[Milsurplus] [ARC5] Very Cool SCR-274N Modulator

[J. Forster]

The brush trick essentially reduced the strength of the field coil seen by
the armature by the cosine of the brush rotation. The dynomotor is
essentially running at reduced field, which means the rotor has to turn
faster to generate the same back EMF.

Running motors at reduced field is NOT the way to treat a motor, IMO.

-John

=============

> Jay,
>
> You can actually make a 24 volt dynamotor run at approximately the
> original
> design RPM off of 12 volts by relocating the grounded brush 90 instead of
> 180 degrees from the ungrounded one.  I did that with a DM-32 back in
> ancient
> times.  But it's a kluge.  I'd have to guess that the one in the photo was
> built for 12 volts.  Pulling the LV end bell would tell.  One possibility
> would be a DY-10 with solid end bells.  But of course the relays in the
> BC-456
> would have to have 12 volt coils as well.
>
> Makes you wonder what they called the receivers and transmitters.  As
> there
> are several of each, they couldn't just call them R-274 and T-274.
>
> In a message dated 7/19/2009 10:17:56 AM Central Daylight Time,
> jcoward5452 at aol.com writes:
>> Is a dynamotor able to be convrted to12V from 24V or is this  orginal?
>> Jay KE6PPF
>>
>>
>> -----Original Message-----
>> From: David Stinson <arc5 at ix.netcom.com>
>> To: milsurplus at mailman.qth.net; ARC5 <arc5 at mailman.qth.net>
>> Sent: Sat, Jul 18, 2009 6:57 pm
>> Subject: [ARC5] Very Cool SCR-274N Modulator
>>
>>
>>
>> Check this out:
>>
>> http://tinyurl.com/ks2hpt
>>
>> Speculations??
>>
>
> Robert Downs - Houston
> wa5cab dot com (Web Store)
> MVPA 9480
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