Why the vibration?

[DadHav]

Hello Gang, I really need some help from my Peers! I have been working on a few motors for a faster style plane. I need a prop speed of about 60mph while having thrust in the 20oz. range. I tried a 12 leg 25mm stator with 10 poles and came up with 30oz. of thrust but didn't do well with props over 4 pitch. Below is another try. This is a 9 leg 25 mm double, with 16 magnets arranged to form 8 poles. The magnets are 10x4x2 mm. The motor will do what I require, but I have a very bad vibration until getting past 1/3 throttle. It almost seems as though the magnets are rubbing, but that's not the case. There's 000 runout and plenty of airgap (.007 inch) Is it possible that the poles formed by the double magnets is to wide for the stator leg? Is 9 leg 8 pole not a good combination? Does anyone have an idea about why I might be experiencing this? I've tried different speed controls and timing settings also. I could try 10 poles without re-winding, but maybe the increase in gearing won't let me get the RPMs that I need.
DadHav

[latrans]

Uhhhhhh............. I'm afraid that I can't answer your questions but.......... could you give a little more info on that motor? 30 oz of thrust is alot.

Latrans

[swatson144]

Probably nothing wrong with it! i built a 10 25x10mm 12arm 14p with 4x10x2 mags and it is nearly as bad. It cogs very hard (OK god awfull hard)and I wrote it up to the flux on the arms has to overcome the magnetic attraction from poles to arm. Runs smooth after it starts turning well. Next was a 10p which I am happy with at 21oz on a 10x8 HD 12.9 amp Using 5x12x2 runs smooth at all rpms and doesn't cog near as bad.

I thought I'd entered it in the db but I didn't and can't find my notes. So I don't know KV or rpms with 10x8 for pitch speed. I'll find my notes or retest and get back to you.

[DadHav]

Hi Latrans. To good to be true? Maybe your right. I just looked at my notes, and I'm looking at 22 to 26 ounces of thrust using various 7 and 8 inch props with pitch of 5 and 6. I'm almost sure that I got 29 or 30 ounces while testing an 8-4 and 9.4/5 props. I'll test it again and let you know. The motor that we are talking about is shown on a string that I started (LRK Torgue) There is a slight difference from stock other than my custom outside parts. I used some round back magnets on this one. If I remember right they were more like 6mm deep and wide, but they were only 1.5mm thick. I would think some standard 5 x 5 x 2 magnets would work as good if not better. Remember though, that I push the limits a bit. The tests were done with a 3 cell 2100mah lithium and at the upper end of the thrust was using 12 and 13 amps. On the motor above, I just tested a lower pitch prop and the thrust went way up. I was getting thrust in the mid to upper 20 ounce range with 5 and 6 pitch props. With my favorite 8-4 Graupmner Slim, I went up to 34 ounces, About 12 amp draw and a prop RPM of better than 11,000. It's just that darn vibration!. I wonder if maybe I missed a wind on one of the legs or something. Do you think that might be the problem?
John

[DadHav]

Hi Swatson, 8 pitch prop. Wow, I'm not able to do that. I'm winding mostly Delta, and flying planes alot faster than a Park Flyer. I have a triple 25mm stator wound distributed with 14 poles, and it runs pretty smooth, but not near as smooth as a 10 pole. This motor is on a Norheast Sailplane Vermont Bell, and it flies vertical almost as well as horizontal. I think I'm gonna go back to 10 pole or something.
C YA

[LBMiller5]

John,

Here's my 2 cents worth. With a standard 9-pole, 12 magnet arrangement, the winding scheme is ABCABCABC. When phase A is energized, there are 3 magnets pulling 3 poles that are equally spaced 120 degrees apart. This causes a fairly equal distribution of forces around the perimeter of the flux ring, which keeps the flux ring centered with respect to the stator.

When you use a 9-pole stator with either 8 or 10 magnets, you use an AaABbBCcC wind (As shown in the chart convieniently located beneath your motor in the photo above). In this configuration, when you energize Phase A, you are pulling against 3 poles that are right next to each other. Even if you are using a 4mm shaft, which it looks like you are from the photo, the magnetic force of these 3 poles has got to deflect the flux ring towards the stator a couple thousandths of an inch or so. Then when you energize phase B, the flux ring pulls in towards those poles. It would seem to me that this would cause the flux ring to oscillate in an eccentric path a couple thousandths of an inch off center with respect to the motor shaft. The frequency of this oscillation would be 3 times the RPM of the motor, (Since the poles are clustered in groups of 3). You may be hitting a harmonic at speeds under 2000-3000 RPM that settles out at higher speeds. As heavy as a steel flux ring with a bunch of magnets is, it does not take more than a few thousandths of wobble to make a LOT of vibration.

Another consideration is that as the motor increases in speed, the centrifugal forces pulling the flux ring out from the stator increase in proportion to the motor speed. At a certain point, the centrifugal forces are great enough that the "Out of balance" magnetic forces are not large enough in comparision to have much of an effect.

Anybody else have any other opinions on this?

Lucien

[latrans]

I think LB hit the nail on the head, asymetric winding scheme.

Latrans

[spoke2570]

I don't think the asym winding has anything to do wtih it. I have a single wound pretty hot on 8 poles turning 20500 RPM on a 6x3 prop. It runs well. I am using a CC Px25 controller and it would not run past 1/2 throttle on the high pole count timing setting, but the standard advance works perfectly. The prop and endbell have both been well balanced.

pete b

[swatson144]

I think it has more to do with the poles coming firmly to rest with the arms. I haven't put a torque wrench on my high cogging/ low rpm poor performing motor and really empirically nailed it down. There is enough anecdotal evidence to support that if they are hard cogging it takes a large amount of throttle to get them moving. In my experience throttling down they perform ok at lower speeds. The motors I have built that seem spongy (little cogging) all seem to perform very well at low speeds and as predicted at high speed.

I have a buddy that can do in CAD in mins what I can do in days. I hope to get him over and draw some schematics and rotate them and see if it can be shown or guessed.

[swatson144]

Hi Swatson, 8 pitch prop. Wow, I'm not able to do that. I'm winding mostly Delta, and flying planes alot faster than a Park Flyer. I have a triple 25mm stator wound distributed with 14 poles, and it runs pretty smooth, but not near as smooth as a 10 pole. This motor is on a Norheast Sailplane Vermont Bell, and it flies vertical almost as well as horizontal. I think I'm gonna go back to 10 pole or something.
C YA

Not sure how man arms we talkin (you bein you) :) Oops distributed 12 arm ok... My 14p is rough as a JAG 12 cyl at low rpm, but then again its too slow at Hrpm. I went to do testing as mentioned earlier and bats in tx allowed only one. I'll continue later but here it is (and I'll put it in the DB before I lose it) didn't get no load yet.

Motor is 16T 25x12mm 12A 10P Delta

9x7.5 GWS HP
10.1v 9.6I 6330 rpm 18.3oz

That gives a pitch speed of 40 mph.

[DadHav]

Thank you Lucien and evryone. I thought somewhat along the lines that Lucien brought up and was planning on trying a larger diameter shaft. Close call Lucien. Actually I tried a 1/8" set of bearings that I had on this one. I'm thinking if I had 4mm I might not be having the problem. Also the magnesium end bell is very soft compared to aluminum. I have balance the rotor so I no the problem isn't there. I even rebalanced the prop while it was on the rotor. To bad, I don't think I can use the motor unless I can correct this problem. Maybe I'll put the bearing holder in the lathe collet and indicate the outside of the flux ring to see how easily it deflects from center. If I find anything interesting I'll let you no.
John

[latrans]

I don't think the asym winding has anything to do wtih it. I have a single wound pretty hot on 8 poles turning 20500 RPM on a 6x3 prop. It runs well. I am using a CC Px25 controller and it would not run past 1/2 throttle on the high pole count timing setting, but the standard advance works perfectly. The prop and endbell have both been well balanced.

pete b

A single isn't really the same thing is it? Think about it, at least twice as much (probably much more, given the length of the flux ring) force is applied to the the bearing/shaft assembly via the flux ring. Then throw in the asymetry and its not a big surprise that it vibrates.

Latrans

[spoke2570]

The loads on a single are sure to be on some exponential factor less, but I have had no sign of vibration problem. -the test stand doesn't even have a "buzz" to it. I would think that at much past starting RPMs that the force would be vectored off radial a long way by by the inertia of the can. I have seen some of the heli guys using 8 poles on 9 teeth with stock cans, which are wimpy by comparison to the GBX, with no trouble. I would sure love to see those lathe tests... want to go double with this wind...

pete b

[spoke2570]

Sorry, interupted mid post.

I guess what I am trying to say is that a physical imbalance dynamically applied would be a more likely cause, A dynamic imbalance is on a factor of magnatude greater if the actual weight imbalance is further from the bell's attachment point and on a factor of magnatude greater at higher RPM.

The can and shaft may balance staticly, but if the actual part of the system that is to heavy is at the open end of the can and the part that was lightened to achieve balance was the attached end of the can, the static balance would make the dynamic imbalance worse.

The magnetic imbalance becomes less at higher RPMs relative to the mass of the can, because of the inertial mass the can carries, so the vibration would be more pronounced at low RPMs.

[swatson144]

DadHav If you are still watching I got some more testing done.

16t 25x12mm 12 arm 10p delta 65 grams

HP 9075
10.1 9.6A 6330rpm 18.3oz

ep 1060 prop
10.8v 9.5A 6870 RPM 25.2oz thrust

HP 1080
10.2V 13.5A 5760 Rpm 21.86oz (this is low because static this prop is stalled, on one of your hotliners it'd cook I think)

EP 1260
10.2 15.6A 5190 RPM 34.0 oz

This motor is just laughing at the loads I give it. 160w in and 34oz thrust. I'll have to get some larger TE props in.

This motor runs well to very slow rpms. It's 14p near twin sucks at lrpm. both are "blue" motors. I have yet to put a prop on the 14p that works that slow motor to near the same levels as this 10p. Both are still 3mm shaft. If you find a good source of 3/16 or 4mm shaft assy please let me know as I can see where this is going :wink:

[DadHav]

Hi Swatson, I'm still around. I have to do the test that I promised about. But I'll tell you what: I'm certain that with these larger motors, there will be a need for larger bearings and shafts. I just ordered some 1/8 and 5/32" bearings from the internet. the price was real good. I can let you no what they look like. Looking at your data above: Are you sure you're winding Delta? That data looks like what I was getting on some of the motors that I wound Star. I'm buying what I hear on this string. I found the 12 leg stator and the 10 pole comination to run extreemly smooth. My 12 leg 14 poles was smooth also though, but it has a 5/32 shaft and bearings. She's really stout. I'll check around for shaft material. I'm thinking something like ejector pins, although they are typically a few tenths of a thousanth undersize. In the mean time I built another motor using the 9 leg 25mm stator and a 6 pole rotor. The rotor is made up of 6 sets of three magnets. I haven't tested it yet, but the cogging is unbelievable. I managed to get 5 strands of #30 wire wound to 11 turns. I think this motor will really crank the smaller props. We'll see.
John

[swatson144]

Yep it's delta. I had originally tested it Wye.
GBL_00073 16T 28AWG Wye (5) 25.05mm (10) 12x5x2mm N50 12 6 2.5A 7.69v 19 2640 8.82

I didn't own any 3s packs when I had it as wye. and knew it was just gonna be too slow so re-termed it delta.

So where'd you find the bearings? I haven't really looked since the initial search proved them to be cost prohibitive.

I'm thinking drill rod for shaft . if thats too soft maybe drill blank, either from enco

[DadHav]

Hi Swatson, I guess I'm just to settled into using 3 cells to realize not everyone does. The bearings are coming from http://www.rcMart.com. Like I said: I have no idea of their quality, but I paid four times as much for the last 5/32 bearings I bought. I should have some next week. I'll keep you posted. I went to the Enco site and looked at the drill rod. The price is good, that's for sure. I wonder if the stock is ground though. They are giving a +/- .001 diameter as a tolerance. .001 small would not be good. I'm going to take a ride to some of the local Mold Building Shops that I have delt with and I'll pick up some cut off pieces of ejector pins. These are, if I remember right, hard but slightly flexable h-13 steel with a nitrited outside diameter. They are typically .0001-.0003 undersize or so. This is to provide a slip fit in the mold parts. I think a tiny bit of locktite would make this work nicely.
John

[swatson144]

I figure the drill rod should be good. Now days I think most of the process makes them pretty darn close. I'll place some on my next order and let you know. If memory serves me the drill blanks are ground and proper size I'll check into that also.

[swatson144]

Ok I had a hard time finding anything on that site,,oriented as a replacement parts site.

did find the drill blanks here. +0 -.0003 3.125 long .78$

http://www.use-enco.com/CGI/INSRIT?PARTPG=INSRAR2&PMAKA=325-5583&PMPXNO=5831436

and the bearings 10 for 20$ here

http://www.vxb.com/Merchant2/merchant.mvc?Screen=CTGY&Category_Code=5-32inch

[DadHav]

OK Back. I see what you're sayng about the drill blank. I didn't go there because I remembered paying a lot more than that for it when we got it to make cutters. I think that would work good. As a matter of fact its what I have on the one pictured. The bearing site looks like a pretty good deal also. I no the rcMart site is hard to find things on, or at least the bearings. If you get on the site you need to pick ACCESSORY, Then in the left hand column near the top pick BEARINGS (184), On that page you cna pick 10 PIECE SET, That will take you to a page listing bearings in fractional sizes. IE: Yeah Racing (YB5003Y/S10) 1/8x1/4/1/10" 10 for $11.90. Or: (YB5009M/S10) 5/32x5/16/1/8 10 for $9.90. On the second page there is about 7 or 8 choices for 4x7x2.5mm and other 4mm I.D. bearings ranging from10 for $9.90 to 10 for $11.90. Like I said, I don't no the quality, but I'm about to find out. Thanks for the information.
John

[DadHav]

Hi Spoke, I checked to see if I could push the rotor very much. Without being impractical about the amount of force against the rotor, I could get +/- .003" It would seem that I could get as much out of the shaft as well. I think it could probably vibrate.
John

[spoke2570]

Thanks for posting that result! I know it was really just a way for you to show off one of your typically beautiful motors.

pete b

[DadHav]

Hi, Pete, It's just that I'm Semi-retired and have a little more time to put into these. Besides that, I have no Grandchildren, so I even name these guys. I believe strongly in pride of crafstmanship, and I'm proud to be part of a program allowing people world wide to express their thoughts and their creativity. I can remember letting some of my Apprentices have the time to make parts or tools that reflected their talents for fine finishing. I may have lost money on some of those occasions, but in a world where all the talented crafstman are being replaced by CNC, there really should be a little more of that. I know CNC machining and programing fairly well. When people see that hook "Cad designed / CNC machined" They think they are getting the best parts. Yep, They're fast parts, and of course dependable, in most cases, but you gotta remember if a mistake is made in programming, a cutter to dull, or a setup not picked up right, you have thousands of bad parts instead of a few. I've seen on many occasions parts like this sent out to the public with hopes of having low returns. I guess what it boils down to is: There's still a few things left that you can make with kits or hand opperated machinery that will catch the eye of your Peers, and draw a compliment.
Thanks
John

[ScubaSteve]

Dad,

You have balanced the rotor right? Sorry, skimmed thru the thread - mostly just to see your pictures;). I also wanna talk to you about some of these.... later though. :wink:

[DadHav]

Hi steve, Oh, Oh, Am I in trouble again with my pictures? Yep, I put a few degrees angle on the ends of the shaft to form a point in the center. This way I can balance the rotor on my magnetic prop balancer. If anyone else has made a double 25mm dia. stator with the 9 leg / 8 pole combination and had no problems, then I gotta figure I did something wrong. Mind you though that the 8 poles were made from 16 magnets. I've rewound the motor with 11 turns 5 strands of #30 wire ABC Delta and changed the poles to 6 using groups of 3. With this the cogging is unbelievable, but the motor runs pretty smooth just after start. I'm still testing the motor but a quick test looked like I will get about 12,000 rpms with an APC 7-4 prop. Drawing about 12 amps with a 3 cell Lithium. The thrust I think was about 20oz. If someone else builds the 9 / 8 combo and has good look, I'll try that one again.
Thanks Steve.
John

[ScubaSteve]

John,

My mistake... dunno what I was thinking. Shortly after my post I remember that YOU were the person I was thinking of that machines the points at each shaft end to balance the rotor. :oops: :roll:

No, no your pictures are fine. I'll PM you about the "other" thing... :wink:

[DadHav]

Hi Steve, Actually the point is such a small angle that someone would have to call your attention to it. You only need enough to make sure the center of the shaft is what's contacting the magnet. While you're here I'd like to mention that I thought I wouldn't have a need for the 9 leg stators after making the LRK distributed motors, but getting both speed and power is a little tricky, at least for me. I think the 9 leg stator is still a good option. Man, There's almost endless combinations to try. Can you imagine: if you took a winding diagram chart and built a motor to represent each possibility and then consider the amount of stator thickness and magnet combinations. I sure hope all our friends here, let everyone know when they've had success or dissapointment with any particular combination.
John

[swatson144]

Hello John and all.

I just got a little garage time in between jobs. and now have 2 8p endbells one 8mag and 1 16 mag. 2 stator assy 25mm 12 arm x 5mm stack, (I'll also do atleast 1 25 9 arm after I catch up). 10t was a little too hot for my uses so I'm gonna go 12 and 14t and test both with each end bell.

I plan to build a couple 12mm stacks of the same motor to see if I can find some KV constant for stacking these things. Unless someone has a constant for this! PLEASE share. My perception is you double the stack and it is like a whole different motor not just 2x the motor values with KV remaining the same.

[Air Mover]

Is it possible for one of you lathe artists make me a bell for the 10X4X2mm mags and the 25mm 12pole stator .. im dying to fire up a monster.. :lol:
Just PM me with your labor price and such and im there with pay pal. :wink:

[swatson144]

It'd be pretty hard to do. The stators ain't perfect, and the magnets being sintered aint either. In my experience it is very possible to make a motor with as large as .2mm clearance and wind up with it rubbing! I use a 3 jaw and John uses collets so his MMV. The way I do the cutting, I can do all the critical cuts in one chucking and flip the endbell over to do the non critical facing on the front. So it should be round and centered. The rubbing just seems to be an accumulation of errors (both mine and the part makers).

Now days I build the rotor too tight, install the mags, and skim the stator a few thous, as needed, for the clearance. Keeps the airgap tight.

I'm building many motors, and will probably have a surplus when I change directions experimenting. I have been thinking about selling a few to recoup some of the expense. IE I've been building little 8p 5mm stack screamers that don't really fit any of my planes. I'll soon be building out 12mm stacks of the same configurations. I hope to finish benching the little ones and start building the bigger ones today. When you start using the long magnets the price gets up to .75$ each so I'll have about 15$ in each laying around and a LOT of time. Hmm rambling.

Any how, The best I could offer is maybe sell a whole motor. It could have the windings/ mags removed and and reconfigured the way desired. I'd be comfortable that the parts fit. I haven't been potting them so they could be potted and flown if desired or the windings easily removed.

Here's a few pics of the 12x5mm 12t 8p 16M. ( not for sale yet as I have to switch rotors and test with 8mags) Not polished or pretty but works well.

John if you see this this configuration runs smooth at low rpms. I finally got a servo tester and makes testing a lot easier!

[Air Mover]

Thankyou !!! I would without question rewind the motor.. also wouldnt want your mags as I have plenty so you could reuse your mags on other projects.. I Use CA to hold my mags in .. if your doing the same then it wont be hard to pop them out with a exacto blade.. its how I gut my mags out...agreed on leaving the stator core alone dont worry about gutting the wire.. that takes time I can do that... I have a large poslishing wheel/grinder and will shine her up like glass... atleast I will have something to work with. Thus far I only have one good working bell for 12pole stators and the bell can only hold 1mm thick mags.. which has nothing on 2mm thick mags. Also its only good for 5mm thick stators. :cry:

Thankyou for the offer!!!!!!! will be looking forward to hearing from you then.

[DadHav]

Hi Swatson, I think the motor I had vibration with was a 9 tooth 8 pole with 16 magnets. I might try that one over again to see if I made any mistakes. I agree with you 100% with finishing all critical surfaces at one time if you can. I do the same even though I use collets. I just happen to incorporate a diameter of some size or another on each part that allows me to get the part back in a collet again for revision or polishing. I also find the same about parts running out. The last double 25mm that I built was fit very tight. Bearings pressed to the maximum. a HSS tool blank 1/8" diameter custom polished to the bearing i.d. with just the right abmount of press, the end bell was made strong from magnesium and was pressed onto the shaft very tightly and still had three set screws. Guess what? under test while swinging good size props, I could get the rotor to hit the stator on the far end from the bearing. I did this buy waving the motor around as though it would be making a tight loop at WOT. I still had to polish a little off the back ot the stator pieces. I'm testing two motors right now as in the picture. One is a 12 tooth 25mm stator with 10 poles. These are made up from 20 magnets that touch each other in the flux ring. This motor has nearly zero coging. You can give the prop a spin like you would be starting a nitro engine and it spins about 10 times. My first test with a 7-7 prop had 8,800 RPMs with a three cell lithium. I was drawing less than 8 amps, if I was checking right. I'm really impressed with this combination. OH the wind is 10 turns of 5 strand #30 wire in star connection. The other motor is a 35m Stator from an Oreck hand held vacuum cleaner. Man this motor is strong I only had a 12-6 prop as biggest to test with. I'll get back with better info on both of these when I get caught up. By the way: if you peek through the cooling hole in the big motor, you'll see I did the Rainbow Wind. I used three strands of GB wire (Different Colors) and wound them at the same time. Man this is fun. Aint it?
DAD

[spoke2570]

I guess it's stime for me to tap in on the 8/10 pole thing again. I have got two single GBx cans together than work so well there is intercchangability between two stators. One a moderate, and one a WAY TOO HOT wind (It folded a prop in testing. I have never done that and I have run some nutty RPMS with 1/2A nitro.). The things work perfect. The 8 pole runs more stably on the standard advance setting for my speed controls (haven't tried anything but Castle Creations) The high advance setting denoted as "for high pole count motors" causes the 8 pole can motor to cut out like it hit the overamp setting, even if it is disabled and the amps are way below limit. There is no touching, no vibration. It is not even trying to hav e a problem. I am quite sure these motors could go to 15mm cans and still have no dynamic issues.

pete b

[spoke2570]

Oh, yeah. The reason I tapped in in the first place was that I would love to get my mitts on a 25 mm 12 tooth setup at between 15 and 25mm stator stack. Any testing waste or surplus... I just don't konw if I can hold m breath for the GBX 25.

pete b

[swatson144]

Hey DadHav, I'm still planning to build a 25mm 9arm stator for testing in the 16 and 8 mag (8pole) end bells I have. Paying costumers are keeping me hopping and I have to go out of town for a week next week. So if you just want to hold off until I get it tested. I'll let you know. I'm expecting about 30% less out of the thing than the 12 arms. but I don't know what the PIN or KV will be all else being equal.

I've got data on the 16mag 12t and the 8mag 14t, the bells are swapped and loctite cured on the shaft keeper. just need data on 8mag 12t and 16mag 14t. I'll say that the results are surprisingly similar. Spot checking shows these 2 are only about 12.5-20 % different and the specs pretty linear. ie less thrust with a givin prop also has a about the right drop in current. I found interesting. 15% would be the dif in turns. I really expected the 8 extra mags to make a larger diff. Well testing them swapped over should be conclusive.

Design, Prop, Type, Dia, Pitch, I amps, V,
100, gws, ep, 7, 3.5, 7.80, 11.10,
101, gws, ep, 7, 3.5, 6.30, 11.20,

Design, PIN, RPM, Thrust oz,
100 , 88.0, 13890, 16.93,
101 , 72.0, 13230, 14.64,

design 101 being the 14t 8mag, 100 being 12t 16mag, not that much diff! seems like it was better propped with the 12t 1610kv, other props tested were about same curve.

[DadHav]

Hi Swat, I'll be glad to wait for your tests. I probably made a mistake or something. I really believe I'm coming down with Adult ADD. I'm finding that the proportional differences that you might expect don't always come out as you expect. I thought doubling and tripling stators would really make the motor rock, but I think in some cases, depending on what your looking for, it might be better to research a larger diameter stator rather than stack hight. I'm in your vote also. I think I may have to sell a few motors to pay for additional supplies. Be careful on your trip. Maybe when you get back the garage will be warmed up a little.
John

[swatson144]

Well John I sure hope to finish these tests soon! I'm typing while waiting on an install.

1: I know there has to be a ratio of turns to drop when one doubles the stack. All mine seem to act as if I doubled the stack and added more turns at the same time. I'll do that by making identical but 12mm stacks of designs 100-104 (really just 2 more motors swapping rotors)

2: I want to see if more magnets/pole REALLY are better. I'm starting to doubt that Idea. Sure there maybe a little difference but initial testing with my gear shows it's minimal. and when mags start pushing 1$ ea I'd as soon not use 8 as spend the money if they don't help much.

3: I suspect there is a point where pole/magnet/arms cause poor low speed performance. Your 9arm 8 pole and my 12 arm 14p, both of which performed well at speed but jerked about at low speed. I think I have more use for 8p than 14p (12 arm) and I'd rather make a stator than a rotor :) so next on my todo list is a 9arm 25mm I'll test with both rotors (8and 16 mag 8 pole). I can't see how either of us screwed up motors to act the same...so I figure If I prove you did or didn't screw up I can condemn or exonerate myself by extension :lol: I'll get on that as soon as I finish testing designs 102 and 103 which are ready to go.

There having listed the plan that is in bits and pieces of several topics, I should have a guide to help with my adult ADD.

[DadHav]

Hi Swat, I have three 25mm motors ready to test, and I also have a triple and another single on planes that I've been flying. Take a look at the motor on the left. This is the magnet combo that I thought might not work to good. There are 20 10x4x2 magnets to form 10 poles. I just finished it this morning and ran a few tests. This is the first time that I've been able to get a 60mph pitch speed with some thrust that might fly an 18 oz plane. The prop was a 7x7. I really was surprised about how well this little guy works. When you get back maybe we can talk about some tests that we wouldn't be duplicating or something. I'm unhappy about a burned out power supply, but I have the watt meter a servo tester etc. that I can still use with batteries. If anyone out ther knows where to get a 20-30 amp power supply for a reasonable price, please let me know.
John

[Air Mover]

Oppwwwwwwahh droooooooooool drooool wish I had a lathe...waaahhhh mommmy... :shock:

[swatson144]

John the motors are gorgeous as always.

I can't believe a good old fashioned tv repairman can't fix a PS cheap.

Another "round toit" I've been planning is a building an adjustable voltage regulator to use with a car battery. I keep a car battery charged in the garage to run my chargers and shop radio ( old car radio) anyway. I'm thinkin maybe kludge something up. I also keep thinking that just useing an rx pack to power the servo tester and power straight off the battery for 3s. just stop the test at say 10.2V to simulate a heavy load on 3s and continue up to 11v to fully test the motor performance as if you had enough Lipo battery to hold it. Haven't really bothered since I like to use the pack I'll likely fly that motor with just so I know what it'll do.

allelectronics has a 25 amp bench supply for 165$ but that's a lot of magnets :)

[spoke2570]

Old, 300 to 400 watt computer power supplies crank some really clean DC, and are cheap to free. Sometimes a Goodwill (yes the thrift store), sometimes ripping power supplies out of copiers from the gabage at copier repair joint.

pete b

[DadHav]

Hi Swat, Pete, Thanks for the advice. I looked at the supply at all elect. It would probably work, but I would probably get the one I have first. for $189 it had 0-30 volts 20 amp cpacitiy. There was also digital meters with course and fine adjustments for voltage and current limiting. I tried to fix it myself but am not familiar with switching supplies. There are a few overload devices that would normal have saved me, but it's not designed to protect hooking a battery up backwards to the supply. Some of the parts have ground of identification numbers. In short: I cant tell whether the problem is in the protection circuits or in the opto isolated re-arming circuit. I might end up buying another of the same. If you have any luck converting a PC power supply or a car battery, I shure would like to know. I have a powerful Lambda supply from a CNC Mill that was never used. It would be a great candidate if it could have voltage control.
Thanks
DAD

[swatson144]

The PC power supplies work fine if you are just looking to power chargers. You have to put a load on the 5v circuit to get 12v. even a taillight bulb will do the 12v is proportional to the 5v so a bigger 5v load you get higher 12v (within reason) The newer ATX style power supplies require an additional momentary switch to tell them you wish for them to come on or off. I'll email the pinouts on the AT and ATX connectors if you want. RED=5v Yel=12v green connected to ground for on. on an atx. If you don't like the voltage you get out 12v (too low) add a bulb etc parallel to the 1st (to high try another in series) You can get as fancy as you want from there. AT ps load it and flip the switch.

I feel more comfortable with the car battery for no real reason. besides when the wife leaves the lights on her car I just carry it out and jump off it. I keep it on 2A charge while I'm in the garage and get about 10yrs out of each. The charger is on a switch tied into the lights.
I'll look up a voltage reg circuit for the battery (so I don't reinvent the wheel) simple high current easy/cheap to build can't see any need for a 1% range circuit

[DadHav]

Hi Swat, I think the battery idea might be more attractive. The reason? It would be nice to find something other people might be interested in using also. I'm sure most would rather not spend the money for a power supply, and also would like to save thair flight packs for flying. I just thought of something. I have a jumper battery for my cars. This has a cigerette lighter receptical in it. Maybe this would be an easy way to use the thing for tests. Keep me (us) posted on a way to regulate the battery power. That sounds interesting.
John

[swatson144]

I'm gonna move this to general OK? as we are getting wot

[latrans]

Dadhav,
For what its worth I built a 25mm 9 leg 12 pole motor and had the very same problem with vibration. So it was definately not a problem with your winding scheme, yes I have a big plate of crow beside me. I'm almost positive that my problem is a short though.

There is another problem with this motor though, when I start it up it turns but vibrates like crazy then smoothes out as I advance the throtle BUT after running it for 30 -45 seconds the stator becomes astoundingly hot. I have a burn on my hand to prove it. I would not have guessed that one of these motors could get that hot that fast. I guess I'll try and rewind it and see what happens.

Adam

[DadHav]

Hi Adam, It sounds like you might have a short. I was able to get one or two myself even with the paint protection. I like using four or five strands of #30 wire. That way you don't need to pull as tight as you round the sharp edges with your winding. I had my vibration when I used eight pole magnets (doubled up from 16 pieces) I think Swatson was going to try that combination also. I might have missed his results, if he got that far. I've had no vibration using the 9leg/12 pole combination. On the 12 leg stators I'm having some good results with 20 mangets to form 10 poles.
Let us know what you find out. I would think your enamal must have been ready to cook if things got that hot. I usually hook either my watt meter or even a clamp meter up before I test a motor for the first time. If I'm drawing to much amperage for what I'm doning, I try to find out why.
Good Luck.
DAD

[latrans]

Your not kidding about the enamel cooking, after I ran it the whole room stank of of burning paint and hot metal. I think that the problem is one of three, or a combination of, three things. A short from the sharp edges of the stator, a short from the three ends twisted together(wye config) against the bearing holder :oops: (yeah I forgot to put shirnk tubing over them, stupid I know). I also filed down the heads of the stator teeth a little could this cause any problems? I don't see how but I couldn;t say for certain. The reason that I'm posting this debacle of a motor is I hope that sharing of this kind of info will help us all diagnose problems more easily in the future. I think that my plan will be to fix these problems one at a time and see what happens. I'll share my results once this is completed.

Latrans

[swatson144]

Heah John, Latrans,

I Just got back from vacation and upted the 12x5mm 12 arm results 85-88.
These are four motors made from 2 rotors (8 p, 8 and 16mags) and 2 stators (12t and 14t) the results were interesting (to me any way). All combinations preformed well with the exception of the 12t 8 magnet combo had a glitch mid range but worked well on the 16 mag rotor, and the 8mag rotor worked fine on the 14t stator.

I'll do a 9 arm stator next, for the same cans. Then on to 25mmx12. I am liking the speeds I'm getting with 8p the APC TE props start to work pretty good. My 10p is pretty lame and needing a much larger prop than I want. only 34 oz with a 12x6 gws and wanting more prop at 150W PIN. with good air flow and potting the 5mm stacks will almost do 150W PIN

I have found that these motors can get hot and stinky quick! The 1st 12t 8p 25x5 12 arm I built for the above test..I was testing in the garage with a friend over. tested a 7x5 at ~ 130w PIN said that was about all that motor could stand, warm but not hot. He said "Ahh it'll do more than that". So I went up a size... Okay let me explain that this guy don't know motors, and just a few mins before I was amused by watching him figure out why the shaft wouldn't turn while holding the flux ring... I propped up any way! it was smoking within seconds. kept waiting for some guy to walk in and say "Here's your sign!" While I was waiting I rewound it.

So they don't have to be shorted to heat up quick. This one had been through the whole test. 2s and 3s. So I doubt it was shorted!

I have taken to trueing the stators. originally I chucked them in the drill press and lightly filed them. Now I use the lathe and skim them. Never tried to file a couple of teeth. I don't see what it would hurt though.

[latrans]

That is interesting! However I still don't know if really applies to my problem as my motor got smokin' hot with no prop. It was a 25x10mm 9 arm 12 pole, 15t of 24g. Any thoughts?

[swatson144]

Nope not aplicable...no prop is as small as they get! :) It'd be a short 4sure. were you using newby wire? I'd guess not. I love the stuff. It don't short very easy at all. I really wish they had called it "heavy duty" or "tough wire" instead of making it sound like something you need to outgrow. OOps I digress. Sounds like rewind time.

[spoke2570]

Hey, I know this is WAY off topic, but I just wound 28 turns of 26AUG noobie (I don't care if it sounds like you should outgrow it. They said that about my planes in the first place.) on a 22.7 9 tooth stator for 12 poles and it all stays cool like a cucumber but the magnet can. What is happening here?! The test data shows no signs of short and the heat is too much to be rub on the stator teeth over a 5 to 10 second shot on the test stand, besides the windings are cool!

pete b

[swatson144]

Heh spoke,

sounds like maybe the can is slipping on the shaft? Ruling out rubbing the mags is easy enough. just pull the rotor and cover the mags with indelable marker... run it and if you see marks it's rubbing.

[spoke2570]

Definitely not the can/shaft juncture. GBx stuff is tight. I hope it is not a rub. I will find out soon. I am wayyy over extended on play time this week.

pete b

[latrans]

Spoke, So the the can gets hot and not the stator? Odd. One would think that if the can was rubbing (the only way for a can to get hot as far as I know) then the heat generated by the friction would be equally distributed to the stator. I'm stumped.

[juki48]

I had a can that would get hot once. it had something to do with the bearing alignment or the shaft being bent. I seemed as though the heat was being generated by the shaft. I rebuilt it with new parts and it ran just fine.

[spoke2570]

Yep, the can only is getting hot. The windings are cool. Only pulls like 5 amps with an 11x4.7. It was getting hot at a lot lower current than that. I was hoping that it wasn't a rub or a slightly bent shaft, but it must be... :cry: :( Oh well, at least isn't some total pain to fix....

pete b

[spoke2570]

The can/shaft was the culprit. Motor will go in the database shortly. My neighbors think I am crazy... out in the front yard with a big@@# bike headlight to get test results. I got a flight in, as well. The wind was horrible. The flight was cut short as I turned across the wind and the horizontal stab folded. The motor worked great!

pete b