You did the right thing getting the Microdan. It's as good as you can get, only costs a hair more, is fairly tolerant of winding mistakes, and seems to have a bit lower resistance at the same gauge. And it is a very good idea to have plenty of "backup" wire when you're just starting out. Goofs will be made!


Dave

Yep, in the past I made some off the hip comments on all wire being the same resistance, but after going through a few spools of MD wire I have noticed a slight drop in Rm's. I verified my suspicion by checking resistances on 1 foot lengths of different gages of MD and alltronics wire, and the MD wire consistently came out a few uOhms lower.

I'm not 100% sure, but I think MD wire is polyamide wire. 200C makes it definitely an amidester. It's slipperiness and resistance against abrasion makes me think it is likely polyamide versus a plane amidester? Then again, I haven't played with a known sample of plain amidester wire. Powerwerx has good prices on polyamide wire, but they only have even gages. Dan's stuff costs a few bucks more, but he carries odds. I don't mind paying a little extra to support a fellow hobbyist. Of course if I weren't poor, I might find out where my local repair shop buys their 5gal buckets of polyamide wire.

Cheers,
Kev

Good to hear that I got a good wire that is a little newbie proof too.

I mentioned BP Hobbies having DAT-750 bearings for 10 Cents, I was wrong about that. The bearings are only a nickel! They are 10 Cents a pair!

So I'm now the owner of 10 pairs of replacement bearings. I can see where the bearing is a little on the small size for the loads and stuff here but sometimes that's just the way it goes. The bearings on the motor I'm using has quite a few hours on it and those are still quiet and smooth. It is on a pusher so the bearings have not been banged on much.

Jack

Jack,

Check your bearings carefully that you got from BP. I ordered 20 pairs from them a while ago and they must have a few packages mismarked because they were the wrong size. Probably 3 of the 20 pair were wrong.

They are all marked 4 x 7 x 2.5 mm (ID, OD, Width) and MR74ZZ and the bearings are all identical too. So I guess I got the right thing.

But thanks for the warning.

On these small sealed bearings like this I lube them before I use them with a Might-Vac brake bleeding vacuum pump. I submerge them in Mobil 1 motor oil in the catch bottle then pull a vacuum and let them set for a while. That ensures that they a filled with some lube if they were not that way already. I let them drain overnight before I install them.

I occasionally see a trace of oil on the bearings when they are in use but it will not hurt anything. I'm of the opinion that if you can't see any lube you might not have enough. And dripping lube on the outside of a sealed bearing does not get much of it in the right place.

Jack

Wow! This is not as easy as it looked.

The photos of Trug's finished 16T21 rewind in post #408 seduced me into thinking that I could do this so I got started on it last night with a newly bared stator and a 72" piece of the MicroDan 21 gauge wire.

I can see now that I have just created my first piece of "practice winding wire." It has been on and off a couple of times already and I'm not ready to start with a new piece of wire yet.

I'm using Daves's tutorial and starting with post #39 for the Delta variant rewind. If anyone thinks I've missed a better way to get started or the right wind I'm open to suggestions.

Looking at Truglodite's photos of his rewind I think I see 7 turns on the top layer so I have been trying to get 9 turns on the first layer and 7 on the top. I'm getting closer to getting it right but will take another practice shot or two at it. If I've missed any clue here I'd be glad to hear it.

When I removed the original winds I found seven strand bundles of wire that is about 0.24mm/0.0095" in diameter. That had a little bit of CA holding some of the last winds in place at the hammerheads but it was easily unwind and the residue cleaned off.

Jack

I wasn't able to duplicate that wind either. Best I've managed so far with 21awg is 14T.

I wonder if the thickness of the coating on the wire accounts for some of the difficulty in getting the 16 turns on?

I measure the MicroDan #21 wire at 0.0313"/0.795mm with a good micrometer. The wire gauge tables show #21 at 0.0285 so it looks like the coating thickness could be a factor.

Maybe trug has stronger fingers?

Jack

Not necessarily stronger fingers, but perhaps the patience and technique to get that fat wire on. Strangely, 16/21 is not a crowded wind; there's plenty of room. But when the wire gets that thick it just doesn't want to bend where you tell it.

32/24 parallel is essentially the same wind. Here's a photo of 36/24, which is considerably more copper. You can see there's still plenty of room left. Admittedly, that's not Microdan wire (this is a cheap combat motor on a slow stick) but still, the caliper is not that different.

It's not a question of too much wire, it's a question of getting it into the right shape. I find 21 awg quite hard to form. It takes patience; you have to keep pressure on it and practically massage it into place.


Dave

I hope I wasn't seen as trying to discourage anyone else from trying this. I just need to work on my learning curve some more. And I have the time to do that.

"..It takes patience; you have to keep pressure on it and practically massage it into place..."

Golden advice!

I spend another hour at it this morning and finally achieved a near perfect two layer wrap on a tooth. My practice wire was a little distressed from overuse and I celebrated my success by breaking the wire as I was making the transition to the second tooth. That was my fault and it was due to an inappropriate choice and use of the wrong tool for that point in the process.

But in the course of getting this far I have found or made some pushing, probing, and pulling tools that are really making a big difference for me. My major discovery was the use of a clothespin as a tool for keeping tension on the wire as each turn was made, that made a big difference in the snugness of the turns and keeping turns in place as I worked. I think that clothespin is compensating for a pair of old hands that don't have quite the strength and dexterity that they may have had once.

I can't say enough about the quality and quantity of the advice and help I'm getting here. Thanks again!

Jack

Good going Jack, I was going to say it'll still work fine if you have to go to 3 layers, since there's plenty of rotor clearance. It sounds like you already willed your way through it. Good thing, cause 16T-21awg isn't all that packed, but it sure looks pretty when it's done clean.

Like Dave mentioned, 21awg is tough to work with. My hands are young, and I work construction, so I may have an advantage when it comes to tugging wires with naked hands.

My hand's aren't going to last forever though... I've started noticing my left hand (stator vise) sometimes gets numb during some winds. Might be a nerve or circulation, but it goes away as soon as I take a break. Still worries me, so I've been trying to get familiar with more sustainable methods. The one time I tried using a vise to hold the stator and a dowel to hold the wire, I gave up out of frustration before the first half phase was complete. The hands on approach and parallel winds just seem like the way to go.

Cheers,
Kev

Well, I have two tricks. First, I don't use 21awg any more unless I have to; I'd rather drop to a parallel. That aside, when I have to do a hard pull, I hold the stator to the edge of my <crappy> work desk and use that as a stop. Takes the strain off the holding hand (left in my case also).

Is that at all clear? Or should I get the missus to shoot a pic? Well, okay. It's not very clear but I think you can figure it out.


Dave

Good idea Dave; that would take the clamping pressure off the hands and torque off the wrists. Thanks...

Looks like a slab door? My current work bench has 1/2" rounded corners, but I've got 16 slab doors that are 58 years old at my new house, and 2 of them are solid fire doors (I'm replacing all of them). They're all very stout compared to modern MDF hollow slabs, so picking a few for benches whenever I get around to setting up shop.

Cheers,
Kev

Nah. It's just one of those old Danish Modern no-drawer melamine-sheathed desks. Left over from an earlier career.

Dave

You guys ever try anything like this? I spent a half an hour this morning and made myself a third hand that never gets tired. Made it out of a scrap of 3/4" thick HDPE lumber.

Works beautifully for me. I keep enough drag on the wire to get the tension right and turn the motor as I wind to keep the wire coming strait at me. I did a few more test winds with my much abused and twice broken now practice wire and am getting some nice winds I think.

I tried a 10 out and 6 back wind and I think that is the one that is going to work best for me. I have not down a full phase yet with all four stators but that will be next. I'll start with a new piece of wire and it should be even better as my practice wire is getting a little work hardened.

Jack