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Old Jan 17, 2015, 12:58 PM
Jack
jackerbes's Avatar
USA, ME, Ellsworth
Joined May 2008
17,486 Posts
That HK prop is a copy of the APC Thin Electric props. APC does not make a 11 x 5 but does have a 11 x 5.5. If you look at the performance on that prop here you can get an idea as to the thrust the prop should be capable of.

APC E 11x5.5 - www.flybrushless.com/prop/view/45

And there is some static testing of that 11 x 5.5 prop on the DAT-750 motor here:

TurBORIX - DAT-750 - www.flybrushless.com/motor/view/600

That shows the APC prop capable of up around 900g thrust at a full throttle RPM of about 7000.

I don't expect HK copy to do as well but I'd think the 813g you got on that motor sounds about right for the motor and prop combo.

How much does your quad weigh?

If you are getting total of 3200g or thrust out of four of those props and don't have enough thrust it sounds like you don't have enough power or thrust for your ready to fly weight.

You don't want to have to go to full throttle to get a quad flying, you really want to be down around 1/2 throttle to 3/4 throttle at the most so as to have something in reserve to make up for falling pack voltages as you fly.

If I wanted to fly a quad with those APC E 11 x 5.5 props I would not want the quad to weight more than 1500-1800g or so ready to fly. That should let it launch at a little over half throttle

Jack
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Old Feb 14, 2015, 06:47 PM
What goes up must come down..
Canada, QC, Saint-Laurent
Joined Jan 2002
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Anyone here ever run 4S on this one?
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Old Feb 14, 2015, 06:57 PM
Chris
The Netherlands, NB, Eindhoven
Joined Sep 2010
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Yeap, for 1.5 years. Half of the time on dt700 and the other on dt750s. They barely get warm even at high ambient temps (40 deg C)
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Old Feb 14, 2015, 07:00 PM
5,200 Led Lighted Bike-Bob P.
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USA, MA, Swansea
Joined Mar 2003
2,940 Posts
I have run a number of these on 14.8 volts with good luck in airplanes . I am thinking of using them in multis at some point next. . I have about 16-18 of these great motors. The bearing is the only weak link. Try balancing the motor stator and props. Oil the bearings also. Bearing are cheap. Buy some. I have only had to put a small amount in on my planes after many flights. One of my favorite motors. Now you need others to give more backing comments.
**Neons** Bob
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Old Feb 15, 2015, 08:06 AM
homo ludens modellisticus
Ron van Sommeren's Avatar
The Netherlands, GE, Nijmegen
Joined Feb 2001
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Quote:
Originally Posted by cmavr8 View Post
... They barely get warm even at high ambient temps (40 deg C)
But what prop sizes? Prop determines current → temperature.

Vriendelijke groeten Ron
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Old Feb 15, 2015, 11:28 AM
Chris
The Netherlands, NB, Eindhoven
Joined Sep 2010
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Quote:
Originally Posted by Ron van Sommeren View Post
But what prop sizes? Prop determines current → temperature.

Vriendelijke groeten Ron
Oops yes I forgot to mention, sorry. 9x4.7 gemfans. Tricopter, 1.3kg auw. Hovers at about 55% with a new lipo.

Haha I still need to use g translate Ron
Cheers
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Old Feb 16, 2015, 07:28 AM
Jack
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USA, ME, Ellsworth
Joined May 2008
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This thread is more about rewinding the DAT750 motors than what they are capable of with the factory rewinds. And one of the real "heros of man knitting" for this motor has been Truglodite. If you had to single out the best wind for the motor it would arguably have to be the Half Parallel dLRK wind. Look at Trug's data (quoted from earlier in this thread) for 3S and 4S:

Here are the specs and 3?S and 4S test data from one of Trug's rewinds on the DT750:

DT750 12N14P motor
20 Turns Half Parallel dLRK terminated Wye
====================
Vitals
Weight: 93gm (w/mount & prop nuts/washers)

Kv = 783 RPM/V
Io @ 11.34V = 1.502 A
Io @ 15.33V = 1.797 A
Rm = 0.046 ohm (measured directly @ 1A)

3-cell Data===================================
No Load
8878RPM/11.34V/1.502A

APC 10x4.7sf (@ 29m alt, 19.7C temp): Zippy-R 3s2000
6901RPM/10.35V/13.49A/30.1oz/78.2% effy 139 Watts

APC 11x7e (@ 29m alt, 19.7C temp): Zippy-R 3s2000
6626RPM/10.22V/15.10A/32.8oz/80.1% effy 154 Watts

APC 12x6e (@ 29m alt, 19.7C temp): Zippy-R 3s2000
6464RPM/10.13V/16.65A/39.3oz/79.9% effy 169 Watts

GWS 1280hd (@ 29m alt, 19.7C temp): Zippy-R 3s2000
6186RPM/10.03V/19.53A/43.4oz/77.8% effy 196 Watts

4-cell Data===================================
No Load
11936RPM/15.33V/1.797A

APC 10x5e (@ 29m alt, 18.8C temp): Impulse 4s3000
9502RPM/14.34V/16.66A/45.1oz/85.1% effy 239 Watts

GWS 1060hd (@ 29m alt, 18.8C temp): Impulse 4s3000
9481RPM/14.39V/17.16A/40.5oz/80.4% effy 247 Watts

APC 11x7e (@ 29m alt, 18.8C temp): Impulse 4s3000
8605RPM/13.88V/27.18A/58.1oz/77.5% effy 377 Watts

APC 12x6e (@ 29m alt, 18.8C temp): Impulse 4s3000
8370RPM/13.72V/28.73A/68.5oz/82.3% effy 383 Watts

*Thrust measured directly, efficiency from Badcock.net

Jack
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Old Feb 16, 2015, 07:58 AM
Jack
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USA, ME, Ellsworth
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Trug's winds are mostly with 20 AWG or 21 AWG wire and it is not an easy wind with that wire. It requires the hands of a skilled rewinder working with stubborn persistence an using all the "tricks" like threaded money turns and the like.

But if you drop down to 23 AWG wire it becomes a wind that even a first time rewinder should be able to do. My thread on rewinding a set of three of them for a tricopter have the details on doing that wind with 23 AWG wire:

hexTronik DT750 Motor Rewind for Multicopter - www.rcgroups.com/forums/showthread.php?t=1892195

And the testing on those motor showed them to be very capable of operation on 4S voltages.

When I ran these up on 3S with the GemFan 11 x 4.7 they looked pretty good and were running pretty close to dead cool too. In full throttle runs of 15 seconds or so the temp was only getting into the mid 80F/27C or so range. This was in static testing and in flight, with the motor a little unloaded, drawing a little less current, having better cooling, and being at a little less then full throttle, I figured these will work well on 4S with this prop.

I ran the motor up with a 5S A123 pack (16.5V charged and rested) as that would closely match 4S LiPO voltages. The image is of a test that is about 2 minutes in time.

The eLogger data is pretty busy to the eye at first. There are five data streams there Watts, cumulative mAH, Amps, Volts, temperature (taken with a probe against the windings), and RPM. The Volts and Temp plots are almost the same color but easy enough to tell apart by their positions and timing relative to the RPM (RPM up = Volts down and then Temp up)

The motor was run at full throttle for about 20 seconds, then stopped for for 8 seconds or so, then it was run for another 30 seconds or so with about 17 seconds of that at full throttle again.

The temperature climb lags behind the throttle. I've numbered four points on the temp trace and this is what is happening.

#0 - The motor temp had risen as the motor was setting from a previous warm up run. At the #0 mark the motor had been started, was at full throttle, and the extra cooling air flow was dropping the motor temp from where it had climbed to setting. It fell from 84F to 78F or so.

#1 - The full throttle run that started at 8 seconds started the temp back up again and it peaked again at 82F. The motor was stopped for a few seconds, then run at about 5,500 RPM for a few seconds and you can see again how the cooling air flow and reduced throttle drops the temp again. At about the 35 second point I went to full throttle again and stayed there until 52 seconds (17 seconds at full).

#2 - During the 17 seconds at full throttle the temp again climbed slowly to 82F or so. It was still rising slowly until I throttled back to 6,000 or so. And you can see the motor start cooling again as I dropped back from one or two clicks from full throttle for a few seconds, then the motor was stopped.

I left the eLogger on to see how much the temp would rise in the stopped motor to get a feel for the internal temperature in the windings. And you can see the heat rising from where it stopped at 59 seconds.

#3 - At 120 seconds, a minute later, the temp had to 101F on the setting motor and was leveled off there. At 101F the windings would be just warm to the finger tip.

When the windings get up to 130F or so they are too hot keep a finger tip on them. In testing I monitor the eLogger's Power Panel display and don't throttle back to take some heat off until the windings get up to 130F/54C or so.

I stopped the test there because the pack voltage was down to about 14V or 3.5V per cell under load and that is about as low as a LiPO should be taken.

So this motor was in no danger at all with this prop and on 4S, it could have undoubtedly sustained at full throttle for much longer or maybe even continuously.

The motor was running at around 240W in the full throttle bursts. To simulate use on a tricopter at about half throttle, it was run at 5,500 and 6,000 RPM and the input power at those levels was about 100W and 140W respectively. The thrust would be about 750-800 grams at that point and suitable for use on on a tricopter of up to about 2200-2400 grams or so OK.

Jack
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