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Old Feb 17, 2012, 07:16 PM
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Help!
Wits end with Great Planes Motor

Bought an electrostik RXR back in December 2011. On a recent flight the plane lost power as I did my final approach. As I was landing I could hear a squealing sound coming from the plane. Luckily I was able to land without incident. I found that if you spooled up the .25 rimfire motor fast it would start to squeal and then stop causing the ESC to get very warm. On normal slow advance of the .25 I would not see this issue but as soon as I asked for a quick increase in power it would start squealing again and stop. I called GP CS and explained the problem. They asked me to send the motor back and would resolve the prolem by sending me a new motor. I got the new motor today and installed it. The squealing started again and had the same exact problem. A friend of mine loaned me his .32 rimfire and after installation everything was OK. So here is my dilemma.

A. It can't be the ESC since the .32 motor works fine at all speeds including fast spool up and the ESC does not get very warm.
B. It can't be the .25 rimfire since they sent me a new one.
C. I have replaced rcvr and battery to no avail.
D. My battery is a 3S 11.1 20C 3300mah as recommended by GP.

SOOO. What is my problem. Could they have sent me a second bad motor. What else can I test to eliminate the second motor as the problem.

Please help!!! Thanks
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Old Feb 17, 2012, 07:40 PM
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Chattanooga, Tennessee, United States
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My money is on ESC timing and/or too big a prop!

Try a far smaller prop and see if the problem persists... then try different timing advance.
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Old Feb 17, 2012, 08:09 PM
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@DR Kiwi - running a 12X6E APC prop which is what GP recommends. As far as the ESC timing why would it be different between the .25 and the .32 rimfire motors? Could not find ESC timing instructions for rimfire engines. Do you have a URL for it.
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Old Feb 17, 2012, 08:39 PM
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12x6 should be okay.. I run everything on default timing and never have a problem... humor me and put an 8x6 on it and see if the problem persists!

Motor: Great Planes Rimfire 42-40-1000 (#4675); 1000rpm/V; 2.5A no-load; 0.0595 Ohms.
Battery: Thunder Power TP3300 (G4 ProPower 30C) (30C); 3 cells; 3300mAh @ 3.7V; 0.005 Ohms/cell.
Speed Control: Castle Creations Phoenix 60; 0.0012 Ohms; High rate.
Drive System: Direct; 12x6 (Pconst=1.17; Tconst=1) direct drive.
Airframe: Anything you want.
Motor Amps = 30.0
Motor Volts = 10.6
Input (W) = 318.1
Loss (W) = 122.3
MGbOut (W) = 195.8
MotGb Ef(%) = 61.6
Shaft Ef(%) = 58.9
Prop RPM = 7128
Thrust (oz) = 48.2
PSpd (mph) = 40.5
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Old Feb 17, 2012, 10:24 PM
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@Dr Kiwi - Problem resolved but answer puzzling. My son loaned me his 60A ESC and I installed it using the .25 rimfire and a 12X6 prop. Thing runs like a charm as does the .32 motor. But I am still in a quandry. How can the ESC work with a high wattage motor and not a lower wattage motor. Could it be that the .25 was pulling more amps with a 12X6 than the ESC could handle? I would think that the .32 using a 12X6 would also pull more amps but that was not the situation. I don't know if I will ever get an answer but I am satisfied that all is working again. The only reprogramming necessary was to remove the braking. Now all I need is to add a little weight to compensate for the larger ESC. Thanks again for all your help.
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Old Feb 18, 2012, 01:30 AM
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@ Bimmerland

Think of it as the valves floating on an engine head, when the the engine runs faster than the valve springs can close the intake and exhaust valves. In other words the ESC and the motor get mistimed with each other and fall out of sync.
Or the engines distributor getting ahead of the pistons and firing at the wrong time.

Since your running a large prop on your motor and you shove the throttle forward quickly the ESC will do what you tell it to do (increase speed quickly) . But with the motor with its load will lag and not keep up and you get that screeching sound when they fall out of sync and the motor stops abruptly. The ESC is shutting its self down in order to save itself from over heating.

I have also seen it go the other way with the motor and ESC ,having very little load or noload and the motor tends to outrun the ESC(6 pole inrunners, helis and EDFs)

The larger the ESC (amp wise ) the slower it is able to operate since they are designed to run slower turning motors. That may be why your .25 Rimfire seems to like them over your smaller amp ESC with its large load.

Have you checked to see how hot your motor is getting after a demanding flight? Or a 15 second WOT run up on the ground with that prop? If you can't keep your fingers on it you need to back off on the load or cell count.

I may not have the details of whats going between the ESC and motor correct ei: MOSfet switching speed in relation to load and pole count. But that's the way I Iook at it in my head and it seems to work out.
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Old Feb 18, 2012, 07:44 AM
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You never mentioned the size of the original ESC... if it was <40A that might help to explain it, since you might have been drawing 30A-35A with that 12x6.

I'd still like you to do the experiment with an 8x6 or 9x6 as a "proof of concept"......I reckon the motor and small ESC will run fine!
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Old Feb 19, 2012, 01:39 AM
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@ Dr. Kiwi

Hi Phil ! How have you been?...this is Jim from GPS...Man its been a while since I was last on RC Groups, I even had to start a new account...LOL

@ Brimmerland

Knowing the AMP rating and brand of your ESC can tell a lot , such as ..Is it programable or an ESC produced with a simple set timing that can not be changed. Also what brand and type of prop are you using?

I agree with Dr. Kiwi that trying a smaller prop with your original ESC and .25 motor to see if it does the same thing will give more indication of whats going on.

I am still betting that your motor and ESC are getting out of sync when you punch the throttle with that big prop. One of the things that our (aircraft) ESC's have to do at start up, is sync its phases to the phases of the motor . Maybe you have seen it when it does this , the motor will give a slight stutter and sometimes make a "PRING" sound and then start rotating. That is the ESC and the motor syncing up ! Now if we used a Hall sensor like what they use for car motors, you will not get this, because the senor tells the ESC exactly what phase wire it needs to fire first. The Hall sensor'ed motor will get a car off the starting line much faster than a non sensor'ed motor will because of this.

Also if one of the motors or ESC's phase wires gets broken, unplugged or burned out, the motor and ESC will loose sync and you get that screeching sound. But I don't think that is your problem, since you say all works fine with the larger ESC.
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Old Feb 19, 2012, 10:28 AM
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Hi Guys, I am bimmerland's Son. His original ESC was a 45amp unit.

I am now using it with an e-flight power 15 in my Wildcat. Seems to work fine in this arrangement. Haven't flown the Wildcat with the new motor and ESC yet as the weather today in Raleigh, NC completely blows.

However, I cannot wait to get this baby in the air. It should scream!
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Old Feb 19, 2012, 11:56 AM
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Hi Jim,

I still use those 2s and 3s GPS 4000mAh packs for testing!

Life is busy... a full teaching load for Adjunct pay, and a '71 MiniCooper which requires constant attention does that to you.

Cheers, Phil
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Old Feb 20, 2012, 12:10 AM
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Wits end with rimfire motors

Hi, I'm Steve's dad and with his help the problem is resolved. I traded my 45ESC for his 60ESC and now everything works fine. I agree with the idea of it being a timing issue but GP recommends a 12X6 prop for a 3.5# plane running a .25 rimfire. I will stick with the 60ESC which allows greater flexability of prop sizes and engine choices. I have a .32 rimfire waiting in the wings if more power is needed.

BTW... If you were running an electrostik with a .25 rimfire, and a 60ESC what prop size and battery would you chose?

Thanks all.
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Old Feb 20, 2012, 12:41 AM
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Quote:
Originally Posted by Dr Kiwi View Post
Hi Jim,

I still use those 2s and 3s GPS 4000mAh packs for testing!

Life is busy... a full teaching load for Adjunct pay, and a '71 MiniCooper which requires constant attention does that to you.

Cheers, Phil
Yea those are good batteries even though they only have a C15 rating , Sold like hot cakes though! I wish I would have kept one for myself for a Spectra ARF glider I have. I was thinking of using an N2830 850kv and a 10X6 APC folder on it.
That battery would have made it, a charge once fly all day plane.

Mini Cooper!....My wife wants one!

I have spent the last 3 years dealing with a "LEMON" truck , If I had the money back from what I put in it, I could have bought oh Xing (XYH,EMP) out as he almost went bust...Juicy news as to what went on there...PM me if you want to know about it.

Jim
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Old Feb 20, 2012, 01:44 AM
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Quote:
Originally Posted by bimmerland View Post
Hi, I'm Steve's dad and with his help the problem is resolved. I traded my 45ESC for his 60ESC and now everything works fine. I agree with the idea of it being a timing issue but GP recommends a 12X6 prop for a 3.5# plane running a .25 rimfire. I will stick with the 60ESC which allows greater flexability of prop sizes and engine choices. I have a .32 rimfire waiting in the wings if more power is needed.

BTW... If you were running an electrostik with a .25 rimfire, and a 60ESC what prop size and battery would you chose?

Thanks all.
There are couple of venders out on the west coast that having been having a problem with their ESC's in the EDF's that they sell. I watched one customers flight on YouTube when his jet went down and then started on fire . It was the ESC being to small amp wise and not being able to keep up with what the fan may have been doing.
I believe what is happening there is that the fan blades are changing pitch (inexpensive 6 blade ducted fan) at that high of an RPM and the motor speeds up with less load. This will leave the ESC behind and trying to catch up but gets passed by the motor, as it is slowing down because of no power. This will lead to a vicious cycle to where the ESC finally gives up and commits suicide....lol

Prop wise for your Electrostik, you want to give your self 3/4 to 1 inch of ground clearance.
If you want to use your 12 inch prop , but it will not clear, then go with bigger wheels and or taller landing gear. Just remember that your 2200 3s 20C battery is only good to 44 AMPs

If you want it to go like a B outta H, then go to a 4 cell 40C battery and a 10x6 (maybe 9X6) E prop. I would try both props going with the 9X6 first and do that 15 second WOT touch test and if all is well move up to the 10X6 and do the test again.

One of the best things to invest in and will save you a lot of heart ache (and $) is a Watt Meter. This will tell you exactly what your power system is doing!

Jim
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Old Feb 20, 2012, 08:09 AM
fmw
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I would agree with Dr. Kiwi if you are using the recommended prop. If you are using a larger one then I vote for that.
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Old Feb 21, 2012, 07:04 PM
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Quote:
Originally Posted by turbine42 View Post

Mini Cooper!....My wife wants one!

I have spent the last 3 years dealing with a "LEMON" truck , If I had the money back from what I put in it, I could have bought oh Xing (XYH,EMP) out

Jim

I could have bought out most of China with the money I have sunk into the Mini!
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