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-   -   Brushless motor cogging (http://mini-zracer.com/forums/showthread.php?t=39987)

tudor_47 2014.11.14 05:42 AM

Brushless motor cogging
 
Hi all!


i jumped on the brushless wagon and got a 10A Hobbyking ESC and teh PNracing bl motor 5500Kv V2,


i have cogging issuis, is there a fix for it?
i know that even on the kyoshos VE board there are cogging when using PNracing motors...

spektrum receiver, Hobbyking 10A ESC(XC-10A),PN 5500kv, 2cell Lipo, 10/52 gearing, chassi P28GT
Ideas?

You guys running the kyoshos VE board and motor do you experience cogging?

abasualdo 2014.11.14 07:55 AM

I run the PN 5500 gen 1 with the VE board, runs perfect.
Think it my be the ESC?

I have tried the AMZ esc(think it's also a hobbywing) with PN 7500 gen1, also perfect.

Can you raise the starting power on that ESC? That may help.

Is the motor direct soldered to the esc or are you using connectors, if so, are the connectors making good contact?

cowboysir 2014.11.14 10:12 AM

I'll be curious to hear the answers....I have just returned to VE's and have purchased a PN v2 5500kv.

Stupid question but how powerful are your cell packs? The limiting factor in my cogging situations is discharge....

TheSteve 2014.11.14 11:37 AM

It is very tough to have a smooth start in an RC car with a sensorless brushless motor. Kyosho has actually done quite amazing with the VE software. I doubt the hobbyking ESC has anywhere near the software refinement.
As Cowboy mentioned though if there is a problem it is likely a lack of power from the batteries.

Rune 2014.11.14 11:58 AM

No cogging on the VE board with PN 9500 motor if you have good batteries. It is sensitive to voltage drop.

tudor_47 2014.11.14 02:20 PM

Thanks for all input guys!

I run Lipo so i think there is plenty of power....
I'll check connections again, they are direct soldered to the motor.

My cell is a 2 cell lipo 7,4v 300mAh with 35C discharge 70C maxdischarge,(Turnigy nano-tech)

According to the setup card (ESC) there is no limit on startup power, I can try to change that around and see if any of the settings works better.

Can there be a difference in wich cable that go on M1 at the motor?
They are on in the correct order now as the motor goes in the correct direstion but what whould happen if the cables from the ESC are in the correct order but start at the wrong place, every cable beeing in the "wrong" place. Whould this alter the 'timing' in the motor?

abasualdo 2014.11.14 02:46 PM

Cable position does not matter, motor will just spin in the opposite direction.

In other words, if motor spins in the wrong direction, swap any of the "two" motor wires to reverse direction.

This can also be done via software on some escs, not the VE board.

gctkaz 2014.11.14 09:11 PM

I have attempted to use that Hobbyking 10A ESC with an Atomic AMZ.

It is definitely the ESC, it just cogs really badly. The setting to adjust is the Start Power Percent. It reduces the cogging when starting from a standstill, but then it's also pretty much impossible to have any smooth acceleration as the car will just take off.

It works nicely with other small motors, but just somehow refuses to play nice with these Mini-Z brushless motors.

Jshwaa 2014.12.30 08:49 AM

Tudor,

A good test for your cells is to put a voltmeter across them while you throttle. If you have a good meter, set up the MIN/MAX feature, because it will stop at a minimum or maximum value voltage. Throttle while voltmeter is applied, and the voltage should drop. If you are truly getting 30C discharge (21 amps for a 300mAh cell pack), then the voltage shouldn't be phased by simply throttling while unloaded(wheels off ground). If you are getting some erratic voltage dips, then this could be pointing towards bad cells.

LED 2014.12.30 10:24 AM

Can you change the timing in the Esc? That often helps with bigger scale brushless motors. If I remember correctly reducing the timing will help with the bogging but may reduce torque a little.

yasuji 2014.12.30 11:49 PM

I have been running the hw set up quite a bit.. 9500kv With pn batterys no cogging @ all... The ddrs start mode makes a big difference I have tested all positions and I have it set on 6 with the max timing... I think it's 8...also I run my neutral on the minimum
One thing that is very important is to set the throttle neutral and max points also the active turbo takes a little getting used to I use a throttle cushion so I can squeeze in to the turbo on the straights

Recently I have been running lithium aaa cells with great results... For that I lower the ddrs to the default... I think 5.. Every thing else the same... But I lowered to the 7500kv motor :)
BTW... The capacitor is very important!

herman 2015.01.01 02:07 AM

Hmm... Lithium aaa cells? Do they need a special charger? Can they be used with the stock 03 board? Sorry to be off topic...

rojak 2015.05.18 09:00 PM

Is it VE board can support 12000kV brushless motor?
Recently I upgrade my motor from 5600KV to 12000 KV,after a while run the car, then suddenly it become cogging when I full throttle. Thinking maybe the battery is weak already, i swap with fresh one,but still same.
I take out the motor and try full throttle with my tx, i fell the motor is cogging at full throttle and it becoming very hot.
Any idea?Is it I need to add more FET at my VE board?since by stock VE board got double side FET.

Jshwaa 2015.05.19 08:16 AM

Quote:

Originally Posted by rojak (Post 457419)
Is it VE board can support 12000kV brushless motor?
Recently I upgrade my motor from 5600KV to 12000 KV,after a while run the car, then suddenly it become cogging when I full throttle. Thinking maybe the battery is weak already, i swap with fresh one,but still same.
I take out the motor and try full throttle with my tx, i fell the motor is cogging at full throttle and it becoming very hot.
Any idea?Is it I need to add more FET at my VE board?since by stock VE board got double side FET.

You could try that. You essentially doubled the power consumption of your motor without enhancing the drive, so it stands to reason your motor is drawing so much more current that the FET's are probably dissipating.

I know the standard brushed version of the board has some overhead for FET stacking, but I'm not sure about the brushless versions. Give it a try and come back and report your findings.

JesseT 2015.05.20 01:37 AM

The hotter motors for the VE require very good batteries, with a low internal resistance to work without cogging. This not only means that the batteries need to be of good quality, but also very recently charged and warm.


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