use shorthand on the forum. For that I apologize. I'm happy it was used in a way that didn't put anyone at risk. 

Harold


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## bubba (Jan 18, 2012)

Harold_V said:


> Lose the idea of putting anything inside to lift the balls.
> 
> Harold



Well, I have to disagree with that. Depends on the material. You would not need lifters on a charge of say,placer gold concentrates and black sand. But try and grind the sniffers out of oxygen sensors without them, good luck. Tough grinds require the smashing action that the lifters, along with a few larger size balls can produce.


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## Harold_V (Jan 19, 2012)

bubba said:


> Harold_V said:
> 
> 
> > Lose the idea of putting anything inside to lift the balls.
> ...


Disagree all you wish---*you're wrong*. A ball mill that runs at the proper speed does not need lifters, and, in fact, they may be detrimental to its operation, for they often interfere with the action of the falling balls. 

If you find you need lifters, it's because you run at an inappropriate speed, and may well be reducing by attrition instead of crushing. It's that simple. Oxygen sensors make no difference. There's nothing about them that is unusual. 

Harold


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## Smack (Jan 19, 2012)

Harold is right Bubba, there are some good videos on youtube demonstrating this. Just don't overfill your mill, only fill it up to about half. Usually between 60 and 80rpm is good from my experience.


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## bubba (Jan 20, 2012)

Harold_V said:


> bubba said:
> 
> 
> > Harold_V said:
> ...


 Explain how inch and a half pieces of flat bar welded longitudinally for lifters in a 36" mill is going to be "detrimental" to its operation? mine has been in constant use since 1998. We grind O2 sensors almost everyday, and if you tried to mill without lifters the same charge would have to run 4 hours as opposed to an hour and a half with the lifters to get to 100 mesh .I welded them in, I know. disagree or not , I am stating fact.


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## Harold_V (Jan 20, 2012)

bubba said:


> Explain how inch and a half pieces of flat bar welded longitudinally for lifters in a 36" mill is going to be "detrimental" to its operation?


Very simple. When the charge drops, it is expected to impact the material. If you have lifters where the balls drop, they may interfere with contact with the material by being deflected to a side. A ball mill (should) function by impact, not by attrition. You added lifters because you weren't crushing. Get my point?


> mine has been in constant use since 1998. We grind O2 sensors almost everyday, and if you tried to mill without lifters the same charge would have to run 4 hours as opposed to an hour and a half with the lifters to get to 100 mesh .I welded them in, I know.


That makes no difference. Had you observed what I've been saying right along, you wouldn't have needed lifters. It's clearly obvious you run the ball mill at the wrong speed. Had you invested enough research before jumping to the conclusion that you needed lifters, you'd know that, too. It's all well documented and available for those who wish to do it right. I know that to be true because it's exactly what I did when I built mine, which had no lifters and worked exactly as was predicted. Why then, is your example right, and my example wrong? I don't think that's the case, but I do think you aren't about to admit that you may not have done your homework. You must win--but you've already lost because you don't understand the issue. 



> disagree or not , I am stating fact.


Yes, you're stating fact---that you welded in lifters. You are not stating fact that they are required. I see no reason why your experiment should reduce the validity of published information that I found to be deadly accurate. The only fact here is that you use lifters. It does not prove that they are required, which is the point at hand. 

You could have welded in any number of lifters, or not, and achieved some degree of success. Your argument is akin to a guy that gets bit by a brown dog, and is then quite sure that all brown dogs bite. That simply is not the case. 

Look, I have no argument that you achieved success. I do have an argument that because you use lifters that it can't be done otherwise. I know you're wrong because I did it, and I did it because I did the necessary research to ensure I achieved my goal. Do your really think large ball mills used in crushing ores contain lifters? Do you really? 

Had you run your ball mill at the proper speed, lifters would not have been a requirement. That's the way it is, and nothing you can say will make a difference. *Case closed.* 

I have no intentions of allowing your lack of knowledge to influence the decisions made by others. If they choose to add lifters, it will be because that's their decision, not because they think they are a necessity. 

I've taken note that you have a rather argumentative attitude on this forum of late (I am not making reference to this conversation, but another). I suggest you lose it. 

Harold


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## bubba (Jan 20, 2012)

Harold_V said:


> bubba said:
> 
> 
> > Explain how inch and a half pieces of flat bar welded longitudinally for lifters in a 36" mill is going to be "detrimental" to its operation?
> ...


 While you are doing your "reasearch" I am at work, perfoming grinding operations on a daily basis. Both with impact mills, and ball mills. Every tool in the tool box has a job, and is application specific.
I don't understand your mean spirited attack, but for the sake of someone reading this and wanting to know how about mills, I guess I have to stand up to you and defend myself, even though its seems pointless to bicker.
Anyway, the basics........big balls make big grinds, small balls make small grinds. simple. 
Where the lifters come in, and the only place where they make a difference, is in larger feedstock say 1/2" or larger material. Lifters and big balls reduce larger material faster in a big mill, and don't let anyone fool you, Lifters make quicker work of larger feed at ANY speed. 
A production operation needs a series of mills, to produce a fine grind, say 300, 400, 500 mesh which is required to achieve liberation on many ores, you need small balls. Our finish mill has 1/2" and 3/4" balls only, AND NO LIFTERS,and this is where I agree with harold, on the fine grinds your rpm's must be exact, and lifters actually get in the way.


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## Smack (Jan 20, 2012)

Guess I'll have to retract my previous statement, I thought we were talking about a ball mill for one of us hobby refiners to build at home. But for all others reading, if I had to build one for myself, I would make it without lifters.


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## Harold_V (Jan 21, 2012)

bubba said:


> While you are doing your "reasearch" I am at work, perfoming grinding operations on a daily basis. Both with impact mills, and ball mills. Every tool in the tool box has a job, and is application specific.


Once again, you've missed the point. I spent but a short time researching this subject, and it was done the hard way, from old mining journals. I had no previous knowledge of ball mills, so research was very much a part of what I had to do. Coincidental to my research, the mathematical equation was provided in the same text. The time spent in calculating the proper running speed for my particular ball mill was most likely less time than you waste on an ongoing basis by making a correction of improper speed by adding items that are not needed, increasing maintenance costs as well as operating costs. 



> I don't understand your mean spirited attack, but for the sake of someone reading this and wanting to know how about mills, I guess I have to stand up to you and defend myself, even though its seems pointless to bicker.


No, you don't have to stand up "and defend yourself". All you have to do is report what you did, and the results you achieved, and do that without making leading statements such as lifters are required. They clearly are not. That's the part you seem to overlook. Just because you corrected an error in running speed by adding lifters doesn't mean everyone must have lifters, which is the point I keep trying to convey to you. All brown dogs do not bite, in other words. 

Your carelessly chosen words, most likely a reflection on your inability to see anything but that which you prefer to see, may be the cause of others following in your footsteps, paying no attention to what matters, and too much attention to your "all brown dogs bite" comment. 

I had no issues with your claim that you needed lifters. I took exception to your claim that they are a requirement, just as I take exception to your badgering readers because you don't happen to agree with what they do with cats. This isn't a matter of you being in charge, trying to promote your methods, it's a matter of free agency, where readers seek information that they hope will aid them in their quest, one that may or may not make sense to you, but one that they are entitled to pursue to their heart's content. In that regard, no, you do not play well with others. You're too caught up with your own thoughts to understand that others may have a curiosity that must be answered by their own means. It's not for you to determine what they do, just as it's not for me to determine if readers choose to process escrap. I chose not to for my own reasons, but that doesn't mean they must share my thoughts. 



> Anyway, the basics........big balls make big grinds, small balls make small grinds. simple.


True--and not disputed--although not relevant to the conversation.



> Where the lifters come in, and the only place where they make a difference, is in larger feedstock say 1/2" or larger material. Lifters and big balls reduce larger material faster in a big mill, and don't let anyone fool you, Lifters make quicker work of larger feed at ANY speed.



If you run slow enough that they are required, the mill won't turn as many times as it should, so in spite of the lifters, production is slower than if they were not needed. Balls do exactly as they should when they operate at the proper speed, which is lift to the top, where they are dropped to the bottom, hopefully without anything to deflect them from hitting the charge. 

You get the illusion that you got increased production because that wasn't happening, but had you increased the speed of the mill, you'd have achieved even better results----more blows per second--more work accomplished. Simple. 

Returning to the subject of large balls, what you had to say is counter to logic. Large balls have an even greater chance of hitting a lifter, which, in turn, offers protection to items that fit between the sides of the lifter and the radius of the large ball. The ball does nothing, although the rapid motion of the ball mill keeps presenting the items over and over, so they are eventually crushed. It's called a loss of efficiency. Sure, you get the job done, but what might take 15 minutes may have been accomplished in ten. 



> A production operation needs a series of mills, to produce a fine grind, say 300, 400, 500 mesh which is required to achieve liberation on many ores, you need small balls. Our finish mill has 1/2" and 3/4" balls only, AND NO LIFTERS,and this is where I agree with harold, on the fine grinds your rpm's must be exact, and lifters actually get in the way.


Funny. You can see the obvious about balls bridging the lifters when the balls are small, but not when they're large? Did you do well in physics? It appears to me you likely did not. 

Regardless of ball size, there is an optimum speed at which a ball mill can operate. If the charge is correct, the balls are lifted, in an ongoing basis, to the apex of the upper curve, at which time gravity causes them to fall. It is a perfectly smooth and ongoing motion, where there is maximum efficiency, not interrupted by lifters that alter the process. Under ideal conditions, the balls fall to the shell (for maximum impact), where there are no balls present to deflect the blows. The longer drop, albeit slight, increases velocity of the ball, yielding a greater impact. That's where the charge is critical. When these conditions are correct, maximum crushing is achieved. I don't give a rat's butt if you're running 6" balls or 5/8" balls, that's the way it works. 

Do not escalate. This discussion is closed. 

Harold


Edit.
There was escalation, which was deleted. This individual has been banned.


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## bswartzwelder (Jan 22, 2012)

Sorry about all the frustration adding lifters has brought to this discussion. There are several points I would like to make. I agree that in a perfect world lifters are not a necessity. However, when researching ball mill speed, I found several equations for calculating ball mill rotation speed. The results did vary over a range. To add more confusion, some places stated that the operational speed is usually 65% to 75% of the ideal speed. That, to me, seems strange. If there is an ideal speed, why reduce it to an operational speed?

Also, while I do not dispute it, I question filling the ball mill to 40%. If you have too much in the mill, don't the balls just drop and hit the charge of materials? If there is that much material in the mill, I would think the level of the charge would add a cusioning effect to the dropping balls. I fully see that the diameter of the balls would definitely not crush any material down near the bottom of the lifter because balls cannot get into the fine corners between the barrel and the lifer.

I do really like the idea of using variable pitch pulleys. I hadn't thought of that. Once I get the mill partially completed, I will determine the ratio between the barrel diameter and the drive pulle diameter. From that, I'll be able to calculate the diameters of the motor drive pulley and the pulley on the barrel drive shaft. The original calculations for a 1725 rpm motor and an 18 inch drum means I'll have to ratio it down something on the order of 37.5 to one. For my system, that seems like a lot for a single pulley system. Therefore, one variable pitch pulley on the motor to slow down an intermediate shaft, then a different (fixed pitch) pulley on the intermediate shaft to drive the circumference of the barrel. 

Many thanks to all who have given ideas or thoughts to what needs to go into this project. Once finished, I'll try to post a video of the mill in action. I will put a temporary end plate made of plexiglass on so I can actually see what's happening inside as it's running. I was off work for almost a year and a half due to completely tearing both rotator cuffs. Very painful and limiting to what I could do. I went back to work on January 9, so I don't have much time to allocate to projects or hobbies. I hope to retire later this year and get back to some serious work involving gold.


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## Photobacterium (Jan 22, 2012)

Harold_V said:


> > disagree or not , I am stating fact.
> 
> 
> Yes, you're stating fact---that you welded in lifters. You are not stating fact that they are required. I see no reason why your experiment should reduce the validity of published information that I found to be deadly accurate. The only fact here is that you use lifters. It does not prove that they are required, which is the point at hand.



i like watching the pro's debate.

for a drum geometry, does it make sense to install a window on the ends, so you can see what speed works best ?

or can you tell just by listening, and by doing test-grinds ?


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## qst42know (Jan 22, 2012)

> The results did vary over a range. To add more confusion, some places stated that the operational speed is usually 65% to 75% of the ideal speed. That, to me, seems strange. If there is an ideal speed, why reduce it to an operational speed?



You calculate "critical speed" not "ideal speed". Critical speed is the RPM where the balls will not drop, they are held to the diameter by centrifugal force. From reading the balls should fall away from the drum at about 60 degrees above the center line, near 1 O'clock on a clock face.

Ball size, drum diameter, charge volume, and wet or dry, all effect the operational speed. Something below critical speed is the point of efficient grinding as I understand it.


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## bswartzwelder (Jan 22, 2012)

The plexiglass window is just a temporary thing so that I can adjust the final rotational speed. The end of the drum will have a 3/16 inch thick solid plate once I set the final rotational speed. I thought the balls were supposed to drop at the 11:00 position. OOPS, my mill was turning in the opposite direction (LOL).


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## qst42know (Jan 22, 2012)

This is the best video I have found on what is going on inside a ball mill at various speeds, in slow motion with no lifters. 

If you don't like German techno music mute this right from the start. :mrgreen: 

http://www.youtube.com/watch?v=O2-gg0C2Asw&feature=related


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## Harold_V (Jan 22, 2012)

To clarify, one of the purposes of this forum is to dispel bad information. The argument is not about using, or not using lifters, although it's clear that they are not a requirement. For a reader to have made a blanket statement, that they must be used, leads others down the wrong path. That's exactly the thing we try to avoid here. You think lifters are needed? Fine. Use them, but don't make public statements about their need, as if there's not an alternative. There is, and following the guidance from those who have gone before us clearly proves the fact. 

We don't ban people on this forum if they have a willingness to cooperate. They are banned when they are unable to coexist with others, and refuse to follow board guidelines. Had this individual posted in such a manner as to suggest that he needed lifters, that his ball mill's performance was enhanced, I'd have had no issues with his comments. That's perfectly acceptable, so long as good and proper information is not dismissed, as it was in this thread. Lifters are one of the ways one can correct for improper speed. To lead others to assume that is the only solution is a disservice to those who might wish to "do it right". 

Hand out your information, then expect it to be scrutinized by those who know. If you're wrong, be capable of being corrected. 

Don't want to do that? 

Don't post. Because sure as the sun comes up, stupid comments are going to be challenged. That's what we do here. A combative attitude, as has been displayed, is a sure trip to the banishment file. 

Harold


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## wwbd (Jan 23, 2012)

Photobacterium said:


> Harold_V said:
> 
> 
> > > disagree or not , I am stating fact.
> ...



i like watching the pro's debate.

for a drum geometry, does it make sense to install a window on the ends, so you can see what speed works best ?

or can you tell just by listening, and by doing test-grinds ?[/ote]
There are no pros here, don't ever disagree with the mods you won't last around here


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## Harold_V (Jan 24, 2012)

wwbd said:


> There are no pros here,


Sorry, but that isn't correct. On this forum you will find over 100 years of refining experience, almost all of which comes from individuals that have worked in the industry, and, included amongst our midst are well educated people. You will, *indeed*, find pros here. 



> don't ever disagree with the mods you won't last around here


You're wrong about that. If you find moderators in error, you not only _can_ speak out, you should speak out. In fact, it's as if you have an obligation to do so. None of us are beyond making errors, so we should be scrutinized every bit as much as any other reader. You find something wrong, posted by a moderator? Post your position, presenting your thoughts in a mannerly fashion, and provide cites if you have them. Do so politely-----it isn't a requirement that you, or any reader, acquire the stance of an antagonist. No one is chastised, here, for speaking truth and honesty---it's when moronic statements are made, such as were presented in this thread, that things get ugly. 

I'd like you to pay attention to one thing I said---the part about all brown dogs biting. Do you think they do? 

I don't. 

The individual in question used his example as the example for the world, and didn't judge the problem correctly. That's not an issue, for anything that could be done to rectify the poor performance of HIS ball mill was his decision. However, to have rectified a problem without addressing the cause doesn't constitute being the sole resolution to an issue, as was implied. I know from personal experience that if the formula for proper speed is applied, a ball mill works exactly as it should. To have an individual discount that information isn't acceptable. Not because I said so, but because it is well documented to be true. If presenting facts doesn't work, and an adversarial attitude is forthcoming ("I don't understand your mean spirited attack, but for the sake of someone reading this and wanting to know how about mills, I guess I have to stand up to you and defend myself, even though its seems pointless to bicker"), something must be done to rectify the misinformation. If the OP isn't willing to listen to reason, he forfeits his privilege of being on this forum. I stress that it is a *privilege*. No one is granted the right to be here and be disruptive or disrespectful. 

Mean spirited attack? A response that proper speed will rectify a problem with a ball mill is a mean spirited attack? And a need to "stand up to you" is required? Pointless to bicker? Indeed it was! There was nothing about which to "bicker". A simple acknowledgment that increasing speed will rectify a problem is all it takes, and that requires no bickering. 

What was required is that the individual in question should have listened to what had been said, and acknowledged that there may be more ways than adding lifters to a ball mill to solve the problem at hand. 

"Standing up" to a moderator, one that is here to ensure that the forum runs smoothly, without rancor, is not my idea of handling an issue as an adult. That was proven nicely by the multiple registrations of this individual, and the filthy language he chose to use on the board (need evidence? See the Members list, page 446, number 22299. Yeah, same guy). It's obvious he has no respect for others. We don't want people like that on the board. 

To be clear, as a moderator, it is my duty to ensure that less than proper information is not allowed to stand. The majority of our readers are here because they've already been lead down the path of ignorance, mislead by others, most of whom would have been better served to have been striving to learn instead of teaching others. 

You can learn a great deal from the events of this thread. Come to this forum with the right attitude and it can be one of the best things in your life. Come here with a horseshit attitude and it can become very unpleasant. 

Harold


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## butcher (Jan 24, 2012)

I see many many professionals on this forum, a few of them are the moderators, these are not the only professionals, there are many, and in many different fields, many of these professionals, have Knowledge gained through many years of on hands experience in their field of expertise, and education, in all the forum has a very wide base of knowledge to gain an understanding from, and in my mind this forum is the best University in the world for learning about gold refining, and it is also very valuable resource on the recovery of gold from ore to electronics and other scrap.

There are many University teachers here at this University, and many students (the teachers are also students of this university), (and the students also teach the teachers).

Here on the forum we expect those who teach us to be correct in their information, if not we the students can and will question them on it, you will find the respected teachers can easily prove their points, if they cannot these good teachers are not so high and mighty to admit they may be wrong on a point in there information, and learn from the student.

Sometimes we can believe something so strongly (whether it is correct or not) that it is hard for others to change our mind about it, these times the debates may get heated, but as long as they are held in a polite non-combative, and respectful manner, we will all benefit in the end when the dust settles.

I am just so glad to be a member and student at this Gold Refining University. And am also so glad to have the professors we have here on this forum (moderators, all members, even our newest members) I learn so much from all of them, they all have experience in such a wide range of fields, and all bring something to the pool of knowledge and understanding.


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## trashmaster (Feb 2, 2012)

Butcher man that was well said ;;  

I hope all the mods read that and of course NOXX, He might even even change the name of the forum from GRF to GRU.. or GRUF :roll: 

Thanks again for that post it was well said.


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## ericrm (Mar 6, 2012)

can someone help me figure out about how much material will i have to put in a ball mill of 19inch diameter and 20 inch wid
also at what speed i will have to make it turn?


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## ericrm (Aug 29, 2012)

i have probleme with my ball mill...if anyone have a clue about my probleme and how to solve them

i want to pulverise material to chalk like powder...
i have no way of testing the speed but by my calculation when build i was in the correct range...  note for those with a brain similar to mine ... to know the speed ,just count them in 1 minute...  

it cannot seem to powderise correctly, i have tryed it with many thing from burned material to ceramic cpu and each time im left with big chunck of material..
my probleme are clearly from the conception(im not an enginere, everything made by myself mr clumbsy...) i cannot put enuf steal in it because the motor slide on the strap and/or freeze. i was wondering if 110v motor is realy strong enuf(i dont have the choice to use 110v...)
ring now i have around 15 1-2inch by 2-3inch cut steal stud but is only cover the boton the the mill even with material...

if you know how to improve it ,i will apreciate any info




edit i think one of my proble is because i dont have enuf ball ,the breaking is done when material is hited between a ball and the cylinder rather than between the ball, because of that when im starting it with material it work and do its job but as soon i have pulverised material this material act like a cushion refraining the hiting action... what you think?


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## butcher (Aug 30, 2012)

Hitting a snag is just part of the fun when your building something, your ball mill is looking good now you just need a little more to get in working the way you want it to,

What I see is a very small pulley on the motor, this small surface area for the belt will not provide much friction for the belt when trying to turn the large heavy drum, the motor speed is probably so fast that the motor pulley will just spin and burn the belt (slipping at the motor pulley, which would probably burn the belt at this spot, before the large drum could begin to move), I would think the motor is strong enough to turn the drum but you do not have a large enough pulley to provide the traction.

Changing the pulley on the motor may help, but a bigger motor pulley would also change the speed provided.

If this was my project I would look at several options, changing motor pulley, and possibly adding a drum pulley on the shaft of the drum (I am assuming the drum shaft is welded to the drum), a larger motor pulley and sizing the drum pulley to give the required speed, with this you could also change the type of belt (v-belt and pulleys would provide more traction).

An option to consider is changing your motor pulley and have the motor turn a pulley on another shaft, this shaft also has a pulley on it to turn the drum (adding this intermediate shaft with two pulleys, basically like a transmission between motor and drum, the motor pulley, belt and shaft pulley for the motor can be different from the drum pulley and belt on this intermediate shaft, you could get any speed desired from choosing the pulley sizes.

I would probably also consider other options also like maybe getting a reducer gear box from an old commercial dryer, or other piece of equipment, even something like an old lawn mower transmission to give the power and speed needed, the pulley sizes can also be chosen with these to get the speed desired, also DC motors are very nice as they are easy to change the speed and you can vary the desired speed needed, they can be run from Alternating current by using diodes to get the current converted to direct current (diodes would need to be sized big enough to handle the current).

Gear chains are another option to consider you can weld gears on to sleeves for your shafts, gears and chains from an old bicycle’s (a ten-speed bicycle could give several gears to choose from)

I hope this gives you some ideas, for improving your ball mill.


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## rusty (Aug 30, 2012)

Take another look at Harold's mill, he has a jack shaft between the motor and drum. Small pulley on motor drives onto a larger pulley on the jack , reduced once more with another small pulley on the jack driving the drum.

My best guess is that Harold's mill was running well below 50 rpm


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## ericrm (Aug 30, 2012)

those are good tough.
i think i will change my motor to make it 1hp rather than 1/2hp, hoping that this will allow to run the mill half full of material.
im also thinking if theyr is a minimum size for the cylinder(barel) to work properly? would 12 or 14 inch diameter be enuf??
and i think i will folow your advise butcher on the new ballmill and put 4 or 6 pulley rather than just 2

good news i found real steal ball (the round one :lol today rather than my cut stud...


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## qst42know (Aug 30, 2012)

Might be a trick of the camera but It looks like your belt is upside down, at least if that is a V-groove pulley.


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## ericrm (Aug 30, 2012)

qst42know said:


> Might be a trick of the camera but It looks like your belt is upside down, at least if that is a V-groove pulley.



no it is a car strap ... :roll: but it did the job in this setting...


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## ericrm (Aug 31, 2012)

i have found on wiki the equation to count critical speed
nc=42.29/√d
in my case i will make the barrel 12 inch
so we have 
nc=42.29/√0.3048
nc=76.6

is this sound ok?
also wiki said the ball mill use should be around 75% of nc, but i have read somewhere else that the speed should be 65% of nc. so i guess that if im between 65% and 75% i will be ok?

76.6rpm x 65% = 49.79 rpm
76.6rpm x 75% = 57.45 rpm

what you think?


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## goldsilverpro (Sep 1, 2012)

Here's a thread on which this was discussed

http://www.goldrefiningforum.com/phpBB3/viewtopic.php?f=40&t=3107&p=27909&hilit=ball+mill+rpm#p27909


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## ericrm (Sep 1, 2012)

thank you gsp ,that post has confir m my calculation 8)


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## ericrm (Sep 8, 2012)

a picture of the new machine ,still in progress.
the strap still slide so im looking for a bigger pulley


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## butcher (Sep 8, 2012)

ericrm,

That is looking good, is that a gear reduction between the motor and the idler shaft?


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## ericrm (Sep 8, 2012)

yes , ive been lucky enuf to find 2 real cheap ,here is the final product


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## butcher (Sep 8, 2012)

Nice


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## ericrm (Sep 8, 2012)

thank you
im happy with my work, i will know for sure tomorow if it powderise material as expected


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## butcher (Sep 8, 2012)

Keep us posted.


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## rusty (Sep 9, 2012)

Here's an idea for those wanting to build a ball mill, I just wrecked out an old Cub Cadet Zero turn mower you may find similar hydrostatic drives on other mowers.

Each rear wheel has it's own independent pump and drive motor, the beauty of hydrostatic is that the motors have plenty of power with fine control over the RPM's, you have several options to drive the drum.

You could use the tire as a friction drive, or remove the tire and add a chain sprocket or V-pulley in place of the tire or make a drive shaft to direct couple your hydrostatic drive directly to the drum. Speed control is easily controlled with the touch of a lever as is forward and reverse.

Most machine and jobber shops make up hydraulic hoses with any end fitting you may require at a fairly reasonable cost. No I'm not planning to make another ball mill just throwing the idea out there for those of you that want a cheap mill.

You can use an old 20 lb propane tank for a hydraulic oil reservoir, run the tank about 2/3 full and make sure your return line is well below the oil level to avoid foaming. Any air in the system will cause cavitation and over heating. For a system this size you shouldn't have to worry about an oil cooler. 







Best Regards
rusty


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## butcher (Sep 9, 2012)

Three point ball mill for my tractor :twisted:

make a good cement mixer also.


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## rusty (Sep 10, 2012)

butcher said:


> Three point ball mill for my tractor :twisted:
> 
> make a good cement mixer also.



The typical P.T.O. shaft can wrap up 424 feet of shoe lace in one minute at 540 rpm, or 785 feet of shoe lace at 1000 rpm. How long is your shoe lace?

A bit fast for a ball mill, you would need a reduction of some sort.


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## ericrm (Sep 11, 2012)

i have had many issue(this is also why my final answer is so late)solder breaking, chain poping, and material leaking ... but for now it seem to work 8)


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## butcher (Sep 12, 2012)

ericrm, Your making good progress, just a few more bugs to work out.

Rusty, I do not have shoe laces on my boots, and I am not going to get my boot twisted up in that tractor PTO. :lol: I do like the idea of a hydraulic ball mill.


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## DONNZ (Sep 12, 2012)

YouTubing the other day and ran across this video. 

Muffin Monster 

http://www.youtube.com/watch?feature=endscreen&NR=1&v=ibEdgQJEdTA

‪This Machine Destroys EVERYTHING‬


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## etack (Sep 12, 2012)

I have a question why no use a variable controlled motor? AC or DC AC is more expensive but any moor with brushes will work think electric lawn mower allot are thrown out now and many work. some dryer motors are variable speed motors. How about a treadmill motor some are real strong they move a lot of weight. treadmills are given away around me. I will have o get me one to try it out.

There may be reasons why this wont work so please share them.

Eric


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## ericrm (Sep 16, 2012)

sorry i just understand your post now.
the most of the 110 motor i have seen where ac, and even if on the short time putting ac motor on a dimmer will work,you will kill the motor (from what i have read). now dc motor aint cheap and i dont know electronic enuf to make myself a systeme like that... in my case it realy is because of the lack of knowledge and the money saving...


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## butcher (Sep 16, 2012)

DC motors can be run off of alternating current using diodes to convert the AC to DC, the speed of these motors can be controlled by adjusting the voltage to them simple as resistors or more complicated using electronic circuits.
The diodes and resistors or other components are sized to be able to handle the current going through them. 

AC motors can be run with adjustable speeds but the circuitry to do so is much more complicated, simple light dimmers could not do this, Ac motors sometimes have wiring for different speeds, but these are usually fan motors (not motors that have a lot of starting or running torque). 

Three phase motors can be run off of single phase power, using capacitors banks or pony motors as phase converters.

Gear boxes, or pulleys, are also a good way to change speed or torque. 

Lawn mowers are made to turn a blade fast, but would not have much torque, same with a dryer motor. the tread mill can possibly use a DC motor and gear box, with an motor speed control circuit, Hey it would probably have a circuit to measure RPM also.

The treadmill would be a good idea, when taking it apart make good notes of where those wires go, check online for schematics also.


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## etack (Sep 16, 2012)

I was also thinking of the mobility scooters They seem to have a lot of toque. Some of the people using them are quite portly. the motors are quite large on them. sometimes you can find them for parts on craigslist. tread mills are proboble the cheapest route. If you get a treadmill with a sliding speed controller you should be all set. one with button controls will be more difficult to use if you don't make a panel for it.



butcher said:


> AC motors can be run with adjustable speeds but the circuitry to do so is much more complicated, simple light dimmers could not do this, Ac motors sometimes have wiring for different speeds, but these are usually fan motors (not motors that have a lot of starting or running torque).



You can get a variable speed controller cheep http://www.google.com/products/catalog?q=variable+speed+controller&hl=en&prmd=imvns&psj=1&bav=on.2,or.r_gc.r_pw.r_cp.r_qf.&biw=1280&bih=655&um=1&ie=UTF-8&tbm=shop&cid=9122903117452595909&sa=X&ei=d4dWUOS8N4Lv0gGV6YCYDA&ved=0CIQBEPMCMAE This should be all you need Its unlikely your motor will pull more than 15amps.

This is a link to an ebay sale that you can see the motor http://www.ebay.com/itm/Pride-Celebrity-X-Mobility-Scooter-Trans-axle-Motor-electric-brake-Wheels-Tires-/150898889840?pt=LH_DefaultDomain_0&hash=item2322465470

Eric


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## butcher (Sep 18, 2012)

The speed controller would work for some types of fan motors, these fan motors would not have much torque, that speed contol would not be good to use for many of the AC motors, not all of the AC motors work the same, I think that speed controller is just like a light dimmer using an SCR circuit.

DC motor and gear box on that mobility scooter would be great if you could get it for almost free.


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## grance (Sep 18, 2012)

I have been reading alot of post about ball mills and such on here and wanted to put this possible idea out there. My dad reloads a massive amount of rifle ammo and he uses a wheelbarrow type cement mixer and a sand looking type stuff to clean the cases first. I would guess you could use it as a cheaper ball mill it was only $150 in Master tool catalog. He use hardware (1/4" steel screen) mesh on a frame he built and 2 5 gallon buckets to filter the cases and the sand from eachother. Just replace the sand with steel balls and the rifle cases with what ever you want smashed up and plug it in I would guess.


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## butcher (Sep 18, 2012)

I grind rock to mud in my old thick metal barrel cement mixer, the larger rocks act as the balls do in a mill, when the mud builds up this is dumped and washed in a tub of water, screens are used to remove fines from the coarser material, the material is sieved for size an returned to mixer, larger rocks added as needed, the smaller material is sluiced, then panned.

This works ok for ore, the speed is just right bringing the rock to the top and dropping them down on material in the center, but not as good as a ball mill.


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## ericrm (Sep 29, 2012)

my ball mill is dead, i was looking to build a new one but i have discover this...
apparently i have eated my gearbox gear.... does someone know if i can change that part for cheap(i have no knowledge about that particular subject...) or should i look to change the whole thing?


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## bswartzwelder (Sep 29, 2012)

I had the same thing happen to my cement mixer. It was only used to mix cement and nothing else. An Internet search sowed I could get a replacement gear. It was pretty cheap as I recall and made of nylon, just like the original. I replaced all the bushings at the same time. Try a Google search of the cement mixer make and model and good luck.

Bert


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## nivrnb (Oct 3, 2012)

I was looking to purchase some ball bearnings to use at a local store and they where expensive. So what I ended up doing was getting the roller balls out of old mice. Has anyone used the balls from old mice?


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## goldsilverpro (Oct 3, 2012)

ericrm,

I have seen ball mills turned on 4 heavy duty solid rubber wheels mounted on a heavy duty frame. One shaft turned freely and the other shaft was driven - by heavy chain, if I remember right. Maybe not.

___________________

nivrnb,

Since ball-milling is a crushing mechanism from the balls dropping onto the material from the apex, you need good-sized heavy balls. I can't see those tiny mouse balls doing anything except burnishing the parts.


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## etack (Oct 3, 2012)

I just bought a MagneTek AC Speed Drive Control that changes the frequency with voltage of 60.00us shipped. I think that this will be the easiest way to get my RPMs right.

It runs on 240v and that OK I can find a .5-1 HP motor around for next to nothing. Max sure when you buy it you have the right voltage available to you. Some are for 480, or 408 ,some are for 115 just make sure you look. I didn't till I won  but I'm luck cause I have 220v in the garage.

With all this manufacturing closing or has closed there is allot of this stuff in commercial liquidators stores. Had I know what they were before I wouldn't of had to buy one I scraped Three last year. 

Eric


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