Lehner 3080 / 8 Brushless Motor ? fault
 

I have been running this motor on a FG monster truck coupled to a schulze 40.160 controller on 10s 6000ma Lipos. However on low rpm the motor stops turning on Load - it stalls. Once the motor stops turning increasing throttle does not help it get moving. It is as if the rotor is locked or stalled. The only way to get the motor moving again is to bring the controller back to neutral and throttle it. If I throttle it hard or load the motor after it has picked up speed it will keep moving past. The motor will accelerate freely to its top rpm but does not like been loaded on low rpm. Once the motor has picked up speed the load does not appear to affect it.

Basically the motor cannot spin from dead on a load but will turn the load once it has picked up speed. In practice it means holding the truck off the ground letting the wheels spin and then dropping the truck. The other way is to push the truck and then accelerate away. Once the truck is moving it will pick up speed quickly and get upto 40mph rapidly.

I coupled this motor with a BK controller 36150 and was running it fine but after 5minutes the controller caught fire when I tried to move from standstill.


Any thoughts? I know the schulze is not faulty as it runs a Plettenber Bolido no problems.

Mohan

I know to run the bolido with the schulze you need high timing. If the lehner is a 2 pole it should have lower timing, but I don't think that would cause what you describe. A smaller pinion is a good place to start

I took the motor out of the car and placed it on the bench. I then connected it to a pulse generator (servo tester). At the neutral it is 0.150 - when I turn it up to say 0.154 the motor starts spinning slowly - you can actually stop the shaft turning by holding between your fingers (at this stage the motor probably has about 100 rpm). when you take the hand off the shaft stays stopped. If I turn the pulse upto say 0.160 the motor spins up faster and the shaft cannot be stopped by hand or stalled.

A large brushless motor should have a lot of torque even at low rpm ?

smaller pinion or more voltage

I dont think lack of torque is the issue here, you seem to be describing the issue that affects high pole count motors in that they have trouble getting moving from a standstill (thinking outrunners mainly but this isnt that far off for all intents and purposes). Higher start power would help, and high timing if those are options on the schulze. If you stall the motor when it isnt turning terribly fast, the esc will 'loose' the rotor posistion and have trouble getting it spinning again, but as you noted once its spinning past a certain velocity you wont be able to stall it terribly easily.

Have a play with a few settings, maybe lower the gearing a tad, but if all else fails there isnt anything wrong with giving the truck a boot to get it moving- is there is adjustable deadband on the radio, maybe try lowering that too.

would changing the winding configuration help? i.e. delta vs. wye?

All the above suggestions are very helpful. This is a Lehner so I think it is 2 Poles?

I intially tried the Delta configuration by attaching 2 leads each to adjacent connectors (yields 984 odd KV). Then I changed it to Y by attaching only 3 leads from the speedo and connecting the remaining 3 connectors as a star (yields 580 odd KV)

Remember the motor is now on the bench. I am holding the shaft with my hand. I think what Neil said is true - it loses position. What puzzles me is that this motor weighs a ton, is as big as a beer can and yet at low rpm I can stall it with my bare fingers. The dead band thing could be a issue. What concerned me is that I switched to my Schulze 40.160 from a BK elektronics 36.150 (rated 150 amps and rated 42V). I switched because the truck was running fine on this controller until it decided to catch fire while I was trying to move from standstill. I wasn't pushing the controller or doing high speed runs. In fact I had less than 2 mins on this controller. This was a very expensive 2 minutes as the controller cost me several hundred Euros. I am wondering if the controller caught fire because the rotor was 'locked' in position and was drawing AMPS +++ .

The Schulze controller is an automatic configuring controller - ie you dont even have the chance of setting the maximum and low position of throttle like standard controller. It simply locks onto neutral. In the BK controller at least you can chose max throttle and full brake positions by taking off the jumper. On the schulze the only options you can change are on a jumper and the only worthwhile options that remain to be changed are timing high /low and gearing high/low. I dont want to touch the 'frequency' DIP switch.

The motor runs freely on the bench. Here is my stupid hypothesis. If say one of the windings in the phases is faulty will it cause the motor to stall at that position or perhaps not feedback to the controller?

I am thinking if say for example once the motor has momentum can say 2 of 3 the phases compensate due to the inertia of the rotor? A bit like a misfiring cylinder in a car engine will cause the engine to turn over but lack power / torque?

I have never managed to stop a shaft of a brushless motor with my fingers and I am really miffed that I can do this with the biggest 10KW brushless motor that I have owned.

I can pair the motor back with another BK controller that I have but I dont really want to toast it in case there is a problem with the motor. Is there a simple way of checking say resistance etc

Mohan

It's the controller that's the problem. Motors are (for the most part) passive devices. Something like this where the motor stops at low speed and wont start sounds like, as others have suggested, a commutation problem, or, start power is too low. I would bank on the latter since you can stop it by hand at low speed. It could be a radio issue, IDK maybe the endpoints the controller was programmed to became corrupted so it's missing a few steps on the low end (in the ESC, not your Tx). I'm assuming the motor has no binding at all at any point, and there are no shorts in it's windings.

thanks for the reply - I will give the motor a try with the other BK controller (36.150). I know the schulze is not faulty as it runs other multi pole motors without any issues. I think the Lehner motor and this Schulze controller have some compatibilty issues. I can only assume that the previous BK controller caught fire and destroyed itself due to bad luck rather than a motor problem.

That ESC was rated for 150 amps and 42 volts. Running it on Enerland 25C 10S packs 6000ma should not have been a limiting factor as clearly the lipos can supply 150amps. However something went wrong and controller caught fire in 2 mins after trying to pull away. I am just worried that my remaining BK controller will catch fire if I cannot isolate the reason for the controllers spontaneous combustion. Luckily I managed to save the lipos, receivers - the aluminium roll cage / frame didn't do that well.

IMO motors either work or they don't, of course there are exceptions, but for the most part I believe this to be true. I know this is a super big super expensive setup, if this was happening to me I would start with the basics as I stated before, a smaller pinion or more voltage. If neither helps at all I would think it's a motor problem.

It could be the Shulze is about to go Mt. St. Helens on you and this is a warning... Lets hope not.

I haven't heard of any 40.160's having problems. It was the 18.97's that torched, and he mentioned it works fine with the bolido........:rules:

You are right - 40.160 works fine with the Bolido. Just dragging my hels on whether to connect the remaining BK controller to this motor to see if it makes a pretty firework. I was going to take my video camera but didnt get a chance to film the debut run - it would have made one heck of a video or maybe not...

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?

ESC fire
 

I had a similar problem with my old setup for my 5" extended Lst2. I wanted to make the Lst2 to go fast on the topend I geared it to high and the same
thing happen but with a lot cheaper components, KB45, Hydra 240 and watercooling setup. I put a +6 pinion on it with a 6S 8k lipo. I think you need to gear it down on your setup. How much does the FG weigh with everything on it? I learned that quick reaction saves other components from going.

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

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.

>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.

>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.

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.

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

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