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Old Aug 10, 2011, 07:23 AM
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Thanks Jack,
The 12 x 6 I have on hand is a MA, so a thick beefy prop. I do have an APC 13 x 6.5 E prop. That half parallel looks easy enough. I'd just have to concentrate on turn direction and label the ends so as not to get mixed up. Unless I order so new wire, I'll be using 24 AWG MD wire for the first wind on this. I've got some 22 on hand,,,,but not enough to wind one of these fellows. I was thinking maybe 20 to 22 turns delta might get me in the ballpark. My foamy is a 42" wingspan 3d yak55. No slick airfoil, so it is pretty draggy in the air. Not looking for speed in this one....just alot of grunt.

Dan
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Old Aug 10, 2011, 08:54 AM
Jack
USA, ME, Ellsworth
Joined May 2008
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The actual number of turns found can vary widely as I'm sure you've noticed. Most consider that the intent was that the DAT-750 was wound DLRK with 18 turns and terminated Delta.

If you enter that into Turn Calculator 5 (TC5) you get the data shown in the attached image. And that is a good starting place for rewinding this motor.

Once you do a rewind and measure the Kv you can run TC5, adjust the number or turns up or down to get the other results to track with your result and that will then be a more accurate table for choosing winds.

But it will come out close enough just as it is there.

I've also added to images of two different way to do the wind.

The first is Trug's image for doing either for Wye or Delta. Older versions of that image can be found with an error in the note on doing the Delta term, this image has been corrected.

Manuel_V's image brings the wires that will be paired for the Delta termination out side-by-side and I would use that if I was going to termination Delta.

I've terminated most of my winds Wye (to get the lower Kv) so I usually use Trug's image.

Jack
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Old Aug 11, 2011, 08:11 AM
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Thanks for the pics Jack,
I stripped one of the motors yesterday. I just have to say hats off to you guys that can get one unwound and count the turns. I'm still hitting zip on that part. I've got it rewound with 22 turns of 24 g half parallel. If I'm reading Manuel's TC table right that should be around 704 kv using a star termination. I wound it in a hurry, so not real pretty. Actually had to rewind 2 half phases as I wound the wrong direction. Here are some before and after pics.

Dan
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Old Aug 11, 2011, 08:32 AM
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Nice work Dan, I will be looking forward for a final analysis of your use of these motors down the road. I almost ordered 4 of these but changed my mind last minute and went with these TowerPros instead. Very powerful motors also with a higher wattage rating. They are for my new Emily seaplane.
http://www.hobbyking.com/hobbyking/s...idProduct=5113
While I was CA gluing the magnets I noticed they have a hefty double row of ball bearings on the prop end. I did not check the other end.

My question is this. Why can"t the Hex DT700 series and the newer 800 motors have an extra row of bearings on the prop end? This may help solve the bearing issue. A slightly deeper bore and insert them in. Simple fix for a person with a small lathe or reamers.
**Neons**Bob
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Old Aug 11, 2011, 08:53 AM
Jack
USA, ME, Ellsworth
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Quote:
Originally Posted by Slow_Buzz View Post
Thanks for the pics Jack,
I stripped one of the motors yesterday. I just have to say hats off to you guys that can get one unwound and count the turns. I'm still hitting zip on that part. I've got it rewound with 22 turns of 24 g half parallel. If I'm reading Manuel's TC table right that should be around 704 kv using a star termination. I wound it in a hurry, so not real pretty. Actually had to rewind 2 half phases as I wound the wrong direction. Here are some before and after pics.

Dan
Looks like you are off to a good start, Dan.

It is traditional to do some of the work over and over...

Getting the turn directions right is the hardest part for me. I don't think I could manage it without the images.

Did you get that as a Hobby King DT750? Or as a Turborix DAT-750? Some minor differences in the details are showing up in these motor and I think there is either a new maker or more than one maker for them.

Is your bearing tube 8mm at the largest diameter on the end? I think some of the newer ones are 10mm and that is allowing for larger bearings (8 mm?) to be used. The older ones used 7mm x 4mm x 2.5mm bearings and that was a weak spot or common failure item on them. But if you love a motor you have to love it warts and all!

Jack
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Old Aug 11, 2011, 08:55 AM
Jack
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Quote:
Originally Posted by **neons** View Post
Nice work Dan, I will be looking forward for a final analysis of your use of these motors down the road. I almost ordered 4 of these but changed my mind last minute and went with these TowerPros instead. Very powerful motors also with a higher wattage rating. They are for my new Emily seaplane.
http://www.hobbyking.com/hobbyking/s...idProduct=5113
While I was CA gluing the magnets I noticed they have a hefty double row of ball bearings on the prop end. I did not check the other end.

My question is this. Why can"t the Hex DT700 series and the newer 800 motors have an extra row of bearings on the prop end? This may help solve the bearing issue. A slightly deeper bore and insert them in. Simple fix for a person with a small lathe or reamers.
**Neons**Bob
It would increase the production costs to do that. Probably make it about 37 cents more to produce...

Jack
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Old Aug 11, 2011, 12:08 PM
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Bob,
Thanks for the kind words. Your Emily is a sweet looking gal. I had watched the vid you posted on it and checked your build log earlier. Did you decide the 750 and 700's were not gonna give enough thrust? In any event....good luck with the upcoming maiden!

Jack,
Took me a minute to find my mic as I'm in the middle of a basement remodel project and most of my hobby stuff is sorta packed away. These motors came from HK and have the newer groove ring for the mount set screw to ride in. My digital mic shows the bearing tube to be 9.38 mm at the stator end and 8.3 at the other end. Hopefully I'll get all the wires stripped and terminated and try to get a test run on it tonight.

Dan
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Old Aug 11, 2011, 01:52 PM
Jack
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"..My digital mic shows the bearing tube to be 9.38 mm at the stator end and 8.3 at the other end..."

I haven't measured the bearing tube end at the front of the stator on my DAT-750's but back end where it goes into the supplied mount is like 7.83mm with a LCD caliper. I'm sure that odd number is so it is undersized a little to be an easy sliding fit into an 8mm mount. So it your's is measuring 8.3mm back there they may have changed the mount to 8.5mm or something like that.

Those still come supplied with that round black not used anywhere else mount, right?

Good luck on the first run up!

Jack
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Old Aug 11, 2011, 04:16 PM
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Quote:
Originally Posted by Slow_Buzz View Post
Bob,
Thanks for the kind words. Your Emily is a sweet looking gal. I had watched the vid you posted on it and checked your build log earlier. Did you decide the 750 and 700's were not gonna give enough thrust? In any event....good luck with the upcoming maiden!
Dan
I tried 2 lift offs a couple weeks ago and the 4 Hex DT 750's just struggled. She got about 6 feet off the water and had to come back down. I think it would have been fine for a plane about 13lbs. I was asking to much from them with the added weight. It is running around 19lbs now because I needed to add 2 lbs to the nose to get it down. The plane is to much weight now for the Hex motors. So I bought the 4 TowerPros which are beasts. They would make some nitros blush with envy. I had to hang on yesterday for the runnup. It was almost scary. And boy what a harmony with the motors in sync. Hopefully she will be airborne tomorrow. Then I can decide what I want for a larger battery in exchange for the bean bag added weight. I hope my video comes out ok. Thanks for you comments.
**Neons** Bob
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Old Aug 12, 2011, 09:11 AM
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Bob,
I'll be sure and keep an eye on your build log for an update. Good luck to you sir!

Well...I managed to get the motor terminated and hooked up...it's a no go....motor just wants to try to start and then turn the other way. I must have something hooked up or wound backwards. Gonna have to start over. If third times a charm....I've 2 to go

Dan
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Old Aug 12, 2011, 11:24 AM
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Well Dan. I must say the third time is a charm also. I just had that said to me this morning with my helper. I had a very succesful Maiden flight this morning with no flaws. My new motors are perfect. I will post a video hopefully later today after I compile it.

You should also succeed too. Thanks.
**Neons** Bob
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Old Aug 13, 2011, 08:03 AM
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Success! After some thought, I decided to just try to reconnect my y-bun as I felt confident I had terminated the pigtails properly. Sure enough that was the problem. Using the same 10 x 4.7 gws prop, I'm now getting 22 amps at full throttle. I'll test a 11x6 and 12x6 later to see how they look. Looks like it's time to stick this motor on my plane and see how I like it.

Dan
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Old Aug 13, 2011, 12:16 PM
Jack
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Congrats! It looks like you got a winner.

At 22A (230 Watts or so on 3S) you increased the power by more than 50%!

The DAT-750 shafts are a little on the soft side, they bend pretty easily. And that long shaft with a rigidly mounted prop is an invitation to a shaft bending.

I use mine with a prop saver as seen here:

http://www.rcgroups.com/forums/showthread.php?t=1419378

Jack
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Old Aug 13, 2011, 02:39 PM
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Thanks Jack,
I"ll look into that prop saver. Not sure if I increased the power level for this one or not. Original wind and same prop, same 3s bat was pulling 30 amps. Of course I have no way of checking RPM yet. (Soon with my eagletree ) I'd really have loved to be in the 11 to 13 amp draw with this prop. Seems like that is more the norm for the stock wind. My internals might not be as good as the original motors or my setup is giving bogus numbers. One thing I know for sure, my esc sure likes it better

Dan
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Old Aug 13, 2011, 05:26 PM
Jack
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I've never really tested the stock winds much at all. I've always taken timocharis's numbers in post #1 as where I think the stock motor is at, to quote that:

Hex DT750 Stock 8strand 34swg ~18 Turn

GWS 10x4.7sf TP 1320 3S:
7210 rpm @ 10.76v/13.96a 962 grams 34 oz/thrust 83.9% Efficient
APC 11x4.7sf TP 1320 3S:
6446 rpm @ 10.5v/17.3a 1218 grams 43 oz/thrust 81.6% Efficient

Those work out to 150 and 181 Watts respectively so I've always considered it to be about a 165 Watt motor stock. And considering it's weight (80 grams) those results would put it right around or a little over 2 Watts per gram.

The original testing got 14A with that prop, you're getting 23A, that is what prompted my remark about the increase. And it will probably run at full throttle all day without overheating too. The difference in the ampacity in 21 AWG and 24 AWG will cost you something as will the 22 turn wind.

If you want to try an interesting prop on that try one of the Great Planes 10 x 4.5 or 10 x 7 slow flys. It you like to run at that mid throttle sort of "sweet spot" those might work well there.

Some would consider 2 Watts per gram on the mediocre side but the motor's lovely "high torque" sort of qualities from the larger than average stator, along with how well it responds to better winds, have made it a winner for many of us and on many planes.

Jack
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