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Rebuilding the 1920's Homebrew Set
https://antiqueradios.com/forums/viewtopic.php?f=1&t=385246
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Author:  azenithnut [ Oct Sat 24, 2020 12:26 pm ]
Post subject:  Re: Rebuilding the 1920's Homebrew Set

Very nice! Your old radio is certainly getting a new lease on life! :D
Are you going to use cloth covered wire underneath?

Either Radio Daze or Antique Electronic Supply was selling what is often called "Push Back wire" which is a low voltage type cloth covered stranded wire.
You simply cut it and then "push back" the cloth a bit to reveal the wire.
For a battery set like this it would be ideal.

-Steve

Author:  Robert Lozier [ Oct Sat 24, 2020 1:38 pm ]
Post subject:  Re: Rebuilding the 1920's Homebrew Set

Love your process pictures...
Robert

Author:  KCs_in_KS [ Oct Sat 24, 2020 2:21 pm ]
Post subject:  Re: Rebuilding the 1920's Homebrew Set

Robert - Glad you enjoy!

Steve - Was planning to just put the original cloth wires back in the set. They seem to be in decent condition other than a bit of excess fraying on the ends, but I guess that is the nostalgia of the whole thing! I labeled and tracked each one as I took it out, so was planning to put it right back in the same spot. Thoughts?

Author:  azenithnut [ Oct Sat 24, 2020 2:28 pm ]
Post subject:  Re: Rebuilding the 1920's Homebrew Set

If the wires are in good shape and you kept track of them, then why not?

I just mentioned the idea just in case. No reason not to reuse them.

-Steve

Author:  jrehkopf [ Oct Sat 24, 2020 4:53 pm ]
Post subject:  Re: Rebuilding the 1920's Homebrew Set

Maybe you can use these.

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Author:  KCs_in_KS [ Oct Mon 26, 2020 6:09 pm ]
Post subject:  Re: Rebuilding the 1920's Homebrew Set

Thanks all for the additional suggestions, input and artwork! I'll see what I can make of it all!

For now - one thousand! Well, at least that is my story and I'm stickin' to it! Bought some .023" annealed wire for core material. This essentially matches the diameter wire from the Hegehog. A cold October night by the fire and a lot of cutting later, I have a pile of core strands!

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Well, OK - the cutting wasn't too bad... I laid out about 20 long strands of wire across the floor and made a little trough of the proper length to lay them in / even them up. One whack with the shears and 20 more wires go in the pile.

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And technically, I'm a bit short of 1000 strands. 20 strands came out to right at 5 grams, and the whole batch came out to 248.4 grams, so technically, it's more like 993 strands, give or take!

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The wire came annealed. Of course there is some work hardening by handling / straightening it. Likely not much, but I gave the wires a quick firing in my 'annealing furnace'. Definitely not perfect, but slowly running the torch back and forth gave each wire a chance to get orange hot and slowly cool, plus, built up a bit of an oxide coating. No eddy current shunting here!

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So after the cool down, time to stuff the cores. I stuffed an initial group of wires in the core, then once the 'easy' wires were in, I fed small groups of 10-15 wires into the center of the bundle with some gentle tapping to drive them fully in. I eventually got all the wires I cut in the cores - almost 500 per core. I probably could have driven more wires in, but it occurs to me that driving the wires in like this may actually be stretching the core out. Would hate to stretch too much and break a strand of copper wire in the winding... then I'm right back to where I was on the original! So going to call it good here!

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Nothing left now but to fold them. The Hegehogs were folded with one side 'prevailing'...that is to say one side of the wires were ALL folded first, then the other side were ALL folded over the them. This gave the wires a specific orientation where then can easily push through the housing in one direction. So I will duplicate that.

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Guess now we start to see where the 'Hegehog' comes from!

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Now I can take measurements for the outer housing. Looks like the original steel is 0.027" thick so that is putting me down in the 24-22 gauge steel area... likely 24 gauge with a thou or two in paint / coating.

I knew this would be close, but the original Hegehog has a very slightly bigger core 0.600" diameter vs 1/2 x 1/2 square on mine... so fits a couple dozen more wires. But my core is 'hand folded' vs what was likely some machine on the original, so it roughly equals out. Bottom line, my cores seem to be a good fit for the same size housing, so that is what we will aim for building in the next round.

Author:  Duane B [ Oct Tue 27, 2020 1:50 am ]
Post subject:  Re: Rebuilding the 1920's Homebrew Set

You've put a lot of work into saving this old radio. Good for you! I can't wait to see the finished project!

Author:  radioer [ Oct Wed 28, 2020 2:30 pm ]
Post subject:  Re: Rebuilding the 1920's Homebrew Set

I am curious to know how long the restoration took.
Also, this is one example of a radio lover, good luck with it.
As for the commentators, is there anything about radios you don't know?

Author:  azenithnut [ Oct Wed 28, 2020 3:01 pm ]
Post subject:  Re: Rebuilding the 1920's Homebrew Set

There is plenty I don't know! :D

That is the beauty of it, I've been in the hobby for 40 years and still find new things to learn!
:wink:
-Steve

Author:  pauls.ironhorse [ Oct Wed 28, 2020 3:09 pm ]
Post subject:  Re: Rebuilding the 1920's Homebrew Set

Quote:
understand there is also supposed to be some pan or tray to help catch/contain the leaks?!? :wink:

Like this.

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Author:  Chas [ Oct Wed 28, 2020 3:22 pm ]
Post subject:  Re: Rebuilding the 1920's Homebrew Set

Duane B wrote:
You've put a lot of work into saving this old radio. Good for you! I can't wait to see the finished project!
I can't wait to know how it performs... chas

Author:  brnhornet52 [ Oct Wed 28, 2020 4:23 pm ]
Post subject:  Re: Rebuilding the 1920's Homebrew Set

KC

Some beautiful work there! A true labor of love, especially
the Hedgehogs.

Author:  KCs_in_KS [ Oct Sat 31, 2020 3:56 am ]
Post subject:  Re: Rebuilding the 1920's Homebrew Set

Duane - Thanks! Yes - way more work into this than it will ever be worth, but it rescues a small bit of history and does really strike a chord with me... I can only imagine some enterprising person looking to save a few dollars, debating over which components or kit to buy...one costs more, claims better performance, but one is a bit cheaper,etc. Finally making the big purchase, carefully assembling all the components, then finally hearing those first crackles of static and finally a voice coming through the circuits. Definitely reminds me of building my first computer from scratch!

radioer - I bought the set mid September (first time I've dealt with an old radio). Spent a couple weeks researching and made a 'hello' / intro post here on Sept 30th. Based on some great community feedback, I decided to dive in, disinfect/clean up this thing and started this thread on Oct 6th to document the restoration. Unfortunately, I can't work on it full time, or even a good portion of part time, but sneak in work when I can. Yes - certainly appreciate the wealth of commentary as I know about zero on antique radios!

paul - Yes! That's the one! :D

Chas - Me too. You've given a lot of great info. I suspect the radio and detection will work great. Homebuilt audio transformers in the output stage?!?!? who knows!

brnhornet52 - Thanks!



Overall, not much to report radio wise - busy on the run-up to Halloween! It's a big holiday for us... part of the reason I bought the radio. I ultimately wanted to sit down on a chilly October 30th evening, crank up a radio and listen to War of the Worlds. The original broadcast was Oct 30th 1938 - so I wanted to listen on a vintage set. I was searching for something when I came across this 'jewel'! Doesn't look like I made it this October 30th. Maybe next year!

Author:  KCs_in_KS [ Nov Fri 27, 2020 3:09 am ]
Post subject:  Re: Rebuilding the 1920's Homebrew Set

Hello again! Happy Thanksgiving! I haven't posted too much over the past few weeks... been busy making parts... to make parts... for parts... to finish the radio! Not sure how much machining, die making, jig and fixturing anyone cares about because it's a little off the typical 'antique radio' subject line, so I haven't been following that too closely. Plus, I think I lost a few of the 'off topic' pics, so this will be a little thin on images.

Anyway - still chipping away at Hegehog housings! I took a trip to the scrap bin, and a little work with a cutoff disk got me a couple of metal strips 1-3/8" wide, by 0.027" thick and 'suitable' length to make the outer round housing of the hegehog. Now I just hope no one notices there are two rectangular holes in the back of the scrap bin! I suppose these should be annealed, too. Easier to bend and we might as well get maximum fidelity out of the cores. So back in the 'annealing furnace'.

[had a photo, but seems to have evaporated... just back up a few posts and imagine strips of metal instead of wires glowing orange hot.]


...and of course, it would be nice to have a mandrel to bend those around and for staking rivets. The original housings aren't perfectly round (being only 0.027" thick steel) and the strip of metal has a simple overlap at the bottom, but on average, I measure the diameter at 1.650" so we can shave another small scrap of metal down to that diameter.

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At 1.650" diameter, if I pi x d it right, should give a length of 4.79" around the circumference + .350" for overlap, and we might as well call it 5.150" for round numbers of the strip length.


The next piece of the puzzle is a metal disk for the base. This time, 0.043 thick x 1.750" diameter with a dimple in the center! The disk is easy - just a quick run on the mill to get all the holes and a jig for the lathe to cut the disk. Might as well make a few since everything is set up.

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[lathe / jig pic has gone missing, so you will just have to imagine the strip above screwed to a plate and a cutter comes in and cuts the circumference of the disk]


The next part was a little more turning work. The base is 'dimpled' by about the thickness of the metal itself - to provide a recess for the rivets and still allow the hegie to set level. So after a bit more work on the lathe I had a punch and die set-up to stamp the bases. I goofed around for a week or more trying to decide what I was going to set up with a hydraulic jack or press to 'stamp' the metal. After kicking around several designs, I thought, "y'know... it's only ~0.040" sheet metal, maybe I can just clamp it in the bench vice", so that is what I ended up doing. Applying only a 'little' more pressure than normally comfortable with and the die closed up tight. So we'll consider that 'stamped'!

One more to go..
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Next up, I need to apply some identification while the strip housing is still flat. P, G, B and F ... Plate, Grid, Battery and Filament - just to keep all the leads straight ...and smaller 'PRI / SEC' stamps, too.


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Unfortunately, I don't have fancy 'typewriter' font stamps, or smaller stamps for the "PRI" and "SEC" lettering. Found one set of fancy stamps on ebay, but of course, it's missing the "B"! Most everything else seems to be a plain arial font. So, my next option is to engrave the letters.

But that gets into another project ...I've spent the past week or so getting my CNC mill in order...and by "in order" I mean finishing installing the stepper motors and building / wiring the 'brain box' ... tuning all parameters to actually work, etc... but that is a tale for a whole other forum!

Hopefully will have more radio progress soon!

Author:  processhead [ Nov Fri 27, 2020 2:52 pm ]
Post subject:  Re: Rebuilding the 1920's Homebrew Set

Not sure how I missed this thread. Some very impressive restoration work going on here and I am eager to see how it all goes up to final assembly and testing.
It really helps to have the machine tools to recreate the unobtainium parts you just can't get anywhere else.
Keep up the great work!

Author:  azenithnut [ Nov Fri 27, 2020 9:16 pm ]
Post subject:  Re: Rebuilding the 1920's Homebrew Set

Agreed! The work you're doing on this is amazing! I'm enjoying the ride :D

I will soon be getting a 9 X 20 lathe myself. I'm not sure where I will put it yet. Its one i've used before, so I'm familiar with it. This will replace the 7 X 10 I got from Harbor freight.

Keep up the great work!

-Steve

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