Brenner

This is really weird, and I'd be grateful if anyone can clue me in as to what's going on.

Yesterday when I was flying I noticed that I was suddenly using about 4000 mah plus per flight instead of the usual 3200 mah per flight. I tried to think what had changed in my setup but I couldn't think of anything. However, today on my first flight my Integral went like a scalded cat for about 3 minutes, and then suddenly the motor wouldn't respond when I advanced the throttle. I landed deadstick, and checked my batteries, and found that in 3 minutes or so of flying I had completely depleted my pack. Which made me very suspicious.

Then I put a watt meter between my pack and my speed control and measured 99 amps at full throttle. So, I figured I either had a problem with the motor, or a problem with the speed control. Fortunately however, I had an extra speed control that I could try, and when I swapped it out I was still drawing 99 amps, so now I know there's something wrong with the motor. I used an ohm meter to measure the winding resistances, and I'm getting a consistent 0.2 ohms.

Does anyone know if this resistance is correct? What could cause a Hacker C50-14XL to go from 60 amps current draw to 99 amps current draw in the space of a day?

Chris Moon

My Feedback: (8)

Brenner - sounds like a slipped rotor. That was (is) common in those motors. I was under the impression the issue was fixed but maybe not. Dave S. (Chicago) had 2 of them do it a couple of years ago and they jumped from normal up to 100+ amps just like yours.

Chris Moon

My Feedback: (8)

Remember also that many meters won't read over 99 amps so if it said 99 amps, it was most likely more than that []

Brenner

Thanks for the info. What exactly is a slipped rotor though. I've taken the motor apart and I notice that the rotor appears to have a counterweight on one end. Is this the part that slips?

flyf3a

Hi

What is the temp reading on the controller, if this is high the controller cut-off is coming into effect meaning that your motor is about to go and subsequently fry the controller.

Have seen this happen on 2 Hacker 14 xl motors.

Regards
Burt

Brenner

I didn't download any parameters from the controller, but everything was very hot to the touch. The motor, the controler, and the batteries. I'd say 60C plus.

joenella

Have You remembered to change the grease in the gearbox? if running more than 50 flights it might be a problem and You will have a destroyed gearbox suddenly, don't ask why I know

67685

Hi,

I have two 14XL, and my oldest needed overhaul after 290 flights. My cooling fan disintegrated, and Hacker,Germany changed 4 bearings ( 2-motor, 2 gearbox ). The planetary gear-bearings was fine and didn`t need replacement. This motor operated normally all time,until i found the broken cooling-fan, probably caused by worn motor-bearings.

I guess frequent inspection/overhaul is an good idea on this motor. Better safe than sorry..

Just my personal experience

Kjell Olav

Brenner

Well, I've ordered a new rotor, new bearings, and a new gearbox. I should get it tomorrow by 10:00 am. I actually can't think of anything else to change. The only thing that I'm not changing is the stator, but the coil resistance seems okay, and there is no evidence of any abrasion, or touching by the rotor.

patternflyer1

My Feedback: (11)

It's a $250 fix at Hacker. I've had my 14xl in 3 times for this. Make sure you have more than enough cooling to your motor. Don't let it get over 160 degrees no matter what.

Chris

Brenner

Well, I got new a rotor from Hacker Brushless via UPS overnight, and it's fixed! I also replaced all the bearings and the gearbox, so I'm hoping that it's as good as new.

patternflyer1

My Feedback: (11)

Just out of curiosity what did the parts cost.

Thx

Brenner

The prices are as follows:

C50 XL Competition Rotor with Fan $184.99
C50 Competition Bearing $6.50 X 2
Competition Gearbox $179.99

All prices are USD

Eggert

.....I have had a similar experience ! Apparently, I had been overloading my motor "with too much propeller", 20x15 APC on a 13 windings, and thus causing the magnets to loose magnetism over time. Hence, i drew 100 + amps from the batteries and the controller cut during flights. Actually "toasted" a couple of cells on that account besides the motor.

pgvillar

What's the trick to keeping the 14xl less than 160 degrees? I just started flying E this winter. When summer temps start hitting the 100's here in Texas I am a little bit concerned. I'm flying the Integral, with the air scoops in the front opened per plan. Do I need to do anything more?

Paul

67685

Hi,

My solutions in my Hacker/Integral ; 2-chambers stator, works good, engine get barely warm... "Hand-warm" ...

Kjell Olav

pgvillar

Kjell,

Wow, interesint engineering there. Thanks for the pictures. What do you for air exit? Do you have exit holes cut into the rear fuselage section somewhere?

Paul

67685

Paul,

Here you can see the exit holes ; the two forward for regulator outlet, and the four aft for motor/battery outlet.

...added one more picture of the stator section how it looks from inside when cowling mounted... I did several prototypes with different shape and size, and ended up with this one.

What ever you choose to get the motor cooled, i would recommend to build some kind of a closed duct; from air-intake to partly surrounding the motor.

... Perfect for hot climate as yours

Kjell Olav

67685

... Forgot to mention a thing here...

What seems effective about the stator,except routing the air directly to the motor ; is that the area from the intake increase all the way to the motor. (airspeed / pressure inside the stator chamber).

Kjell Olav

hezik

Magnets de-magnetise when they get too hot. Basically the stronger the magnet, the lower the temperature at which point this will happen. As far as I know, scorpion is the only manufacturer that uses magnets that can withstand high temperatures. Overall any RC electric engine shouldn't get much hotter than the mentioned 160 degrees, wich is already on the hot side. Most used magnets will start to de-magnetise around 185 degrees, and keep in mind that if you measure 160 degrees on the outside, the magnets might be even hotter than that.

You can imagine that if one would replace the default magnets on an engine by magnets that have 'halve the strength', then the current will go up. This is since your ESC will still want to try to spin the prop at the same RPM, so it will just pump more power into it.

Having a good airflow over your engine is pinnacle in this, but it's useless to make all kinds of tunnels if your exhausts aren't functioning or not big enough. Roughly you should have at least 1.5 (preferabely more) the exhaust-opening vs the intake opening.