cleaning, lovejoy, black box tach, linear scales, making pulleys

1) Thanks for all the advise re cleaning circuit boards. I was
concerned that water might be too corrosive--but obviously it's
worked for lots of people.

2) I just picked up some new / surplus helical connectors. These
things do wind-up; hold one end in one hand, the other end in the
other and tweak. I din't put the thing in a fixture, use an oz-in
torque wrench, etc--but I could feel the wind-up without twisting all
that hard. I bet that with the right choice of (urethane) elastomer
for the spiders, Lovejoys will work just as well for low inertia
loads.

3) In answers to a previous post I learned that both tachs and
encoders are used in servo systems because at one time processor
speed was too slow to calculate motor speed from the encoder output.
But why do tachs persist? I understand that certain amplifiers and
control boards want a separate tach input--but wouldn't it be easier
to make make a black box which takes encoder input, calculates RPM
and outputs x volts per 1000 RPM as wanted by other components of the
system. This sounds easier, more reliable, less fussy and maybe even
cheaper than mounting 2, 3 or 4 mechanical tachs. But this doesn't
seem to be current practice ...

4) If fast responding, high resolution linear scales existed, isn't
it the case that (at least for closed loop systems) backlash, ball
screws, helical connectors, etc would all be irrelevant? Trying to
measure position indirectly from a rotary encoder seems like the root
of all evil. Maybe really high-grade scales wouldn't seem so pricey
if you didn't have to retrofit ball screws. I understand there's a
problem with table movement within the backlash zone, but why can't
the motion controller mimic a human machinist's habits of taking up
backlash when reversing direction?

5) Somewhere (maybe in this group) I read a suggestion about making
HTD pulleys by drilling holes around the desired OD and then taking a
clean-up cut on the lathe. Flanges could be screwed on ex post? Has
anyone done this? Unless I'm reading the price lists altogether
wrong, an afternoon spent this way could be quite rewarding. Of
course you'd go mad without a rotary table or index setup.

Thanks.

--Jack