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Old May 12, 2010, 09:17 AM
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Chicago, IL
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Okay motorheads... please help recommend a wind that'll pull a Turnigy 11x8.5 3-blade prop with enough oomph to lift a 50oz seaplane (foamie Beaver) from the water. I probably don't need more than 40oz thrust for the job, and I'd like a good balance of thrust and speed... maybe 35-40mph prop speed.

I am currently running a stock DT750 with a Turnigy 11x7SF prop and it easily pulls the plane around in its current configuration with wheels... but the extra weight and and drag from water might require a bit more thrust... plus I like the scale looks of the 3-blade prop.

Any suggestions? I have a few different gauges of GB Newbie wire: 24, 26, and 28... hopefully I can work with what I already have.
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Old May 14, 2010, 12:40 PM
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rodrigocunhars's Avatar
Joined Jan 2009
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Hello!

I'm new here, and I have a Hex Tronik DT750 motor rewind. This engine I Anhe a friend, but he come without wires and do not know how to rewind. I have 26 awg wire, I use this yarn? qunatas turns in each stator do with this thread if it is possible. I usually rewind motors cf2822, I use the same forama Rewind to Dt750?

Ass: Rodrigo. - BRAZIL
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Old May 14, 2010, 01:01 PM
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Carmichael, CA
Joined Feb 2007
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warhead, I'm not at all familiar with that Turnigy 3-bladed prop; can't find any data on it, so I couldn't recommend a wind for it.

Rodrigo, welcome to the forums!
The stock DT750 wind is 18 turns delta, using 8 multi-strands of 34awg. You could do a 36 turn half parallel delta using your 26awg, and get nearly double the copper in the stator. Take your time though, since 36 turns is a lot; miscounting turns gets easy.

Cheers,
Kev
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Old May 14, 2010, 01:57 PM
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Thanks Truglodite !

Truglodite Is it possible to rewind it with a single wire 26 Awg?
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Old May 14, 2010, 02:42 PM
Jack
USA, ME, Ellsworth
Joined May 2008
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Kev,

Or anybody for that matter, where can the DAT750.xls spread sheet be downloaded from? I have that file but wanted to post a link to it and couldn't figure out where I got it from or find it again.

Jack
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Old May 14, 2010, 08:21 PM
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Rodrigo, the 36turn I'm talking about does use a single strand of 26awg. The parallel part is just the way it's terminated. Make sure you understand well what a parallel wind is in this context before you start winding. It's not a multistrand wind, but it is a bit different than the standard wind. Here's a parallel delta schematic... sorta:

http://www.rcgroups.com/forums/showp...7&postcount=88

It's not a schematic, but you might get the idea by just looking at the pictures. It's wound like a standard DLRK delta, but the 4 poles per phase are split in to 2 pairs, and terminated parallel to each other.

Jack,
The DT750 spreadsheet is located on my blog. I think the version on my blog is a little old; my newest spreadsheet is much better... uses the latest DCalc constants and removes a lot of the fudging we often see with efficiency and thrust numbers. I'll upload the latest version after this post.

Cheers,
Kev
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Old May 16, 2010, 01:26 PM
Jack
USA, ME, Ellsworth
Joined May 2008
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Thanks for the help on the spreadsheet Kev.

I have another question on the 16T21 Delta rewind I've been working on. I got it all finished and it look pretty good until I found that I'd made a mistake.

I wound one side of the green phase in the wrong direction. In the image the green phase on #11 and #12 was wound with #12 first and then #11 so the end of the wire emerges between #10 and
#11 instead of between #12 and #1.

I've stopped crying and I'm over it now.

But before I unwind and rewind that I thought I'd ask, does it make much of a difference? Like would the motor run OK like that?

Jack
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Old May 16, 2010, 01:38 PM
Dave North
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Quote:
Originally Posted by jackerbes View Post
But before I unwind and rewind that I thought I'd ask, does it make much of a difference? Like would the motor run OK like that?
If the wire enters between 11 & 12 (at the proper place) that 1/2 phase would be wound in the correct direction and the motor would run normally. The only difference would be a slight increase in Rm due to the extra wire, and a decidedly ugly termination. But functionally, you'd never know the difference.


Dave
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Old May 16, 2010, 02:05 PM
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Carmichael, CA
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Agree... as long as the winding directions are correct, it will work fine. Having a little more or less wire length won't show up in testing, but with deltas you should put effort in to making each phase the same length. Having one phase 1/2" longer than the others will hurt efficiency much more than having all 3 phases equal length but 1/2" longer. So the right thing to do technically: strip the red & blue phases a tad longer to match the extra length of the green phase. It'll run either way, but will be a few steps closer to perfect if you put effort in to matching the lengths.

Cheers,
Kev
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Old May 16, 2010, 02:40 PM
Dave North
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Actually, unless you do some strange wire routing to one wire, there will always be different wire lengths on one phase (take a look at how the termination works). That's not an incurable problem, but I've never seen anyone bother.

Some folks ease this a bit by cutting the wire ends all the same length, but that just moves the problem out to the pigtail (which will have less resistance, but you still have a slight phase imbalance -- which you can "fix" by making one pigtail longer).

If it's worth it to ya, go for it. But you'll never know it one way or the other in practical application. And frankly, my measurements indicate the error is often lost in the "noise." Which is to say, wire drawing inconsistency, stretching inconsistency during winding, regional impurities in the wire, wire proximity in the solder, and quite a few other annoying little imperfections.


Dave
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Old May 16, 2010, 03:02 PM
Jack
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OK, thanks for the answers. I studied that little bit and see that I not only wound the wrong stator first, I wound it that in the wrong direction.

I've got the wire off 11 and 12 and it's still in good shape so I'll see if I can get it right. Worst case, I'll just rewind that phase.

I'm older and smarter now. In the course of winding that I got that Delta wind image printed out and studied it. I understand what I'm doing now much better than when I started.

And in the end I'll feel better about having done it right!

Jack
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Old May 16, 2010, 03:10 PM
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Carmichael, CA
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Quote:
Originally Posted by timocharis View Post
Some folks ease this a bit by cutting the wire ends all the same length, but that just moves the problem out to the pigtail (which will have less resistance, but you still have a slight phase imbalance -- which you can "fix" by making one pigtail longer).

Dave
That's what I do... sorta. I cut my wires about 1/2" from the stator, and solder equal length pigtails (so yep, one's longer). I figure that's unecessary, since the part where equal length matters is in the joints between phases. Of course, there's a lot of variables involved, but my perfectionist nature forces me to weed out the obvious ones.

Jack, good to hear you're on the right track now. Once you've done a couple it becomes automatic.

Cheers,
Kev
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Old May 16, 2010, 03:16 PM
Dave North
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Well now, if you want to do it right, you should rewind the phase. Re-using wire is just asking for it!


Dave
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Old May 16, 2010, 04:22 PM
Jack
USA, ME, Ellsworth
Joined May 2008
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But that *was* still new wire! I know what you're talking about though.

At any rate I've got it wound right now and and I'm going to give this guy a try as it is now.

But I got some work to do first of course. I've got to get it terminated and then I have some motor rebuilding links I have to study a little before I actually put power to it.

Here it is, the world's newest 16T21G DAT750!

Jack
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Old May 16, 2010, 06:10 PM
Dave North
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Lookin' good!

Dave
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