pyrosailor99 Posted August 10, 2011 Posted August 10, 2011 Hi! i'm building my ball mill! i've rods, bearings and i'm going to make holes in the wood panel to place bearings. i want to know what distance i have to set between rods to place jars that have diameter between 15cm and 20cm.at the moment, in my project i set 10cm of space between center of the rods (rods ar 15mm diameter) i have also another big question.in some commercial ballmill (see picture) the rods are not placed on the same horizontal plane. a rod is upped than the secondand the upper rod, i imagine, is the rod that receive the load from the top... i intend that the jar seen from the picture perspective round counterclockwise . is this a good pratice to avoid the jar slip out the the rods? what is the suggested distance (height) between rods?
pyrogeorge Posted August 10, 2011 Posted August 10, 2011 What dimension jar do you plan to use?In my mill i put the rods in the same height without any problem..
PersonGuyDude Posted August 10, 2011 Posted August 10, 2011 That's almost entirely dependent on what jar size you plan to use.I in a typical Sponnenburgh mill, the rod on the bottom is the drive shaft.
Mumbles Posted August 10, 2011 Posted August 10, 2011 The bottom roller is the drive shaft. You can see the bolts for the motor and the protective housing for the belt in the picture. The roller spacing depends on the jar size. If you plan to exclusively use the 8" jar, I'd space them at around 5-6" of gap between the rollers. You may want to invest in Lloyd Sponnenburgh's book on ball milling. It will answer a lot of your questions and help you with design.
pyrosailor99 Posted August 10, 2011 Author Posted August 10, 2011 i have that book. Lloyd don't speak about distance S of the rods for Jars above 6'' (mine is about 7,8'') and he don't speak about vertical distance (as you see in my previous pic) of the rods...
oldguy Posted August 10, 2011 Posted August 10, 2011 My unpowered roller can be moved over to accept multiples of 6, 8 or 12 in jar.Here its set for a 12 inch jars
pyrogeorge Posted August 11, 2011 Posted August 11, 2011 i have that book. Lloyd don't speak about distance S of the rods for Jars above 6'' (mine is about 7,8'') and he don't speak about vertical distance (as you see in my previous pic) of the rods...Don't worry about the distance..it isn't so critical..In my mill i put the rollers with some tests with the jar on it..Did you find the rpm for optimum milling?
pyrosailor99 Posted August 11, 2011 Author Posted August 11, 2011 (edited) Don't worry about the distance..it isn't so critical..In my mill i put the rollers with some tests with the jar on it..Did you find the rpm for optimum milling? yes, for my jar optimum RPM is 64,94... so about 65. with the pulley and the motor regulator i can reach that speed. But this optimum speed will change as i calculated it thinkin i've got 3/8 inches media... actually i can't be sure of this... Edited August 11, 2011 by pyrosailor99
guntoteninfadel Posted August 11, 2011 Posted August 11, 2011 So how does that work? I'm turning my 6" jar at almost 100 rpm. I read on here somewhere that optimum rpm was 90-100 so that's what I used. Will it change with jar size?
Mumbles Posted August 11, 2011 Posted August 11, 2011 Yes, it changes based on jar size. The 90-100 RPM is really only optimal for 4" jars. For a 6" jar, about 75 is optimal for most commonly used sizes of media. It's largely dependent on the jar size for the general scale we work on. The media itself only adjusts it slightly.
guntoteninfadel Posted August 17, 2011 Posted August 17, 2011 mumbles am I correct to assume that this info is in Lloyds book? I really got to get me a copy.
Mumbles Posted August 17, 2011 Posted August 17, 2011 It's on page 8 for whenever you get it. It is on passfire as well under one of the ball mill articles. There's much more information in the book, but the formula for optimum speed is below: Critical Speed = 265.45 / sqrt(Jar ID - Media Diameter) Both the ID and diameter of media are specified in inches. That is the critical speed, the speed at which the media in theory begins to cetrifuge away from pile instead of cascading. The optimal speed is typically around 65% of the critical speed. This speed is not dependent upon media material or weight, only size.
gilv58 Posted August 22, 2013 Posted August 22, 2013 oldguy- I am building a ball mill myself. I just ordered a 1/2HP TEFC electrical motor which spins at 1725 RPM. I am using a 6" diameter jar so rotating speed should be about 76-80 rpm. According to all calculations I have made if I have a 1/3" diameter drive pulley i shoulld have a 16" diameter pulley at the object shaft. Is that correct? Your ball mill does not look like it has a 16" pulley at the top. What am i doing wrong?
Col Posted August 23, 2013 Posted August 23, 2013 2" pulley on the motor, 6" pulley on a 1/2" od driven shaft (3:1 reduction / 575rpm) . Heater hose or similar to bring the shaft diameter upto 3/4", a 6" jar gives you an 8:1 reduction for ~72rpm .
gilv58 Posted August 23, 2013 Posted August 23, 2013 2" pulley on the motor, 6" pulley on a 1/2" od driven shaft (3:1 reduction / 575rpm) . Heater hose or similar to bring the shaft diameter upto 3/4", a 6" jar gives you an 8:1 reduction for ~72rpm . Got it...thanks. After I thought about it I kinda figured it out after I posted. Thanks for the confirmation.
Inkyfingers Posted September 7, 2013 Posted September 7, 2013 Nicely built mill oldguy. I especially like that you built the idler rollers to be adjustable for different jar sizes.
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