[GreenKeys] Powering Series (Governed) Motors (LMU6) - 87.6 VPS

[John Spigel]

Hi Paul, good that you've been able to get the motor speed tuned. I've 
suspected for a while that you only need to get close.  I've been able 
to use my tuning fork to do the adjustment, but then questioned the need 
to have the entire shaft and assembly powered. For the printer, should 
it be run open during the test? And how about the TD? Surely the load 
will slow the motor. To determine how much would be difficult with the 
tuning fork, but how about trying with your digital tach?
As far as ozone, I wonder how much is result of deterioration of the 
filter capacitors or motor brushes. Anyone have some experience in this 
area?
73, John W1AN


On 10-Jan-24 15:00, pbirkel at gmail.com wrote:
>
> 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.
>
> *From:* greenkeys-bounces at mailman.qth.net 
> <greenkeys-bounces at mailman.qth.net> *On Behalf Of *John Spigel
> *Sent:* Tuesday, January 2, 2024 10:17 AM
> *To:* greenkeys at mailman.qth.net
> *Subject:* Re: [GreenKeys] Powering Series (Governed) Motors (LMU6)
>
> 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
>
> On 02-Jan-24 14:07, pbirkel at gmail.com wrote:
>
>     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
>
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