Thank
you John, as well as Bruce (Gentry) and Doug (Jones) who
responded directly with useful observations. I try to be a
“measure twice, cut once” sort of guy when it comes to
entering unfamiliar territory. After BRPE base disassembly,
wiring harness exploration, schematic preparation, and
general surface cleaning, I reassembled and put the LMU6
successfully to the test. Interestingly there was quite a
bit of ozone production originally (but no evidence of
sparking), however ozone production appears to have become
more moderate after ~10 minutes of running time. I can’t
recall how much ozone production to expect from brushed
motors. It does bring back some memories.
The
BRPE, just idling, is LOUD. Admittedly I don’t have a cover
for the motor area but it’s the shaft-and-punch mechanism
that’s the noise source; the motor alone just hums along. I
can’t imagine multiple BRPEs running at the same time in a
room without also imagining ear plugs. Just the one makes
more racket than most anything else around here!
Which
brings me to my next experience, assessing the governed
speed. I fired up my 87.6 VPS tuning fork (previously
unused) under a strong incandescent light and pretty much
failed to get a good “look” at the 35 spot row – just a blur
– although the 6 spot row could be seen slowly revolving so
I evidently was close to the correct speed. Obtained an
inexpensive digital tachometer and tweaked the speed
adjustment for 14400 rpm (4 spot row) after I taped off the
adjustment opening; only a half-turn speed-up seemed to be
sufficient. After going back to the tuning fork and trying
various “postures” I found that the best viewing was when
the fork was at maximum vibration, thus maximum window
periods. However mostly looking tangentially towards the
rim was more productive than trying to observe the band(s)
directly under the fork. But I did get more-or-less
stationary to slow-moving bands at last.
The
manual states “essentially stable at 3600 rpm”; just what
amount of variation should I expect both within a single run
period and then between run periods hours/days/weeks apart
(assuming constant environmental conditions)?
What
is the recommended setup & procedure for using a tuning
fork for evaluating/adjusting timing of these governed
motors? (lighting, eye placement, view angle, …)
Anyway,
as the BRPE is driven by parallel signals the exact motor
cps isn’t as critical as in a serialization/deserialization
situation. If anything the cps needs to “align” with the
controller timing/expectations for the duration of a full
revolution, and that expectation will be under software
control (Arduino) so adjustable.
Paul, Page 2 of
the manual in the B295B link states that the LMU6 assembly
is for use with AC. It likely will not be suitable for DC
with the peripheral items provided with it. So 50/60 CPS is
good. I would check for leakage and ground the base for
safety. The targets on the fan allow various ways to adjust
speed.
73, John W1AN
As
related in another thread I have acquired a BRPE21 with a
governed LMU6 motor unit.
The
motor plate states: 5PA66HV2A / Type: PA / V: 115 / CY:
60/50 / WD: SERIES
Bulletin
295B “Technical Manual for Motor Units” (https://www.navy-radio.com/manuals/tty/295B-6504.pdf)
states that the LMU6 series (governed) motor is AC/DC. I
infer that if I simply supply 120VAC 60Hz the governing
components/circuitry will have no adverse effect, but
that’s not made clear anywhere. The curved-blade power
socket seems to suggest that this installation was
intended for DC operation, so I’m reticent to simply
supply AC “and see what happens”. (Shaft turns freely and
depressing the four spring-ball oiling ports appears to
indicate the presence of sufficient light-weight oil, so
other than modest cleaning the motor assembly appears to
be ready-to-go.)
In
the TM, Figure 5 “Typical Series (Governed) Motor Unit
Schematic Diagram” (PDF page 16 of 52) is the applicable
schematic; there’s no indication of polarization at the
LINE connection. Is this correct for 115 VDC operation
(either orientation is fine)?
Can
I simply power the LMU6 with 60 Hz, 120 VAC without any
changes?
-
paul