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First-Time Emerson DC Ceiling Fan Restoration - Tips Needed


Derek Warnecke

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Hey folks, I'm working on a complete restoration of a ~1924 Emerson 45041 56" "DC Longnose" ceiling fan.  It is my first DC fan restoration and I have a few questions:

  1. The Nichrome resistance coil stack has a broken wire just 3 wraps from the end tap on the low speed.  Would I be okay unwinding it to the break and re-terminating it, or would it be prudent to rewind the whole 3-layer Nichrome / Asbestos sandwich with fresh Nichrome wire?
  2. The brushes are about 0.6" long and seem to have enough life in them.  What is the best method to clean the brushes and brush holder sleeves so that they move smoothly?  Also, I cannot seem to find replacements online in the correct size for swapping them in down the road.  They are 0.36" square and 0.6" long.
  3. It is my understanding that the four series-connected field coils are then connected in series to the armature brushes, making this a Series DC motor.  Is there any concern to polarity with this connection?  My thinking is this:  Positive lead in at one motor terminal, down to the speed switch, up to the Nichrome resistance coil, up to the armature brush, from the other armature brush to the four field coils, then finally to the negative motor terminal.
  4. I'm planning on installing a 1000V 50A full wave bridge rectifier (heatsinked) in the canopy.  Is there any need for a filter capacitor on the DC side?

Thanks in advance.  This is definitely a fun and different type of fan restoration for me.

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1. You are better off just rewinding the choke with fresh resistance wire. When you try to unwind it it will more than likely break or break later. Take readings from end to end on each stack or will be needing to measure several broken sections. Kanthal carries a higher resistance per foot vs Nichrome so you will not need to squeeze in as much length vs Nichrome. Both are cheap and 100’ spool under $10 will likely be enough for 2-3 jobs. Never done a DC ceiling fan but 12” are 2 plates at 85-100 ohms each.  You can add resistance if wish to run slower. Curious with your 3 stacks if ceiling fans would be total of 275-300 ohms. Also curious if your fan is 4 speed? The 3 speed desk fans on high bypass switch and get full power with 2 stacks designated for Low/Med. 

2. I clean my brushes and holders with rubbing alcohol. Darryl Hudson can make new carbon brushes or you could take 3/8” and 800 grit the sides down to your .36 diameter. Current .60” length likely originally longer and .75” should be ok.

3. Cant help you with this but can check current polarity with suppling 24-32vdc voltage using compass against the fields. Armature removed. Not looking to run the fan, only to see magnetic fields.

4. Would imagine bridge all would need

 

Only curious, but can you post pic of switch stack ?

94C327EF-9C89-4E42-B971-286CE54A9F30.jpeg

Edited by Chris Campbell
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Chris,

Thank you for your help, especially regarding the more modern Nichrome wire solution. 

It's a 3-speed fan.  I believe it uses one stack to drop to medium and the other two to drop it to low, but I'll have to verify and sketch it out when I get home.

I’ve attached some pics.

A7A357CD-FF94-45D3-9690-97DBD173B3CA.jpeg

8629C63E-24D4-4AC4-A73D-A8A71403CF81.jpeg

C2399832-1A82-4788-A81D-294A66D665D6.jpeg

Edited by Derek Warnecke
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17 minutes ago, Derek Warnecke said:

 

 

8629C63E-24D4-4AC4-A73D-A8A71403CF81.jpeg


 

 

These are the more commonly used later plates by Emerson and even found in most Northwinds. Much easier to wrap vs mica sheets. 
 

The lower two plates will carry less resistance. Be sure to mark how they tie into switch. 

Do the two lower plates tie together in series as one larger resistance unit?

When you wrap the wafers slightly pull as you turn the corners and wire will bend and hold tight. 

Wire has some spring to it and will uncoil on you. I tape one end to a pipe and wrap until I have resistance available then tape other end followed cutting. You can wrap the wafers as wire unspools from pipe and keep it from tangling or kinking up.

08FC5D76-0162-4BA8-B51C-CA3F7F7F934E.jpeg

Edited by Chris Campbell
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Thanks for the pipe trick idea.  It looks like the original stack uses a thinner gauge on the top plate and thicker on the bottom two.  I should be able to wind it with a 20% or so higher resistance than the original to offset the higher supply voltage vs. the original 110V.  Factory speeds on this fan were 230/180/140 RPM.

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6 minutes ago, Derek Warnecke said:

Thanks for the pipe trick idea.  It looks like the original stack uses a thinner gauge on the top plate and thicker on the bottom two.  I should be able to wind it with a 20% or so higher resistance than the original to offset the higher supply voltage vs. the original 110V.  Factory speeds on this fan were 230/180/140 RPM.

With the 3 RPMs (3 speed)would imagine thicker gauge used in series for higher resistance across two combined plates. 
 

Temco sells wire on eBay. All gauges. It is plentiful for the DIY e-cig vapor people

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Ok, finally some measurements.

The medium speed uses the two stacks with thicker gauge nichrome and the low speed adds the single stack of thinner wire in.

4B6901C5-E0C8-46F4-804F-D6FA7CC52398.jpeg

68EBEB6B-E588-4428-AF0B-1D0D5921AD66.jpeg

E6BA0AED-E48E-4A19-BDCD-063F5C043827.jpeg

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Looking at the Kanthal resistance table and doing some rough calcs, it seems that spools of 28 ga and 32 ga would get me where I need to go.

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You should easily get 8’ on the wafers and be able to squeeze in 10’ . Wanted extra resistance on this and dropped down a gauge. Think it was 125/80 ohms. I have 3mm fiber glass sheathing that you can use on end leads to prevent any cross contact. Looks like you still have original asbestos. If need some pm me and will mail some.

 

 

604C56CF-1118-4968-B2AF-5CC6F5A16274.png

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  • 2 weeks later...

I usually buy common brushes that are larger than what I need, then file them to fit. But, Darryl Hudson could make you duplicates. 

There are different grades of brush material, with different hardness and different resistance, but it should not matter to a fan. 

I clean out the brush holders to get rid of any corrosion or foreign debris. Acetone on a Q-tip  


You should be able to use a much smaller full-wave bridge rectifier. 

if it draws 2 amps, get a rectifier rated for at least 4 amps. 

Each diode (there are 4) in the rectifier drops about .7 volts. At 2 amps, each diode dissipates less than 1.4w. So, the rectifier dissipates about 5w. No need for a heatsink. 

I have used these:

D0AE0728-0CC9-4155-A8CB-F0AA8C16E21D.png

2FD31DFF-9502-4305-809C-44C80EDD0F0A.png

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I purchased a 1000V 50A full wave bridge rectifier and a small aluminum heatsink to bolt it to.  Should do the trick.

I rewound the old, very brittle Nichrome with new Kanthal.  Even with 4 fewer turns per asbestos stack, my resistances were quite a bit higher.

IMG_1107.jpg

IMG_1111.jpg

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IMG_1116.jpg

Edited by Derek Warnecke
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Good news - It is all painted, reassembled and running!  I had to swap the leads on the brushes to attain the needed CCW rotation, but it's otherwise electrically fine.  It has enough torque to reliably start on the new Low speed and pulls just 0.27 Amps unloaded.  I've attached some FLIR images.  You can see that the Kanthal is pretty spicy as expected, but the rectifier isn't even warm to the touch.  I may not need that heat sink after all.

1.thumb.jpeg.e3401658dd8280c38472dc52c74b673d.jpeg

 

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On 1/25/2022 at 6:34 PM, Chris Campbell said:

 ...carbon brushes...  ...you could take 3/8” and 800 grit the sides down to your .36 ...

I too usually buy them a
bit oversized and whittle
them down to size.

29000316_b8ba_11.jpg.0625401345d338d58e537866b91978d8.jpg

Edited by Jim Kovar
  • Haha 3
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Dereck,

You did a great job with this.

 

Doesn’t appear as if needed, but Eurton does sell brushes which are .70 square x 1”.  Very close to the .68 Emerson brushes.
 

$7.50 each. 

Edited by Chris Campbell
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Thanks for your help, Chris.  I'll be installing the new thrust bearings today and I may have a little run video up for everyone.

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On 2/19/2022 at 7:11 AM, Mel Lagarde said:

Very nice restoration, Derek.  Great work. 

Thanks, Mel.  It really is a treat working on such a unique fan.  I'm planning on writing an AFCA mag article on this fan since the origin story is so cool.

Currently repairing some blade splits (at the expected outer screw holes), then I'll strip, sand, stain and clear coat the blades.

Edited by Derek Warnecke
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