Lehner 3080 / 8 Brushless Motor ? fault

[mohanjude]

I found that putting the BK controller back makes the motor behave as it should. However I dont want to risk another expensive controller catching fire. I have come to conclusion that the motor is not defective but something else in the setup may have been the limiting factor. It could have been a faulty controller or it could be that the truck that weighs nearly 20kg is too heavy. However anybody watching the truck would have been impressed with the torque / acceleration for the first 2 minutes..... Remember the pinion has nothing to do with the motor and Schulze controller - I have the motor on the bench and holding the shaft with my fingers. I can stop the shaft rotating with my fingers when the motor is coupled to the schulze at low rpm. On the BK controller I cannot stall it that easily. I coupled it to a watt meter and noted that stalling the rotor drew about 14 amps and low rpm but once the rotor stalled the schulze stopped drawing amps. What I dont know is if the BK controller overheats when the rotor is stalled. I cannot hold the rotor with my fingers to test it out.

Mohan

[mohanjude]

Originally Posted by lincpimp

Motor may have demagged... There is a method of testing the phases against the can to check for shorts, and there must be some sort of resistance spec. If two of the phases are shorted it would act as a brake on the motor, and would also cause some massive current draw thru the esc. I would investigate the motor further. Did you buy it new, or used? Any physical damage?

I bought the motor off a german seller it looked practically new. If the motor is demagged will it run full throttle on the bench? On the bench the motor draws about 14 amps at full throttle on 39V with no load. The motor heats up slightly but no other issues identified.

[lincpimp]

Originally Posted by mohanjude

I bought the motor off a german seller it looked practically new. If the motor is demagged will it run full throttle on the bench? On the bench the motor draws about 14 amps at full throttle on 39V with no load. The motor heats up slightly but no other issues identified.

If you run a brushless motor unloaded it can over rev... I would not do that...

Unloaded amp draw is not very useful. Put it in the truck and try running it under alot of load.

Are you sure that it is 20kg? 2.2lbs per kg... over 40lbs? If so then you need a much bigger esc, or a 20s setup. Is the chassis steel?

150 amps at 39v is only 7.8hp, and that is before any losses are considered. That is not enough to run a 40lb vehicle, IMO. You may on the edge with that setup, the motor should be good for 10hp or so, but that esc is a bit undersized.

[othello]

>The other way is to push the truck and then accelerate away

The schulze 32.170 coupled with 11s1p A123 and a 4 pole Neu 1515/2Y (1100kv) was not able to start up the motor properly in a 5.2Kg 1:8 truggy especially in car mode. Heavy cogging from a stand still although the ESC is well overdimensioned in a 1:8 car. Schulze put the A123 cells at fault. We tried it with lesser A123 cell and nimh cells which helped somewhat but we were never able to start the motor up without cogging - we never expected such a behavior from such a high priced ESC. From a stand still pushing the car slightly helped the ESC to overcome cogging and as long as the car was moving the ESC worked flawlessly. An MGM 12545 starts the same setup from a stand still with absolutely no cogging. A small Jazz 55-10-32 ESC has no problem at all with a similar setup.

As you say it does work properly with your bolido motor, one might guess that the ESC has an easyer job to start up a higher pole motor as it will get better/faster a back EMF from the motor when compared to a 2 pole motor. Be prepared that when contacting Schulze everything else is to blame but the ESC.

14A @ no load seems a bit too hefty -> translates to 546 Watt (39V). Which kv version do you use? I have no experience with those big motors but my Neu 1515/2Y (1100kv, 340gr) uses no more than 2A @ 33V.

I looked through the motor data which is hosted on lehners website. Even a 3080/6 is "only" @ 11A (40V) with no load and i think you chose a less hotter wind for your 1:5 car. A 3080/12 is @ 6A (40V) with no load. You may want to contact Lehner on this subject and you may want to try posting in boat forums where you will more often encounter those big Lehner motors.

One thing you might want to try is to start up your setup with lesser voltage (less cells). Maybe this helps somewhat. But in the end it will not be a satisfactory solution (if it works at all) since you will loose top end speed.

[othello]

>If you run a brushless motor unloaded it can over rev... I would not do that...

Hmm ... as long as motor kv x Volts does not exceed max allowed RPM there should be no issue revving a motor without load (aside from a fast rise in temperature as there is no airflow aroung the motor). The 30 series Lehner motors are specified up to 50000rpm. 50000rpm / 39V = 1282kv. Even the hottest 3080 motor (3080/5) is below that mark with 1050kv which might tranlate to a max of 1150kv with no load. Still safe @ 39V ... but i suppose you chose a kv well below the 1050kv mark.

[mohanjude]

The 20kg is due to the weight of the lipo cells - I had 2 banks of 10S 6000MA - which works out to 37V @12000MA.

I also going to shed all the alloy including the alloy rollcage.

Thanks for all the tips - the motor is a Lehner 3080 /9 -> the amp draw was with me trying to stop the shaft with my fingers using a Leather glove. I would not let a motor just simply rev full blast. I must say my thick leather gloves got very hot!!

The bottom line is that I have taken the Lehner off the truck put the Bolido in their shed some weight by taking the heavy aluminium rollcage and only running one back of 10S 6000MA lipos. The trucks appears to run well and I will post some videos shortly. I will weigh the truck and give you the correct loaded weight including batteries.

Mohan

[lincpimp]

Originally Posted by mohanjude

The 20kg is due to the weight of the lipo cells - I had 2 banks of 10S 6000MA - which works out to 37V @12000MA.

I also going to shed all the alloy including the alloy rollcage.

Thanks for all the tips - the motor is a Lehner 3080 /9 -> the amp draw was with me trying to stop the shaft with my fingers using a Leather glove. I would not let a motor just simply rev full blast. I must say my thick leather gloves got very hot!!

The bottom line is that I have taken the Lehner off the truck put the Bolido in their shed some weight by taking the heavy aluminium rollcage and only running one back of 10S 6000MA lipos. The trucks appears to run well and I will post some videos shortly. I will weigh the truck and give you the correct loaded weight including batteries.

Mohan

Wow, that is alot of lipo! Anyways, sounds like you cured the issue. From what othello says the esc just does not like 2 pole motors... Seems weird to me.

Glad to hear that you did not let it run unloaded! 10s 6000 should do fine, loosing the weight probably helped too.

[mohanjude]

I changed the motor and controller - I started a new thread.

http://www.rc-monster.com/forum/show...041#post248041

Lety me know - I am a real chicken I am not opening it up on this narrow stretch of road.

I am looking forward to taking it to a field and given it a good blast. You can see in my first clip as soon as I gun the throttle this monster flips over.

Using a pretty similar setup with slightly less power my first hints would be to choose a shorter gear ratio and to use real high-amp connectors between Lipos and ESC (6 mm gold)!
As you know I'm driving the FG 4WD with a Lehner 3040/12, Schulze 32/170 and 8S2P (12 Ah). The weight of my monster is "only" 15 Kg but from my point of view the pinion or gear ratio is key in this weight-league.
The general problem of brushless-setups in such heavy cars is to overcome the initial startup due to the missing clutch. I could see from your pictures that you are using the original pinion (16/48). Try 14/48! It's only two teeth less but it makes all the difference.
Another way to prevent stalling might be to change the throttle EXPO in your RC. Just put it to + 100% and check it out. I am down to + 50% but I still use it.
Compared to the 40.160 the 32.170 only works up to 10S but it can face higher Amps. (up to 220 peak) and you can set up things like higher or lower timing and softer or harder running. I tried all those switches but they didn't have big effects.
As mentioned, key is the appropriate gear ratio.
The Schulze ESCs have a kind of self protection once they face a situation that they can't cope and they just stop to work - other than the BKs that try to do it until they burn (and I know the smell of burned BKs...).
BTW. 150 Amps. is by far not sufficient and that's the reason why I haven't used eagletree yet. At least at 8S you have to think about 200+ Amps. at the start.

Regarding the 4WD-thing I'll send you a message.

Last but not least I don't want to make you jealous but with the 3080 your monster should at least performe like mine:-)

http://www.youtube.com/watch?v=mZQR_Xubr8o

Regards,
Hermann

[mohanjude]

Originally Posted by E-VO-Maxx

Using a pretty similar setup with slightly less power my first hints would be to choose a shorter gear ratio and to use real high-amp connectors between Lipos and ESC (6 mm gold)!
As you know I'm driving the FG 4WD with a Lehner 3040/12, Schulze 32/170 and 8S2P (12 Ah). The weight of my monster is "only" 15 Kg but from my point of view the pinion or gear ratio is key in this weight-league.
The general problem of brushless-setups in such heavy cars is to overcome the initial startup due to the missing clutch. I could see from your pictures that you are using the original pinion (16/48). Try 14/48! It's only two teeth less but it makes all the difference.
Another way to prevent stalling might be to change the throttle EXPO in your RC. Just put it to + 100% and check it out. I am down to + 50% but I still use it.
Compared to the 40.160 the 32.170 only works up to 10S but it can face higher Amps. (up to 220 peak) and you can set up things like higher or lower timing and softer or harder running. I tried all those switches but they didn't have big effects.
As mentioned, key is the appropriate gear ratio.
The Schulze ESCs have a kind of self protection once they face a situation that they can't cope and they just stop to work - other than the BKs that try to do it until they burn (and I know the smell of burned BKs...).
BTW. 150 Amps. is by far not sufficient and that's the reason why I haven't used eagletree yet. At least at 8S you have to think about 200+ Amps. at the start.

Regarding the 4WD-thing I'll send you a message.

Last but not least I don't want to make you jealous but with the 3080 your monster should at least performe like mine:-)

http://www.youtube.com/watch?v=mZQR_Xubr8o

Regards,
Hermann

Hermann

Thanks for your detailed message. Did you read my bit about putting the motor on the bench and holding the shaft with my finger. I am not talking gears here - just my fingers. With the Schulze when the timing signal is increased to 0.154 (neutral is 0.150) the motor stalls. If I go straight to 0.157 then the motor will not stall. I will try expo which means that the motor will jump straight to say 0.160.

You are right about the BK's - I just love when I can smell them. I feel my wallet just going up in flames. What did you think of the Bolido? You dont think it is powerful enough?

Next week when Lehner opens his shop again I am going to ring him and ask what ideas he has.

My truck runs fine on the current gear ratio using the Plettenberg Bolido and the schulze controller. Why can't it run better on the Lehner 3080 which is a bigger more powerful and heavier motor.

I might be tempted to return the truck to the Lehner with bigger wires and bigger 8mm power connectors.

Mohan

Mohan

Unfortunately I have no technical background but I read your postings and I am wondering if this should be possible. But I am hesitant to try that too because I have sealed my pinions.

The Bolido is a very powerful engine but even the H+M guys that love the Bolido had to admit that the Lehner is able to outran the Bolido - based on the performance of my car.
A way different approach to controlling power in our cars might be a so called "Sinus-Leistungs-Steller".
I haven't tried it yet because it would be an approx 700 Euro-Check but this ESC promises to move a car like a trial-car but also be able to run very good top-speed.
If you check my favourites at youtube you can find two videos of a monster with this type of ESC.

Hermann