taiwanluthiers Posted June 23, 2012 Posted June 23, 2012 It just needs a set of pulley and belt, otherwise its finished. The motor is 1/4 HP, probably came from a drill press or something. I used 1/2" aluminum rod as shaft but the weird thing is, while rod stocks are all imperial bearings are all metric, leading to some serious fit issues. I sanded the aluminum rod down with a belt sander to get it to fit the bearing, and kept the sanding dust for use in whatever pyrotechnic composition.
marks265 Posted July 2, 2012 Posted July 2, 2012 If you haven't bought bearings for the other side I would try to match them correctly and use that shaft to drive with. If there are no keyways in the shafts I would also drill a dimple into the shaft for the set screw on the drive pulley and shaft. You are surely on your way with the mill. Another option is to hang the motor on a hinge from the verticles so that motor adjustment for belt tension or pulley change is easier. Keep us posted of course. If you're really bored put some wood glue on the joints you screwed together and by the time you're done you'll be spinin' big jars!. Mark
taiwanluthiers Posted July 4, 2012 Author Posted July 4, 2012 (edited) Finished and running. Yes the belt is a bit loose but it doesn't matter... the pulley turns fine as it is, and I am not running such a big load anyways. Edited July 4, 2012 by taiwanluthiers
graumann Posted July 4, 2012 Posted July 4, 2012 It should be easy enough to put a small tensioner pulley on the frame at the side there to stop the belt slipping when it warms up a bit
taiwanluthiers Posted July 4, 2012 Author Posted July 4, 2012 Been running for nearly 3 hours, still good. I have to think of what to use for the tensioner because I don't want to buy another pulley + bearing... its pricey enough already.
marks265 Posted July 4, 2012 Posted July 4, 2012 The cheapest way to tension the belt is to mount the motor 90 degrees from what you have and let the weight of the motor swing on a hinge to create the tension. Mark
taiwanluthiers Posted July 5, 2012 Author Posted July 5, 2012 A question... It seems it would be safer to do a 3 component milling by slightly dampening the powder, then the resultant paste can then be corned or riced. Is it possible to do this on a ball mill? I notice there's always a problem with the powder caking onto the container while milling...
Shadowcat1969 Posted July 5, 2012 Posted July 5, 2012 A question... It seems it would be safer to do a 3 component milling by slightly dampening the powder, then the resultant paste can then be corned or riced. Is it possible to do this on a ball mill? I notice there's always a problem with the powder caking onto the container while milling... I seem to remember reading in another thread that BP becomes more impact sensitive when dampened (I think it said 6% moisture was the magic number for maximum sensitivity), which would not be good when running in a mill. I also remember other threads talking about caking in the mill and that the way to get away from that is to make sure your components are all TOTALLY dry immediately before placing them in the jar, that moisture is usually the culprit when caking occurs. I haven't had any issues with caking in my mill, but I live in a climate with very low humidity naturally.
Mumbles Posted July 5, 2012 Posted July 5, 2012 6% is going to cake very badly. I'll see about finding the actual original source for the sensitivity statement, it is however fundamentally true. Somewhat moist is more sensitive than bone dry. I thought the actual value was much lower on the scale of 1-2% or less even, but I don't recall the details. At some point the sensitivity does decrease again as it becomes increasingly wet. I believe that it's the sensitivity to static that increases as well. It is good to be safe and take precautions. However the fact of the matter is if you're working in an area that could not handle an explosion, you really shouldn't be working at all. Every operation, no matter how careful one is has the potential to go catastrophically awry.
Timm Posted July 10, 2012 Posted July 10, 2012 7% rings a bell, but its a small one from way in the back.. Was it from that really old (and equally awesome) reference someone put up early this year? It was scanned from the original and was hard to read almost, but filled with good info, section focused on charcoals maybe
Mumbles Posted July 10, 2012 Posted July 10, 2012 I think I found the source I was looking for. There is an excerpt from a book that is circulating around the internet as "The Chemical and Ballistic Properties of Black Powder" that states the sensitivity is to flame/temperature and it peaks at 1%. It references a handbook called "Ordnance explosives train designer's handbook". There is a diagram on page 2-22 of that handbook that I am assuming this statement came from. It looks like potassium nitrate based BP peaks around 1%, and sodium nitrate peaks around 2%. There is another peak for potassium nitrate based "blasting dust" which looks to peak around 5%, however it appears to me that it doesn't really peak as much as it just stays sensitive from 1-5% instead of falling off like most of the others do. There are some data points that fall significantly off the fitted line as well, so I'd take the data for this material with a large grain of salt.
Col Posted July 24, 2012 Posted July 24, 2012 Good job on the mill. You can usually recycle a tensioner arm, pulley and spring complete from a broken washing machine. I would add a bit of ply or something similar underneath the top timber frame to catch any errant dust.
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