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Old Nov 08, 2011, 12:37 AM
Wingbreaker
Italy, Lazio, Albano Laziale
Joined Oct 2008
156 Posts
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TP 450-Size 2415-03T how to rewind?

By mistake I purchased this motor.
It is an heli motor with a very high (4850)kv.

I fly fixed wing aircraft so it's pratically useless for me. Maybe I can find an EDF but I would prefer to use it with a prop.

At this point the best solution (I think) is to rewind it (if I'm able to dismount it).

It's a 6 poles motor. How can I rewind it and what could be the lowest kv I can reach?

What will be the max Volt - amp it handles and will handle?

Could you also suggest me the wire thickness (in metric units if possible)?

Thanks for your help

Al
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Old Nov 08, 2011, 09:59 AM
Jack
USA, ME, Ellsworth
Joined May 2008
16,924 Posts
Quote:
Originally Posted by asimmetrico View Post
By mistake I purchased this motor.
It is an heli motor with a very high (4850)kv.

I fly fixed wing aircraft so it's pratically useless for me. Maybe I can find an EDF but I would prefer to use it with a prop.

At this point the best solution (I think) is to rewind it (if I'm able to dismount it).

It's a 6 poles motor. How can I rewind it and what could be the lowest kv I can reach?

What will be the max Volt - amp it handles and will handle?

Could you also suggest me the wire thickness (in metric units if possible)?

Thanks for your help

Al
I assume it is a 9 arm stator, right? That would mean that the only choice for a wind would be ABCABCABC. You can see that here:

http://forumrc.alexba.eu/nutpol_e.htm

You could get a slight better wind for a lower Kv motor if you raised the magnet count to 8 or 10 and used the AaABbBCcC wind that is shown in blue. But the ABC wind will work too.

I used Manuel's Simple Turn Calculator and assumed a Delta termination on 3 turns (that turn count is based on the model name) and it generated the attached wind counts and Kv's. They will probably get you in the ballpark for a new wind.

As to the wire size, you want to find the size of wire that will give you the best fill for the turn count you choose.

If you measure the windable length on the stator arm and know how many turns you want on the first layer, you can use that length, the number of turns, and come up with a wire diameter estimate as to the size of wire you can use.

All the rest of the numbers will emerge in testing and be based on your prop choice and battery.

Jack
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Old Nov 08, 2011, 10:40 AM
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lectroglide's Avatar
United States, WA, Puyallup
Joined Aug 2006
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I see in that simple turn chart you can enter your own numbers,but where do you go from thier?
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Old Nov 08, 2011, 12:01 PM
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Truglodite's Avatar
Carmichael, CA
Joined Feb 2007
3,517 Posts
What prop/plane/lipo is this for?

High Kv heli motors are designed with low pole counts, which makes them better suited to high rpm applications (low torque). If you rewind a low pole count heli motor for a very low prop appropriate Kv (higher torque), it will not be as efficient as the same motor/Kv with more poles. In other words, this motor is best suited for high rpm applications, and rewinding for a prop will more than likely be disappointing. It depends on the answers to my above question, but as a wild guess I'd say below around 3500Kv on 3s, the motor will be no good.

Kev

[edit: This motor hasn't been extensively hacked by anyone that I know of, so finding the ideal wire thickness, as well as max A and V for your rewind will require trial and error testing. I was told in the past by a well respected motor guru, "You must suffer the arts." This goes beyond the pain your fingers experience. ]
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Old Nov 08, 2011, 02:24 PM
Jack
USA, ME, Ellsworth
Joined May 2008
16,924 Posts
Quote:
Originally Posted by lectroglide View Post
I see in that simple turn chart you can enter your own numbers,but where do you go from thier?
I got the numbers I entered in the calculator from the specs for the motor's original wind. At home I would get them by counting the turns and noting the termination. If I can, I would measure the no load RPM and get the motor's actual Kv before I stripped it for rewinding. I know that will be a more accurate Kv than the advertised one.

Then I would:

1 - Decide a prop size for the rewound motor and make sure it has the thrust I think I want. That also shows me the prop RPM I want to have. Or I simply calculate the maximum safe RPM for the chosen prop.

As an example, the maximum safe RPM for a GWS EP 9050 prop would be about 90,000 / dia. in inches or 90,000 / 9 or 10,000 RPM.

2 - Determine the no load RPM needed. I know that most motors have a max efficiency at about 75% of their no load RPM. I want a motor that will turn that prop at 10,000 RPM under load so 10,000 = 75% of the no load RPM I need. That makes the no load RPM needed one third more than that or 13,333 RPM (10,000 x 1.33 = 13,333)

3 - Choose a cell count for the battery. The charged and rested voltage for the chosen cell count will help determine the Kv needed to get the 13,333 no load RPM. For this example I'll use a 3S pack and the voltage will be 12.4V (4.13V per cell). I could use 12.6V (4.2Vper cell) but using 12.4V allows for a small voltage drop under load.

4 - Determine the Kv. Divide 13,333 RPM by 12.4V and that is your Kv. In this case the Kv needed would be 1075.

So I look up the turn count that is closest to 1075 and start trying different sizes of wires to find the wire that will fit on the arms and give me that turn count.

I would actually be using Turn Calculator 5 instead of the Simple Turn Calculator at this point so that I could see what options I would have to choose from other winds and both Delta and Star terminations.

The yellow data entry boxes in Simple Turn Calculator and Turn Calculator 5 both assume that you are entering data for a DLRK wind. If you strip a motor and find another wind there and/or another termination method there and then enter that in the yellow boxes in TC5 or STC it will generate a wind table that is less accurate.

But, as Trug says, "You must suffer the arts." and keep re-doing the work until you perfect your wind! If you want some good background music for motor rewinding, I suggest Ringo Starr's "It Don't Come Easy."

Jack
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Old Nov 08, 2011, 04:46 PM
Wingbreaker
Italy, Lazio, Albano Laziale
Joined Oct 2008
156 Posts
It doesn't look an easy task.
I see on HK that there are other 3 2415 motors named:
6T 4400Kv
7T 3850Kv
9T 2700Kv
I suppose that 2700Kv is the minimum value I can expect before efficiency will drop dramatically.

So it will suit a fast ship (like the easyjet) with a 3s lipo and a small prop around 6x4 or 5x5. Isn't it?

9 arm stator was the Jack right guess!

I see that the motor seems wound using two wires in parallel. In case I'll decide to rewind it, it's better to use a single thicker wire or use two as the original?

Thanks for your help
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Old Nov 08, 2011, 06:21 PM
Jack
USA, ME, Ellsworth
Joined May 2008
16,924 Posts
They probably picked two wires because it is easier to get the smaller strands wrapped around the stator.

The ideal thing would be to use one wire of a size such that it will fill most of the available space on the stator arms. Normally the limitation will be that you have to share the space at the bottom of each "V" with the two adjacent arms so it would be typical to have two layers of turns on each arm and the size of the wire would be the largest that would let you do that.

A single thicker wire is better as long as it will work. Sometimes we will replace a larger number of strands with just two or three strands. If you measure the wire that is on it now and look at the surface area figures on the wire a good start would be to pick a strand that has a surface area that is the sum or the two wire or larger. A larger strand will carry more current of course.

The advice you've gotten about the motor being intended for use as a high RPM motor is good advice. Most nine arm stators have 12 or 10 magnets for Kv's down around 1600 or lower. More magnets is more power and at the lower RPMs the ESC can keep up with commutation requirements. Too many magnets too fast and it loses it's place...

But you can try yours and see what you get, it will almost undoubtedly fill some need even if you have to build another plane for it.

The attached images of a TP 2409-12T motor that had three strands of 0,32mm in 12 turns. It was rewound in the ABCABCABC wind with a single strand of 23 AWG wire and that increased the surface area of the wire to 159% of the area of the original strands.

The original motor was a 1600 Kv motor, I terminated that one Star instead of Delta and got a lower Kv of 1201 because it suited my needs best.

The motor developed more power, ran cooler, and was a better motor. The work is a hobby, the time it takes does not matter. It does not make sense to some but many of take a lot of satisfaction out of doing it.

Jack
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Old Nov 08, 2011, 10:40 PM
Registered User
Joined Sep 2010
104 Posts
I was looking at spec, I saw the idle current at 5.5A for that 3 turn motor, but doesn't show at what volts. I assume they do the test at 10V. The 9 turn version is 1.7A at idle, similar to hk2221-10 at 1.79A 10V. (seeing that your motor has 24mm diameter, 15mm length stator, it should be comparable to hk2221).

If you wind it 9 turn but terminate it "Y" (I'm guessing the original wind was terminated delta), You should get around 1550kv and get idle current right around .8A.

I doubt any of the version of that except for that 9turn have good efficiency. I'm seeing 72% efficiency and below. I think you could go up to maybe 18 turn and have good efficiency at 75% and up.
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Old Nov 09, 2011, 09:53 AM
Wingbreaker
Italy, Lazio, Albano Laziale
Joined Oct 2008
156 Posts
Nice winding Jack.

Now I'm a bit confused about winding the notor.
I need some tutorial. Some time ago I found a couple of short manuals and videos on Youtube that showed the basics. Differences between Y and delta and so on.
I had a look at the first post in this section but it's quite confusing.

Could you suggest me something easy to start?

Thanks

Al
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Old Nov 09, 2011, 10:35 AM
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lectroglide's Avatar
United States, WA, Puyallup
Joined Aug 2006
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Quote:
Originally Posted by asimmetrico View Post
Nice winding Jack.

Now I'm a bit confused about winding the notor.
I need some tutorial. Some time ago I found a couple of short manuals and videos on Youtube that showed the basics. Differences between Y and delta and so on.
I had a look at the first post in this section but it's quite confusing.

Could you suggest me something easy to start?

Thanks

Al
havent been winding too long but after coming here and asking questions got me thru some pain, I could be wrong but think the ABCABCABC single stand wind would be the easiest to start with,meaning all turns are clock wise,you can terminate with WYE or DELTA, WYE prolly being easiest to deal with at 1st.......ask questions here or go to the "kamoto page and click on tutorial, it will take you stepXstep and is a very good visual tool
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Old Nov 09, 2011, 07:24 PM
Jack
USA, ME, Ellsworth
Joined May 2008
16,924 Posts
Quote:
Originally Posted by asimmetrico View Post
Nice winding Jack.

Now I'm a bit confused about winding the notor.
I need some tutorial. Some time ago I found a couple of short manuals and videos on Youtube that showed the basics. Differences between Y and delta and so on.
I had a look at the first post in this section but it's quite confusing.

Could you suggest me something easy to start?

Thanks

Al
Hi Al,

As a guy that has been winding motor about a year, I can feel your pain!

I don't do good with videos, I am a book and printouts kind of guy. These are the slightly earlier versions of the "kamoto page and click on tutorial" manuals that electroglide mentions. The page he mentions is at http://www.komodohobby.com/ and you can click on the Tutorial Download link at the top of that page to get to a list of the latest versions of these manuals.

I fumbled and stumbled my way through it with the various threads here and all the other internet pages that helped. As I got older and smarter I developed an eye for stuff I wish I had found in the beginning. One of the things I found post facto were the Komodo kit motor assembly manuals. Those are the best written and illustrated manuals I have found for explaining the parts, walking you through the rewinding of a motor from start to finish, and getting it terminated.

Here is a copy and past from my notes about those manuals and links to downloads for them.

Komodo kit motor assembly manuals
---------------------------------------------------

Title: KH–257D Outrunner Motor Kit

Link: http://www.micronradiocontrol.co.uk/.../KH-257D-1.pdf

Shows marking and mounting of 10, 14, or 16 magnets to endbell and gluing a 12 arm stator onto a bearing tube. Show winding schemes for 10, 14, or 16 magnets and DLRK, LRK, and ABC winding schemes, preparation and mounting of 12 magnets, and ABCABCABC winding of phases with 12 turns of wire. Shows Delta and Wye terminations, details of preparing and soldering winding leads, and fitting of bearings, motor shaft, and prop savers.

Title: KH -278 Outrunner Motor Kit Version 2

Link: http://www.micronradiocontrol.co.uk/.../KH-278-v2.pdf

Shows gluing of two 9 arm stators onto a bearing tube, preparation and mounting of 12 magnets, and ABCABCABC winding of phases with 12 turns of wire. Shows Delta and Wye terminations, details of preparing and soldering winding leads, and fitting of bearings, motor shaft, and prop savers.

Title: KH -283 Outrunner Motor Kit Version 2 (Stick Style)

Link: http://www.micronradiocontrol.co.uk/...-283_stick.pdf

Shows gluing of two 9 arm stators onto a bearing tube, preparation and mounting of 12 magnets, and ABCABCABC winding of three phases with 10 turns of wire. Shows Delta and Wye terminations, details of preparing and soldering winding leads, and fitting of bearings, motor shaft, and prop savers.

Title: KH -283 Outrunner Motor Kit Version 2 (Back Mount Style)

Link: http://www.micronradiocontrol.co.uk/...H-283_back.pdf

Shows gluing of two 9 arm stators to make a double stator, preparation and mounting of 12 magnets, and ABCABCABC winding of three phases with 10 turns of wire. Shows Delta and Wye terminations, details of preparing and soldering winding leads, gluing of double stator to stator mount, and fitting of bearings and motor shaft.

Pick the one of those that best matches the stator you want to rewind (9 arm or 12 arm) and they will probably get you going.

Jack
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