Author Topic: AXI motor problem (Read 3762 times)

Robertc · « **on:** February 15, 2009, 07:35:12 PM »

Today while at a contest, my AXI 2826/10 had problems. Practice flight, engine spooled down after inside squares. It sounded like there was a "buzz" the whole flight. Took off the cowl, didn't see anything, so I turn it back on. Seemed normal. Took everything off the front and tuned it over. Seemed like there was a spot or two where the can was brushing something.
Couldn't find anything and it's a contest so I recharged the battery which was not down any unusual amount and got ready for my first official. Took off and that buzzing was still there. Made it thought the triangles and the motor spooled down for a lap or so, then went back up, few more laps and the same thing. Then made it to the normal cut off. Motor was very hot. I pulled it out and it doesn't spin freely as it did. It sounds like dry bearings when I spin it. No unusual smell.
Any ideas and anyplace I can send it? Previous flights during a three week period never resulted in a hot motor.

Robert Compton

Alan Hahn · « **Reply #1 on:** February 15, 2009, 08:05:16 PM »

I'm wondering if a magnet has detached.

On the motor end that the 3 wires exit, there is a tiny split ring around the motor shaft (next to the bearing). Carefully remove the ring--watch out that it doesn't launch into unknown corners of your room. Once that is off, you should be able to pull the two halves of the motor apart. Be careful, the magnets are pulling quite strongly on the heads of the stator. Also when it pulls apart, the bearing might drop out, so do it over a cloth which "de-bouncifies" any part that falls off.

Once apart, look in the bell and see if any magnet looks like it is out of place. Also check to see if you can see any abrasion marks on the magnet surface.

You can glue a magnet back in with CA or a thin film of J-B Weld. In either case, scrape away any excess glue still on the bell or magnet. Clean off both the back side of the magnet and the iron cylinder with some acetone. But don't oversoak things, you don't want the adhesive on the other magnets to loosen. Be careful that you glue the magnet back in with the correct polarity. The side that glues onto the bell should repel from the front surface of the two adjacent magnets. I don't recall if the AXI magnets have curved front and back surfaces (to match the curvature of the iron cylinder). If they do, then the curvature shows you which side is the outer side, Try to center the replaced magnet equidistant between the two adjacent ones along its entire length. If you bias too much one side or the other, it will jump to that magnet, possibly nicking the nickel plating off. If it does get nicked, put on a drop of CA to seal the underlying material. Let everything cure. The magnets are a bit fragile, so don't let them jump around and hit each other. They are very strong, and believe me they will jump to magnetic items very easily!

Assuming this has all gone well, you can start putting it back together. There are two things to look out for. #1, when you slide the two pieces back together, there will be a point that the magnets will really try to pull things together with a strong force. Resist letting this cause the two halves knock --this can damage the bearings. Now carefully try to put that split ring back on. I think I just slipped it over the end and slid it toward the groove in the shaft.

Spin the motor, hopefully you won't feel any binding.

If it was the bearings causing problems, then to remove them, you need to separate the two halves anyway.

Good luck!

Alan

Mark Scarborough · « **Reply #2 on:** February 15, 2009, 09:04:44 PM »

Robert,
that sounds like exactly what I had happen with my AXI motor, I am sending mine in for a warranty replacement. They are honoring the warranty despite me not having a sales reciept,, well they are replacing the motor for half price. Its on its way there now, they have told me they are going to honor it, look at the warranty as an option unless you want to repair it?
Mine was a magnet that came loose just as Alan said except mine broke a corner off the magnet in the process.

Robertc · « **Reply #3 on:** February 15, 2009, 09:35:58 PM »

Mark,

Who are you sending your motor to for warranty?

Mark Scarborough · « **Reply #4 on:** February 15, 2009, 10:33:40 PM »

I contacted Hobby Lobby warranty customer service, its on their website

Dennis Toth · « **Reply #5 on:** February 16, 2009, 01:43:42 PM »

Robert,

Sorry to hear about the motor problem. At first it sounds like a cooling problem. But was the amp temp much higher than what you had been practicing in? I thought you posted that the motor was only warm. Unless there was a major temp difference it may just have been something that let go.

I noticed that at the KOI and during the cooler (<70F) that I am pulling about 150 - 250MA less than during the summer 85+days last summer. Seems the motors are sensitive to cooling as bad as the IC engines. In my profile Excitation the fuse is hollow and I opened up the front of the facade cowl to flow air through the hollow fuse over the timer, ESC. I also drilled and angled hole through the motor mount (I am using the front mount and bolt the mount plate to the original maple motor mounts) to blow some air over the motor. Since the motor is part exposed it seems to get enough cooling. Hope you get some answers, your motor is not very old. If it is a magnet dropping off or a bearing seizing AXI should make good. I have wondered how long the bearings in these motors can run without some re-lubrication. Scorpion offers a bearing lub kit, maybe they know something (Alan?).

The bigger question is what do we need to do to make sure we don't start having this type of failure happening all the time. Please post what you find out from AXI and what their remedy suggestions are.

Best, Dennis

Alan Hahn · « **Reply #6 on:** February 16, 2009, 03:39:16 PM »

Dennis,
All I know about the Scorpion lube kit is that I think it is primarily directed at the helicopter market---they are spinning up those motors pretty high--+20krpm if I remember correctly--also note they are working through gears to get to the main rotor blade!

Boca Bearing also sells some lube. Probably doesn't hurt to apply some, but only downside is that any left on the surface will tend to grab dirt. Maybe there are more knowledgeable people out there.

I do know that our bearings are pretty fragile and can easily be damaged if they are knocked too hard. I am not sure whether our square corners count for abuse of not!

Robertc · « **Reply #7 on:** February 16, 2009, 06:46:24 PM »

Took apart the motor and several magnets have moved. See attached picture.

Mark Scarborough · « **Reply #8 on:** February 16, 2009, 07:35:16 PM »

Robert,
yep that looks just like mine did inside! though I had a few chips out of mine

Dean Pappas · « **Reply #9 on:** February 17, 2009, 12:04:57 PM »

Hello Robert,
It sounds like overtemp has led to magnet glue failure ... Ouch.
Have you ever measured the motor temperature immediately (I mean really immediately) after a flight?
Can you at least stick a fingertip into the cowl to feel the motor bell?
If it hurts, then it's too hot.
Do you have any pictures of your installation, both the inside of the cowl and entire works with the cowl off?
When Bob and i first installed the 2826/10 in his old Genesis, the motor temps were up over 150 degrees, and that was not good at all. A chintzy little baffle took 1/3 of the inlet air and deflected it up at the front of the motor, and while this was still far from what I would have liked, motor temps dropped to where you could solidly grab the motor maybe 30 seconds after the landing without burning yourself in the Summer.

Heta is also bad for the bearings, not just the bearings themselves but also the fiut of the bearings into the thin-walled aluminium tube pylon that supports the entire spinning structure. Hunt and I (with some help from our Buddy Wieder) are prototyping a mounting system to improve bearing and motor life. We're doing it with an AXI, but it should work with any motor that does not already have a big bearing in the circumference of the bell. Either Bob or I will create a thread when we have pictures.

take care, All ...
Dean P.

Robertc · « **Reply #10 on:** February 17, 2009, 02:08:41 PM »

Never thought I had a heat problem. I checked the motor after several flights and it was never too hot to hold on to.
I'm thinking one magnet slipped and I flew not knowing the problem and then it got HOT and let several more go.

It would really help to have a shaft extension of at least a 1/4" to have space to direct more air toward the front of the motor.

Dean Pappas · « **Reply #11 on:** February 17, 2009, 04:56:43 PM »

Hi Robert,
Are you mounting the motor from the back or from the front?

Dean P.

Robertc · « **Reply #12 on:** February 17, 2009, 08:45:19 PM »

Mounted from the rear.
Picture from Sunday before my first flight.

Mark Scarborough · « **Reply #13 on:** February 17, 2009, 09:29:50 PM »

NICE,
FWIW my AXI suffered this indignity without ever having been overheated by me. I have an infrared temp gauge and checked it regularly. It was also on a profile not that THAT is any garauntee. When I suffered my problem, the consensus was that my motor was an early version (?) AXI and that those were prone to magnet problems.

Alan Hahn · « **Reply #14 on:** February 18, 2009, 08:13:37 AM »

One thing to remember is that the outer bell, with the magnets is rotating at ~9000 rpm is moving itself at ~40mph (I assumed a 2cm radius). So you would hope that with a little bit of air movement that it could cool itself adequately.

I don't really know how much air actually gets inside the motor to cool the stator itself. If you look into the front holes of these motors, it is pretty dark, especially if they have done a good job of stuffing as much copper wire as possible. So my guess is that not a lot of cooling happens through direct air flow through the motor.

As a order of magnitude guestimate, I think we are probably flying these motors with efficiencies in the 75-85% range. If you take an average input power of ~300 watts (maybe a little low for most of us), that implies we are leaving ~60 watts (I took 80% efficiency) in the motor (I am ignoring the poor ESC!). That clearly is a significant amount of heat so it makes sense to get some airflow directed at the outer bell---where again I think most of the heat is being released.

I can't say a lot about my E-Nobler, since I haven't pulled the cowl off to really check its temperature after a real flight, but in my bench testing (described in my Throttle efficiency thread), I did touch the outer motor shell at the end of each run and the motor didn't feel that warm to my touch. Note that there wasn't a lot of airflow over the motor since I was running the test in a pusher mode, but then again, it was certainly open to the ambient air.

It may just be that unless you are really abusing these motors, that most of the loose magnet problems are coming from poor gluing. I know that Scorpion had some issue with the carrier guys, and I had an issue with my 3020-16--but since I was the one who glued it, it was my fault!

. I know most of the motor home-building guys recommend wicking CA between the magnets and the iron cylinder. I used a rubberized CA specifically recommended by one kit manufacturer, but I realized after the failure that it was too thick to actually wick in under the curved magnets (the gap is really small with curved magnets). When I fixed it, I made sure that I got some of the adhesive under the magnet, and also added some to build up a slight ridge on all the other magnets. Haven't had a problem since. In my next build, I plan to use a thin film of JB Weld on the underside of the magnet and also put a thin layer on the entire inner surface of the iron ring. Having a motor eat a magnet on the last turn of the clover, just before the exit would certainly ruin my day

, even if Russ G. might enjoy it a lot!

Mike Anderson · « **Reply #15 on:** February 18, 2009, 10:39:37 AM »

I guess I'll jump in here since you mention the "Carrier Guys" and Scorpion motors -- that was me that originally had problems with loose magnets in Scorpions. And you guys are chasing "poor glue" when the problem is probably mechanical.

(The following is more conjecture than provable fact, but it is my thoughts on what might have caused my problems and the engineering at Scorpion that seems to have fixed it --)

If you think about it, centrifugal force is trying to force the magnets through the rotating "bell" in addition to the magnetic force that makes them attracted to the bell in the first place. No matter how hot the glue gets, magnets simply flying off or dropping off is unlikely. What I believe to have been the problem is "shaft whip" - where the motor shaft bends while running, allowing one or more magnets to "crash" into a stator tooth. So the magnets get knocked loose.

The problem showed up in the Scorpion 3032-xx series - a relatively "long, thin" form factor (ie: the rotating bell is much longer than it's diameter). The symptom was that after very short running times, there would be an un-natural noise, the motor would be shut down immediately, and magnets would be visible in the gap between the rotating bell and the fixed base. This happened with the first motor I received after about 5 seconds of running on a test bench. With the second motor, I got it out to the field, flew it once successfully changed props and it happened as I ran it up to full throttle. The third motor, took off and flew high speed successfully, but after throttling back and while accelerating back up the symptoms and problem appeared again. Coincidentally, that same day the problem happened to Lucien Miller (Scorpion importer) on a similar motor on HIS testbench. It turns out it had been reported by several other users since my initial motor (incidentally, my first motor was one of the first 3032-8's in circulation, at that time).

I had noticed that there was a "resonance" vibration at certain points in the throttle curve - much more pronounced when using APC "Sport" series than when using either wood props or APC "Thin Electric" series. I figured that this vibration may have been a significant event and made a couple of sketches that I sent to Lucien, who sent them on the the Scorpion engineers. The upshot was that they recalled all the 3032 series and re-engineered them for a large ring bearing at the open end. I haven't had any problems with this latest version. I also do NOT rear mount the motors, anymore.

I'll try and post something of a drawing that resembles what I observed and sent --

At any rate, the problem seems to be a combination of things - Long narrow form motor, rear mounting, heavy (probably not well balanced) props, etc. -- All are mechanical and probably any one not enough to result in motor damage by itself. I don't discount that glue may also be problematical, but in none of my cases was heat involved.

So, here is my drawing, and take all this for what it's worth - just something else to think about.

Mike A

Alan Hahn · « **Reply #16 on:** February 18, 2009, 11:08:38 AM »

Mike,
You've got some good points about the mounting and the propeller. I agree that the front mount is a sturdier mount (of course all my planes except the Super Clown are just the opposite!).

At least in my case, the problem was my gluing--I didn't see any evidence of scraping of the magnet. I first noticed it when the magnet itself started peaking out in the small gap between the iron shell and the back aluminum plate. I don't recall right now why I actually noticed it, since normally the motor is inside the cowl.

Dennis Adamisin · « **Reply #17 on:** February 18, 2009, 11:14:14 AM »

Mike:
You called it conjecture but everything you wrote rings true. Mechanical impact rather than hot or failed glue makes sense. A follow-up:

* You mentioned a resonance at certain RPM's - was that with the rear mounted motor? Does the resonance vanish - or occur at different RPM's - with a front mounted motor? Seems it should because the masses and harmonics should be different.

* You said your resonances occur with the APC Sport prop (heavier than wood or APC-E) were you also using a spinner of some kind? Put another way, a light prop with a heavy spinner might put things art risk too.

* You mentioned the form factor of the motor - long and skinny - as a contributing factor. It could be surmissed that the short/fat motors could also be at risk because the bearings are so close together...(?)

I am flying 1 rear mounted motor with an APC-E and a 2" e-spinner (plastic shell with open alum backplate) You just made me nervous!

Mike Anderson · « **Reply #18 on:** February 18, 2009, 12:02:25 PM »

Quote from: Dennis Adamisin on February 18, 2009, 11:14:14 AM

Mike:
You called it conjecture but everything you wrote rings true. Mechanical impact rather than hot or failed glue makes sense. A follow-up:

* You mentioned a resonance at certain RPM's - was that with the rear mounted motor? Does the resonance vanish - or occur at different RPM's - with a front mounted motor? Seems it should because the masses and harmonics should be different.

* You said your resonances occur with the APC Sport prop (heavier than wood or APC-E) were you also using a spinner of some kind? Put another way, a light prop with a heavy spinner might put things art risk too.

* You mentioned the form factor of the motor - long and skinny - as a contributing factor. It could be surmissed that the short/fat motors could also be at risk because the bearings are so close together...(?)

I am flying 1 rear mounted motor with an APC-E and a 2" e-spinner (plastic shell with open alum backplate) You just made me nervous!

* - The "resonance" (and I don't know if that is technically a correct term) is just like most any RC plane will exhibit if you advance the throttle slowly - at some RPM or at a couple of RPM's the nose will vibrate and then smooth out again. I am guessing that changing props to a "Sport" model changed the resonance frequency to something that was in the range of RPM's I hit. Yes, all of the above motor problems were on the same plane - rear mounted, with a firewall supported much like a Baby Bee might have - thick blocks backing up a plywood motor mount/firewall. I eventually needed a new plane anyway, because while the Scorpion was travelling back and forth to California and China I was flying an AXI - so when the Scorpion finally got back with the ring bearing installed, I built a new model that front mounts the motor. I have not noticed the same type of RPM dependent resonant vibration, but I also have only run APC and MA "electric only" props. And I agree, the resonances would be different, as they also would be if one made a more rigid front end, longer or shorter front end, etc. Just for reference, the model(s) are Sig Skyrays, pretty much stock, with a stock nose length. The second one has hardwood rails, just like the glow version, and lite-ply doublers. The first had no maple in the front end at all.

* - No spinner on any of them but you are correct, any change in mass at the front will change the frequencies at which noticeable reactions occur.

* - AHA ! - the bearings are closer together, yes, but they are NOT in the system (at least for the rear mount). The only thing resisting the shaft whip is the shaft itself - so case harden the shaft, increase the diameter or make it of a more rigid material, and you might change the frequency to something not in our range. But if you change the form factor of the motor to something short and squat, you decrease the distance that the mass of the bell/magnets is (so they add less to the vibration system), and you increase the distance that the shaft has to deflect before the magnets crash, because they are on a shorter arm.
- note also: with front mounting, if the bell itself is out of balance, the magnets still might crash if the joint between the bell and shaft (where the grub screws are) is not a VERY tight fit. So it might be a good idea to balance the bell on a magnetic prop balancer .... couldn't hoit!

Like I said, this is all my own reflection on my own observations. I currently have built smaller models with rear mounted motors, and they fly fine. But I'm currently finishing up a Twister for a Turnigy 3548. My motor mount consists of two pieces of aluminum angle, and the T mount supplied with the Turnigy. I don't EXPECT to have problems, but it won't shock me if I do - I will probably go to the 4240 or 4250 Turnigy if I have to.

One other consideration - Carrier planes don't have to do square corners - I will be listening carefully to my motor during those parts of the pattern with real tight maneuvers at least for the first few flights.

Mike A

Mike Anderson · « **Reply #19 on:** February 18, 2009, 12:06:10 PM »

Quote from: Alan Hahn on February 18, 2009, 11:08:38 AM

Mike,
You've got some good points about the mounting and the propeller. I agree that the front mount is a sturdier mount (of course all my planes except the Super Clown are just the opposite!).

At least in my case, the problem was my gluing--I didn't see any evidence of scraping of the magnet. I first noticed it when the magnet itself started peaking out in the small gap between the iron shell and the back aluminum plate. I don't recall right now why I actually noticed it, since normally the motor is inside the cowl.

I won't disagree with you, Alan. I do understand how glue can be inadequate or how it can fail. I will only ask one question - and it is the same question I started asking myself when my magnet(s) started sliding to the rear: Assuming the glue did let go, what force caused the magnet to move? I couldn't think of anything that made sense besides a mechanical force.

Mike A.

Alan Hahn · « **Reply #20 on:** February 18, 2009, 12:50:52 PM »

Quote from: Mike Anderson on February 18, 2009, 12:06:10 PM

I won't disagree with you, Alan. I do understand how glue can be inadequate or how it can fail. I will only ask one question - and it is the same question I started asking myself when my magnet(s) started sliding to the rear: Assuming the glue did let go, what force caused the magnet to move? I couldn't think of anything that made sense besides a mechanical force.

Mike A.

Actually I wasn't completely disagreeing with you. What force caused the glue to break---I don't know. It could have been some type of vibration. Clearly the lousier job you do with gluing, the easier it is to break the glue joint. I know that I also had an issue that the glue joint (same glue) between the stator and the aluminum nose piece (the one that holds the two small bearings) also was loose. I don't recall if when I was fixing that is when I noticed the loose magnet--or whether it was during one on my many bench motor tests. Like I said, normally when the motor is mounted in my Nobler, I don't see anything. Should have paid more attention.

I was aware of the 3032 problems --either from you or by posts on RC Groups. That's one reason I have stuck with the shorter 3020 motors, not even going to 3026's. I do agree that separating the propeller and motor rotating mass by the front mount is a smart thing to do in general. That way the rotating propeller is on the other side of the big bearing, and any square maneuver sort of balances the forces on the rotating motor components. A back mount doesn't have that feature.

Alan Hahn · « **Reply #21 on:** February 18, 2009, 12:59:43 PM »

One thing I should mention, is that there is a pretty strong magnetic force which is both pushing and pulling on each magnet due to the current in the stator. So every magnet feels that force cycle about 12 times (one cycle for each tooth on the stator). If your glue joint is crummy, it could loosen. Then maybe that vibration might walk the magnet out a bit of the iron cylinder. Might explain what I saw in my case (which I am not arguing is what others have seen.

Another thing to remember is that at low rpm, the "centrifugal" force is small, while the magnetic attraction between the magnet and tooth (depending on how hard you punch that throttle!). I guess if you glue joint is crummy, that also could affect things.

However if the motor shaft flexes and the magnets hit the teeth, all bets are off!

Mike Anderson · « **Reply #22 on:** February 18, 2009, 01:13:24 PM »

Quote from: Alan Hahn on February 18, 2009, 12:59:43 PM

One thing I should mention, is that there is a pretty strong magnetic force which is both pushing and pulling on each magnet due to the current in the stator. So every magnet feels that force cycle about 12 times (one cycle for each tooth on the stator). If your glue joint is crummy, it could loosen. Then maybe that vibration might walk the magnet out a bit of the iron cylinder. Might explain what I saw in my case (which I am not arguing is what others have seen.

Another thing to remember is that at low rpm, the "centrifugal" force is small, while the magnetic attraction between the magnet and tooth (depending on how hard you punch that throttle!). I guess if you glue joint is crummy, that also could affect things.

However if the motor shaft flexes and the magnets hit the teeth, all bets are off!

Plausible I imagine. In the case of the Scorpions, though, one of the early fixes was to change the "pre-gluing" and the glue or adhesive process. Then they ran the motor at ~2000 Watts until it smoked out the rear end, and the glue didn't fail. But my magnets again moved - on the motor that came with this description attached! (In the Navy, we had an expression "All electronics is FM (F**kin' Magic)". In my current job I play with permanent magnets and electro-magnets on a daily basis. I have changed the saying to "All Magnetics is FM".

@

Dean Pappas · « **Reply #23 on:** February 18, 2009, 01:42:53 PM »

Hello All,
Robert, the Desparado looks great! Now I'll be humming that tune all afternoon ...

The discussion about shaft/bell whip is meaningful stuff, and the RC Pattern guys have had possibly even more trouble with the 3 kiloWatt sized motors, despite the lack of blinding square corners. What Hunt and I are now trying is to:
1) front mount our AXI,
2) put the old rear-mount style prop mount back on the motor,
3) Using an appropriate spacer, put a ball bearing on that rear prop mount (skateboard size!)
4) bolt a former with a snug fitting hole to the bearing so that it supports it radially but not axially.

We are hoping to start testing as soon as the weather permits. I'll put some pictures of the test-bench setup in the forum asap.

As far as motor cooling is concerned, yes we should try to force air through the motor not just over it. Cool copper is less resistive and cold magnets are stronger; what's not to like?

later Friends,
Dean P.

Alan Hahn · « **Reply #24 on:** February 18, 2009, 01:54:31 PM »

Quote from: Mike Anderson on February 18, 2009, 01:13:24 PM

Plausible I imagine. In the case of the Scorpions, though, one of the early fixes was to change the "pre-gluing" and the glue or adhesive process. Then they ran the motor at ~2000 Watts until it smoked out the rear end, and the glue didn't fail. But my magnets again moved - on the motor that came with this description attached! (In the Navy, we had an expression "All electronics is FM (F**kin' Magic)". In my current job I play with permanent magnets and electro-magnets on a daily basis. I have changed the saying to "All Magnetics is FM".

@

Remember, I am talking about the crummy glue joint I made (Scorpion kit) , not the one in the stock motors.

Alan Hahn · « **Reply #25 on:** February 18, 2009, 02:03:03 PM »

Quote from: Dean Pappas on February 18, 2009, 01:42:53 PM

Hello All,
<...snip.....>
As far as motor cooling is concerned, yes we should try to force air through the motor not just over it. Cool copper is less resistive and cold magnets are stronger; what's not to like?

later Friends,
Dean P.

Dean,
not arguing that it isn't desirable, just that it may bevery hard to get air to flow---the openings between the teeth (blocked by the windings) or between the teeth head and the outer shell/magnets are quite small. I am not sure how much air actually can flow inside the motor--the windings are packed in pretty densely.

Sounds like an opportunity for another test run.

Run with cooling holes blocked (for a minute or two maybe--no reason to push my luck!), then without. Hmmm, where is my "el cheapo" motor. I do have a temperature probe for my Eagletree, but have never hooked it up.

Dennis Toth · « **Reply #26 on:** February 18, 2009, 02:03:50 PM »

Guys,

I have used the front mount in two ships with the AXI 2826/10 motors with no problems to date. These ships were converts and I left in part of the maple motor mounts that I bolted the e-motor mount ring to with two "L" clips the bolt to the mount ring and then to the motor mount. I decided to use the front mount because it seem to make sense to balance the forces of the prop and motor over the front bearing rather than hang it off the rear. The discussions here do seem to support that. to use the front type of mount you could either have the small conventional motor mounts (reduced as it passes the motor) or install a front fire wall to the fuse sides. If you use the conventional mount it allows easy removal of the motor, prop and spinner much like an IC installation. You need to have the cowl designed to accommodate the mount half ring but this works well with the conventional IC type cowl. If you go with a front firewall you need to design the cowl to uncover at least the motor and shaft Length behind the firewall. This allows you to remove the spinner/prop and prop shaft then pull the motor back and out of the mount for removal. Both systems are a little more work than the rear mount but can be done with common shop tools (plywood for the mount ring and heavy gauge brass strip to make the "L" clip).

All this brings up a point for discussion. Does the "in-runner" NEU design have some advantage for our application? It seems that one would use either a tube mount (off the rear firewall) or a clamp around the motor that bolts to side motor mounts to hold this type of motor. Either way the main body of the motor is supported and two (or more) bearing support the bending load on the shaft (much like an IC crankshaft support). Maybe Mike P can jump in a tell us how his is holding up.

Best, Dennis

Mark Scarborough · « **Reply #27 on:** February 18, 2009, 02:46:23 PM »

FWIW, Rob Smith, my RC buddy, relates how the pattern guys are doing this now, capturing the other end of the motor with a bearing in a firewall to stabilize it. Been thinking the same thing myself. I do have some issue with front mounting the motor as it agravates soem of the loadings by the motor whipping opposite directions from the prop, but its only instinct and not anything I can quantify. Most of this is per discussions with Rob about maximizing mounting stability

Dennis Adamisin · « **Reply #28 on:** February 18, 2009, 03:35:33 PM »

Quote from: Mike Anderson on February 18, 2009, 12:02:25 PM

Like I said, this is all my own reflection on my own observations. I currently have built smaller models with rear mounted motors, and they fly fine. But I'm currently finishing up a Twister for a Turnigy 3548. My motor mount consists of two pieces of aluminum angle, and the T mount supplied with the Turnigy. I don't EXPECT to have problems, but it won't shock me if I do - I will probably go to the 4240 or 4250 Turnigy if I have to.
(snip)
Mike A

Mike
Thanks for the reply. Regarding the Turnigy 34-48's, the "normal" Turnigy uses a 4mm shaft but the Turnigy SK series 35-48 uses a 5mm shaft and 3 bearings. I don't know which you have but in the context of this discussion the SK looks like a good idea.

BTW, I think the 35-36 would have been more than enough for the Twister, the 35-48 ought to just loaf along - or you can put a 13" prop on it and go 3D'ing with Deano!

Dean Pappas · « **Reply #29 on:** February 18, 2009, 03:35:48 PM »

Hi All,
There are mounting holes in both ends of the Neu motor, though mounting from the front should suffice; and yes the inrunner configuration should have it all over the outrunner mechanically.

Here is a photo of the modified AXI 2826/10 on the plans for Buddy's new ship. The rear motor mount former will have a large hole in it, and a small ox-yoke like piece will be screwed to it so that it captures the bearing.
regards,
Dean P.

Mike Anderson · « **Reply #30 on:** February 18, 2009, 04:10:24 PM »

Quote from: Dennis Adamisin on February 18, 2009, 03:35:33 PM

Mike
Thanks for the reply. Regarding the Turnigy 34-48's, the "normal" Turnigy uses a 4mm shaft but the Turnigy SK series 35-48 uses a 5mm shaft and 3 bearings. I don't know which you have but in the context of this discussion the SK looks like a good idea.

BTW, I think the 35-36 would have been more than enough for the Twister, the 35-48 ought to just loaf along - or you can put a 13" prop on it and go 3D'ing with Deano!

We have both the normal and the improved - between three of us, we also have both the 800 and the 1100 Kv models - mine is gold 3548-1100 - last year we had a Top Flite Tutor (the old kit version) flying on this motor with 3 cells and an 11-5.5. It was a pretty good combination, power wise, but the plane was warped. My buddy put the SK version on and reports 300 RPM increase with just a motor swap, so we'll see. Another buddy has the 800 version and 4 cell batteries that should be flyable as soon as the weather cooperates which I think will be a good ".46" size - he'll be starting off with 12-6 props.

So based on the 3-cell Tutor, I think the mildly Fancherize Twister will be right in the ballpark with the gold motor. You are correct though - I had forgotten the 4 mm shaft, but we didn't notice any problems on the Tutor

< we need a "fingers crossed" smiley, but this one looks sort of like a guy holding a handle>

@

Dean Pappas · « **Reply #31 on:** February 18, 2009, 04:27:24 PM »

Quote from: Mark Scarborough on February 18, 2009, 02:46:23 PM

I do have some issue with front mounting the motor as it agravates soem of the loadings by the motor whipping opposite directions from the prop, but its only instinct and not anything I can quantify.

Mark's instinct has an excellent basis. Having the center of percussion far behind the mounting point(s) of the system can lead to whirl-whip flutter if the mounting system is too springy. The rear mount should obviate that problem.

best regards,
Dean P.

Dennis Toth · « **Reply #32 on:** February 26, 2009, 01:32:08 PM »

Robert,

Did you put the new Turnigy motor in your ship? If so how does it compare to the AXI?

Attached is the front mount I've been using for the past 9 months.

Best, Dennis

Dean Pappas · « **Reply #33 on:** February 26, 2009, 01:41:42 PM »

Hi Dennis,
Is that a 3S-2P A123 I see in the Excitation or are you just happy to see us?
later,
Dean P.

Dean Pappas · « **Reply #34 on:** February 26, 2009, 01:50:58 PM »

Hi again Gang,
Here is the ground abuse testbed for the two point mount described earlier.
Yes, it is not the same (backwards) as what some of my RC buddies are doing, but there is a reason for that.
If you are going to put a fixed bearing mount into the nosering, then the bearing mount must be finely adjustable for axial alignment with every thrust angle change. Here the bolted in former "traps" the rear bearing alleviating an interesting (P.I.T.A.) alignment process, or an expensive spherical outer race bearing.
Regards,
Dean

Mark Scarborough · « **Reply #35 on:** February 26, 2009, 04:01:18 PM »

Dean, great installation, I have been toying along similar lines mentally,,
I do wonder however,, with the backwards, or is it forwards installation like you have,, YOu are forced to use one of them there collet prop adapters,, that puts the prop on a 5mm shaft ( or 4mm on some motors) To me this seems a lot of load to carry on that small of a shaft,,second thought, I dont know,, but if you wanted to use a spinner,, how does that play out for aligment, dont the collets have the ability to move for and aft while you are tightening the prop nut down? to my way of thinking, using the prop adaptor on the other end just like a standard crankshaft, and then putting a bearing on the shaft end at the back would work more to our advantage...
Please bear with me, I am thinking out loud here,, of course then you rotate the bell instead of the stator but from my observations the stator is heavier and would equal or have greater affect on GP,, but with the short axis of rotation I doubt either one makes a significant difference,,
so help me understand your logic in the installation, what am I missing,, because I know you have WAY more background in this than I do
tjhanks

Dean Pappas · « **Reply #36 on:** February 26, 2009, 06:01:33 PM »

Hi Mark,
That there shaft is the same one that the bell and magnets are hung on. There is less overhang in this direction: look at the folks who have been running front-mounted without a tail bearing and they are apparently seeing better results than those of us who firewall mounted, at first.

For most outrunners, the bearing at the fixed end is bigger. That should help.
Turned the other way around should work fine too.
Ideally, you want to nearly bottom the collet out onto the shaft, but once you have tightened the prop the first time, it takes effort to loosen the drive washer from the tapered collet so that it would move. The cautious might use a thin smear of low-temp Loctite so that a little flame or decent soldering iron will allow removal when necessary. I find they hold just fine as long as everything is cleaned before assembly. Body oils are a better lubricant than you would think.
Hope that helped,
Dean

Robertc · « **Reply #37 on:** February 26, 2009, 08:34:08 PM »

Dennis ( Stuntguy)

The motor I bought was the Emax. Have not done anything with it.
Have started on the next two electric planes, but with this thread,
I'll have to re-think how to mount the motor.

Crist Rigotti · « **Reply #38 on:** February 26, 2009, 09:13:34 PM »

On my profile I'm building, the motor will be front mounted and rear supported.

Dennis Adamisin · « **Reply #39 on:** February 26, 2009, 09:18:13 PM »

Dean
QED. The rear mount you pictured is clearly the best way to mount an outruner. SUpporting the motor on both ends makes the bending moments all but dissappear. The deflections Mike and Mark both talked about got to nearly zero. The newfound stiffness also should eliminate the resonant points Mike described becuase the new system will have a totally different, likely MUCH higher natural frequency.

HMMMM, thats why YOU are the moderator, right?

Dean Pappas · « **Reply #40 on:** February 28, 2009, 02:10:15 PM »

That's funny, Dennis!
I thought you and I had discussed that idea. I rely on talking to you and a few other folks for the good ideas i can suck out of your heads.
Gimme a call, (609) 584-1539

Dean

Dennis Adamisin · « **Reply #41 on:** February 28, 2009, 02:41:07 PM »

Deano:

Ideas are easy, EXECUTION is where its at!

Dean Pappas · « **Reply #42 on:** March 02, 2009, 10:41:56 AM »

Exactly, I could keep Hunt in his dungeon forever!
(insert evil laugh here)
Dean