24 Sep
2009
24 Sep
'09
2:11 p.m.
The conversion of the drives we did for shipment to
south america
involved a different spindle pulley and a different belt. The belts
At least one type of drive that I've worked on (and I can't remember what
it was) had 2 sets (of 4) screw holes for the motor. They were offset by
45 dgrees from each other _and_ one set put the motor further from the
spindle pulley than the other set. To do the 50/60Hz conversion you had
to change the motor pulley, then unbolt the motor and re-mount it using
the other set of holes. The difference in distance between the 2 pulleys
meant you used the same drive belt for both frequencies.
were located locally here that were equivalent to the
CDC drives prior
to any conversions we did because they sold them for such a ridiculous
price.
the motors themselves were strapped easily to run on the different
frequency and voltage, as I recall. However the pulley was another
IIRC most (old) DEC drives used 115V motors, and used the primary of the
mains transformer as an autotransformer to run them off 230V mains. The
frequency difference wasn't a problem for the motor, it ran fine on
either freqeuncy, just at a different speed.
matter. The ones that we got drawings for and had
duplicated were
worked from aluminum stock with quite a few processes to harden them and
form the drive surface so as not to eat the drive belt. The shape of
the pulley causes the drive belt to ride in the center when properly
done, there are no "edges" to retain it. If you have or can get
Known as 'crowning', at least over here.
It's surping the first time you see it, but the pulley is smaller in
diameter at the edges than in the mdidle. The belt runs on the largest
diameter part -- and mves itself there when the pulleys turn. If you
naively make a pulley with a smaller diamter in the middle (with the idea
being that he larger diameter edges will keep the belt in place), the
belt will fly off.
mechanical drawings of the pulley for either
frequency, I'd think you
could figure out the other. In this case maybe get the 60 hz pulley,
and scale it to the 50 hz size.
IIRC the OP has at least one 60Hz drive. Which maks life a lot easier.
It shouldn't be too hard to turn a replacement pulley. I suspect you can
get the profile either by using a form tool, or by swinging the cutting
tool as in a sperical turning attachment.
There is no adjustment for spinning the disk stack at a different speed,
it still goes at the same angular rate regardless of frequency. The
electronics are running from DC which adjusting the power supply
compensates for.
The other issue is to change out muffin fans for the 60 hz model. I
don't know if you drive has 120v (or 220v) and are AC, or run off of +12.
Jim
The RK05 has a tangential lower fan with a capacitor-run motor. All RK05s
have 115V fans [1] and AFAIK there's no change when you change frequency
either.
[1] Runn of the mains transformer as an autotransformer for 230V mains,
of course. The were wired on the 'live' end of the primary winding with
the result that the motor insulation has to stand 230V. And some don't.
RK05 blowers catching fire is not uncommon over here.
-tony