Monday, September 10, 2007


I finished the subframe and got the motor properly aligned with the transmission (not so easy) and bolted everything down for a live test (without the driveshaft installed-- no driving through the shop wall). I rigged up a 300-volt DC power supply to run the motor drive, just to make sure it wouldn't complain about running off of batteries instead of its normal diet of 3-phase 240 Volt AC. It worked great. On to the powered test of the motor/transmission assembly. I ramped up the speed of the motor slowly, and everything was fine. I took things up a notch by quickly accelerating the motor, to simulate an actual load. Suddenly, the adaptor hub that I had spent a few evenings turning on the lathe twisted right in two. Oops. I had followed the design guidelines given by Lovejoy, the shaft locker supplier in machining the hub. The lock holding the transmission to the adaptor hub works by compressing a thin tubular section of the hub onto the shaft. I had my doubts that such a thin tube would be strong enough to carry the 150-220 ft-lbs (200-300 Nm) of torque Lovejoy advertised. It wasn't. Although, strictly, the shaft lock device was still securely in place, so I guess the book value was right. That's a little bit like building a ship in a bathtub, though...

Nevertheless, I shall continue! The next plan is to snag a splined hub from an old clutch disc, and attach that to the hub that is still locked on to the motor shaft, using bolts or perhaps my new bowhunting TIG welding skills.