Twitches at high speed/high power

How-Tos & Esk8 mechanics
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#1

I recently picked up a board that was a diy build from a guy off facebook marketplace. I’ve had it for about a week now and it’s been my main mode of transportation (about 30 miles a day). I’ve been riding esk8s for just over 4 years now and have built a few in my own, but I have never come across this issue before

Firstly the board does great at lower speeds (0-20mph) but once it gets over that 20-22mph zone I feel the board shift really hard to the left. I notice the deck will lean to the right (toe side/regular stance) which throws my brain into speed wobble mode and I get off power. Once I taper off power I notice the board goes right back into where it was before and doesn’t pull to either side. That being said too i’ve been able to get over that 22ish mph border going downhill, with no power, but when breaking there is a noticeable pull to one direction at the higher speeds (this makes slowing down fairly sketchy as you can imagine)

Secondly, i’ve already changed what I think would fix it, Riptide bushings, check check double check belt tension, new bearings in the wheels and a double check of the vesc parameters all show good.

It’s setup on 7 inch trampa wheels and tires, flipsky 15” DKP, 6374 Superbeast 140kv motors with a fox box tenka running 12s. I’ve been trying to chase it down every time I ride but I just can’t seem to fix it.

Wondering if anyone has any ideas as to what it might be? Or even whether it’s a mechanical problem or a vesc problem so I can go farther down the rabbit hole.

Thanks in advance

#2

Differently tensioned belts can create different loads on the two sides of the esc and one side can be delivering its power more effectively to the wheels, causing it to spin faster, causing you to skew to one side. At lower speeds, this might not be as apparent as the forces are less and thus its felt less and also it requires more force to skew you like that, force which the board doesn’t have at lower speeds (unless you full throttle, idk, I haven’t had boards delivering high amounts of current).
Apologies, missed the line where you said that you triplechecked the belt tension.

Alternatively - after checking the drive system, re-do the motor detection and set new limits for the two sides and make sure that they are both equal.

Alternatively - experiment with different amps, even lower than you’d expect. Lets say you start with 40A Battery, 60A Motors, 100A Motors max. Then you try 60A Motors, 70A Motors max, then you try 45A Motors, 100A Motors max, then you try 45A Motors, 50A Motors max. Then you try the same but with 30A Battery. At some point, if it is caused by inconsistent current - you will know where the problem is after trying some of the settings.

Alternatively - just tighten your bushings and make sure all bolts are tightened (for the baseplates for example.

Alternatively - make sure that the tires have equal pressure.

Alternatively - check if the wheels are balanced.
Edit : Try switching the wheels around, I think its a good Idea to do this regardless of issues anyway

Alternatively - try a TKP if that is an option.

Alternatively - swap the motors around and see if it skews you to the other side.

I didn’t mean to write 10 alternatives, it was supposed to be a single one.

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#3

No, Thank you! This is perfect, I feel like I went down all the rabbit holes I know, Just needed another view on it.

I will do some tests on motor amperage and see if that is it.

It is my first board with DKP so I am having a hard time deciphering whether the problem is something from them, or from the vesc. I do have some TKP on the way, just hoping I can get my daily commute a little less stressful for the time being.

#4

Just got to work this morning and let me tell you, now it actually feels like a working board! I didn’t realize how bad the twitch actually was.

Upon further digging I did find that it was probably due to over spinning the motors? I checked gearing and it looks like its top speed should be closer to 23-25mph. With your info I was able to get it in the perfect spot, where I have torque all thru the accel. curve.

1 Like
#5

from rereading your post it sounds like you’re overgeared. a local buddy of mine runs his board overgeared and once you get over a speed threshold, high speed brakes become problematic.

#6

I’ve basically come to the same point as you said, I checked the pulleys and it’s a 16tooth/64tooth so on 165mm wheels it’s not wanting to go faster. I’ve had to turn it down to keep it feeling good and not “overspun”. Because of the low kv on the motors i’m thinking about going with a 20t or 24t Motor pulley and seeing if I can get more speed with the torque still. Hopefully there isn’t too much of an amperage problem. Eventually I will go to 8 inch wheels where this would’ve been less of a problem but an extra set of pulleys never hurt anyone (other than the wallet sometimes)