[Milsurplus] Re: aircraft transmitter & dynamotor

[J. Forster]

Hue Miller wrote:

> I have some questions on how WW2 aircraft transmitters and dynamotors
> worked together. I have to admit i've never really followed out the full
> system schematics in the manuals to see the big picture. Maybe some of
> you who have replicated full system setups can help me out.
>
> 1. When does the transmitter dynamotor kick in? It cannot be spun up
> every time the talk button is pressed, right?

Dynamotors spin up pretty quickly, especially with a big vehicle battery nearby. The
WS 19 MK III has a vibrator for Rx and a dyno for Tx. It spins up in under 1 second,
more like 1/2 second.

> And it would be a waste of power and longevity to have it run fulltime.

In a WS 19 MK II, the dyno runs all the time, for both Rx and Tx. A typical dyno
should have a service life of 1000 to 5000 hours, and then needs new brushes and
possibly commutator and/or bearing work. That's a lot of missions. Most planes didn't
last that long in wartime.

> But i don't recall any switch
> on the control boxes for receive/ transmit. Maybe when switched to "A1"
> the transmitter dynamotor goes on fulltime for cw.
>
> I am talking about medium high power HF equipment. I mean like SCR-287,
> Bendix RTA-1, etc.
>  I can see how in some vhf set with only a few watts, like the ARC-4, you could
> run the transmit B+ all the time, no trouble.
>
> 2. How about sending distress messages, cw, via the push to talk button on the
> pilot's mic?  That would be real hard, right?

Probably not all that hard. You'd send perhaps 10 morse characters and repeat. If the
dyno were switched, it'd not spool down all that much between keyings.

FWIW,
-John

>