slipring pictures are up. The whisper set looks pretty good considering that it has been in operation for many years before a horrible crash finished the machine (I got it from Lawrence McKay, a local expert in renewables that runs a small solar/wind/hydro energy business to study while I'm rolling my own machine, I've been at it for 18 months now, many failures but I have learned a lot
. The brushes belong to the whisper sliprings, they fit in the rotating part of the housing (but the housing picture are not fit to print, it's a wreck). The wiring is in pretty sorry shape, but that's mostly due to the fall.
The machine was a whisper 1500.
The sliprings I made myself have three strands of #6 wire coming out of the bottom as well as a piece of bowden cable (not visible) to connect a winch cable for mechanical shut-down. The bowden cable would still need a 'swivel' type connection to stop it from getting entangled. I've tested them at 60 amps, 66 volts AC, no noticeable arcing. The spring pressure is pretty strong, my guess is that the material is something other than ordinary copper. Resistance of the contacts is <100 mOhm, which is about as low as I can measure with the stuff I've got here, losses should be fairly small. (60 Amps through .1 ohms is still a 6 V drop, but they are probably much better than that, I just don't have a reliable meter for mOhms). <P>
The material I used for the rings is ordinary brass stock, the gray 'goop' between the rings is locally sold as 'epoxy steel', it takes a bit longer to set up than ordinary epoxy but is much better machineable. And it does not conduct electricity, even though the name suggests it does. After setting of the glue I turned the whole thing on the lathe to make it perfectly round, which reduces the stress on the brushes. The bearings are 80 mm od, 40 mm id, they are pretty strong because the machine that will sit on top of them is quite heavy, if you are going to make a lighter machine you can probably safely make the whole thing smaller.
Note the little copper shaped pieces on the whisper brushes that match the curvature of the brushes to the curvature of the sliprings, this increases the contact area, reduces wear and decreases the resistance of the connection. You could probably try to bend the brush springs in the shape of the rings if you don't want to add the little shaped pieces with similar results in resistance but you'd significantly reduce the life (there is quite a bit of pressure on the springs to avoid 'hopping' or 'stick slip' or whatever you want to call it which would lead to arcing and very fast degradation of the contacts, that does mean a little more wear due to friction). Worst case you'd have to replace the brushes every couple of years (no big deal).
