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Old Jul 20, 2010, 07:54 AM
ggonsalv is offline
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What are the tools needed for rewinding? Wire will be needed that is enamel coated.

Since you are in Mexico, can anyone in the US (Long Island, NY is where i am) where is a good location to purchase the wire needed without going online. I will need to read the thread to get the exact gauge or has anyone had any luck getting a motor rewound at a place that does this, if it even exists...
Last edited by ggonsalv; Jul 20, 2010 at 08:03 AM.
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Old Jul 20, 2010, 12:24 PM
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Maybe:
Timocharis and Kev, has this motor, rewinded to 16t, to low price.

Manuel V.
Old Aug 13, 2010, 03:10 PM
**neons** is offline
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5,200 Led Lighted Bike-Bob P.
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I posted some info on 2 new planes I built. They use the stock unwound Hex DT-750 motors. They work about the same with the HK copy props of APCe 12X6 and the HK TGY-11X7 SF props. Still my favorite motor. All the build log and the specs are there on the planes along with video links.
https://www.rcgroups.com/forums/show....php?t=1281931
**Neons** Bob
Old Sep 02, 2010, 09:00 PM
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I picked up a couple of these motors in a batch of stuff. Reading this thread a bit I guess a rewind to higher kv for a 7x7 on 3cell is not the best idea?
Old Sep 02, 2010, 10:31 PM
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Probably not. It's more of a torque motor. But you never know!


Dave
Old Sep 03, 2010, 01:31 AM
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How about Dave.

Recently finished a tutorial as an Electric Motor Rewind.
I hope you do not mind, and to use some of your photos in some forums.
Thank you very much for publishing.
I send the PDF file for you to see. is only in Spanish.
(Time to practice)


Manuel V.
Old Sep 03, 2010, 04:55 AM
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Quote:
Originally Posted by Stall'n_N_Haulin View Post
I picked up a couple of these motors in a batch of stuff. Reading this thread a bit I guess a rewind to higher kv for a 7x7 on 3cell is not the best idea?
No reason not to. I suspect that at sensible RPM they would be quite powerful. WE love em because they are easy to wind to very LOW KV I suppose. And low kv small motors are rare things.
Old Sep 03, 2010, 11:23 AM
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Bueno Manuel! Great job. And of course you're welcome to use the photos.


Dave
Old Sep 03, 2010, 12:41 PM
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It already looks to be wound to your rewind of 18T 22awg timocharis. If I had a plane to put it on as-is, I probably would. It looks good and showed no shorts although a stator tooth has some cracked off enamel (? green stuff). It does feel a bit rickety though.

But since I've only wound one motor so far and it was fun enough, I was going to practice on this one for a plane I already have. I've got an old twin jet that I tried a single motor on a long time ago. It was a 5x5 cam speed and went ok. An 8x8 or 8x10 on it might be good for some fast vertical. Or the funjet on a 7x7 or close to that, that handles well. Something similar to this wind, depending on kv when finished.

vintage1, what's a knowledgeable 'sensible' rpm? I was guessing that keeping it under 2x the present rpm of approx: 7200 might hold up? But this is just a total guess.
Old Sep 03, 2010, 12:52 PM
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Jack
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Quote:
Originally Posted by Stall'n_N_Haulin View Post
I picked up a couple of these motors in a batch of stuff. Reading this thread a bit I guess a rewind to higher kv for a 7x7 on 3cell is not the best idea?
The safe maximum RPM on a 7 x 7 (like a GWS HD or DD) would 90,000/prop diameter. So you don't want to run that prop much over 6,300 RPM.

At that RPM you are already out of the RPM range where the prop is efficient and adding more RPM won't add anything to making a plane fly.

The 750 Kv of a stock DAT-750 means that it will turn 8,250 RPM at full throttle on 3S battery at 11V. So you can probably get that 7 x 7 up to its safe RPM limit with that motor as it is. And it makes no sense to rewind for a higher RPM.

So there you have it, a plane with a 90 gram motor and a prop turning 6.300 RPM or so. What's wrong with this picture? The motor is probably only pulling 10A or so at that point, generating about 100 Watts into the propeller, and is wasting at least half of it's power potential. It is a lot of dead weight on the nose of the plane basically.

You can get 100 Watts out of that prop with a motor that weights half as much as the DAT-750. Probably with something that is in the 1,400-1,600 Kv range.

If you want to get rid of those motors offer them up here. Or even PM me.

There are more DAT-750 lovers on this forum than any place else in the world. It is a cult motor of sorts...

Jack
Old Sep 03, 2010, 04:24 PM
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Quote:
The safe maximum RPM on a 7 x 7 (like a GWS HD or DD) would 90,000/prop diameter. So you don't want to run that prop much over 6,300 RPM.
On a twinjet I wouldn't use such a prop but one rated for 16,000rpm in the aeronaut. The apc e 8x8 can go a couple thousand more rpm at 145,000/prop dia. The TJ is what I have and after reading another thread I think it might be fun to try on a 8" lower rpm prop. Not for top speed, but vertical speed/torque.

I'll just have to try and see what I get. Probably put new bearings in it too. If it doesn't work out and survives I can rewind it back to low kv.

I got these to learn on, play with, so I don't want to get rid of them yet. Good to know they're a cult classic of sorts.
Old Sep 03, 2010, 04:49 PM
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Jack
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OK, that makes more sense now.

One of the regulars here, manuel_v, posted this table earlier in the thread and that will give you an idea as to the approximate Kv you can expect from different numbers of turns and by choosing the Delta or Star termination method.

As you can see there is some turn counts that produce higher Kv winds. I'm not one to testify if any or all will work though, I'm new here too. It does seem that the results of winds are always approximate and then can you start fine tuning by adding or removing winds if you're not close enough.

The small bearings do seem to be one of the weak points in the motors. There are two 4 x 7 x 2.5mm (MR74ZZ) bearings, the dimensions are I.D. x O.D. x Width.

Jack
Old Sep 03, 2010, 05:11 PM
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Thanks for the bearing data and chart as I missed the chart so far.

I'll be dropping it to 10P too so gearing will go from 7:1 to 5:1 (and 4:1 if I want to go 8P) since I was planning on running 3cell as 4cell. Might want to go 4cell for efficiency and stay 10P?

Still have to figure out this connection from the linked motor too... "Interconnected, the whole gruppenparallel star (YY)".
Last edited by Stall'n_N_Haulin; Sep 03, 2010 at 07:12 PM. Reason: add pic
Old Sep 03, 2010, 06:32 PM
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Dave North
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The first 750 I got was grindy-cruddy sounding, and everyone else got good ones. Kind of miffed me. But when I got my second one, I tried that bell/shaft combo with the original tube/stator and whaddya know? Smooth as silk.

So I tried stuck the other two halves together and they were smooth too.

The moral is, try doing that with your pair. If you're as lucky as I was, you'll be in good shape with no further ado.


Dave
Old Sep 03, 2010, 07:57 PM
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Jack
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Maybe Dave or Chris or one of the other experts here can help figure out the winding and termination that was used there.

I zoomed in on the image and tried to figure it out but cannot make any real sense of it. The zoomed in image is attached if anyone else can help Stall'n figure it out. The three leads at the top in heat shrink are the three motor leads to the ESC, the other six leads (three hanging out to each side) are unaccounted for.

I sort of wonder if the six leads are bonded together in either one or two "bundles" as would be done in a typical Wye termination. And I wonder if the "YY" in the description implies that there are two "Y" (Wye) terminations here. Could it be a DLRK half parallel terminated "Y" or something?

It is described, as you say, as "Interconnected, the whole gruppenparallel star (YY)" after google translates the page that image is on.

In German it reads "Verschaltet wurde das Ganze gruppenparallel Stern (YY)"

and google translates that as "Interconnected, the whole gruppenparallel star (YY)"

Jack
Last edited by jackerbes; Sep 06, 2010 at 09:39 PM.


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