Adding capacitors to improve performance

[Ben Kim]

On 3/11/2022 at 2:56 PM, Number1stunner said:

Ok, so has anyone actually tried this on the Sherman?.....

 

I personally have converted my begode Rs (black board version) to 1845wh 18650cells and I included the super capacitor.

 

For me I love the capacitor instant difference the pedal is solid I wouldn't revert the rs back..... 

 

However, I haven't tried this on my Sherman as there is limited space and I just don't know if it would actually make a difference....

 

Who is willing to be the guinea pig?

What spec capacitor is being used for these?  Just curious.  

[Medhi Baclet]

How ufarads do you put in your rs ?

[RagingGrandpa]

3 hours ago, supercurio said:

additional capacitors do not play a role, since you've not been able to overpowered the wheel before and after.

3 hours ago, techyiam said:

You are absolutely wrong.

There is another factor at play you haven't understood yet.

3 hours ago, supercurio said:

What am I missing?

Right, so I think the subtle principle underneath all this discussion is "rate of change of motor current." 
Self-balancing control is constantly changing the motor current, to react to its measurement of pitch angle. 
Even during normal riding, far from the overlean limits, these small changes in current are happening constantly. 

Rate of change of current is a function of input voltage. 
And with less voltage sag (resulting from more input capacitance, different cells, larger packs, or however), input voltage will be higher for the same riding maneuver. And therefore: the rate of change of motor current is increased.

EUC self-balancing control firmware is tuned by engineers to create a response that feels pleasant to a human rider. 
Nearly all riders have felt the difference in self-balancing behavior caused by changing the EUC firmware "pedal mode" setting from hard to soft. These "modes" are simply different combinations of tuning values used for the self-balancing control, and importantly: the effect of the tuning values depends on the electrical system they were tuned with. 
If the system parameters change but the original tuning values are used, we expect the response will feel different to the rider. 

So by changing the electrical system (e.g.: by reducing voltage sag and increasing rate of change of current) without re-tuning it, we expect a change in response. 

We have direct evidence of this effect from EUC riders, such as: 

On 12/14/2021 at 10:10 AM, Chriull said:

Once the capacitor legs in my wheel broke
it drove like in a very strange super soft mode

 

And separately, when adding capacitance, the total motor current limits have not changed, and so the overlean force has not changed, as @supercurio pointed out.
But please be open to the possibility that approaching the overlean limit will feel different. Having the rider sense and react to an overlean pedal dip is very relevant, so this type of modification may still have merit for those daredevil racers who need to ride right against the limit. 

Such benefits must always be weighed against their drawbacks: adding components to the system adds failure modes. 
 

As a personal note: I have overleaned at speed. I've been hurt. Now, I respect the overlean limit enough to avoid it deliberately (by using speed discipline), and am not intending to modify my EUC's in order to change that response.

[Phi1osopher]

On 3/3/2022 at 1:21 PM, Tawpie said:

Me, being a fan of KISS, would use a dumb resistor to deal with braking. When the battery won't absorb the braking energy, dump it into a big power resistor. Even that adds complexity, but not a whole lot. It seems straightforward enough to make me think that it was deemed unnecessary for 'typical' operation—now that we like to operate our wheels beyond their designed limits though, such a decision could/should be revisited. Or not. You don't want to lose traction because the brakes were able to lock up.

I have been thoughtfully re-reading the four or five "technically smart" threads related to capacitors since the GOD-MOD thing popped up as I have tried to make heads or tails of it...
 
However, as an aside, Twapie's comment about skidding while braking caught my eye as I have been just recently been practicing some radical braking moves on my 40t battery Master.
When I am going along at a quick cli p (say 20-30mph), I can try to brake so hard that the wheel momentarily spins backwards, doing a reverse burnout while I continue moving forward. 
I was inspired by hockey ice skaters spraying ice while doing a "hockey stop." When on a group ride on loose terrain (gravel, dirt, grass) I can effectively "spray" my friend in front of of me with this very hard braking "reverse burnout" move while more or less maintaining my speed. 
 

Aside from its novelty, and the *cough cough JOY it must cause my friends, it utterly astonishes me that my wheel has the raw torque to do this at 20-30mph.

 

[InfiniteWheelie]

@Phi1osopher 

Have you ever wiped out as a result of skidding, either by slipping straight backwards, or just having the wheel wash out underneath you?

Or do you find it's predictable and controllable? Could you reliably emergency brake to the point of traction loss, then back off a bit? 

 

Edited February 2, 2023 by InfiniteWheelie

[Phi1osopher]

16 minutes ago, InfiniteWheelie said:

@Phi1osopher 

Have you ever wiped out as a result of skidding? (either by slipping straight backwards, or just having the wheel wash out underneath you)

Or do you find it's predictable and controllable? Could you reliably emergency brake to the point of traction loss, then back off a bit? 

 

I have been actively practicing lateral slides or drifting on the wheel on soft or loose ground (not clean, dry pavement), and sometimes will slide out and crash sideways like this. I believe I ride fairly aggressively and crash somewhat often doing all sorts of things....  Learning to slide laterally was a precursor for me to learning to do the reverse burnout while moving forward.
On an original Sherman I had it cut out twice under heavy braking, but this was more of an intentionally initiated emergency braking -- as in I was with friends and was showing off how fast and hard I could brake. I braked very hard, the wheel beeped, was overpowered, and dumped me backwards on my butt. I have never actually skidded to a stop on dry pavement, nor have I really tried.
With my Master I have never successfully overpowered it on pavement to skid while braking on dry pavement. I can do this on grass or gravel, but it rarely is actually a skid, it usually will be more of a reverse burnout into hard deceleration. When I am doing my "reverse burnout trick" while moving forward with minimal deceleration it feels mostly controlled and predictable. As I do the braking I induce a partial unweighting of the wheel to help it break traction, and I can spray a roostertail of grass or gravel 10 to 20 feet in front of me while traveling 20-30 mph so that the debris strikes the back side of a rider who traveling the same direction and speed who is about 8 to 10 feet in front of me.  I have been practicing this fairly hard as a trick and it feels like a controlled move. 
Did that answer the question?

Edited February 2, 2023 by Phi1osopher

[Cerbera]

1 hour ago, Phi1osopher said:

I have been actively practicing lateral slides or drifting on the wheel on soft or loose ground (not clean, dry pavement), and sometimes will slide out and crash sideways like this. I believe I ride fairly aggressively and crash somewhat often doing all sorts of things....  Learning to slide laterally was a precursor for me to learning to do the reverse burnout while moving forward.

Good grief, have you ?! You got any video of that ?

I'm very much not that sort of rider, but am fascinated by people that are truly pushing the boundaries of what's possible with these things. Have you had any motherboard burn-outs with all this massive torque action ? And how is the Master holding up to all these wipe-outs ? What mods have you done to protect / improve it ? Sorry for all the questions...

Edited February 2, 2023 by Cerbera

[techyiam]

For cars, drifting normally implies the driver intentionally breaks traction of the rear wheels in a controlled way, so the driver can steer with the rear wheels too. 

On an electric wheel, there is no front nor rear wheels; there is just the one wheel. And the rider can steer it all he wants without breaking traction.

On an electric wheel, the act of breaking traction is purely for the sake of losing grip. There is no gain in steering. 

Edited February 2, 2023 by techyiam

[Phi1osopher]

I had a trails race in Austin, Texas in January 2022. It was lightly raining and the trails were that kind of clay that gets very slippery when wet. I had previously never before ridden on anything slippery and I was utterly terrified, but I am pretty good at quickly adapting to these things and gave it everything I had. During the course of the race I learned the beginnings of how to slide sideways on my wheel. I was racing on an original Sherman, as it it was my best wheel at the time.  I didn't want to slide sideways, but there was no other option under those conditions.  
Afterward I realized it was just one more skill that could be learned, and I have been practicing for a year now how to intentionally break traction to do silly things.
Also, I won the race.  Sadly I do not make videos of my riding, though I really probably should.

Anyway, none of that is relevant to the original discussion about capacitors on the mother board, other than it is amazing how our wheel tech has increases such that a trick such as a "reverse burnout" is possible at speeds over 20mph.

For my Master, it is holding up well. It has lots of 3D printed armor and a knobby tire. I design custom suspension setups and have the suspension dialed in very well, like a high-end mountain bike with custom designed linkages and a top-shelf RockShock.  I am currently working on a 100mm long travel suspension for the wheel to help me ride some particularly horrible trails near where I live.  I have also designed a dual-pressure tire system that helps me not damage the rim on big jumps, rocky terrain, and hard drop-ins.... In my opinion the Master with 40t batteries and the LiTech system is an apex-perfect trail wheel when modified with custom suspension, provided that you don't need to go over 35 miles on a charge.  It also serves me well on those big jumps that are taller than me, though I am not as good as some of the local bicyclists, nor the few YouTube superstars who are so impressive with their huge jumps.... but the custom suspension and special tire system help protect the wheel and rim as I flail about.

Again, my apologies for hijacking a thread. Thank you for asking about my setup.

 

Edited February 2, 2023 by Phi1osopher

[InfiniteWheelie]

 

@Phi1osopher I didn't realize you were just talking about off-road. I was thinking in terms of road riding.

We already have cells capable of over 25kw continuous in a 3kwh pack. Once the motors and controllers catch up, we're going to have extremely powerful wheels capable of breaking traction at virtually any speed.

I'm curious to know if breaking traction can ever be controlled on road. One scenario is purposely doing tire spins as an advanced trick (like you talked about). Another more practical purpose could be during emergency braking, where you brake as hard as you can until you feel the slip, then back off a bit for maximum braking. I'm trying to figure out what's possible and what's not.

Another interesting subject is whether any kind of traction control can be implemented. On it's face it seems the answer is no (due to the self balancing nature). That said, perhaps there could be partial methods such as holding a skid (instead of spinning backwards), or perhaps some kind of momentary traction control that lowers power until X degrees of tilt happens, before trying to balance again (giving you a chance to regain traction momentarily).

Anyway this is somewhat off topic, so I'll won't clutter the thread up any further.

Edited February 2, 2023 by InfiniteWheelie

[RagingGrandpa]

Cool! 

1 hour ago, supercurio said:

 @Kevin Graehl, Alien Rides CTO showed his own build of a capacitor add-on, titled KEVMODS KCAP

https://www.facebook.com/groups/ElectricUnicycle/posts/5962121190552461

From the discussion we had a few weeks back and the post itself, it's likely made just to make fun of the ridiculousness of GODMOD and its creator's marketing, but he listed a price for it anyway 😆

And I mean as a pedal stiffness hack on wheels where it does that, at $80 why not.
I love that he lists what's inside and the actual capacitance. You can guess why.

Edited March 6, 2023 by RagingGrandpa

[RagingGrandpa]

Oh, not quite a "real product" yet...  

16 hours ago, GoGeorgeGo said:

AR Isnt really selling the mods.
the post was 80% in jest. they did/are considering it.
but they have mostly been talking more about warranty issues when it comes to the god mod. they will not cover a wheel damaged by a godmod installation as of right now