Friday, November 04, 2016

Setback Friday

Today was hoped to be a milestone, as we were all set to install the replacement motor in the Grumman, and also completed re-soldering of a broken field wire in the Smithco trike.  Alas, it was not to be.

Prior to installation, we did a test spin of the whole assembly (motor with mounted hub, flywheel, clutch and pressure plate).  It wobbled.  A lot.  It wasn't expected to be a perfectly balanced assembly, as the clutch centering tool isn't that accurate and the heavy Rabbit MK1 flywheel with a scallop cut out for clearancing obviously wasn't high-speed balanced at the factory.   Here's the video (With apologies for the authentic mechanic's shop color commentary.)

So, as a team we discussed whether to cross our fingers and run with it, or investigate further.   Out came the dial indicator.  We all learned how to use it, and found 20 thousandth's of an inch in runout. A coupla' thou would be okay, but not 20.  So off comes everything except the hub, and we dial it up again.  Still at 20 Grand.  SIGH, ...despair briefly raises its ugly head.  One team member even said "Well what did you expect, bringing the truck to a bunch of dumb high school kids.  If you wanted it fixed, you shoulda gone someplace else!"  

We popped off the hub, which was easy because we hadn't painted the thing with locktite like the Texans did waay back during the Carter Administration when this thing was first assembled...  BUT, there wasn't a setscrew in the keyway either.   Matter of fact, the setscrew hole wasn't even tapped.  WHAT IF?
So, out came the taps, and a bolt was quickly installed.  WELL WHADDA YA KNOW!!
Upon reassembly, the hub spun true, at 1.5 Thousandths of runout.  The threads weren't tapped exactly straight on axis, and our key was fractionally shorter than the slot, so this opportunity to correct both of those situations was seized upon, and we'll reassemble it all and install on Monday.

Similarly, two teamsters had tackled a very challenging soldering job in the Smithco trike motor and managed to get the motor fields intact again.   However, it was still a dead short when we tried to do a test spin.  I now think that the field wire snapped during disassembly, as it wasn't scorched like a short should be, and the heavier-gauge motor leads showed a lot of heat...  Back to the drawing board for this motor, but we eliminated a variable.

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