So, it's been busy the last couple of days, to put it mildly...
We've been working hard on #2, we made the second rotor, wound all the coils and installed them in the frame and bored a hole through the shaft lengthwise (24" long!!).
Then we put the whole thing together and ran some tests.
The machining did not go without incident, drilling a hole that deep is far from trivial (as I've found out), it took forever. Peck 1/8", pull drill all the way out, flush the hole, clean the bit, oil everything for the next peck, back into the hole and so on. It took 4 hours for that one hole...
The machining of the rotor was also lots of fun, at least it was until the parting bit broke when we were cutting it to size as the last operation. It jammed, broke off, then the fragment jammed, then the whole toolpost got ripped off it's mounting bolt. Very impressive that lathe ! Pretty hard to stop at low revs...
The good news is that the workpiece wasn't damaged, so we hacksawed through the last little bits, and cleaned up the side with an outside bit.
Then I machined the flats on the rotor while Johannes was busy winding the coils and inserting them into the stator.
That was tons of work, but late Friday evening we had it all done and put together, and it looked like it was going to work just fine. Hardly any cogging noticeable, but I'm sure that it can still be better.
The test results are a mixed bag, I blew up the fet booster circuitry through a stupid error (not enough supply voltage on the pulse circuit), so we'll have to wait for another time to get low rev data, higher rev data is: 300W@240 RPM, 930@343 RPM, 1860W@480RPM. We were trying for a 675 RPM reading, but that threw the breaker on the trace inverter so we won't be testing it that fast, at the moment the breaker tripped we were doing about 60A into the batteries, or about 3KW. Pretty impressive to see that little motor stall a 3:1 geared down 1750 RPM 2HP motor !
240RPM is of course a ridiculously high cutin speed, and we still haven't reached the 2.4 KW (so I officially owe Dan $5 now, at least on the basis of these figures...) but it's fairly decent power from a frame this size, though I'd hoped for more.
Each coil is 70 wdg, three of them are seriesed and six of those sets have their leads brought out. These measurements were all done in 'delta/parallel', when I get back I'll run another test using 'star/parallel', then we'll take this machine off the lathe and put Zubbly's on there for a side-by-side comparision.
The 18 coils are excited by 24 1x2x1/2" magnets, for the precise arrangement see the photographs below and the cad drawing in one of my earlier diary entries.
Starting of the drilling of the hole for the inside work:
Boring it out to final diameter, 50mm:
Cleaning up the outside:
Parting off the excess: (this was about 30 seconds before things went really really wrong, I don't have any pictures of the wreckage, I had other things on my mind at the time...)
Finished rotor blank:
Drilling the holes to mount the rotor on the indexer:
Johannes starting on the winding of the coils: (notice the cheerful smile here)
Centering the bore on the indexing table:
Milling the sides:
The stator is filling up nicely:
Finished rotor #2:
Pressing on the second rotor:
Johannes nearly done with the coils: (notice the psycho look, compare to the picture above)
Both rotors side by side:
A view of the magnets glued to the rotor:
Epoxied in, waiting for the epoxy to set:
The last three coils on the pegboard:
The finished rotor:
Inserting the rotor:
The rotor in place:
Test setup:
A single coil on the scope:
Everything in delta-parallel, a single leg on the scope:
Another view of the test setup:
