Need info. on how to power an DYNAMOTOR DM-32A

[NP4ZB]

 Hi to all in the group, I have an ARC BC-455 RECEIVER.
It has an DYNAMOTOR model: DM-32A. I would like to know
how to start the dynamo.? Where do I hook up the 28vdc input
of the DYNAMOTOR? If anyone any idea please let me know.
Thanks for your help.

73's de NP4ZB/GEORGE.

[Opcom]

Possibly the dynamotor has not been spun up in a long time, so it might not start.

Before starting the dynamotor, be sure it turns and the bearings have been lubed, especially if it has not been done in a year. It's very important. A dry bearing and a full voltage start up to 3500-7000RPM operating speed is real bad. At least get some grease in there, or whatever lube it takes. Usually they do not use oil, but a light grease. in a emergency, anything will do for a very short test as i have just described.

[Opcom]

Here are the links to the books on the gear that set belongs to.

It is part of the SCR-274 radio set:

http://bama.edebris.com/manuals/military/scr274/
and
http://bama.edebris.com/manuals/military/scr274n/

In there are the complete info on the BC-455 part of the set you have. From this, you can see in the diagrams how the 455 was controlled in the set. But the above schematic should do what you want.

If you have done that, and it does not spin with power applied, see if it is free to turn, how dirty is the commutator, how free the bearings, etc. You can see if it is free to turn by removing the brushes and spinning it. BE Extremely Careful to put the brushed back in -exactly- as they came out:
1.) same positions
2). same alignment, do not flip them!!
The reasons for the above is because they have 'worn in place' and are 'broken in' to those locations and orientations.

Before removing brushes for any reason, remove power and use your finger or a little stick to turn the rotor, being careful not to damage the wiring etc. It should turn but will require a little force due to the pressure of the brushes, a set at each end.

haha be sure the dynamotor does not start with your finger inside it.

Let us know if this was useful, if you have gotten the set going!

[NP4ZB]

 OK, Thanks for information it was very helpful.
Once I get the receiver up and running I'll let you know.
Thanks again.

73's

[Todd, KA1KAQ]

Much more than you're looking for, but a worthwhile read before attempting any dynamotor work:

http://aafradio.org/docs/Dynamotors.html

Mike is a member here and chimes in from time to time. He's worked on these things for decades and has a vast amount of experience to call on.

One thing he suggests if you're looking to power up the dynamotor for brief testing or such is to pull the end bells and shoot some WD-40 into the bearings at the very least, to loosen up some of the ancient grease products and provide some level of protection. For long term use, you'll want to pull, clean, flush, and re-lube the bearings as described in Mike's article.

The good news is, once it's done you shouldn't need to do it again for a while or perhaps ever, depending how often you use the set. Better lubes available today that shouldn't harden or separate as easily as decades ago.

[NP4ZB]

 Thanks to all for your help. I recapped the receiver, changed
the tubes, the dynamotor greased and lubed and WD-40ed.
I have the receiver up and running. Works great. I have 12.6vdc
going to the LV+ and have 115vdc HV+ output. The dynamo
running no problems so far. Thanks again to all.

73's de NP4ZB/JORGE

[Opcom]

Todd that article is a godsend!

[Todd, KA1KAQ]

Mike's aafradio website is, in my opinion, the best on the web for information about WWII and other aviation radio gear. He's helped me out on many levels over the years, and I cannot begin to count the hours spent perusing his site for information or just plain reading enjoyment. If you do any machine shop work, he has an excellent section covering projects there, too.

Good job on getting the receiver working, Jorge. It looks like the typical/average ARC-5 type set of the day. Always enjoy seeing or hearing of another one coming back to life. And there's nothing quite like hearing a dynamotor purring along.

[NP4ZB]

  Hi Todd,
Thanks for the message. You are right, it's a geat feeling
to have this radio up and running again. I'm hearing radio station
far and near. I'm able to receive staton as far as China. I retune
the radio and works great. Well thanks again.

73's de NP4ZB/JORGE

[aafradio]

Todd is far too generous.  The only addition I would make is to be somewhat cautious of using WD-40 as a lubricant.  I use it for coolant in machining aluminum, but its lubricating abilities are very short lived because of the very light weight and small percentage of the lubricating oil in it.  Most of its content is composed of a solvent and a waxy protectant that retards rust for a short time, neither of which is very useful in lubricating a bearing.  You can definitely use it for a short time, but after all the time needed to pull the end bells off, perhaps another lubricant might last a bit longer.

Grease is simply a convenient way to store lubricating oil in a form that doesn't leak out of a bearing.  The problem with its storage element is that the lighter components of the oil do evaporate over the decades, and then you are left with the soap thickener, which doesn't perform as a lubricant very well.  If you must operate anything with bearings that have 60 year old grease in them, I really prefer putting a few (3-4) drops of a synthetic oil like Mobil I in them.  Too much will begin migrating into the brush area, and that's not a good thing...the 2-3 drops is a quantity that I found adequate over the years of experimenting with various quantities.  The only drawback to this short term solution is that you need to keep repeating the application much more often that simply cleaning and relubing the bearing with a proper small bearing grease.  The synthetics have a vastly improved lubricity that will last much longer without damage than putting a normal oil in the bearings.  Still, anything is better than nothing.

[aafradio]

Duplicate.  Any way to delete a post?