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Old Sep 02, 2012, 11:19 PM
Jack
USA, ME, Ellsworth
Joined May 2008
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The original motors were called a Turborix DAT-750 and were sold by a number of dealers, then it became the DT750 at Hobby King. Now there are a number of them that look quite similar.

I don't shop at HK so I bought mine at R2 Hobbies, they still sell it as the Turborix DAT-750:

Turborix DAT-750 - http://www.r2hobbies.com/turborix-rc...ess-motor.html

They seem to sell a nearly identical motor for a little more and call it the Eurgle DAT-750. The specs are a little different, it has an odd sounding shaft size 3.68mm (??) , it has the connectors fitted, and the magnets are black instead of silver.

Eurgle DAT-750 - http://www.r2hobbies.com/rc-accessor...ess-motor.html

And I think the HK DT750 is still the same motor with fewer accessories and without the Turborix label. Email the people at R2 and ask them for their price on a larger quantity, they are very quick to reply to emails and easy to deal with. My business dealings with R2 Hobbies have all been very prompt and pleasant.

I would insist on getting the Turborix motors though, that Eurgle motor has an odd shaft size or it is a mistake in the specs...

Jack
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Old Sep 03, 2012, 05:29 AM
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ikorman's Avatar
Croatia
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Quote:
Originally Posted by jackerbes View Post
The original motors were called a Turborix DAT-750 and were sold by a number of dealers, then it became the DT750 at Hobby King. Now there are a number of them that look quite similar.

I don't shop at HK so I bought mine at R2 Hobbies, they still sell it as the Turborix DAT-750:

Turborix DAT-750 - http://www.r2hobbies.com/turborix-rc...ess-motor.html

They seem to sell a nearly identical motor for a little more and call it the Eurgle DAT-750. The specs are a little different, it has an odd sounding shaft size 3.68mm (??) , it has the connectors fitted, and the magnets are black instead of silver.

Eurgle DAT-750 - http://www.r2hobbies.com/rc-accessor...ess-motor.html

And I think the HK DT750 is still the same motor with fewer accessories and without the Turborix label. Email the people at R2 and ask them for their price on a larger quantity, they are very quick to reply to emails and easy to deal with. My business dealings with R2 Hobbies have all been very prompt and pleasant.

I would insist on getting the Turborix motors though, that Eurgle motor has an odd shaft size or it is a mistake in the specs...

Jack
Thx. I contacted them...

Btw. beside brute force of cutting and stripping the wires, did you try some some kind of solvents? I have looked into ca & epoxy removal stuff, but I suspect that it would also affect stator and lamination insulation...

Ivan
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Old Sep 03, 2012, 08:00 AM
Jack
USA, ME, Ellsworth
Joined May 2008
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Quote:
Originally Posted by ikorman View Post
Thx. I contacted them...

Btw. beside brute force of cutting and stripping the wires, did you try some some kind of solvents? I have looked into ca & epoxy removal stuff, but I suspect that it would also affect stator and lamination insulation...

Ivan
Here is a recent thread that is destined to become famous for helping with getting epoxied windings off of motors:

http://www.rcgroups.com/forums/showthread.php?t=1709338

It describes how you can use the small jet of hot air from a plastic welder, direct it right at the point where a bundle of strands is glued down on top of a winding, and simply lift the strand away when the epoxy has softened:

http://www.rcgroups.com/forums/showthread.php?t=1709338

I had made a similar discovery earlier when I used a small butane torch to remove the windings from a D4023-850. You can see the details on that here:

http://www.rcgroups.com/forums/showp...7&postcount=40

I have since acquired a small pencil type torch that has a smaller, more focused flame, and it will probably work even better than that slightly larger torch seen in that link above.

And I once used a more brute force attack successfully on a DAT-750 and described that earlier in this thread:

http://www.rcgroups.com/forums/showp...postcount=1122

The earlier DAT-750 motors that I purchased from R2 Hobbies did not have any epoxy on them at all, you can see one of those in the attached before and after winding image.

There have been two distinctly different versions off the DAT-750. The motors are not marked or described as V1 and V2 or anything but the differences are fairly easy to spot:

V2 - Has a 9mm bearing tube and uses larger 8mm O.D. bearings

V1 - Has 8mm bearing tube and uses 7mm O.D. bearings

V2 - Hole in motor mount is 9mm

V1 - Hole in motor mount is 8mm

V2 - Magnets are flat

V1 - Magnets are curved (there may have been some V1 motors with flat magnets also)

If you are going to use these in large numbers it will do you well to browse this thread. Solutions have been found for all of the "annoyances" that might arise with this motor and everything you'd want to know about rewinding it is here too.

Jack
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Old Sep 03, 2012, 04:10 PM
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Thanks Jack. I really appreciate your help

Ivan
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Old Sep 03, 2012, 05:08 PM
Jack
USA, ME, Ellsworth
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No sweat, I love this motor and cannot stay away...

Jack
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Old Sep 16, 2012, 05:57 PM
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i have bought some Brushless DT750 from Hobbyking. Last week, one Brushless have a broken e-clip and i need a possible replacement part for this. The thickness is 0.35mm. Could someone tell me where to buy this part. And is there any replacement shaft with thread. Thank you.
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Old Sep 17, 2012, 10:12 AM
Jack
USA, ME, Ellsworth
Joined May 2008
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You haven't looked in this thread, have you?

A DAT-750 Get's the Shaft! - http://www.rcgroups.com/forums/showp...postcount=1080

Tired of bending shafts? More info here fitting prop savers - http://www.rcgroups.com/forums/showthread.php?t=1419378

And making your own shafts is here - http://www.rcgroups.com/forums/showthread.php?t=1240725

Good luck with it!

Jack
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Old Sep 17, 2012, 10:40 AM
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Quote:
Originally Posted by Headi1986 View Post
i have bought some Brushless DT750 from Hobbyking. Last week, one Brushless have a broken e-clip and i need a possible replacement part for this. The thickness is 0.35mm. Could someone tell me where to buy this part. And is there any replacement shaft with thread. Thank you.
http://www.rctimer.com/index.php?gOo...1&productname=

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Old Sep 18, 2012, 10:05 AM
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Southern Vermont
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Quote:
Originally Posted by jackerbes View Post
And making your own shafts is here - http://www.rcgroups.com/forums/showthread.php?t=1240725
Jack
That's a gem!
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Old Sep 20, 2012, 05:16 PM
I can fix that.
United States, PA, Mountain Top
Joined May 2006
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Where is the best place to buy the V2's, R2 Hobbies? Hobby King has the DT700's at the USA warehouse - are they V2's?

Not worried about the Kv as they will be rewound for use in a tricopter.

Thanks!
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Old Sep 20, 2012, 05:34 PM
Jack
USA, ME, Ellsworth
Joined May 2008
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As near as I can tell the HK DT750 and the R2 Turbofix DAT-750 and Eurgle DAt-750 are all the same motors with no labels or just different labels on them:

http://www.r2hobbies.com/eurgle-rc-p...ess-motor.html

http://www.r2hobbies.com/turborix-rc...ess-motor.html

For the $3 savings I would order the Turborix. I have had good luck with emails to and from R2. If you email them and ask if you will get three identical motors and if they will be the newer ones with the 9mm bearing tubes, they will give an answer within a day.

I also saw that R2 has them on eBay with free shipping included in the slightly higher selling price:

http://www.ebay.com/itm/160822762007

Jack
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Old Sep 21, 2012, 08:51 AM
I can fix that.
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Thanks Jack!

Email sent to R2!
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Old Sep 21, 2012, 04:15 PM
Jack
USA, ME, Ellsworth
Joined May 2008
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Let us know how it works out.

Some of the V1 motors (our nickname, they don't use it or refer to them that way) had curved magnets and that lookd better to some of us. But if the flat magnets on the V2 motors work as well or better it is a moot point.

If you want trouble free mounting with the supplied mounts, I recommend drilling and tapping a second set of grub screw holes at a right angle to the originals and then, when you use them use any two at 90 degrees to each other or even three for screws. As long as you push that bearing tube full up against the inside of the mount opposite the screw it will work well. It is when you use the two opposing screws that problems with the mounts occur.

Jack
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Old Oct 03, 2012, 10:22 AM
Jack
USA, ME, Ellsworth
Joined May 2008
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LRK Wind on DAT-750 - It's a good one!

I did a LRK wind on this motor to compare it to a stock motor. I had a new in the box TurBORIX motor and used that for the test. It is a motor I got from R2 Hobbies a couple of years ago. It is the original version, TurBORIX marked motor, with the curved magnets and the smaller 8mm bearing tube.

I picked one prop that loads the motor to it's specs to use for the comparison. That is a Great Planes PowerFlow Slow Fly 10 x 4.5 prop. That prop has been tested by Dr Kiwi, I am using the thrust data from flybrushless.com to estimate the thrust as I am not set up to measure thrust directly.

I ran the candidate motor and got a raw Kv of 780, then ran it with that prop to get some data. The result for a full throttle run was:

GP SF 10 x 4.5 - 5,338 RPM, 11.02V, 19.12A, 211W
temp rise 75F to 81F in 15 seconds

Most dealers rated the DAT-750 at around 160-180W so this motor was performing to those standards. At 80 grams, it was handling 2.25 Watts per gram continuous and would surely be able to handle 3 Watts per gram as a peak load.

I played around with the Turn Calculator 5 spreadsheet and my scrap wire collection and did some test winds. I found that I could get 18 or 19 turns in two full layers with 21 AWG wire. TC5 indicated that 19 would give me a 780 Kv terminated Star. The TC5 DAT-750 screen shot is attached.

If a higher Kv was wanted, this wind could be done with fewer turns and larger wire. As you can see, 18 AWG wire at 13 turns with would give a nice two layer fill and a 1164 Kv with a Wye termination. The test wind seem in the image is 18 turns of Micro-Dan 21 AWG. In the end I chose to add a 19th turn and used Tech Fixx Green 21 AWG wire for the final wind.

As you can see, there is quite a bit of latitude here for playing with the wire size, turn counts, and termination on the LRK winds on this motor.

I wound the motor A-b-C-a-B-c- using the attached image from the powercroco winding calculator. If you copy the "A-b-C-a-B-c-" scheme, go to the advanced mode and paste that in, enter 14 poles and choose Y, it will show you the wind. A screen shot of it is attached too.

There are other images and methods for doing the LRK wind, I like that one because it brings the starts (motor leads) out near each other on one side and the ends, for the Wye bundle, over on the other side and also near each other.

This is a pretty easy wind, I used my 3rd hand device to keep tension on the wire as I rolled the stator arms up the wire. To get 19 turns, the last turn or two was "money turn" threaded due to the crowding at the bottom of the "V".

I did a temporary termination for testing and added 3.5mm bullets. I got lucky again and it ran smooth and quiet. When I ran the rewound motor with the test prop I got the following:

GP 10 X 4.5 SF = 5,744 RPM, 11.58V, 10.00A, 116W
full throttle temp rise 74F to 92F in 38 seconds
estimated thrust = 688 grams

And for comparison, the numbers for the stock DAT-750 motor are:

GP 10 x 4.5 SF = 5,338 RPM, 11.02V, 19.12A, 211W
full throttle temp rise 75F to 81F in 15 seconds
estimated thrust = 600 grams

So the LRK wind give me an 8% increase in full throttle RPM, a 48% reduction in current draw, and a 15% increase in thrust.

I am a little surprised but pleased at the differences, especially the lower current draw. I have done LRK rewinds on some other motors, and been happy with them in use, but none those were done with as direct a comparison in mind.

So this motor has gained in power and become much more frugal on using the battery up. That is a good thing, right? It is not overheating at all, that slow steady temp climb seen in the test will probably not be there at all in flight and that is an easy continuous full throttle motor with that prop.

I have to re-orient my thinking a little on the LRK winds. I tend to think of good motors as being able to handle 3 Watts per gram continuous. But this motor is producing the kind of thrust that you would get out of a 3 Watts per gram motor but getting it at 1.45 Watts per gram.

You cannot buy very many LRK wound motors but it looks like a LRK-Wye wound motor at 1.5W per gram can be the equal, in thrust at least, of a dLRK motor at double that power.

This stator, with it's longer arms, lends it self to the theory that LRK winds are best on certain types of stators. I've also read that LRK winds are better when the magnet coverage is reduced to 75% or so. Since the magnet coverage is about 100% now, it sort of makes me wonder what a magnet change would do for this motor.

Jack
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Old Oct 03, 2012, 11:13 AM
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Bishopville S.C.
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Very impressive results! I would be tempted to try larger props after seeing that.
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