spinningmagnets said:
Absolutely not possible by throttle...So I ask, why not just put in a flywheel and clutch?
Why not both?
Competition improves the breed. If a certain configuration dominates a competition, so be it. It sounds to me that controllers and electric throttles need development and improvement.
If there was a competition for electric trials motorcycles, what would the givens be? If they all use the same voltage,, what should it be? 52V? 72V? 28S/102V?
How many amps are ideal?
WARNING - another very long read. Sorry, can't help it. This stuff occupies a lot of my thinking time.
Why not both?
- Weight. The bikes used at Trial GP level are amazingly close to stock. This reflects that stock trials bikes are actually highly refined competition machines. Electric trials bikes are currently so overweight compared to ICE that they simply can't compete at the same level. This is just considering weight, not all the other factors that leaves them so far behind. Add bigger motors, bigger controllers & bigger batteries to supply them and it becomes completely out of the ballpark.
- As I suggested, more power can be a disadvantage not an advantage. Traction and control are the name of the game, power can be their enemy. Once there's "enough" then more is worse.
I could probably add a bunch more, but these are really sufficient.
Electric throttles aren't really too much of an issue - yes they could certainly be improved, but when it's understood that a throttle can
only be a coarse control then it's not such a big issue. Durable, consistent, linear - all good.
Controllers certainly need a huge amount of development to really solve the curious needs of trials. Having said that, I'd suggest that if controllers became capable of the needs of trials then I suspect those capabilities would find uses in other applications.
There are e-Trials competitions, both at club and Trial GP level.
[youtube]R30nle0v9wA[/youtube]
Albert was at the pointy end of Trial GP for many years until retiring to e-trial in 2018.
This year for the first time e-Trial GP will ride courses the same as the main support class (Trial 2). Previously their courses were below even that level.
That's not to understate the difficulty of those courses though. The level of skill in any of the world round classes is absolutely mind boggling! The best riders in the USA, Australia and many other countries can barely complete many of the Trial 2 courses, let alone be competitive, and so very, very far from competitive in Trial GP. The best rider in the USA (by a fairly decent margin for a long time) once said he was at around 60% of the skill level of the top Trial GP riders!
At open level events (not closed classes) I believe the "givens" are pretty much restricted to similar standards as ICE bikes - tyres, minimum weight, safety features. I think there might be a maximum voltage but it's more around electrical safety than anything else - trials is pretty open about what you can ride. It's nothing like car "formulas".
How many amps are ideal? That's unanswerable.
See above about control, traction & power. If control was ideal then the amps might only need to be relatively low. If a heavy flywheel is incorporated amps might be low. If no flywheel then amps would need to be
considerably higher.
I suspect it's very hard to comprehend the needs of trials without some significant experience in it.
One of the fundamental skills for trials (beyond the basic entry level riding) is being able to completely separate throttle and clutch, and to be able to use this to provide short, sharp, controlled accelerations.
One exercise is to ride walking pace along flat ground, with 3 markers 2 meters apart.
At first mark increase revs considerably but don't increase speed (slip the clutch).
2nd mark - squat down into the bike. Keep revs and speed steady.
3rd mark - release the clutch and extend up - "Go"
The bike will stand up into a small wheelie (depending on the rpm) but immediately drop back down - quick but controlled.
Easy hey?
Not!
Absolutely invariably people will either give the throttle an extra tweak as they Go which causes the wheelie to be far less controlled and encourages wheelspin, or they will try to pull on the bars or move their body backwards or forwards, etc.
This exercise builds the essential ability to drive the bike off the clutch. Notice that there is no mention of closing the throttle in there, but that's what will happen as you Go, it is far harder to keep the throttle on as you extend than to let the movement naturally roll the throttle off.
This simple exercise underpins all of the advanced moves that the Trial GP riders do, you can see it left right and centre - Rev, Squat, Go.
Sometimes it's really obvious, like when they stand there stationary in front of a big step, then pin the throttle wide open until the engine peaks before a massive explosion up as they drop the clutch - the bike rotates almost instantly, going well past vertical in a fraction of a second, the rider leaps up, often completely off the pegs, and pulls the bars up toward them trying to help lift 65kg up into the air. A fraction of a second later the rear wheel impacts and they control that impact with their legs to help maximise traction. Any excess rpm is managed with the clutch, by pulling it to the slip zone and controlling power with clutch slip.
I think there's a lot of relevance to e-trials design in understanding that basic exercise and how it transfers up the skill level.
It doesn't take a lot of imagination to see in it that the throttle can
only be a coarse control - it's just not possible to keep a rotating handgrip accurately positioned while you're on a bike going from stationary to semi-inverted while trying to dead lift 65 kg into the air while jumping off your feet, then impacting a vertical wall and rotating forward again while trying to control the power at the wheel to the degree that the wheel might do just 1/4 of a revolution - all in well under a second! Mind boggling that some humans can do it at all really.
DanGT86 said:
I'm still hung up on the idea that if a controllers current ramp is too slow then dumping the clutch wont increase the instant power hit without a flywheel at least equal or more massive as its ICE counterpart. Ultimately the controller gets the final say regarding the time it takes the torque to ramp up to full. I don't know how fast this happens in an ICE bike. I would imagine it is within a few revolutions of the crank.
To make the bike well mannered it seems like the controller is going to have to be able to differentiate between clutch dumps and normal throttle application.
This is indeed at the nub of it. But it doesn't stop there.
I completely agree that the controller somehow needs to have a ramp for the throttle control. But I strongly believe that simple current ramping is vastly inadequate. It has to be a current/rpm ramp.
One of the commonly reported problems with e-trials bikes of all makes is that they have a horrible tendency to spin up wildly as soon as they lose traction for a moment. That's where there needs to be an rpm rise rate built in so it's possible to catch the spin and stop it before it goes too far. It's yet another function provided in ICE bikes by low power combined with big flywheel - the rpm always rises relatively slowly.
You could easily create an anti-spin routine, but that would be a severe hindrance in situations where you actually want a significant amount of wheelspin (they exist).
And as you say, when the clutch is dropped, in the absence of a serious flywheel, that motor had better provide
instant amps or it's a complete fail. Again, an ICE bike provides that instant torque by virtue of the flywheel and also the nature of ICE.
An ICE produces power completely differently in one repsect to an electric motor.
In an ICE the throttle supplies a metered amount of fuel/air to the engine that effectively is irrespective of the power demand on that engine. I twist the throttle to 1/4 and it gives the same metered amount of fuel irrespective if I have the bike in neutral or am climbing a hill (more or less).
So if I have the motor spinning freely at half throttle, let's say the wheel is airborne, and the wheel impacts the ground then the engine is instantaneously going to provide all the power that comes with half throttle. The fuel/air mixture is already there, the spark is firing, it's all there waiting for a force to work against. The ramp rate is a maximum of 1 rev. in a 2 stroke.
That's not what happens with any controller/motor combo I'm aware of. The controller would have the motor freewheeling at low current and would have to react as the load gets applied. You'd need seriously fast current response for that situation!
So the controller needs to differentiate between clutch & throttle, but also be able to autonomously instantly switch current in repsonse to wildly varying load.
And those current ramp rates have to be tied to rpm ramp rates too.
And I'd argue that the response to load should be tied to a decaying RPM rate, certainly it has to be the slow rpm ramp at the very least.
I'm sure it's all doable in software, and maybe one day it will. It just seems like there isn't a controller in existence that can address all these needs yet.
speedmd said:
Given the much higher torque of the electric motor at low rpms, they should (spin up the flywheel faster) be able to out perform the ICE setup with equal rotating mass.
Therein lies the problem - you
don't want it to spin up too fast.
It's one of the problems people have with the EM - it's really hard to use the clutch effectively because the motor/flywheel are too digital. They are either at idle or they are zipping up to full rpm at a rate of knots. Even if you only give it modest throttle, at zero load it just spins right on up.
This is where the throttle needs a relatively slow rpm ramp rate, independent of the current ramp rate.
In every other motorised activity it seems like power is the key goal. It just isn't in trials!
As I said peviously people on 125's can seriously compete almost all the way to the top of the sport agains people on 300's. Find me another motorsport where a vehicle with less than half the power, almost the same weight and identical design can seriously compete in the same race!
So I do keep coming back to the thought that a lot of this stuff is done so elegantly by a flyhweel, whereas it's just such a kludge to make it work electronically at present.