HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old May 31, 2014, 07:51 AM
Jack
USA, ME, Ellsworth
Joined May 2008
16,682 Posts
Rave
World's Best Rewinding Tool is Found!

I recently broke a 10 x 4.5 CF prop. It was not easy, I had to work at it a little.

I brought the broken off tip home and it was laying on my bench when I was rewinding a motor recently. I have an assortment of thinned and narrowed APC prop tips that I considered to be essential tools. And I also have a few popsicle sticks and tongue depressors that are used for things like pushing the turns back to get arm filled to capacity with perfectly concentric windings.

The prop tips worked good for doing things like pressing winding back against the arms in the slots, guiding a wire past a sharp corner on a hammer head as it dropped in on an arm, and sliding the tip through between adjacent arms while winding to get that tiny bit of extra room for the last turn or so.

I picked that CF prop tip up and as soon as I touched it to the winding I knew that it was the best single winding tool in my inventory! It is so stiff and smooth, and it just does everything better than the APC tips as far as making room for wire and pressing both windings back. And it also replaced the popsicle sticks for pushing the turns together.

Now it is in one of my hands all the time and getting used frequently. I could not work without it!

I still treasure my 3rd Hand Accessory too of course, it is always going to be there for me but when it comes to tools, a CF prop tip is the bee's knees!

PM me for a mailing address if you want to send me a CF prop so I can make a tool for you! I like the 10 x 4.5 best, an 11 x 4.7 may be a good alternative.

And if you are a man knitter and motor head and have not tried any CF props yet, you are missing a major break through in delivering Watts to an airframe. I'm getting my CF props on eBay for only $3.02 each including shipping, and they are in hand in less than a week. Don't let the $3.02 price scare you off, these guys will survive many things that would be the kiss of death for a plastic prop.

Jack
jackerbes is offline Find More Posts by jackerbes
RCG Plus Member
Sign up now
to remove ads between posts
Old Jun 09, 2014, 08:45 PM
Registered User
Canada
Joined Nov 2000
6,871 Posts
OK glad yer happy .
By the way, old 5" Master Airscrew props are ..Also ..rigid enough to equal epoxy glass props.. at least for Wind stuffing duties.
Bare is offline Find More Posts by Bare
Reply With Quote
Old Jun 15, 2014, 01:27 PM
Registered User
Joined May 2014
41 Posts
Quote:
Originally Posted by jackerbes View Post
I recently broke a 10 x 4.5 CF prop. It was not easy, I had to work at it a little.

I brought the broken off tip home and it was laying on my bench when I was rewinding a motor recently. I have an assortment of thinned and narrowed APC prop tips that I considered to be essential tools. And I also have a few popsicle sticks and tongue depressors that are used for things like pushing the turns back to get arm filled to capacity with perfectly concentric windings.

The prop tips worked good for doing things like pressing winding back against the arms in the slots, guiding a wire past a sharp corner on a hammer head as it dropped in on an arm, and sliding the tip through between adjacent arms while winding to get that tiny bit of extra room for the last turn or so.

I picked that CF prop tip up and as soon as I touched it to the winding I knew that it was the best single winding tool in my inventory! It is so stiff and smooth, and it just does everything better than the APC tips as far as making room for wire and pressing both windings back. And it also replaced the popsicle sticks for pushing the turns together.

Now it is in one of my hands all the time and getting used frequently. I could not work without it!

I still treasure my 3rd Hand Accessory too of course, it is always going to be there for me but when it comes to tools, a CF prop tip is the bee's knees!

PM me for a mailing address if you want to send me a CF prop so I can make a tool for you! I like the 10 x 4.5 best, an 11 x 4.7 may be a good alternative.

And if you are a man knitter and motor head and have not tried any CF props yet, you are missing a major break through in delivering Watts to an airframe. I'm getting my CF props on eBay for only $3.02 each including shipping, and they are in hand in less than a week. Don't let the $3.02 price scare you off, these guys will survive many things that would be the kiss of death for a plastic prop.

Jack
Wow! Lets see a picture of this cool new tool you've created.
Rockworthy is offline Find More Posts by Rockworthy
Reply With Quote
Old Jun 15, 2014, 01:43 PM
Jack
USA, ME, Ellsworth
Joined May 2008
16,682 Posts
Quote:
Originally Posted by Rockworthy View Post
Wow! Lets see a picture of this cool new tool you've created.
I don't know what I was thinking! I might be the only guy that has broken a CF prop so far!

And, as much as I hate to admit it, have broken more than one!

Jack
jackerbes is offline Find More Posts by jackerbes
RCG Plus Member
Old Jun 16, 2014, 12:12 AM
Registered User
Joined May 2014
41 Posts
Huh. Well to be honest both ends look pretty much exactly the same. You were able to get the broken end a lot smoother than I would have predicted. I would have thought there would be carbon fibers all poking out and stuff. Hmm. You know, I have to admit, I clicked on this post because I thought it looked interesting. It is very interesting but I have no idea how to rewind a motor! I'm still pretty new to this whole sport in general, but all of it is fascinating to me. Out of curiosity, I am amazed that human-wound turns would be better or more precise than whatever robot made them in the first place. #1 Why is this true? #2 How much better is a really good hand-rewound one than than a mass-produced original?
Rockworthy is offline Find More Posts by Rockworthy
Reply With Quote
Old Jun 16, 2014, 06:36 AM
Jack
USA, ME, Ellsworth
Joined May 2008
16,682 Posts
Quote:
Originally Posted by Rockworthy View Post
Huh. Well to be honest both ends look pretty much exactly the same. You were able to get the broken end a lot smoother than I would have predicted. I would have thought there would be carbon fibers all poking out and stuff. Hmm. You know, I have to admit, I clicked on this post because I thought it looked interesting. It is very interesting but I have no idea how to rewind a motor! I'm still pretty new to this whole sport in general, but all of it is fascinating to me. Out of curiosity, I am amazed that human-wound turns would be better or more precise than whatever robot made them in the first place. #1 Why is this true? #2 How much better is a really good hand-rewound one than than a mass-produced original?
I have a combo 1" x 42" belt and 6" disc sander in my shop and that is what rounds and smooths the broken ends so nicely. It has a port on it for a vacuum nozzle so I am not putting my lungs at risk when I use it. But I move it to a stand outside the basement door for use at longer periods or bigger jobs.

My rule of thumb is that, if I start with a typical average quality, hand wound, cheap Chinese motor and rewind it with a single strand wind I can expect to be able to run it at up to double the input power that it would handle originally. And that will be with a wind other than it can be bought with and with winding that have a cross section surface area that is only a little more than the motor had to start with.

The magnetic karma of the neat concentric turns makes it a smoother running motor and that is something that, while it cannot be seen, is sensed almost immediately if you had ever used the motor with it's original factory windings.

And the limits always come down to heat. When I test a new motor I look for a load that gets the winding up around 130F/54C at the most. And that is the temperature where I back off on the throttle when testing rewinds.

If you rewind one motor and then can't leave it alone, you are a "man knitter" or a a "motor head" and the addiction will probably never be severed if you stay in the hobby.

The image says it all to me, that is a DAT-750 motor that was advertised at a 135W motor, it is now able to handle a continuous input power of 250W and bursts up to 400W.

Jack
jackerbes is offline Find More Posts by jackerbes
RCG Plus Member
Old Jun 16, 2014, 02:25 PM
homo ludens modellisticus
Ron van Sommeren's Avatar
near Nijmegen, Netherlands
Joined Feb 2001
10,455 Posts
/* Oops. Wrong planet. */
Ron van Sommeren is online now Find More Posts by Ron van Sommeren
Last edited by Ron van Sommeren; Jun 16, 2014 at 02:34 PM.
Reply With Quote
Old Jun 16, 2014, 02:30 PM
homo ludens modellisticus
Ron van Sommeren's Avatar
near Nijmegen, Netherlands
Joined Feb 2001
10,455 Posts
Quote:
Originally Posted by Rockworthy View Post
... It is very interesting but I have no idea how to rewind a motor! ...
Sticky: (Re)winding and building motors

Quote:
Originally Posted by Rockworthy View Post
...Out of curiosity, I am amazed that human-wound turns would be better or more precise than whatever robot made them in the first place. #1 Why is this true? ...
By 'hand-knitting' your motor, with one single wire, you can use thicker wire -> lower copper losses -> higher efficiency, albeit at the cost of sore fingers

Efficiency governs power/weight ratio
Higher efficiency does not only mean that the motor makes better use of the batteries' power, it also means the motor is able to handle a higher power input before hitting its maximum temperature mark, i.e. a the power/weight ratio will be higher.

An example
Say the motor has an efficiency of 70% and it can handle 50watt input. That means it can get rid off 30% 50 = 15watt excess heat. Now, by cramming in thicker wire (and/or using better stator-iron, segmented magnets), efficiency increases to say 75% (I'm a bit optimistic here). The motor's ability to loose those 15watt has not changed (by radiation, convection and conduction). This means the motor now can handle 60watt before it hits the 15watt (25% 60watt) losses mark. An efficiency increase of 5% gives an increase in the power to weight ratio of 20% (from 50watt to 60watt). That's why efficiency plays such an important role, in any motor design: efficiency governs maximum power. The motors weight may have increased a bit due to more copper.
A rather extreme example, just for calculation's sake/fun: going from 80% to 90% efficiency would increase the input power the motor can handle by a factor two (a.k.a. 2).

Even a company like Kontronik improves their motors by offering a hand wound series, resistance changes by a factor of 2/3.
www.kontronik.com/index.php?option=com_content&view=article&id=371&I temid=208&lang=en
Winding of a 4" Brushless Motor in Faz Elektrik / 4" Fırçasız Motor Sarım (1 min 5 sec)
Ron van Sommeren is online now Find More Posts by Ron van Sommeren
Last edited by Ron van Sommeren; Jun 16, 2014 at 02:39 PM.
Reply With Quote
Old Jun 17, 2014, 01:42 AM
Registered User
Joined May 2014
41 Posts
I'm AMAZED!!! I'm actually quite shocked that you can see up to a doubling of power output per current in. Thanks for your interesting and detailed responses to my "new guy" post. Lol and I love how it's called "man knitting". That's hillarious. Hey tell me: are most brushless motors easily disassembled to the point where you can see the windings clearly, to be able to tell if they've got sloppy windings or not? Okay, okay, I need to go read that link you gave me, and I will. I can't wait actually; I find electric motor theory in general really fascinating right now.

...And I guess a big plus is if you can re-wind your motors, you could easily rewind an overheated/shorted motor too.

Thanks for the killer info, links and replies. I will check them all out.

Edit: I think I got that wrong. I think you guys said that you can potentially double the amount of electricity the motor can handle before it gets to a given temperature. Thereby increasing the power-to-weight ratio of the motor, so you don't have to use nearly as heavy of a motor to accomplish the same job.
Rockworthy is offline Find More Posts by Rockworthy
Last edited by Rockworthy; Jun 17, 2014 at 02:26 AM.
Reply With Quote
Old Jun 17, 2014, 08:19 AM
homo ludens modellisticus
Ron van Sommeren's Avatar
near Nijmegen, Netherlands
Joined Feb 2001
10,455 Posts
Quote:
Originally Posted by Rockworthy View Post
... I find electric motor theory in general really fascinating right now. ...
www.consult-g2.com
-> course

Quote:
Originally Posted by Rockworthy View Post
...And I guess a big plus is if you can re-wind your motors, you could easily rewind an overheated/shorted motor too. ...
And as you rewind them with thicker/more copper, you get a better motor. Unlesssssssss ... the magnets got to hot, that will weaken them, giving a higer Kv leading to a much higer current. And that case magnets should also be replaced.

See also these before<>after pictures
translate...www.modelbouwforum.nl/forums/model-elektronica/126944-scorpion-hk3026-hk4225-hk4020-hk4025-hk4035-buitenloper-wikkelen.html

Vriendelijke groeten Ron
Ron van Sommeren is online now Find More Posts by Ron van Sommeren
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Rave The world's 14 best aviation museums. porcia83 General Aviation 5 Feb 21, 2014 04:05 PM
Discussion Best Tool(s) For Cutting Round Holes In Foam Airplanes? itsme2 The Builders Workshop 10 Jan 12, 2014 06:19 AM
Found --Found-- Trade my Graupner 9x5's for Graupner 10x5's --Found-- jmisuraca Aircraft - Electric - Multirotor (FS/W) 2 Sep 20, 2013 04:49 PM
Discussion What Is the best Cable Grease? "World's Best RC" any good? MikeBiv Racing Boats - Internal Combustion 9 Jun 03, 2006 12:21 AM
What's meant by "tooling" in the composite world ? yclui The Builders Workshop 3 Jan 17, 2003 05:39 PM