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Old Oct 16, 2012, 09:58 AM
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Dr Kiwi's Avatar
Chattanooga, Tennessee, United States
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Original wind (723.9cc) has 96% more copper than the LRK wind (367.6cc).

Pedantic professor again... how do you get this copper volume.. you can't fit almost a liter of copper in a tiny motor.

I tried to calculate the volume: According to my chart AWG 18ga wire is 0.0403" diameter (= 0.102cm diameter)... thus radius is 0.051cm... square that and multiply by pi and you get cross section of 0.0082 square centimeters... multiply that by length of winding wire (116.8cm)... and you get 0.954cc.
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Old Oct 16, 2012, 10:24 AM
Jack
USA, ME, Ellsworth
Joined May 2008
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Here is what I did:

Volume of copper:

Pi = 3.142, volume of cylinder = pi * r2 * h

8 strands of 0.24mm diameter x 2000mm (78") wire

wrong answer = 3.142 x 0.12 x 0.12 x 2000 = 90.4896cc x 8 strands = 723.9cc of copper

right answer = 3.142 x 0.12 x 0.12 x 2000 = 0.904896mm3 x 8 strands = 0.7239mm3 of copper

1 strand of 21 AWG 0.723mm x 1168mm (46")

wrong answer = 3.142 x 0.3165 x 0.3165 x 1168 = 367.6cc of copper

right answer = 3.142 x 0.3165 x 0.3165 x 1168 = 0.3676mm3 of copper

I've been struggling with math for 70 years, I'm never surprised when I don't get it right.

Jack
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Last edited by jackerbes; Oct 16, 2012 at 10:53 AM. Reason: Correct my bonehead math errors
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Old Oct 16, 2012, 10:39 AM
Jack
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It now occurs to me that my units should have been cubic millimeters, not centimeters...

I have corrected it I think.

Jack
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Old Oct 16, 2012, 06:10 PM
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Chattanooga, Tennessee, United States
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Yes, Jack... the factor of 1000 was the missing bit... we didn't use exactly the same wire diameter, so we don't get exactly the same answer... but we both ended up in the correct order of magnitude!
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Old Oct 17, 2012, 02:10 PM
What goes up must come down..
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Interesting Jack...!
I can't wait here for the results once it's all wind.. lot more copper!
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Old Dec 25, 2012, 06:37 PM
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I just saw this in HK and spotted this motor. Has anyone tried one of these monsters? Hex DT-750's big brother.
http://www.hobbyking.com/hobbyking/s...ner_900kv.html

**Neons** Bob
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Old Dec 25, 2012, 09:03 PM
Jack
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I don't think it has been mentioned here before.

Looking at the specs and dimensions it is nearly identical to the DT750, but they say it will handle twice as much current? Not sure I'll believe that until is has been proven by independent testing.

DT750 - http://www.hobbyking.com/hobbyking/s...ner_750kv.html

DT900 - http://www.hobbyking.com/hobbyking/s...ner_900kv.html

Jack
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Old Dec 25, 2012, 09:49 PM
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Theres also a 1000Kv that looks to be the same thickness as the D4023-850 where the 900 seems to be same as the DT 750. I've not tried either one but am interested in any info or tests anyone might do.


Richard
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Old Dec 25, 2012, 11:13 PM
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Mexico, BC, Mexicali
Joined Aug 2004
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My effort to 909Kv.
DT750, 16T 21awg.

No load: 11,000 rpm, 12.1V, 1.7A, 909 kv.

APC 12x6e, 7500rpm, 11.2V, 24A, 263Watts, 1590g.

http://www.rcgroups.com/forums/showt...=777998&page=5

To 400 watts is a cafe heater.
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Old Dec 26, 2012, 12:01 AM
What goes up must come down..
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Merry Xmas all!
MAnuel v I finally found some tests (wattmeter) around the L3010C motor that you post before (previous page) on youtube that too is "impressive" results for a stock motor!
I can only guess what you or Jack among other here with your nice rewind could do to this one by rewinding one it would almost need a new thread.
I just got one but I lack a good ESC or I have to find out how to properly hook an "opto" one I have on hands...
Here FYI:
Turnigy L3010C-1300kv (420w) Thrust Test (1 min 25 sec)

Roger
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Last edited by rodair; Dec 26, 2012 at 12:11 AM.
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Old Dec 26, 2012, 05:09 AM
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Fourdan's Avatar
Antony (France)
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Hi Rodair
L3010C questions
Could you measure the diameter of the stator tube to go in the flanged support ?
Is the L3010C a 12N14P ?
Is the stator 30x10 mm ?
Are the magnets flat or curved ?

Recent DT750 (4 bought in 2012):
Stator is 34x7mm 12N, 14P flat
Stator tube is around 9mm
Rotor extra blue cylinder is around 10mm no flat, one set screw
No connectors

It seems that DT900 has a flat on the rotor small cylinder ?

Louis
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Last edited by Fourdan; Dec 26, 2012 at 05:42 AM.
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Old Dec 26, 2012, 08:36 AM
What goes up must come down..
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Louis,
physically the L3010C (1300kv) also under the name EDF in Europe, is a different motor than the DT750!
The alum tube is only 7mm instead of 8mm on the one's thus smaller tube bearingd OD
The bell is also smaller in dia. the stator and bell a little longer but not by much, finally same arrangement as for the magnets and poles 12Poles 14Magnets and came with 4mm bullet connectors installed.
Maybe I'll post some pictures later but I really don't want to hi-jack this thread.
So thanks for the heads up since it look like some previous made DT-750 (Jack post) for the bearings size thus for me a problem I thaught to just remove 2 set screw and try this one in my planes! I am now in a defferent ball park... furthermore "lock tight" will be a MUST to avoid the heavy torque of this one...and I can also forget about the bearings that I have in stock since they are not compatible! @ 7mm x 4mm x ?mm lg. and tiny.
One will also have to be carefull when thigthening the set screw not much meat on the alum. bearing tube for the same matter.
On the other hand this one will fit the alum. with heat sink extrusion motor mount for the 24gr. "blue motor" smaller motor that can attach to a 10mm sq. beam and it might the way to attach this one in a more secure less stressing way for the bearing tubes.
I also order it's brother motor the 3010B one that is having a sturdy common mount and bigger bearings althogether...again let's not deviate from the DT-750 here.
I hope this help...defeneatly mauel v is still the winner here with his rewind one!
Roger
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Old Dec 26, 2012, 10:09 AM
Jack
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Here, from a previous post summarizing the DAT-750/DT750 changes, are the versions of the DAT-750 we have noticed

"..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)..."

The V1 and V2 thing is not marked on the motor or mentioned in the specs or listings. That is just something we use in discussion here.

If anyone is looking for DAT-750 motors, check R2 Hobbies and look for both TurboRIX DAT-750 and Eurgle DAT-750 motors as they list it both ways sometimes. And if R2 does not show any in stock as them about it in an email. They seem to be able to re-stock quickly to meet your needs.

"..I can only guess what you or Jack among other here with your nice rewind could do to this one by rewinding one it would almost need a new thread..."

Don't worry about that, we are always willing to hear about any motors here, particularly anything similar to the DAT-750.

That video is a typical "misleading to dishonest" Hobby King video. Yes, the motor did show 1630 grams of thrust but it was only at that level for 3 seconds or so. HK testing usually just ramps up, holds it at peak for a few seconds, and then reports all the big/high number in a manner that says nothing about them being peak readings.

Separate threads for each motor is a good thing and it logical, particularly as the rewinding gets started. We have a thread for the 8043 too now:

http://www.rcgroups.com/forums/showthread.php?t=1491875

But it will not show up in the thread listing here unless it has been active recently. But don't be afraid to "wake up" an old thread. Most of us are subscribed to those threads and will see any new posts automatically.

The D4023-850 had had some initial teething pains in both stock and rewound forms. Things like ripping itself out of the mounts and stuff like that. I have played with the ones I have a little and found solutions for most or all of the issues that came up and they are not that hard to figure out.

To avoid problems with keeping any of these bigger CD-ROM style motors from loosening themselves in the supplied mounts, the secret is to use better screws than the socket head 1.5mm grubs screws (I like the 2mm drive button head socket head screws best).

Another solution is to drill and tap mounting screw holes so they are at 90 degrees to each other instead of 180 degrees opposed. That keeps any looseness in the mount from letting the bearing tube rock on the points of the screws.

I need to spend more time with the D4023-850 but I have not been flying it yet...

Jack
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Old Dec 26, 2012, 10:33 AM
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**neons**'s Avatar
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Quote:
Originally Posted by jackerbes View Post
I don't think it has been mentioned here before.

Looking at the specs and dimensions it is nearly identical to the DT750, but they say it will handle twice as much current? Not sure I'll believe that until is has been proven by independent testing.

DT750 - http://www.hobbyking.com/hobbyking/s...ner_750kv.html

DT900 - http://www.hobbyking.com/hobbyking/s...ner_900kv.html

Jack
Beng nearly identical motors there has to be some strong differences in the windings and weight.. It is a lot to get more power out of the DT-900 over the DT-750. If this DT-900 uses the same 7mm bearng as the 750 motors it will be a load of stress on them if the power claims are correct. I am still thinking maybe the tube can be reworked to take 2 rear bearings to make it a double row.

I wonder if the DT-900 is a better way to go than the DT-750 or 700? This is where I hope to see a side by side comparison sheet in operation tests. Or, would it be advisable to abandon the DT-900 and 750 series and just start a change over to the L3010C motors. I know very little about the L3010C motors. This is my only motor thread I am subscribed too. I will look at the new posted link on this motor also.

**Neons** Bob
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Old Dec 26, 2012, 11:19 AM
Jack
USA, ME, Ellsworth
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Quote:
Originally Posted by **neons** View Post
Beng nearly identical motors there has to be some strong differences in the windings and weight.. It is a lot to get more power out of the DT-900 over the DT-750. If this DT-900 uses the same 7mm bearng as the 750 motors it will be a load of stress on them if the power claims are correct. I am still thinking maybe the tube can be reworked to take 2 rear bearings to make it a double row.
The later DAT-750's had the bearings increased from 7mm to 9mm O.D. And those are an OK size. Not optimal for long life or anything but OK. Most of us will damage bearings and replace often as they are cheap.

Quote:
I wonder if the DT-900 is a better way to go than the DT-750 or 700? This is where I hope to see a side by side comparison sheet in operation tests. Or, would it be advisable to abandon the DT-900 and 750 series and just start a change over to the L3010C motors. I know very little about the L3010C motors. This is my only motor thread I am subscribed too. I will look at the new posted link on this motor also.

**Neons** Bob
The 900 is certainly worth a try. It is the same weight as a DAT-750, probably has the bigger bearing tube, bigger bearings.

The L3010C is also worth a try. It is interesting that it is 4mm smaller in O.D. at 37mm, appear to have about the same stator height as the DAT-750, but is listed as weighing 87 grams or about 9-11 grams more than a 750. Weights are a good indicator of potential but HK is notorious for being a little inconsistent in reporting weights.

I think I'll always have an inordinate fondness for the larger diameter CD-ROM style motors because they are so easy to work on and I also think that their larger diameter contributes to their power. I say that because of the "longer lever" effect it you will when the out runner gearing effect is applied. The magnets are standing further from the center of the motor, they must have more leverage, no?

Jack
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