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Old May 06, 2012, 02:14 PM
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Carmichael, CA
Joined Feb 2007
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Quote:
Originally Posted by 2400RDR View Post
Regarding the thrust bearing and clip-

I couldn't find it now if my life depended on it, but I read a post in another thread where a guy said he ran his DT750 motors without the clips and washers. He said they were just fine that way.

I'm not sure I'd want to try it on a quad because if a motor separated, it would be a crash for sure, but maybe not on a plane. I find it pretty believable that it could be done though, because there seems to be a tremendous amount of magnetic force to overcome when you take one of these motors apart. I wonder if that force changes much while the motor is running?

Rick
Dave (aka Timocharis) tested this on smaller motors. His data showed that the decrease in performance running without an e-clip was surprisingly small (only a few efficiency points less). Also, as the RPM climbs, rotor gets more displaced, which decreases efficiency... so the only way the rotor will come off is if you crash. One caveat, I don't think anyone has tested this on a fast pusher; in that application I imagine it would be possible for drag to pull the rotor off in flight.

There are good arguments for leaving the e-clip off on pusher setups... there's no rotor displacement being a pusher, and not having an e-clip allows the rotor to pop off in a crash. This can save the shaft from being bent, but it also means the rotor can be lost forever if you crash in to tall grass.

Myself... all the motors in my fleet use e-clips or some other form of retention. I like to keep a supply of assorted e-clips and brass washer shims in my rewinders box. You can be as careful as you wish, but no matter what you do you'll have an e-clip flying across the garage at some point. Best be prepared for that.

Kev
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Old May 06, 2012, 03:48 PM
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Canada
Joined Nov 2000
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Aware of that real posiblity of fastener loss/ failure on these cheapy motors.
I, last year bought several packages of E clips and grub screws and mounting screws in... All... the possible permutations I could think of.
From "deal extreme" or such such other cheap as chips.. Free shipping place in China.
A lifetime supply (Yup!) cost me less than $8 at my front door.
And Yess (happily :-) the quality is at least as good , if not Much! better, than any OEM fasteners found on My motors.
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Old May 06, 2012, 04:17 PM
Jack
USA, ME, Ellsworth
Joined May 2008
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I just noticed today that one of the Chinese RC sites, RCTimers, will sell you 10 clips for $1.00 and ship them for free.

http://www.rctimer.com/index.php?gOo...wt&goodsid=191

They have selected items listed as "shipped for free", when I added a couple of 4mm shafts ($1.20 each) it then wanted $2 to ship the order...

But I bailed out on the order, I didn't really need anything.

Jack
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Old May 07, 2012, 05:48 AM
What goes up must come down..
Canada, QC, Saint-Laurent
Joined Jan 2002
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Bob +1 idea for retreiving, at arrival on the retrival site Kev, the plane already had lost a few feets maybe 20-25' I was happy so without knowing you had done this B4, I have done what you just explain above except I used 4 AA dead batt. pack for thr weight on a 50 # fishing line...I ask a guy name "Raphael" that was really a good "pitcher" form the baseball winning team next to us since I am really poor at throwing things up.
On his fifth attemp, he succed to pitch over and down the other side !
Then holding each ends of the line we started shaking the branch where the plane was stock in..and after ~1 min..the Cub start to move... bouncing left then right to almost to a dead stop but slowly moving and kept on doing this little dance, you should have ear the: Yoouuu, HAAAAaaa, EEEeee until the plane finally hit the ground ppl started clapping & laughting ! The Cub with all it's gear (rewound DAT 700) was retrived.

So most of the parts are saved, I"ll investage the DT motor since it hit pretty hard with a broken prop and cowling + firewall...I am hoping / praying for a straght shaft here and I know there is an unweld ESC wire time to install the STRONG motor PCB end plate :-) .

Thanks everyone, if I would have read this B4 it would have save me time by trying with all kinds of imaginable contraption(s) and God knows I am creative..i.e. "Kind of spear gun" with a tube with a round dowel to bring the line over..lines with heavy weights ( too heavy) a kid bow and arrows.
Thanks for the help, I'll read first next time promise..

Roger

Update: shaft is NOT fine NOR are the connectors thanks to the high density foam used as a DT700 motor adaptor to reach prop position vs end of cowling.
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Old Jul 03, 2012, 10:43 PM
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Joined Jan 2010
496 Posts
Has anyone thought about putting a small rubber washer between the prop and the bell when using a locknut to hold the prop on?

I've been reading about (and somewhat experiencing) the issues of pulling too tightly on the shaft when cranking the nut tight enough to keep the prop from spinning.

I've read many of the solutions like using propsavers instead, or replacing the shaft and using collets, but I was thinking perhaps an easy solution would be using a rubber washer, o-ring, donut shape piece of mounting tape, or something similar between the plastic prop and metal bell to give some extra friction, and that way not have to tighten the locknut nearly as tight, but still keep the prop secured. And even if the locknut slipped a little bit, the expanding force of the compressed material could keep the prop still secured.

Not sure how well it will work, wondering if anyone has tried already.
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Old Jul 04, 2012, 02:39 AM
What goes up must come down..
Canada, QC, Saint-Laurent
Joined Jan 2002
1,724 Posts
Good day all,
I taught everything was fine with the DAT after the retreival but I was wrong! lots of vibrations now + when I apply power above 55-60% a strange sqeaking sound appear and a great drop of power results in no more possibility of take in off applying going full throotle rapidly. It's also strange that if I do progressively I had no problems and was able to do some flights ( 2 off).

I received new bearings intalled them,everything was looking fine running free as it should be I was happy with my work being done as per the book.

I came back home run the motor without a prop I have no issues but as soon I install a prop I can see that quickly applying WOT RPM looking at the prop center it became evident I loose of the prop center hole become as a needdle point + vibrations problems appear.

A torn out prop saver? or srews of this one that aren't seat properly or a mix of both? bent motor shaft?

I would like not having to revove the shaft since I don't have the proper tooling to do so (a press is almost mandatory here that shaft is realling having a good press fit to the bell) and I don't have any replacement shaft...

I just set it aside for now, I didn't investigate more, I'll still have 2 new bearings on hands but I beleive I did OK when I changed these oiling then using a vise and parallell bars..no play can be felt and everything seam to turn like a clock..eyeballing the shaft I cannot see even with straight edge any bent I cannot fell any play ond the bearing/shaft assy..!

Could it become from 2 new props totally out balanced or because my idea to use high density foam isn't a good idea after all? that particular new impact dempering foam part isn't having enough density?

Or could it be because at a certain rpm the "harmonic" got to a point that everything start to vibrating due to all over condition of fatigue airframe condition?

Any comments are welcome here, the idea of the previous post sound very interesting maybe shortening the shaft to the point that the bell become the prop saver at the same time will reduce some vibes if my shaft is bent...

I'll investigate more later ) time factor) so I'll wait for your inputs here..meanwhile I'll recut / refit a new "demper" part maybe this time using balsa block of known density..and check prop for proper balancing the latest not so obvious being the cause here...up to 3 new GWS ones were installed so far...

Roger
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Old Jul 15, 2012, 06:11 PM
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Joined Mar 2011
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My first rewind ever !

A quick word to describe my first rewind

HK DT750
Brocott 21AWG wire http://www.brocott.co.uk/enamelled-m...ww071-250.html
dLRK-Delta zig-zag (10-6)
kV : 897 rpm/V

Only 16 turn were possible. My best bet has been to start every wire at the same time, it permitted to stay absolutely symetric and terminate in about 3 hours. Not an easy task but the excellent Brocott wire helped a lot.

The new kV is 897, what I intended for my GemFan 11x4.7.
With 3S Lipos, the thrust is progressing from 1224g to 1586g and power from 207W to 339W, under the 30A limit of my ESCs. Not bad for a $10 motor

4 of them will equip my quad. I'm working on clamping mounts...

A special thank to Jack

Zaggy


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Old Jul 15, 2012, 08:23 PM
Jack
USA, ME, Ellsworth
Joined May 2008
17,141 Posts
Beautiful looking rewind zaggy, nice job.

I don't understand the use of the term "zig zag" in winding.

There was some mention of zig zag winds or turns added to a wind in a zig zag manner here early in this thread but not enough detail to explain it to me. That was also 12 on 13 turn dLRK wind I think. The mention of it is here but there is no real detail or explanation:

http://www.rcgroups.com/forums/showp...&postcount=224

On your images, you might want to try going to the "Go Advanced" posting mode, scrolling down, and uploading the images from the Manage Attachment menu. That puts the images on the server and keeps them available for as long as the thread is here. It also helps people on slower connections. I usually try to crop images to 800 x 600 or so as long as I don't lost details. The images show as a thumbnail and can be clicked on for a full size view (I usually do that in a separate Tab in FireFox).

Is you wind the dLRK for Delta variant? I have a version of that in the attached image, your's might not be exactly the same (turn directions, etc.) .

As far as good winds for this motor, the Half Parallel dLRK wind has been the one that has produced the most power here. On 4S that static tested to around 400 Watts with an APC 12 x 6 prop. That was a 20 turn wind with 21 AWG wire, Half Parallel DLRK, terminated Wye.

But that is a tough wind to do, I was able to do it with 23 AWG wire but not 21 AWG, my hands and fingers are not strong enough I think.

You have a thrust stand, I have been avoiding those....

Jack
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Old Jul 16, 2012, 04:40 AM
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Quote:
Originally Posted by jackerbes View Post
Beautiful looking rewind zaggy, nice job.

I don't understand the use of the term "zig zag" in winding.

There was some mention of zig zag winds or turns added to a wind in a zig zag manner here early in this thread but not enough detail to explain it to me. That was also 12 on 13 turn dLRK wind I think. The mention of it is here but there is no real detail or explanation:

http://www.rcgroups.com/forums/showp...&postcount=224
Is you wind the dLRK for Delta variant? I have a version of that in the attached image, your's might not be exactly the same (turn directions, etc.) .
Thank you, it is visually rewarding
Indeed, I'm not quite sure of the term. It has been used a few time, like here http://www.rcgroups.com/forums/showp...5&postcount=99. This winding has been HOW-TOed by Timocharis http://www.rcgroups.com/forums/showt...=736580&page=3 (from #39)
Basically I choosed this method because as the wires come out by pair, there's no way to be wrong, it almost 'certifies' the winding.
I tried a strand of 2x24AWG, but it wasn't very easy to manage. The 21AWG has the advantage to be rigid enough to be inserted with a plyer for the last 2 turns. The bottom of the arms is almost full.


Quote:
Originally Posted by jackerbes View Post
On your images, you might want to try going to the "Go Advanced" posting mode, scrolling down, and uploading the images from the Manage Attachment menu. That puts the images on the server and keeps them available for as long as the thread is here. It also helps people on slower connections. I usually try to crop images to 800 x 600 or so as long as I don't lost details. The images show as a thumbnail and can be clicked on for a full size view (I usually do that in a separate Tab in FireFox).
Corrected, thanks. But I still have thumbnails & big pictures.

Quote:
Originally Posted by jackerbes View Post

As far as good winds for this motor, the Half Parallel dLRK wind has been the one that has produced the most power here. On 4S that static tested to around 400 Watts with an APC 12 x 6 prop. That was a 20 turn wind with 21 AWG wire, Half Parallel DLRK, terminated Wye.

But that is a tough wind to do, I was able to do it with 23 AWG wire but not 21 AWG, my hands and fingers are not strong enough I think.

You have a thrust stand, I have been avoiding those....

Jack
The thrust stand is remotely managed just in case... : a camera is used to film the elogger and scale displays ;-)
I'm using a delta termination. 6kg of thrust should be enough for now.

Zaggy
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Old Jul 16, 2012, 05:59 AM
Jack
USA, ME, Ellsworth
Joined May 2008
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Thanks for the additional details and info. I realize now that the 'zig zag' wind is another name for what is also called the 'DLRK for Delta' wind. So that is another mystery solved for me..

"..Corrected, thanks. But I still have thumbnails & big pictures..."

And now I realize that I don't know how to remove the original images. Probably because I have never done them that way. In most cases when people do that it is because the images are uploaded to a third party storage site like a "photo bucket". But yours dont seem to be that way. Can you click on the Edit button and see html links to the original images? If so, I'd think that removing those would remove the images.

Jack
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Old Jul 21, 2012, 10:59 PM
TeachSeventh
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Houston
Joined Dec 2008
121 Posts
medium or high timing

Running four of these on a quad copter. My ESC is a Hobby Wing, Medium Timing works and what I used for first test flights today, Medium Timing for this ESC is 16 degrees where the high timing is 26.25 degrees. Would I be better off using the high timing choice?

Thanks,

Joe
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Old Jul 21, 2012, 11:00 PM
TeachSeventh
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Houston
Joined Dec 2008
121 Posts
Props are Slo Fly style 10 x 4.7
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Old Jul 22, 2012, 08:47 AM
Jack
USA, ME, Ellsworth
Joined May 2008
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As long as the motors are starting easily and smoothly and going to full throttle without any stuttering or squealing the default timing setting is working fine.

Usually the need for timing changes shows up when you are running at very high RPM and/or with unusually light or heavy prop loads.

If you go to high timing the motors may still run fine but will probably be using a little more current and getting a little warmer than they were at the default setting. So there is no gain in the change.

Just out of curiosity, are you running four motors off of a single ESC on a quad? Or using four ESCs?

Jack
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Old Jul 22, 2012, 11:51 AM
TeachSeventh
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Houston
Joined Dec 2008
121 Posts
Thanks Jack

Using four hobby wing 30 amp. The four receiver channels plug in on one side of kk board and each of the four ESC on the other. Use just one of the internal BEC from one of the ESC. Going to leave at medium for now.

Thanks

Joe
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Old Jul 22, 2012, 12:53 PM
Jack
USA, ME, Ellsworth
Joined May 2008
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Good luck with it, if you have a thread for the build and other details post it here please. It will be interesting to see how it goes.

Jack
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