[Milsurplus] Arcing dynamotor brushes.

Mon Oct 9 20:24:56 EDT 2023

The 490T-1 HF antenna coupler for the ARC-94 HF transceiver was pressurized to 5 psi to prevent arc over at altitude. Worked on them years ago in the mil. Don't know if it would work with a dynamotor though.

Garrett
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Sent: Monday, October 9, 2023 4:27:24 PM
Subject: Milsurplus Digest, Vol 234, Issue 10

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Today's Topics:

   1. Re: Recognize this Dynamotor? (Ken Kinderman)
   2. Re: Interesting dynamotor fact (Jim Whartenby)
   3. Re: Recognize this Dynamotor? (Dave Merrill)
   4. Japanese Morse Code Trainer (Hubert Miller)

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Message: 1
Date: Mon, 9 Oct 2023 14:35:21 -0400
From: Ken Kinderman <scr274 at gmail.com>
To: Dave Merrill <r390a.urr at gmail.com>
Cc: Military Surplus net List <milsurplus at mailman.qth.net>
Subject: Re: [Milsurplus] Recognize this Dynamotor?
Message-ID: <6F86F145-6421-4C54-A964-23FE4E85518B at gmail.com>
Content-Type: text/plain; charset=utf-8

Could be for the ARB

> On Oct 9, 2023, at 10:44 AM, Dave Merrill <r390a.urr at gmail.com> wrote:
> 
> ?
> Any clue where was it used? Same dimensions as a DM-32.
> 
> Dave N9ZC 
> <IMG_20231009_082557061~2.jpg>
> <IMG_20231009_082720298~2.jpg>
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Message: 2
Date: Mon, 9 Oct 2023 18:44:55 +0000 (UTC)
From: Jim Whartenby <old_radio at aol.com>
To: Milsurplus <milsurplus at mailman.qth.net>
Subject: Re: [Milsurplus] Interesting dynamotor fact
Message-ID: <1811266375.13255082.1696877095231 at mail.yahoo.com>
Content-Type: text/plain; charset="utf-8"

Charlie, your guess is confirmed, see:http://catalog.teledynereynolds.com/Asset/1431.html#:~:text=At%20sea%20level%2C%20about%2030%2C000,will%20arc%20across%20the%20electrodes.

Wonder if a capacitor across the brushes would reduce the spark?? Works for point ignition systems.Regards,Jim
Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy 

    On Monday, October 9, 2023 at 12:41:48 PM CDT, CL in NC via Milsurplus <milsurplus at mailman.qth.net> wrote:  

 The fellow based in Atlanta that refurbishes WW II aircraft electric turrets, known as "The Turret Guy", has to also rebuild the amplidynes that make the power to run them.? We were talking brushes and I asked him where he was buying his.? But, he said that the amplidynes and dynamotors that run at ground level, last almost indefinitely compared to those that actually ran at 20-30,000 feet in their heyday.? Guessing the lower air pressure at altitude promotes more arcing and burns them up quicker.? He mentioned he had one turret he uses for demos he put brushes in many years ago and they still look almost brand new, after countless shows and demonstrations.

Charlie, W4MEC in NC
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Message: 3
Date: Mon, 9 Oct 2023 14:32:35 -0500
From: Dave Merrill <r390a.urr at gmail.com>
To: Ken Kinderman <scr274 at gmail.com>
Cc: Military Surplus net List <milsurplus at mailman.qth.net>
Subject: Re: [Milsurplus] Recognize this Dynamotor?
Message-ID:
	<CAGRTi8W-7nesjABk1TmU1_z05cFndMufQRzqN+Y7JBPCR+b+hw at mail.gmail.com>
Content-Type: text/plain; charset="utf-8"

Just went through the ARB manual and - BINGO!

Thanks, Ken.

On Mon, Oct 9, 2023 at 1:35?PM Ken Kinderman <scr274 at gmail.com> wrote:

> Could be for the ARB
>
> > On Oct 9, 2023, at 10:44 AM, Dave Merrill <r390a.urr at gmail.com> wrote:
> >
> > ?
> > Any clue where was it used? Same dimensions as a DM-32.
> >
> > Dave N9ZC
> > <IMG_20231009_082557061~2.jpg>
> > <IMG_20231009_082720298~2.jpg>
> > ______________________________________________________________
> > Milsurplus mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/milsurplus
> > Help: http://mailman.qth.net/mmfaq.htm
> > Post: mailto:Milsurplus at mailman.qth.net
> >
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Message: 4
Date: Mon, 9 Oct 2023 20:27:15 +0000
From: Hubert Miller <Kargo_cult at msn.com>
To: "milsurplus at mailman.qth.net" <milsurplus at mailman.qth.net>
Subject: [Milsurplus] Japanese Morse Code Trainer
Message-ID:
	<CO6PR19MB54340621D6F4B6E918C9D181E4CEA at CO6PR19MB5434.namprd19.prod.outlook.com>

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Here is a Japanese 1943 built 'Morse code trainer'. The chrome wheel has bumps and flats which are read out by the flexible metal arm switch.
It looks to me like tube #12 in the schematic is just a "noise generator", like the contacts that feed its grid "drag" on the chrome wheel. That's
my guess. Tube #1 is the tone generator which goes right to the output transformer. The two tube plates are paralleled. Some years back i
transcribed the characters sent. Some are uniquely Japanese not used elsewhere in the world. I only have the one chrome code wheel which is
frozen on the axle anyway. A clockwork spring inside, cranked up, plays it for a few minutes.
-Hue Miller
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