FAQ cd-rom tricks

[Ron van Sommeren]

Please don't ask general questions or give pats on shoulders in this thread, just add your tips and tricks and discuss them. Use http://babelfish.altavista.com for automatic online translation.

1. Never ever connect a brushless motor (whether in- our out-runner) directly to the battery, the motor will act as a short and go up in smoke! Brushless motors MUST be operated with a brushless controller!
2. Use a DC power supply with a current limiter to protect the ESC during first test runs. Batteries are hardly current limited, to say the least and may fry up the ESC if the newly wound motor has a short in it. If you don't have a power supply, put a heavy a car lamp or a duty resistor between the battery and the ESC. Use few cells that are almost empty. Even empty cells can deliver a lot of current for a very short period of time. However, this period is long enough to ruin your ESC.
3. LRK and CD-rom motors have different winding diagrams.
4. Manuals
   * Several excellent articles on building lrk and cd-rom motors, pictures, winding diagrams, by Brian Mulder a.k.a. 'Mr DIY' on E-zone:
   www.southernsoaringclub.org.za
   -> Articles from Southeasters
   -> Electric Motors - part 1 ... part 5
   * Motor construction articles by Christo v.d. Merwe (nice motor colours )
   www.bavaria-direct.co.za
   * Two motorwinding video files, 14 & 10Mbyte respectively:
   www.utahflyers.org
   -> video
   -> instruction
   * One hour instructional video (on DVD)
   www.strongrcmotors.com
   -> instruction docs
   * Most, if not all, motor kit suppliers have manuals on their sites, very useful e.g.
   www.gobrushless.com (link "Brushless 101", must read diy articles)
   www.aircraft-world.com
   www.strongrcmotors.com/
   www.e-foamies.com
   www.dionysusdesign.com/files/CDROM_Instructions.doc
   * Very good LRK and dLRK manuals (winding diagrams differ from cd-rom diagrams)
   ClassicLRK winding tutorials
   pictures:
   http://www.rcgroups.com/forums/showthread.php?t=523039
   bible_1:
   www.powercroco.de (English and German)
   bible_2:
   with the original LRK articles (in English) published in the German ElektroModell Magazine in 2000 and 2001)
   http://www.aerodesign.de/peter/ -> English
   Building/winding manual:
   http://www.torcman.de/index_e.htm
   -> Manuals
   -> Assembly Procedure TM280, 350, 430
   Excellent dLRK winding turorial
   http://www.rcgroups.com/forums/showthread.php?t=736580
   
5. winding tricks, better packing
   http://www.rcgroups.com/forums/showthread.php?t=249007
   http://www.rcgroups.com/forums/showthread.php?t=447174
   http://www.rcgroups.com/forums/showthread.php?t=445750
   http://www.rcgroups.com/forums/showthread.php?t=401641
   http://www.rcgroups.com/forums/showthread.php?t=381117
   http://www.rcgroups.com/forums/showthread.php?t=400958
6. Personal homepages
   www.flyelectric.ukgateway.net/motors.htm (lots of motorbuilding lathe and mill tricks too)
   www.id.ethz.ch/people/allid_list/korosec/privates/ae/motoren/electric/cdrom/ -> link "cd-rom conversion story"
   http://homepages.enterprise.net/jayjay/cdrom_motors.htm (cd-rom conversion for helicopters)
   http://haero.free.fr/maxx_motors/300-manual-2.bmp
   http://www.btinternet.com/~michaelhogg/piccolo/cdrom/cdrom_conversion_final.jpg (step-by-step, one large picture)
   http://users.compaqnet.be/retlaw (Dutch/Nederlands and English)
7. More in this two page thread, manuals, homepages, material (magnet!) sources:
   http://www.rc-unionen.dk/nytforum/to...68&whichpage=1
   http://www.rc-unionen.dk/nytforum/to...68&whichpage=2
8. The metal ring must be mild iron (piping steel). Carbon/aramide/kevlar, plastic, stainless steel, copper, aluminium, glass, ceramics(with the exception of ferrites), wood, resin etc is not suited. These materials behave like air to magnetism, they do not concentrate the flux.
9. Windingdiagram-table and -calculator:
   www.powercroco.de
   -> English
   -> winding table and scheme calculator
10. clear instructive winding diagram pictures
    http://www.powercroco.de/
    -> English
    -> (Tools) winding schemes in pictures
11. An article by Ludwig Retzbach (the 'R' in lrk) about winding errors:
    http://www.modell-aviator.de/content...elt/index.html
    Use e.g. http://babelfish.altavista.com for translation
12. Airgap, magnetwidth and -thickness, #magnets, stator- and rotor-diameter calculators:
    http://www.gobrushless.com/testing/m...calculator.php
    http://kreature.rchomepage.com/calculators/airgap.htm
13. Use good quality wire from a motor/transformer refurbisher/rewinder, they have very good quality double coated wire. Bring your motor (plane, RC equipment) along and you'll probably get it for free. They love to see a motor that can be handled without a crane
14. Don't use cyano-acrylate type glues for gluing the coils, it can be aggressive on some types/makes of wire.
15. To prevent shorts, round/chamfer/bevel the stator corners a bit with a Dremel (carefully) or a fine file.
16. When in a very tight winding situation, round the top of the wire to prevent it from scratching the insulation of the previous winds (shorts). Dull the end of the wire, when sewing the last turns in to remove the burr/sharp edge that occured when cutting the wire.
17. Stator insulation
    Making stator isolation plates, video and pictures:
    http://www.rcgroups.com/forums/showt...6#post10651516
    Pictures:
    http://www.baronerosso.net/forum/sho...09&postcount=5
    Don't use teflon tape for insulation, it flows under pressure (the way it's supposed to do):
    http://groups.yahoo.com/group/lrk-torquemax/message/153
    Use glass/epoxy(cyano) on both stator faces. See the pictures here:
    http://www.modellflug-hager.de/lrk.htm
    An alternative stator insulation method:
    http://groups.yahoo.com/group/lrk-torquemax/message/135
    Insulation discussion:
    http://www.rcgroups.com/forums/showthread.php?t=373184
18. Don't pull the wire to tight around the stator corners to prevent shorts.
19. It can be difficult to keep track of the number of winds during the winding process. Cut wires to equal lengths before doing the winding. If you're one winding of (off?), it will show. This method will not guarantee you get the correct number of windings but at least it will guarantee that all poles have the same number of windings.Take care with thin wires, they can stretch quite a bit.
20. Winding tricks:
    http://www.torquemax.de/TipsMitteWickeln.htm
21. Try to cram as much copper as possible in the slots. It makes for a lower motor resistance, less losses, lower temperature and a higher efficiency. Use thicker wire or wind 2-3 wires in parallel.
    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 more power before hitting its maximum temperature mark.
    An example:
    Say the motor has an efficiency of 70% and it can handle 50Watt input. That means it can get rid off 0.3*50=15Watt excess heat. Now, by cramming in thicker wire, efficiency increases to say 75% (I'm a bit optimistic here). The motor's ability to loose those 15Watts has not changed (by radiation, convection and conduction). This means the motor now can handle 60Watt before it hits the 15Watt (0.25*60Watt) losses mark. An efficiency increase of 5% gives an increase in the power to weight ratio of 20%. That's why efficiency plays such an important role, in any motor design: efficiency governs maximum power.
22. Use a toothpick or a broken prop to push/squeeze the wires a bit.
    http://www.rcgroups.com/forums/attac...d=560137&stc=1
23. List of possible errors, do's and don'ts, tips:
    http://www.powercroco.de/ (English and German)
24. Checking for shorts during winding:
    Connect a battery and buzzer in series. One lead connects to the stator (make sure there's contact with the stator, remove lacquer insulation!) the other lead goes to the beginning of the wire to be wound. Once a short occurs, you will hear it. You can also use an Ohm (resistance) meter for this purpose, some even have a buzzer.
25. Check for shorts between the phases BEFORE you hook them up in star or delta. Also check for shorts between each phase and the stator.
26. You can try and use a battery or condensatorbank to 'blow away' a short between a winding and a stator. Connect one lead to the stator and another to the shorted coil for a very short time but be careful! See
    http://www.powercroco.de/
27. Removing magnet wire insulation can be tricky, especially when using thin or litze/multistranded wire. Just heat the end of the wire with a soldering iron on an aspirine tablet. Nasty/acrid fumes.
28. Neodymium (NdFeB) magnets have a very strong magnetic field. They are also brittle (ceramics). Don’t let them ‘jump’ another, they may chip/break. Randy little buggers them is
29. Be careful with metal filings/parts and magnets. Use sticky tape or sticky paper to remove it.
30. Gluing and placing magnets
    http://www.rcgroups.com/forums/showthread.php?t=452514
    http://www.torcman.de/motoren/manual...o_200e_scr.pdf (chapter 3)
    http://www.solcon.nl/gjkool
31. Make sure magnets are glued in alternatingly: NSNSNS ...Checking magnet placement: use a spare magnet to feel orientation of the magnets. Attract, repel, attract, repel ... You can use several magnets to create a larger surface magnetpole (cascading/tiling) e.g. NNNSSSNNNSSSNNNSSS is a still a 6 magnetpole motor.
32. Optional: use an oven to cure and temper the epoxy used for gluing the magnets inside the iron flux ring (bell). But be careful, set the oven to no more than 60°Celsius (140° Fahrenheit) and wait at least an hour for the temperature to stabilise. Ovens have an initial temperature overshoot that will make the Neodymium magnets loose their magnetism irreversably
33. Use a tool or an extra person to slide the bell&magnets over the armature, you won’t be able to hold it. It will slam home, this is bad for the magnets (any type of magnet) and for the rear ball-bearing on bigger motors.
34. Spin the finished motor with a Dremel/powerdrill, it will act as a generator. Now measure the voltages between the phases (select AC voltage, not DC), they should be the same. Differences may be due to different number of windings, a short between adjacent winds or shorts between phases. This method will not detect a (+n) winds error on tooth x and a (-n) winds error on tooth y (both teeth same phase) because these errors cancel eachother out. Keep speed the same for all three measurements or you will measure three different voltages anyway due to different voltages induced at different speeds.
35. Use a DC power supply with a current limiter to protect the ESC during first test runs. Batteries are hardly current limited, to say the least and may fry up the ESC if the newly wound motor has a short in it. If you don't have a power supply, put a heavy a car lamp or a duty resistor between the battery and the ESC. Use few cells that are almost empty. Even empty cells can deliver a lot of current for a very short period of time. However, this period is long enough to ruin your ESC.

Met vriendelijke groeten Ron
• diy outrunner discussion group
• int. E fly-in & diy outrunner meet, Nijmegen, the Netherlands

[olmod]

On some small cdroms i use small pieces of card between the magnets to stop them jumping together,when im happy with the placement i put a drop of Loctite Black max on each end of every magnet then chuck it in the Dremel hold it inside a toilet roll tube and spin it for a min' or 2,this forces the locktite to even out and mantain ballance as well as fill behind mags'. When cured trim any excess card flush with mag's with scapel then clean up with cotton bud lightly dipped in laquer thinner. It will surprise you how well this works, just check what is spun out inside the tube . Black max is good to 100c by the way. Good thread starter too Ron .cheers all.

[olmod]

Try going through your collection of shafts with a micrometer and select the smallest diameter,carefully grind a radius on the end then with a dremel grinder grind across halfway up just past the radius,you will have what is known as a D bit,it acts like a cross between a drill and a reamer,of course you will have to drill a pilot hole first before using the D bit use slow speed and metho' as a coolant lubricator.and so long as you dont keep it spinning in the hole to long you should have a press fit.

[olmod]

Use a black marker pen and blacken the inner face of the end bell and the face of each stator end allow to dry,then gently fit and rotate a couple of times,take apart and examine blackened areas for any signs of rubbing,its not unusual to have a group of stator ends rubbing just either file down or dremel sand the high spots but not the whole lot.if end bell rubs ,add small washers onto shaft till you have clearance.

[olmod]

Drum sizes for different magnet configurations.

[olmod]

You can line the existing bell with old transformer ( i ) lamination iron..a guilloutine helps in cutting the strip width to the depth of bell required, cut longer than needed, hand roll around something wich is about 4 mm smaller to allow for spring back, then start trimming the ends off as they will have a flat on them,when you get close to the inner diameter of your bell,lay on a flat metal surface,take fine flat file one with a smooth edge to go down on the metal surface,squeeze the ring together so you file both ends together on the draw back stroke.by trying you can get a push fit and a perfect butt join.I use a little loc tite black max to glue them in and spin them with a drill in a toilet roll tube to even out and get rid of excess loc tite. I place the first magnet over the but join, when finished placing the magnets,i place a single drop on each end of magnet and use the same spin technique.when fitting stator i use the black marker to show witness to any rubbing and grind accordingly. so i might not be able to use max' thickness magnets but the lamination iron flux ring helps too.

[rysium]

Originally Posted by Ron van Sommeren

@Rysium/Richard
Might be a good idea to put your double/triple stator torque/power/#wind/force explanation here too. Very instructive

Here you go:

Originally Posted by KreAture

adding more iron like that increases the max wattage you can stuff into the motor before the iron is saturated with the magnetic flux created by the coils. Basically, it increases the max power-handling of the motor.

Not just straight so easy. It can increase the max torque achieved by the motor. The torqque will be square to to the stator lenght. Torque easy tranclates to magnetic force between stator and rotor.

In example in twice longer stator you can get twice more MF at the same saturation level but at the same time you can use longer magnets in the twice longer rotor. So the force will be 4 times stronger.
How it translates to power? At the same number of turns you can run twice more current before stator is saturated (this is the part of twice stonger MF from stator). So the power at the given voltage is just twice bigger than in single. But wait, the torque is 4 times stronger, so it must be lower rpm. Yes. Kv of that motor will be 2 times lower.

So how to bring it back to the original Kv (and original rpm)? Use twice less turns. But wait again - you need again twice more amps to get the the saturation level.
So now we have motor that is twice longer with twice longer magnets, with half of original turns (and probably thicker wire) and drawing 4 times more current. It runs the same rpm and delivers 4 times higher torque.

Isn't it slick?

RysiuM

[Ron van Sommeren]

Remove original magnet ring by letting it soak overnight in acetone.

[bz1mcr]

Originally Posted by olmod

Try going through your collection of shafts with a micrometer and select the smallest diameter,carefully grind a radius on the end then with a dremel grinder grind across halfway up just past the radius,you will have what is known as a D bit,it acts like a cross between a drill and a reamer,of course you will have to drill a pilot hole first before using the D bit.and so long as you dont keep it spinning in the hole to long you should have a press fit.

olmod
This sounds like just what I need. Does a D bit look like this?

[Fishnut]

Originally Posted by Ron van Sommeren

Airgap is not only the gap between the magnet and the stator, the gap between the magnet and flux-ring has the same effect as magnet-stator airgap. Both have to be taken in account. Put iron shims in the space between the magnet and the fluxring, thus reducing the total airgap. Magnetic resistance will be lower, flux increases, less rpm/volt (=Kv) and more torque per ampere (=Kt). Also less chance of local saturation were magnet edges touch the flux ring. More glueing surface too.

Groeten Ron

Along those lines, I now glue magnets to the bell with JB Weld epoxy. Don't know what's in it, but magnets attract the stuff (will even pick up a tube of JB), so it should help in moving the flux along. Put a dab on the bell and place the magnet on it. It will squeeze out the excess. Airgap is zero, though I don't know how efficient the JB Weld is in the flux department.

Kurt

[DEPENDS]

To help prevent windings from rubbing the inside face of the bell, put the wound stator between two hardwood blocks place in vise or heavy C clamp and squeeze for all you're worth. This "flattens" the windings a few thousandths and may be the difference between rubbing and running freely.

JT

[DEPENDS]

If you have problems with windings rubbing on a GB kit, it may be that the plastic retainer ring has been pushed too close to the inside face of the bell. Using a drill press or arbor press, "push" the shaft back into the bell a tiny bit. Because the bearing holder/stator is locked on the shaft by the plastic retainer, moving the shaft back also moves the stator back and provides the clearance needed. Unless there is severe rubbing, just 3-5 thousandths is usually enough to free things up.

JT

[davidsons]

When finished winding, I like to use hot glue to hold the leads tight to prevent them from possibly uncoiling and rubbing.

[olmod]

It will certainly be better than other adhesives,why i say that is because i have read and i did post somewhere a couple of links to the csiro wich have a couple of papers on materials made of compounds i suspect are similar and are useing and testing for manufacture of stators ect, the main thing is not to have any between the magnets as this is detrimental so ive been informed by a manufacturer here in melbourne. imagine moulded stators if you are interested try checking my past posts.

[rysium]

Originally Posted by davidsons

When finished winding, I like to use hot glue to hold the leads tight to prevent them from possibly uncoiling and rubbing.

1. For that I use a nylon thread (it's NOT a dental floss, this one comes from the string from old blinders). One yard is good for going 4 times around each pole. I wrap it by doing a "slalom" around the poles, so after first round (9 poles) the string is comming out from the other side, this way two rounds around wrap evry pole from both sides (I hope it's clear).

2. To hold a stock can on the shaft use a prop adapter (or even a collar) that fits tight on the shaft and it's glued to the front of the bell. Any good glue for metal will do (Locite, plasti-zap, JBWeld).

RysiuM