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Old Jul 07, 2010, 09:31 AM
Jack
USA, ME, Ellsworth
Joined May 2008
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Mini-HowTo
3rd Hand Motor Winding Accessory

The 3rd Hand Motor Winding Accessory

I needed something to help me keep a little tension on wire while winding motors and I came up with this, I call it my "3rd Hand" for motor winding.

The white material in the first photo is the primary component of the 3rd hand. It is a scrap of the HDPE (High-density polyethylene) lumber. That is a light, rigid foam, lumber that is much used for trim wood around doors and windows and things like that. You can get it at Home Depot or Lowes but the best source is a scrap pile at a construction site.

The piece seen there is about 3/4" thick and 2" wide, I think almost any fairly soft clear grained wood would work.

As seen in the first photo it is clamped to the edge of a bench top. The small piece of light plywood gives me something to lay the motor on and a light colored background to see the motor against.

The second photo shows the slot cut in the end of the board, that is open to the end so the wire can be easily slid into place in the slot. I filed the end of the slot to a "<" shape so it guides the wire in.

The wing nut can be adjusted to control the drag on the wire as it is pulled through the slot. The wire will be pulled through the slot without damaging the coating on the wire or bending the wire, even when there is enough tension on the wire to make the winding process go well.

The third photo is the winding process simulated. I get a few inches of wire sticking out from the 3rd hand and pull lightly on the motor to apply enough pressure to the wire. I can adjust the wing nut to change the restraint. I turn and roll the motor to put the turns of wire on, keeping the wire coming straight out of the slot. I pull more wire out every few turns or so or as it is needed.

You have both hands on the stator and can use your fingers to help guide the wire into place, I keep a old prop blade, and wooden turn pusher, and a couple of other tools handy to use as I work.

So the process is that I cut a piece of wire, center the wire on the motor, and take a couple of light turns on the end I'm not going to wind to restrain it. Then I clamp the end I'll wind first in the 3rd hand, and wind away. The other end of the wire hangs off of the motor to one side and stays out of the way.

When you get near the end of a series of turns you can pull the wire out of the hand to thread the last turn or two through the previous windings. You can re-clamp the end in the slot again to apply a little more tension to those last threaded turns if it is needed.

Details for making the 3rd Hand:

The fourth photo is the saw I used to cut a narrow kerf in the end of the board. The fifth photo shows the hole drilled (3/16" or so) and the end of the cut.

I drilled a 5/16" hole for a 5/16" x 1-1/2" or so carriage bolt. That hole is about 1" back from the end of the board. In the sixth photo, on the bottom of the board, I drilled a 3/8" or so relief so that the square shank under the carriage bolt head would pull down into the board to retain the bolt and keep it from turning with the wing nut.

The seventh photo is the hardware:

1 - 5/16" x 1-1/2" carriage head bolt
1 - 5/16" wing nut
1 - 5/16" fender washer
1 - 1/2" long piece of shrink tube

I put the piece of shrink tube around the bolt to protect the coating on the wire if it rubbs against it the bolt.

The last photo is some of my practice winding work on a DAT-750 stator with 16 gauge wire. The 3rd hand really improved the quality of my winds, especially with the heavier wire.

15 September, 2011

I added a piece of water pump gasket material between the jaws on my 3rd hand to improve the control of the friction on the wire. Otherwise this thing is working great and really helping my 69 year old finger to get motors rewound.

I've also included a photo of the essential tools. A broken APC prop tip, a all plastic stylus sanded to a tapered down, flat, blunt end, and a popsicle stick.

Jack
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Last edited by jackerbes; Sep 15, 2011 at 02:32 PM. Reason: add more photos
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Old Sep 15, 2011, 02:53 PM
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Fourdan's Avatar
Antony (France)
Joined Sep 2003
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Hi Jack
What thickness for your gasket piece (neoprene ?)
Both internal faces or only one side ?

Bamboo or plastics chinese sticks are also convenient
Keep them next time you have a chinese dinner !
Louis
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Last edited by Fourdan; Sep 15, 2011 at 03:32 PM. Reason: chinese sticks
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Old Sep 15, 2011, 03:10 PM
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modisc's Avatar
United States, MI, Ann Arbor
Joined Aug 2011
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i envy you guys have lived long enough to build professional tool on your own, i will definitely do the same thing when i retired .

it looks pretty nice to me, kind of like the winding machines for a badminton / tennis racket. i played a lot badminton and tennis so i am familiar of how the machines works.

how this tool work with thicker wires? say 1.2mm diameter copper wire?
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Old Sep 15, 2011, 10:19 PM
Jack
USA, ME, Ellsworth
Joined May 2008
17,001 Posts
Quote:
Originally Posted by Fourdan View Post
Hi Jack
What thickness for your gasket piece (neoprene ?)
Both internal faces or only one side ?

Bamboo or plastics chinese sticks are also convenient
Keep them next time you have a chinese dinner !
Louis
The foam board I used is sort of soft so eventually the wires put some small grooves in it and the drag varies. The gasket material stopped the grooving thing. I used the 1/32" (1mm +/-) or so thick material used for water pump gaskets on cars. It is like a heavy waterproof paper. But almost anything similar would probably work.

I used one layer of that but with a wider saw kerf a doubled up or folded piece would work as well.

The chop sticks are a good idea too, I have a bag of several hundred of those green plastic stylus, they were left over from long ago a Palm Pilot advertising campaign or something...

Jack
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Old Sep 15, 2011, 10:32 PM
Jack
USA, ME, Ellsworth
Joined May 2008
17,001 Posts
Quote:
Originally Posted by modisc View Post
i envy you guys have lived long enough to build professional tool on your own, i will definitely do the same thing when i retired .

it looks pretty nice to me, kind of like the winding machines for a badminton / tennis racket. i played a lot badminton and tennis so i am familiar of how the machines works.

how this tool work with thicker wires? say 1.2mm diameter copper wire?
I have used it with up to 15 AWG (1.45mm or so) and use it with 21 to 26 AWG mostly. The 15 AWG wire worked OK with it. That big wire was a one time thing, I was ignorant enough about winding to think that I could do a LRK wind on a Dualsky PR.40 stator with wire that size. It did not work of course. The guys over on powercroco make that look so easy.

The idea for the 3rd hand came to mind because of a fishing rod building fixture I had used in the past. That had a thing for putting tension on spools of thread as it was wound onto fibreglass fishing rod blanks to hold eyelets on and for decoration.

I take the bearings out and put a dowel through the bearing tube (wrapping the dowel with tape for a snug fit) and the dowel gives me a nice set of handles and also a place to tie off the end of a wire to with a few light wraps at the start. I usually have the stator about 10-12" away from the clamp as I work and having the light tension on the wire and moving the stator around seems to make it much easier to lead the wire into the slots and get it positioned as I work.

Glad you guys dropped by, I'm thinking the guys that are doing all the winding and know all the tricks might share a few of those with me here.

I learned quickly that the best way to learn about motor winding was to start a thread with a few photos and a description of what you were trying to accomplish. As the experienced guy read that they would spot things and point out mistakes and better ways to me.

Jack
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Old Sep 16, 2011, 01:08 AM
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United States, MI, Ann Arbor
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It s indeed a third hand, since you will mainly rely on both of your own hands to do the windings. LRK seems to be quite difficult to wind if you are aiming at maximum copper, filling the room of adjecent teeth on both sides of the winded tooth.
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Old Sep 16, 2011, 06:57 AM
Jack
USA, ME, Ellsworth
Joined May 2008
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Quote:
Originally Posted by modisc View Post
It s indeed a third hand, since you will mainly rely on both of your own hands to do the windings. LRK seems to be quite difficult to wind if you are aiming at maximum copper, filling the room of adjecent teeth on both sides of the winded tooth.
The LRK wind has turned out to a pretty amazing wind for me. I think it is generally under rated and ignored by many motor winders in favor of the winds that that use all 12 arms. But when you wind only six arms you can get quite a bit more wire on each arm.

I rewound that Dualsky PR.40 LRK with two strands of 21 AWG wire and terminated it Delta. The stator only lost about 5 grams of copper weight in the change from DLRK to LRK.

I was using it on a glider at 250W to 400W and it was barely even getting warm with 13 x 10 and 15 x 12 folding props. I needed a 200 gram motor to get the CG right so I used the PR.40 for it's weight more than it's power. It came to me used with a shorted winding so I rewound it to a 1024 Kv as that seemed to suit the 13 x 10 folder.

The PR.40 was originally rated as a 900W peak (maybe 500-600W continuous?) motor with a DLRK Delta wind and I think it is still fairly close to that, I just don't use or even have any props big enough to really test it to those levels with.

Jack
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Old Sep 16, 2011, 09:27 AM
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United States, MI, Ann Arbor
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Quote:
Originally Posted by jackerbes View Post

I rewound that Dualsky PR.40 LRK with two strands of 21 AWG wire and terminated it Delta. The stator only lost about 5 grams of copper weight in the change from DLRK to LRK.

I was using it on a glider at 250W to 400W and it was barely even getting warm with 13 x 10 and 15 x 12 folding props.

Jack
Only losing 5 gram of copper is not an easy thing from dLRK to LRK. good for you!
I tried winding LRK once but it seems a bit more difficult to wind neatly comparing with full teeth windings, not very easy to wind beautifully.

Given the size of the motor, I guess 400watts is absolutely too "cold". Anyway, the conservative power consumption ensures long time safety flight, if it can already provide enough power.

One of my modified fan from a 12CM pc cooling fan, with total aluminium body (outer frame) but plastic blades, winded with 1.2mm wire and 5 turns each tooth, consumes 500watts to give about 1.2kg thrust at 3S input, get warm after 5 mins full power run. This is quite close to the data shown here, presented by Ron from that german website:

"See
http://www.powercroco.de/
-> English
-> Tools and links
-> Wire and magnetic characteristics

Vriendelijke groeten Ron
diy motor tips Drive Calculator
diy motor group Cumulus MFC "

The 1.2mm wire can actually handle about 40A current for short time safely.
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Old Sep 16, 2011, 10:14 AM
Jack
USA, ME, Ellsworth
Joined May 2008
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Your stators have six arms, right? As I understand it, LRK is winding six arms on a 12 arm stator. And the windings are done A-b-C-a-B-c.

For your six arm 8 pole motors, there are only the six arms and the windings are done ABCABC.

To try LRK on yours, would you wind AbCaBc instead of ABCABC? Is that the difference?

Al of this sort of makes my head hurt. I'm best at finding an image of something that already has been worked out and just copying it. You are experimenting with something that is more of an unknown, right?

How do those cooling fans work out as far as the power production for the motor weight? Is it similar to what they get from the ducted fan motors?

Jack
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Old Sep 16, 2011, 10:59 AM
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Antony (France)
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Quote:
Originally Posted by jackerbes View Post
Your stators have six arms, right? As I understand it, LRK is winding six arms on a 12 arm stator. And the windings are done A-b-C-a-B-c.

For your six arm 8 pole motors, there are only the six arms and the windings are done ABCABC.

To try LRK on yours, would you wind AbCaBc instead of ABCABC? Is that the difference?

Al of this sort of makes my head hurt. I'm best at finding an image of something that already has been worked out and just copying it. You are experimenting with something that is more of an unknown, right?

How do those cooling fans work out as far as the power production for the motor weight? Is it similar to what they get from the ducted fan motors?

Jack
Hi
If I call S(slots), C(coils), P(mag poles)
There are some correct configs with only 6 slots(6 arms) = 6S-xC-yP
6S-3C-4P or 6S-3C-8P := A-B-C-
6S-6C-2P or 6S-6C-10P := AbCaBc (and also 6S-6C-14P)
6S-6C-4P or 6S-6C-8P := ABCABC
Of course there are other equivalent configurations by isomorphisms (same or reverse rotating sense)
(circular permutation, exchanging upper/lower case, exchanging B and C + b and c, and so on ..)
Louis
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Last edited by Fourdan; Sep 16, 2011 at 06:10 PM.
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Old Sep 16, 2011, 02:54 PM
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modisc's Avatar
United States, MI, Ann Arbor
Joined Aug 2011
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Quote:
Originally Posted by jackerbes View Post
Your stators have six arms, right? As I understand it, LRK is winding six arms on a 12 arm stator. And the windings are done A-b-C-a-B-c.

For your six arm 8 pole motors, there are only the six arms and the windings are done ABCABC.

To try LRK on yours, would you wind AbCaBc instead of ABCABC? Is that the difference?

Al of this sort of makes my head hurt. I'm best at finding an image of something that already has been worked out and just copying it. You are experimenting with something that is more of an unknown, right?

How do those cooling fans work out as far as the power production for the motor weight? Is it similar to what they get from the ducted fan motors?

Jack
you are right, LRK is for 12-teeth stator. the 12cm fan i am talking about has 12 teeth stator. sorry i didnot mention that. the 280mm sized fan has 6 teeth.
so far as i know, 6P4N or 6P8N only has ABCABC winding, 6P2P which is different directional winding, it sucks, ignore it.

Im not experienced in RC. I just started this hobby since 2 month ago. I used to love collecting high-power DC cooling fans only.

I have no equipments to test more details about the fans i modified, except for the voltage, current, weight and roughly thrust with a kitchen scale. . I cannot even test speed. My bad...

12CmX12CMX3.8cm outer aluminium frame, total weight with steel finger guard on is about 400 gram. Thrust on 3S input, around 40A current, is roughly 1.2Kg tested on kitchen scale, net thrust excluding self weight would be around 800gram. how does it sounds to you comparing with an EDF. Cooling is good for this fan since the whole body is made of metal, only the blade is plastic./

LRK on a 6 teeth stator, i guess not good. as the size difference between the magnet width and teeth width would be huge...not sure though.
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Old Sep 16, 2011, 07:00 PM
Jack
USA, ME, Ellsworth
Joined May 2008
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I'm almost sorry I asked. I didn't consider how little I know about EDF power systems. I have never had one. And I've only been rewinding a short time too, a lot of the technical stuff about motors and motor theory is just over my head. Like that graph you posted above, I really don't understand what that is about..

I did a goodle for "edf thrust measurements" and everything I read was over my head, I didn't understand it or find an easy answer. I read in one thread that a .33:1 thrust to weight ratio was considered to be a minimum for EDF powered flight and that .57:1 would give you very good performance. If that is correct, it sounds like the thrust requirements for EDF planes is similar to propeller dirven planes.

To be honest, I really don't like all the noise they make either.

Jack
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Old Sep 17, 2011, 04:18 AM
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Quote:
Originally Posted by jackerbes View Post
I'm almost sorry I asked. I didn't consider how little I know about EDF power systems. I have never had one. And I've only been rewinding a short time too, a lot of the technical stuff about motors and motor theory is just over my head. Like that graph you posted above, I really don't understand what that is about..

I did a goodle for "edf thrust measurements" and everything I read was over my head, I didn't understand it or find an easy answer. I read in one thread that a .33:1 thrust to weight ratio was considered to be a minimum for EDF powered flight and that .57:1 would give you very good performance. If that is correct, it sounds like the thrust requirements for EDF planes is similar to propeller dirven planes.

To be honest, I really don't like all the noise they make either.

Jack
The graph, I find it quite useful to me, as i am making RC-grade motors from brushless DC fans. I need to know how much current my wires can handle, since the heat is basically the barrier of limit for the brushless motor. For example, for the 12CM fan, 1.2mm 5 truns, 12N8P, star configuration, i tested it under 6S once, current is extremely high, roughly 100A. I dare not to pull it to highest power at 6S input, as the sound is a bit like screaming to me...From the table, i learnt that 1.2mm wire can only handle about 40A current. therefore i use 3S input for that fan, now it can work well without any heat problems after running at full power, 3S input, for 10 mins or more.
The graph serves as a standard for me, which is quite useful, otherwise, i will not know when to stop before some tragedy can happen.

I love the sound of a balanced EDF, i just now balanced a 90mm metal EDF from Leopard. Finally it is balanced...now i have one more 65mm metal EDF with a aluminium blade (retrieved from another cooling module for telecom severs) to balance. EDF is my favorite, it is simply a compact power source with limited size. Biggest problem is the balancing of the blades/rotor. Though most metal EDFs are stated to be balanced in factory, i find it not quite true. the 4 EDF i purchased, only one of them is well balanced...I will have to balance the other three, cost me a lot time since I never played with it before.

thrust : total weight of the jet plane, 0.5:1 = fly well; over 1, excellent jet. A guy in this forum told me this, i guess he would be Z-matrix.

what i made from those DC brushless fans, are actually something between propeller and EDF, considering the size. it's depth is too short for an EDF, but it has outer frame matching the size of the blade, concentrating the air flow, which is similar design of an EDF. The size of the blade is a bit too large for an EDF, a bit like a propeller. however, the thrust is not that good. i mean, a commercially available professional 12CM metal EDF, may have 5kg thrust on 3000watts. This leads to other huge problems for the "EDFs" i made, the comparatively fragile plastic blades, slow rotation speed since its an outrunner, etc. Heat dispersion for the bell is another issue since the blade is not metal, though the coil maybe well cooled via the aluminium outer frame. Though those DC brushless fans i chose are of excellent quality, but only as a brushless fan with around 10K rpm speed. AS others in this forum pointed out, the blades may explode if speed is too high. Anyway, I balanced them well since no obvious vibration of the outer frame is felt.
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