Monday, November 7, 2011

UABMM2 New Mount

After the disappointing test of the UABMM2 last week I was ready to stop working on it.  A large amount of work and money had been expended on it, and there were no results to be had.  So after a few days of being disappointed I realized that the potential of this device is great, and this was really a small set back.  So I began gathering materials to build a new, stronger mounting system for the UABMM2.  The shaft needed to be much stronger, but also the way that the rotor mounts to the shaft needs to be much stronger.  Here is a shot of the new materials.
I am doubling the size of the shaft, from 1/4 inch to 1/2 inch.  Then we'll need 1/2 inch bearings, and new bearing mounting plates.  The hardware to hold the rotor was a bit of a puzzle at first, but after some research I found a split taper bushing.  A split taper bushing is designed to hold a pulley, sheave, or sprocket to a shaft.  Its a hefty chunk of metal that has a precise hole in it for the shaft and then a couple of grade 8 screws to hold the rotor to the bushing.
For the bearing mounting plate I used another couple of AMS4051, or 6061 Aluminum, 1/4 inch plates, the same plate that is used to fabricate the UABMM2 rotor, and stator.  They are high tensile strength, and are also fairly easy to machine.  Both plates will be identical, so I can machine them concurrently, which will also let them be identical after they are machined.  I had marked up the plates a couple of days ago, and got them on the Mini-Mill last night.  In this pic I am spotting the holes using a 1/4 inch, 90 point, M42 Cobalt spotting mill.
When I am spotting I clamp a fence to the machine table to help get everything square.  Then I use the cam action table clamps to hold the plates to the table.  I am using the same sacrificial block that I had used on the UABMM2 plates so the holes will line up when I assemble the stack.  After spotting I bored out the holes to 1/2 inch with the step drill.  Then I am using the sacrificial block to hold the stack together while I machine the shapes into the plates.  So I needed to countersink the holes in the corners on the back of the sacrificial block to accept the grade 8, 1/2 inch, countersunk machine screws that hold the stack together during the machining process.
The pivot stud in the middle of the plate is jammed into the table so it won't move.  It is the center of the radiused cuts, while the cam action table clamps keep everything tight during each individual cut.  The alternative to doing this is getting a Rotary Table, which are pretty expensive.  This is my low cost work around.  Now the stack is assembled, and the table is set up to do the radiused cuts, and the next time I can get to the shop I am ready to start cutting the new bearing plates.
I also got a piece of the 1/2 inch shaft cut, and fitted the split shaft bushing on to it.  I need to machine a slot in the shaft for a 1/8 inch shaft key to lock the split taper bushing on to the shaft.  So I made good progress yesterday in relatively little time.  Can't wait to get back to the Metal Shop...

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