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Old Oct 04, 2012, 10:31 AM
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United States, WA, Seattle
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In my bench testing and observations the PZ 10x8 is a better prop than the GWS SF 'noodles' in that size range. Like GWS no data is published to you have to go by sound and gut feel.
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Old Oct 04, 2012, 10:57 AM
Jack
USA, ME, Ellsworth
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Quote:
Originally Posted by flydiver View Post
In my bench testing and observations the PZ 10x8 is a better prop than the GWS SF 'noodles' in that size range. Like GWS no data is published to you have to go by sound and gut feel.
OK, all that is good to know. And that is pretty much my standard approach.

Jack
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Old Oct 04, 2012, 11:43 AM
What goes up must come down..
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I rarely rev my DAT motor inside if I do it's mostly at low RPM...or sometime at oiling period without prop but the PKZ prop don't flutter @ WOT and full air speed...doing pretzel figures.

I found this video of my bipe stock with the DAT motor then after some mod..but the user didn't say about his motor but I beleive it's a Turnigy Air L3010C (420 W Jack please find us a winding) ? and to me a PKZ prop on 4S..
Link:
modified HOBBYKING Pitts Special foamy (2 min 27 sec)


Roger
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Last edited by rodair; Oct 04, 2012 at 12:02 PM.
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Old Oct 04, 2012, 01:13 PM
Jack
USA, ME, Ellsworth
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Something went wrong as I was testing the LRK wind on 4S and I cooked it this morning. But I got some good data before that happened and it looks good for this being a nice 4S motor.

Prop = APC Thin Electric 14 X 10, battery A123 2300 mAH 5S pack

The 5S A123 pack closely emulates the voltages in a 4S LiPO pack. This pack was charged and rested and at 16.98V at start of test run. A LiPO would have been at about 16.7V or so. As you can see during the testing, the voltages get to those that are comparable for a 4S LiPO (I don't own a 4S LiPO).

This is how the test went:

0-7 seconds = 1,391RPM, 16.97V, 0.79A, 13W
temp rise 70F to 71F

8-21 seconds = 2,496 RPM, 16.75V, 2.82A, 47 W
temp rise 71F to 73F in 13 seconds

23-38 seconds = 3,285 RPM, 16.11V, 8.34A, 135W
temp rise 73F to 89F in 16 seconds

40-54 seconds = 4,032 RPM 15.27V, 15.75A, 241W
temp rise 89F to 120F in 15 seconds

A few seconds from the end of that I noted a sudden and rapid temp rise on the eLogger's LCD Power Panel. I think the problem (short or whatever) had already occurred. I started reaching for the throttle control (servo tester) and may have been turning it down as the following readings occurred:

@ about 60 seconds
431 RPM, 8.48V, 104.36A, 885W temp 134

At the same point in time the motor stopped with a squeal, a big spark was noted, and some smoke leaked out of the windings.

The autopsy shows one motor lead has a melted break in it and all the wound arms showed some evidence of discoloring from over heating. Several had charred insulation also.

I think this motor was doing fine until a short occurred. In fact it was looking very good on 4S at that point, I had some throttle travel left and was still way short of the RPM limits for a APC TE 10 x 14 prop.

I had insulated the Wye bundle and finished up the terminations this morning. I added one of the Strong Motors winding terminators and flexible (16 AWG) motor leads. I can't help but wonder if maybe I didn't damage some insulation or something in the process. The melted spot on motor lead was where it crossed over the Wye bundle, maybe that shorted there.

Let's see, 80 gram motor, 885W peak reading, that is over 11 Watts of input power for each gram of motor weight. Maybe I could get a job testing motor for some of the vendors here?

The good news is that my Phoenix 80 ESC is still alive and well in spite of the 104A peak.

Jack
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Old Oct 04, 2012, 06:43 PM
What goes up must come down..
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Well like you said you still have the ESC intact and some wires, time to rebuild!
Thanks for sharing your taughts and results..too bad I don't have # 21AWG wire gauge looks so slim and well vented on the stator...will you rebuild it?
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Old Oct 04, 2012, 06:48 PM
Jack
USA, ME, Ellsworth
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Oh yeah, it ran to good not to have one and be able to gather up the rest of the pieces to the puzzle. I wouldn't be surprised that the short was my fault, it is sort of crowded in there with the Wye bundle and that winding terminator I like to use. On the next one I won't do that...

I'll probably have it together again tomorrow, it is already stripped. Got your PM and will get those bands off to you tomorrow.

Jack
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Old Oct 04, 2012, 09:01 PM
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885W that's a record!! Am I understanding that the prop is 10" diameter with 14" pitch?
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Old Oct 04, 2012, 10:24 PM
Jack
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Quote:
Originally Posted by zeroback View Post
885W that's a record!! Am I understanding that the prop is 10" diameter with 14" pitch?
Yeah, it would make for some good advertising and sell some motors though!

The prop is an APC 14 x 10 = diameter x pitch, that seems to be the standard format for listing those so no one really ever explains which is which.

The motor was just starting to wake up that prop with the 4S voltages, the temp was climbing but not real fast. And then the temp shot up and it fried. I was thinking I could get it up to maybe 6,000 or so before it was over. Not sure how long it could have held on there but it will be interesting to see.

Jack
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Old Oct 05, 2012, 03:16 AM
What goes up must come down..
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Maybe the max amp that can pass throughout a #21AWG wire... to reach 800 Watts on 4S was to much expectation thus reaching the max load your copper wire can take.
V= voltage I=current W=watts (power)
V x I = W so W/V= I
Voltage here on 4S= 3.7v x 4 = 14.8 v
To be conservative I use 800 Watts (what you want to get from your re-winding)
W=800watts so 800w/14.8v = ~55Amp! that's a lot for the poor little thing!

Do you seriously think you can pass those Amp through a "nick free" #21AWG wire without having any burn out even if well vent?

Just something to look at before re-winding maybe a larger size s/b consider here if you want to use such large props!

Roger
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Last edited by rodair; Oct 05, 2012 at 03:28 AM.
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Old Oct 05, 2012, 08:14 AM
Jack
USA, ME, Ellsworth
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Quote:
Originally Posted by rodair View Post
Maybe the max amp that can pass throughout a #21AWG wire... to reach 800 Watts on 4S was to much expectation thus reaching the max load your copper wire can take.
V= voltage I=current W=watts (power)
V x I = W so W/V= I
Voltage here on 4S= 3.7v x 4 = 14.8 v
To be conservative I use 800 Watts (what you want to get from your re-winding)
W=800watts so 800w/14.8v = ~55Amp! that's a lot for the poor little thing!
If it wasn't obvious, that was an accident. I did an autopsy and can post an image of the melted wire and charred windings later if you want to see it.

Quote:
Do you seriously think you can pass those Amp through a "nick free" #21AWG wire without having any burn out even if well vent?

Just something to look at before re-winding maybe a larger size s/b consider here if you want to use such large props!
It was doing fine at 4,000 RPM, barely even getting warm at 16A or so. And I wasn't at full throttle yet. So it was the short developing that messed every thing up. I think I could get that prop up to more RPM than that and get more current through those windings so I'll try it again.

When I get to the point where it overheats (gets to my 120-130F personal limit) at full throttle that will be my quitting point. I think on the bigger props you'll be able to use them in bursts but not continuous. And I don't usually fly anything at continuous full throttle anyway.

Truglodite got one of his Half Parallel dLRK wound DAT-750's up to where it would handle about 400 Watts of input power on 4S with an APC TE 12 x 6 prop. So when I get this one rewound I am going to try that prop too just to see how the LRK and 2PdLRK winds compare there.

Winter is closing in on us here, this is keeping me entertained, maybe I'll get some time out in the snow with too like you plan to do.

Jack
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Old Oct 05, 2012, 10:53 AM
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Quote:
Originally Posted by jackerbes View Post

Truglodite got one of his Half Parallel dLRK wound DAT-750's up to where it would handle about 400 Watts of input power on 4S with an APC TE 12 x 6 prop. So when I get this one rewound I am going to try that prop too just to see how the LRK and 2PdLRK winds compare there.

Jack

Yes please do.


Richard
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Old Oct 05, 2012, 01:33 PM
What goes up must come down..
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Trugloditewas 20 turns DLRK had a lot more copper into it..gee 400W (probably the max. before it start smelling..) with a 2" less dia. prop.
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Old Oct 05, 2012, 02:06 PM
Jack
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So here is a photo of how the motor was terminated. As seen there the Wye bundle was behind the bearing tube.

The second photo has the ends of the melted wire circled in red, the discoloration and charred insulation is also visible.

When I stripped the windings the insulation on the inner layers had softened melted a little in most places and the winds were adhering to each other.

I think was was going on in the final moments is that there was an arcing short between one motor lead across to another wire (maybe one of the Wye bundle wires) and that started the over heating. And it just worsened and eventually the one motor lead melted. The motor may have stopped then, or the ESC may have stopped it doe to the overload, I'm not really sure about that.

Once it was stopped there was not more heating and burning. I disconnected the ESC from the battery but at that point it was already over.

Jack
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Old Oct 05, 2012, 02:11 PM
What goes up must come down..
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Jack, the stator looks fine!
For sure you'll rewind this one with success.
What size of a plane do you intend to put this one into?

Wye and Y terminaison are similar? are they?
I suppose, I have use the diagram on the right when I wound mine..for some reason it was easier for me to "see" ...
I know it's important the way the flow of current is done on an LRK wound DAT.
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Last edited by rodair; Oct 05, 2012 at 02:36 PM.
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Old Oct 05, 2012, 04:13 PM
Jack
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"..Wye and Y terminaison are similar? are they? ..."

Yes, Wye and Y and Star are all the same termination. Thankfully, there is only one name for the only other way to do it, Delta. I tend to use both Wye and Y sort of hit and miss.

Here are the difference in those two winds.

First, there are some differences in some of the turn directions on the one I use. That is what brings the Wye bundle wires out on one side and a little closer to each other, and the motor wires on the other side also a little closer to each other.

Another difference is that your wind image is considered to be "unbalanced" by the LRK experts. I think it will work but it might not be the best choice.

Note the winding scheme used on mine, it is A-b-C-a-B-c-. The winding scheme on yours, if was listed, could be a-C-B-A-c-b-. That is if the arm at 12 o'clock is considered arm #1 and the numbers proceed around the stator in a clockwise direction.

The German winding scheme generator takes my A-b-C-a-B-c- winding scheme and generate the image you posted. Note that is says is has a winding factor of 0.96593.

When I put the winding scheme you prefer, a-C-B-A-c-b-, into the German calculator it generates a wind image like the one you have, adds the terminations to it, and instead of giving it a winding factor, it says it is unbalanced.

I consider the unbalanced wind to be a bad thing although I am not certain why nor can I explain it.

For the sake of discussion, I have attached a screen shot of the "bad" or unbalanced winding. I don't recommend anyone using it for now. Not until we can sort out the details as to if it is a better or worse wind or not anyway.

Jack
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Last edited by jackerbes; Oct 06, 2012 at 09:18 AM. Reason: corrected winding scheme...
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