Bad startup problems - Cogging and no torque

C

couka

10 µW
Joined
May 8, 2016
Messages
6
Hello everyone :)

Some days ago, I took my electric longboard outside for a test the first time and was pretty disappointed.
Starting without pushing is completely impossible, because even without any load there are serious cogging problems. I know that sensorless systems don't run as smoothly at low rpm as sensored, but this is unusable.
I've seen so many builds that use sensorless systems and noone ever mentioned any problems like those I have.

What did I do wrong? Is the ESC shit? (SkyRC Toro TS 150) The motor? It's a no name motor (5060 270kv 80A) to be honest, because hobbyking is always out for stock on pretty much everything I need for months :p

Here's a little video. Note that the Transmitter and receiver are custom made and - unlike usual RC gear - not proportional. It doesn't control speed, but acceleration and brake-rate. Just to avoid confusion.

https://www.youtube.com/watch?v=RCjwVKBo6bQ
[youtube] RCjwVKBo6bQ[/youtube]

lg, couka
 
Try a standard transmitter and receiver and compare.
Sure, a bit of cogging is to be epected from standstill (who ever gets on without at least a very small push? I presume people do but I find it even more unstable)
With that motor and ESC it should be very rideable though.
 
4th picture - timing.
I understand timing is set at 30 degrees. Set it to 0.
 
There is nothing that reacts to clicking/dragging/scrolling or anything else. It seems like the is only auto-timing available :(

lg, couka
 
Nope, I'm afraid, no input. I'll see if I can borrow a standard RC Transmitter and Receiver, but I don't think there's any difference. The PPM-Output from my diy receiver looks clean and stable on the oscilloscope.
I would be very grateful if someone could post a video to show how a working eBoard launches. I don't have any experience with serious RC gear, could be that what I'm seeing is normal, but that would be really disappointing.

lg, couka
 
Nope, that is not normal.
Even with my 6S, 50mm motor and FVT120 contoller I can do a standing start. It cogs for sure but does work. And under no load, as in your video, it should not cog at all, unless you really inch the throttle.
Youtube has hundreds of E-Board videos.
 
OK, then... What is more likely to be the culprit? The motor or the ESC? Since I don't have any spare ESC and motor, it would be good to know what to replace first.
The connections are triple checked of course.

lg, couka
 
Check the bullet connectors. It might not be soldered properly. Try pulling them to see if it comes off easily.
 
Nah, the connections are fine. The problem has been there since I received the parts. For testing purposes, I have used them with different wires and the setup always behaved the same.
I thought the problems would go away, when there is some load on the motor.
Turns out I was wrong :(

The seller of the motor sent me a replacement to test, but since it will be the same motor, I still can't be sure that the ESC is the problem.
I'll take a closer look at the ESC Output with the oscilloscope now...

lg, couka
 
If you are looking to test/compare a different component i would focus on the ESC, not the motor. If you can't adjust your timing on the ESC - again this is likely what would help here.

Try one of the recommended RC ESC's (Car only - i'm sure you know the perils of boat/heli ESC's and no brakes). XERUN/FVT 150 is a good option, also DIYes has a couple good ESC's. Of course my favorite is VESC if you can find one.

If you get a RC ESC - make sure you get the programming card or usb/software to adjust timing and brakes.

Before you do that, have you reached out to SKY RC to see if they can help you adjust timing of this one?
 
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