Observed trials bike designing

[speedmd]

Good point on the slower turning clutch basket. My first choice would be more mass/ larger diameter in the rotor. Higher kv would spin faster for certain at the expense of lower torque and efficiency at lower rpm ranges. Possibly a good trade off.

The fall off in power when approaching the rpm limits in typical surface PM motor designs is nothing new. Internal vs surface mounted magnets will for example have much more rpm range extension with the use of field weakening. Trials would be perfect for this as these extended rpm ranges are only used momentarily so the wasted energy is less likely to build up and cause issues as it would in a road race setup. Internal magnets will typically have slightly less torque but extend the power bands significantly as well as have better heat transfer -cooling of the magnets. If your looking for much higher RPM extension, adding more reluctance characteristics to the rotor may be a solution to this. Many auto designs are now going this route to get some impressive top ends.

 

[DingusMcGee]

bikerpete,

The nice option on a good impulse controller is that you can easily program it to do just as YOU say [a littoral] , “the power needs to fade as it is delivered and if traction is lost the system must not accelerate further. A flywheel does this totally automatically”

Sensing acceleration by circuitry is quite easy with an inertial load cell. And slips of the wheel (lost traction) are easily detected by mechanisms on any modern car with skid control. The likes of which could be added to edirtbikes control.

“Totally automatically”. I say,”Bull Shit”: a rotating flywheel does not automatically quit spinning the wheel when traction is lost. It takes an agent to pull a clutch or brake.

Do you have an understanding of what is doable with sensors and actuators hooked to a very programmable controller? You program the controller to output a decreasing torque (amps) wave form.

If not, proceed thinking a flywheel is the only solution for etrials bikes.

Besides, if you have likely added too much torque, seize the rear brake handle (left side) to keep from losing traction. Doing that will decrease the torque input to the rear tire.

 

[bikerpete]

bikerpete,

The nice option on a good impulse controller is that you can easily program it to do just as YOU say [a littoral] , “the power needs to fade as it is delivered and if traction is lost the system must not accelerate further. A flywheel does this totally automatically”

Sensing acceleration by circuitry is quite easy with an inertial load cell. And slips of the wheel (lost traction) are easily detected by mechanisms on any modern car with skid control. The likes of which could be added to edirtbikes control.

“Totally automatically”. I say,”Bull shit”: a rotating flywheel does not automatically quit spinning the wheel when traction is lost. It takes an agent to pull a clutch or brake.

Do you have an understanding of what is doable with sensors and actuators hooked to a very programmable controller?

If not, proceed thinking a flywheel is the only solution for etrials bikes.

Perhaps I should have prefaced with "Without requiring hundreds or thousands of hours of software and hardware development". Your idea of "easily program" is obviously very far removed from mine. I've done some VBA, that's about the extent of my programming ability.

No question that it's possible to build a controller interfaced with load cells, accelerometers, etc. and that does all the calculations to give a useful result. I fully expect that trials bikes will increasingly head in this direction.
But is that realistically available to the typical ES participant right now? I expect not.
While this thread certainly dives off into the realms of possibility rather than practicality, I'm only interested in that which is ultimately possible for me to use and trial.

As for the "totally automatically" thing, I maintain I'm correct there. I said two things:
1. power needs to fade as it is delivered.

As a flywheel delivers energy it slows, reducing the energy available to deliver further power. Automatic, no intervention or control strategy required. In a bonus for trials this also means the acceleration starts very high but only progresses to a relatively low top speed. Speed is most often your enemy in trials.​

As an aside this is one of the reasons single speed e-trials bikes capable of 50-60kmh are such a bad idea - even with a reducing acceleration it's way too easy to end up with the back wheel traveling forward much too fast. A low gear completely avoids this without having to limit the energy put into the system.​

2. if traction is lost the system must not accelerate further.

If traction is completely lost (wheel airborne) the flywheel will not accelerate, never-ever, unless the engine supplies it with more power. The real-world result is that when the wheel regains contact it will be rotating at the same or lower ground speed as it left the ground. Therefore when the treads hit ground they will grip, not spin madly until something causes the wheel to slow down and gain traction, or not.​

​

Do I have an understanding of what is doable with sensors and actuators hooked to a very programmable controller?
I believe so. I was an industrial designer for many years and developed various electronically controlled systems, but others did the electronics and software. So I've a sound understanding, but few hard skills in that area.

Can you point me to the very programmable controller you have in mind?
That's a serious question, not rhetorical or tongue in cheek.
I've been asking for suggestions of just such a thing in another thread and thus far the best option seems to be VESC which I'm considering, but not entirely convinced it's worth investing that much time on. I'm also looking at a CAN capable micro to interface to the Nucular, it would receive throttle input and motor RPM, do the maths to somewhat simulate the response of a flywheel when throttle is cut. That fills me with dread - many, many frustrating hours ahead as I learn to program such a thing.

So bang-for-buck a lump of steel on the end of a motor is light years ahead of the currently unproven Unobtainium controller.
It'd be nice to start to move that along a little, but in the end what works best is best.

 

[bikerpete]

Sensing acceleration by circuitry is quite easy with an inertial load cell. And slips of the wheel (lost traction) are easily detected by mechanisms on any modern car with skid control.

I missed this bit in my reply above.
Consider that trials riders frequently ride on one wheel only.
We also sometimes deliberately spin the wheel to gain traction ie digging down through mud.
Often we deliberately give the wheel a brief impulse without wanting to move at all - for instance to create a nose wheelie while stationary in order to step the rear sideways, front brake fully locked, compress suspension then clutch impulse to "flick" power into the back wheel to force the suspension to react and to drive the bike over the forks more - the wheel spins for perhaps 45 degrees rotation. Or to hop both wheels simultaneously while stationary.

My understanding of skid control on cars is that it compares wheel speeds - very hard to do when riding largely on one wheel! Typical road motorcycle traction control relies on monitoring for sudden changes in wheelspeed. And trials relies on very sudden changes in wheel speed at advanced levels.
But it also demands extremely subtle control to absolutely prevent slip when traction is low.
So there's a lot of complexity in trying to come up with a traction control routine that can sense traction from response of a single wheel on the ground, in wildly differing frame attitudes, that permits wheelspin in some cases but not others.
Or the rider can just become better and use skill instead.

This brings me back to a fundamental question - where is the sweet spot in the cost/performance/weight/time investment balance?
More copper & iron to get sufficient max torque & power + expensive electronics with a lot of time sunk into them to make it work, or smaller motor with simpler electronics with a cheap hunk of steel on the end of the shaft?

Currently I'm largely in favour of simple electronics with a hunk of steel. But I'd like to have a go at shifting just a little toward the electronic solution.

 

[DingusMcGee]

bikerpete,

Industrial Engineer or whatever you seem to have missed some very fundamental concepts in the physics of time and motion — sort of the simple calculus of an elementary differential equation.

Employing a tri-axial accelerometer on the bike frame, a rotation measuring accelerometer on the rear wheel and that data feed to numerical integrators, wheel spin/slip can be detected far more precisely than the detection you can achieve. The detection does not matter if only the rear wheel is on the ground.

Basically whatever physical variables you assert are changing, the instrumentation exists to measure it quantitatively and in real time. And that instrumentation can produce far more accurate measurements than you can do by employing your descriptive methodology.

As for specific controller advice, the two controller approach I suggest as a start on this allows for supper-positioning of power inputs. So no immediate advice on which controller for you as we believe in somewhat different approaches.

To put is simply, all that may be needed for this trial ebike is a numerical clutch emulator. You would actuate it with a clutch lever and its output feed to the controller would make the rear wheel behave accordingly i.e. as a clutch modulated flywheel coupled to the rear wheel sometimes.

 

[speedmd]

To put is simply, all that may be needed for this trial ebike is a numerical clutch emulator. You would actuate it with a clutch lever and its output feed to the controller would make the rear wheel behave accordingly i.e. as a clutch modulated flywheel coupled to the rear wheel sometimes.

This would be great for many segments not requiring max power-torque possibly. It would however be limited to max motor torque you could get from it at fully saturated current. Adding some flywheel mass and allowing it to spin up would open a whole level up in capability when - if needed. Nothing worse IMO than coming up short on jumps. Joining both concepts may have some legs.

 

[speedmd]

lockup

 

[bikerpete]

Employing a tri-axial accelerometer on the bike frame, a rotation measuring accelerometer on the rear wheel and that data feed to numerical integrators, wheel spin/slip can be detected far more precisely than the detection you can achieve. The detection does not matter if only the rear wheel is on the ground.

Basically whatever physical variables you assert are changing, the instrumentation exists to measure it quantitatively and in real time. And that instrumentation can produce far more accurate measurements than you can do by employing your descriptive methodology.

As for specific controller advice, the two controller approach I suggest as a start on this allows for supper-positioning of power inputs. So no immediate advice on which controller for you as we believe in somewhat different approaches.

To put is simply, all that may be needed for this trial ebike is a numerical clutch emulator. You would actuate it with a clutch lever and its output feed to the controller would make the rear wheel behave accordingly i.e. as a clutch modulated flywheel coupled to the rear wheel sometimes.

I happily stand more informed about traction control. It would be very interesting to see how that style traction control panned out in real-world riding where there are requirements for amounts of slip. I expect sometimes you'd just turn it off, other times you'd want it to be fairly relaxed in it's response and others moderately strict. A few modes available on the handle bars might be sufficient.
My guess is that lower end riders would think it was miraculous and high end riders would curse it and turn it off 90%-100% of the time.

Personally I like trials because it is staggeringly difficult to do well due to the precision, timing and control required. I'm not sure I'd get anywhere near as much satisfaction if I knew the machine was actively compensating for my inadequacies.
And yes, I know it's somewhat contradictory to be riding a fancy modern bike with incredibly good suspension, refined motor and current soft tyres when from what I've said I should get just as much satisfaction from from a 1970's twinshock. But I feel there's a difference between a machine that is well tuned and responsive but does nothing to correct your mistakes and one that actively intervenes to compensate. But that's just me.
Either way, traction control is an interesting digression but purely navel gazing - I don't have anything like the skills, resources, time or interest to investigate it.

I'm struggling to get my head around the two controller idea. It sounds like you're talking about the 'clutch' being more or less a switch.
Fine control is the heart of trials clutch use. So always dumping power isn't an option. We need to be able to dump it instantly sometimes, feed it out other times and use clutch to control the almost steady state drive other times.
It's not just about speed & power, it's also about the fact that trying to accurately control a twist grip throttle while jumping the bike about the place, rotating it beneath you from horizontal to past vertical and back again, turning the bars lock to lock, hopping front and rear wheels and tying to physically jump a meter or so up a rock face just isn't possible!
The twist grip is best considered coarse "available power", the clutch is accurate "applied power". eg I can rev the bike way up but then just creep along on slipping clutch, if I then need a quick zap of power it's just a flick of the index finger away.
Manipulating a clutch lever with one finger while your hand is securely anchored to a grip by the other 3 fingers is vastly more controllable through all the gyrations of a trials bike.

So the clutch has to be able to go from zero power to maintaining position balanced on the back wheel half way up a slope to slamming full power into a big leap. For the really advanced riders they can land that jump to a slipping clutch that maintains balance on the rear again.
That means you need to control the second controller just like the primary controller, but quicker response. So I don't see why you'd bother with a complete second controller. Plus a second controller is just dead weight and bulk - a Fardiver 9 series is 3kg and quite big - deadweight and I've no idea how to fit two controllers into a trials frame and still have room for battery and reduction drive.

It would be better to have the facility to have two inputs, clutch & throttle, with differing response profiles. Maybe an extension of the idea of a processor between throttle and the controller, but with inputs from clutch and throttle. The controller is set for zero response damping and the intermediate processor handles that - fast for the clutch and slow for the throttle.
Of course a controller with all that built in would be best, but I'd almost guarantee that's not available off the shelf!

 

[bikerpete]

To put is simply, all that may be needed for this trial ebike is a numerical clutch emulator. You would actuate it with a clutch lever and its output feed to the controller would make the rear wheel behave accordingly i.e. as a clutch modulated flywheel coupled to the rear wheel sometimes.

That's easy to say, but exactly what do the algorithms for a numerical clutch look like? Therein lies the million dollar question.
EM and others have gone down the electric clutch route and abandoned it in the performance end of the spectrum. It's OK for basic riding, but there are so many limitations when it gets to the high end.
Possibly, maybe probably, it will eventually come into common practice, but I'll bet there will have been many, many tens of thousands of dollars spent developing it before it gets even close to a clutch and flywheel.
I think @speedmd is on the money, it might be a useful adjunct to a 'real' clutch and flywheel. That's how I'm looking at it.

Another one to add to the mix - the rider needs to be able to judge how much power is going to be released when the clutch is released. Currently we largely do that by sound. It's really quite accurate and effective. It takes people a little while to learn how the sound of an electric motor relates to the power output when the clutch is released. I think you'd need to add a little audio generator coupled to throttle position. No big deal, but the total is the sum of all the little parts.

I've said it before and I'll say it again, I really don't get why so many people involved in electronics are so keen to replace everything mechanical with an electronic alternative. I love what can be done with electronics, but sometimes mechanics are just as elegant a solution.
I put that mindset down to a large part of why none of the current e-trials bikes are really pushing the ICE bikes. The designers are so focused on and overconfident about the electronics side of things they keep dismissing the mechanical solutions. EM are furthest down the development path and it's no surprise to me that they're also using a drive system closest to ICE bikes.
In 70 years of development people have learnt a thing or two about what makes a good trials bike. Throwing that knowledge out wholesale isn't very smart.
So yes, I'm currently fairly committed to a flywheel and clutch, they work sensationally well - just watch Toni Bou doing his stuff then point out where the shortcomings of the current system are! But interested in nudging the dial a little toward the electronic solution.

EDIT: I was mulling some of this over while I was out riding today and it occurred to me that one of the reasons ramping an electric motor up doesn't seem to work compared to using a clutch & flywheel is that torque isn't power.
With a clutch & flywheel everything can be sitting there with power, not just torque, fully available instantly. With an electric motor kicking off from low or no RPM, despite it having lots of torque it doesn't produce peak power until well into the rev range. The graph below is just a random, but it's good enough for the concept.

This feels right to me based on my experience with my e-trials. When you bang the throttle open when the front wheel is pushing into an obstacle (pretty common trials move) not much happens really until the back wheel gets moving a bit, then it starts to really kick. But that's way too late to be of any use at all. It feels really 'soft' in those first moments, which is the exact opposite of what you need.
On ICE bikes skillful riders wind up the motor with clutch in, then they release the clutch and wind off the throttle just a moment later. Throttle is probably pretty much closed by the time the back wheel loses traction (due to lift). So for that short moment when the wheel is really driving they get not just the energy out of the flywheel, but the engine is on song and right around it's max power point with WOT. I'm pulling figures out of my hat, but you might be looking at 20kW+ (motor & flywheel combined) for that short time.
So to get the same reaction out of a fully electronic 'clutch' you'd maybe need a motor that develops 20kW down near say 50-100 RPM. That's going to be a big sucker of a motor! These are random figures, but maybe they illustrate the problem.

I also reminded myself once again that although I often use the big powerful clutch dump as an example here, much of the time trials riding we are making tiny low RPM impulses with the clutch, virtually at idle. A tiny pop to lift the front a few inches, or to grab that spot of traction on a small stone poking out of the ground. It would be interesting to measure those impulses, but based on many hours of analysing trials video frame-by-frame I'd say they are often little more than 0.1s duration. You have the clutch just at the slipping point then flick your finger out and in again, the movement might be a matter of 3mm (1/8"). But that's enough to get a solid response. And the disengage is just as important as the engage.
Another one I thought about out there was when you gap across to an obstacle and stop dead on it. Relatively easy with a clutch where nearly all the rotating mass is completely disconnected from the wheel, but even a moderately light rotor has quite significant inertia which will make the instant stop that bit harder. Really good riders will land a jump onto a square edge and just stop there, balanced on the back wheel right on the corner where they get positive traction from the tyre wrapping around the edge, and a kick up when they go for the next move. And that balance is being held by landing with a slipping clutch so they have instant response from their finger to keep the front up where they want it. They land with the brake locked, but immediately release it so they can balance on clutch, all the while keeping the back wheel basically stationary on the edge. Absolutely nuts skill level!

 

[DingusMcGee]

bikerpete,

Please apply the relevant? You got the wrong graph…..

You have submitted a PWM graph showing power, torque and efficiency plotted by (a fixed current max) current vs RPM. And then you ponder?

What you need to see to better understand PW motor torque production relevant to this discussion is a plot of how fast a motor can reach a given torque for some controller fixed WOT response with a set of batteries that have a very high discharge rate. In other words you need to know how fast the motor-controller-battery system can produce a given torque. If you need more torque faster, slam it with more amps which may require higher discharge-rate batteries. PW motors in the right system can generate a super high torque in very short time interval. This time constant for torque generation increases is of less time than you make worldly responses like the time it takes you to modulate a clutch lever.

The clutch transfers momentum by torque from the flywheel to the rear wheel which is conserved. Energy is not conserved across a slipping clutch plate and we have to account for energy losses if we want to make predictions of what it can do. Whatever momentum the MC flywheel needs to loose by clutch modulation, a fitted PWM system can easily match momentum changes for the smallest time constants you operate at.

Now that maybe you understand torque rise times for PWM systems, you likely can understand that if some value is too high (and we loose traction) we can decrease it on a PWM system?

And for your edification please do find graphs of how fast a PWM system can produce power. They totally beat any IC engine of comparable max power. The high discharge batteries “supercharge” them.

 

[speedmd]

I think having been playing with maxing out motor -controller -battery systems for a bit that we understand the super fast power - torque response on the electrical side. You still will be limited to saturation levels and limits of what your motor - drive can produce. Adding momentum of an attached flywheel clutch system, can be multiples more energy at hand and most certainly easier to control than throttle alone. Anyone trying to get over 3 foot sized blocks or logs knows well of the many whiskey throttle induced crashes one deals with learning the trade. Not sold its a either-or approach being best but rather combining the controls some way.

As a energy store indicator, thinking, a simple color grid led indicator with rpms across the x axis and torque -current in the Y. It would mate well with the quiet nature of the EV being a visual analog.

 

[DingusMcGee]

Speedmd,

The method I have stated is about super positioning of 2 controller outputs with 2 different actuators for changing the controlling motor input. You are not controlling all the energy with a single throttle in my system whereas all the power setups you state you have experienced while handling max power had a single (throttle) or actuator ? Think outside the box. This method is different than your setup/experience as it has more than one actuator.

My initial method is by “combining the controls in some way” as you suggest may be the solution.

Your posted color graph without a time axis cannot show rise rates of a given motor/controller/battery system outputs — useless.

All systems are finite systems and that means all such systems will reach saturation. That also means that any surge rate is finite — no Dirac Delta functions happen in the real world — finite gradients. You cannot power very well a MC with hair clipper motor regardless of the size of the controller and batts.

 

[speedmd]

No doubt it can be done. Not seeing how to combine the super positioning of two controllers just yet. Nor seeing the user interface halting the momentum of the system for the hop and stops. Would love to play with what your suggesting. Flywheel mass has both pro's and con's.

Agree, a more capable motor and drive system would certainly handle what ever you throw at it easier. Old saying some have voiced is that Nothing improves performance more than copper, flux and amps. As for indicating rise rates, simple flashing rates have been used in other devices and do a good job of showing them.

 

[bikerpete]

I like that you keep challenging my pre-conceptions. It's fun being challenged and I enjoy exploring new concepts.
But I think we are coming at this with very different goals and so thought processes though.

I want something I can get on and ride this lifetime - ie in the next decade. I'd like to nudge things a tiny bit toward increased electronic control of what's currently done mechanically - if that's of real world value. Mostly just for the sake of it.
You are exploring what is possible given access to the right hardware, and software engineers who know what they're doing. I'm not sure I've got access to the first & I in no way resemble the second!

The theory of what you can do with an electric motor and capable controller is all great, and I'm willingly accepting you know what you're talking about, which you'd have to agree is verging on gullibility in a public online forum.
But your early comment about dumping yourself on your arse with a burst of power makes me wonder a couple of things.

Do you understand why you went off the back?
You didn't go off the back because there was too much torque/power applied. That's absolutely certain without me knowing anything about the bike involved. It could be the world's fastest electric drag bike for all I care - the fact remains the same.

The other is what understanding/knowledge/experience do you have on a trials bike?
It's not at all a pre-requisite for valuable input into the problem, the more skills and knowledge brought to bear from a wide area the better. But it does point out where there is actual knowledge about the problem and where it is simply ideas being floated that need assessment by an expert (I'm not an expert trials rider, let's be very clear).
This is where the line I quote below suggests you may not be grasping the problem from a complete understanding of the desired outcome. Power is not the issue here, trials bikes are gutless quite intentionally. And that's disregarding the fact that the power of a trials bike engine is really only a part of the total in the clutch-dump power.
It's the control the rider can exert over the power and the nature of the delivery that's critical. There's a fine line between automation helping and hindering.

They totally beat any IC engine of comparable max power.

You cannot power very well a MC with hair clipper motor regardless of the size of the controller and batts.

To an extent I'd argue the toss with you on that one, a hair clipper motor that spins to a zillion rpm and a decent flywheel could be surprisingly capable for certain trials conditions. If you've ever looked at what a skilled rider can send a 125cc trials bike over you'll see a case in point. Those things are seriously gutless, a Honda CT125 posty bike isn't too far out of the ballpark. But they sit there WOT until the thing's at absolutely max rpm then drive off the flywheel, sending the bike and rider up massive obstacles. They hit their limits if there's a sustained hill though.
But yes, you're mostly correct, and that leads me to this:

The idea of using the motor to supply all the power seems to me to lead into a mass:benefit problem.
If I choose a motor that at saturation provides me with sufficient power for all my sustained power needs then it's not going to have anything available for the big bursts. So now I add more copper & iron and a bigger controller (or indeed a second one) to get the bursts.
That bigger motor probably also needs a bigger battery to supply the additional current while retaining the target duration capacity.
And all that has to fit into a fairly seriously volume constrained trials bike.

How many kg does that add up to vs how many kg does a flyweel weigh that provides for the burst power?
My guess is that it's at best even, and maybe the flywheel might win.

And we haven't even started looking at the actual rider/machine control interface and how it all interacts.
If you don't ride trials (do you?) you may not realise how finely tuned clutches are on trials bikes. They vary individual plate thicknesses by fractions of a mm, use a variety of low viscosity oils to get the feel they want, adjust the diaphragm springs (coil sprung clutches are dinosaurs for trials) in tiny increments ... This all to get the exact feel the rider needs to perform at their best. It mostly makes no difference to the measured characteristics of the clutch - it releases cleanly when asked and locks up when asked. It's the bit in the middle that they are working with.
Pro riders will sometimes travel from country to country with their favourite clutch pack and rear shock in their bag, throw them on a stock bike and race. They wouldn't dream of racing on the stock shock & clutch, but the rest of the bike - whatever, maybe change grips and pegs to their preferred ones.

So the electronic version had better have some pretty good advantages. It might well have, but assuming it does certainly doesn't cut it.

Your posted color graph without a time axis cannot show rise rates of a given motor/controller/battery system outputs — useless.

What? The time axis is time, as it passes us by, right now.
My interpretation of the proposal is that as you manipulate the controls in preparation for a launch at an obstacle the colours and amplitudes reflect the state of the control. The time scale is that you can watch them change, in real time, right in front of your eyes. So stating "useless" isn't true or helpful.

Having said that, my eyes are fully occupied when riding a section - no way I'll be looking down at the bars just before throwing myself at a scary obstacle!
We've got four senses, let's use more than two of them. Ears are good jiggers, I find them generally quite useful.

 

[bikerpete]

More riding, more contemplating.

I thought compiling a Requirements list might be helpful - keep things clear in my head and maybe make it easier for others to target suggestions to specific requirements.
So here goes. This is just as it comes to mind, no particular order, it could probably be prioritised to a certain extent.

What	Why	Notes
Smooth, progressive throttle response.	For low speed accurate control. To avoid nasty surprises when winding on increasing power.	May be linear, may be non-linear. Probably user preference.
Absolutely no hesitation from zero speed.	We are frequently stationary before committing to maneuvers. Any hesitation can throw timing way out.	So far the best solution is clearly a motor that idles and a clutch.
Ability to set coarse 'available power' with throttle, but accurately control delivery with 'clutch' finger.	Twist grips are unstable, slow to move and impossible to control accurately enough during the gyrations of trials. 'Clutch' levers are stable, accurate & responsive without interfering in the riders ability to move around too much.
Power delivery by 'clutch' finger should be separated from the "available power' by throttle.	We frequently need to adjust available power in anticipation of changes in terrain or due to inaccuracies in the original delivery.	With a mechanical clutch in the slip zone the delivered power is almost independent of the rpm. eg You can maintain a very slow creep forwards on clutch while simultaneously increasing RPM ready for the next move without having to compensate on the clutch as RPM rises. This behaviour is load dependent not lever position dependent - ie if you increase load the clutch lever will need to move out further, but the slipping behaviour remains the same at the new load. The clutch remains a power delivery device with little correlation to available power (as long as available is above that currently required). An important aspect of this is that the clutch delivers power within the range provided by the throttle. In effect the available clutch power is scaled by the throttle, but the delivered power is unaffected by changes in scaling for a constant lever position.
Both RPM and torque/power need to be adjustable prior to launching maneuvers.	Sometimes we want to accelerate quickly to a very low speed, other times to a high speed. Both available speed and power need to be adjustable.	In ICE bikes this is achieved by increasing RPM and so energy in the flywheel. As RPM increases you know that when the clutch fully engages you are going to be travelling faster. To an extent these two are intimately connected, but particularly with lower speed & power moves it's possible to moderate this by maintaining, increasing or closing throttle as the 'clutch' is released. If wanting to accelerate to a high speed but very short power usage the clutch is used to cut off the excess power from the high rpm flywheel.
'clutch' power delivery must be progressive and accurately controllable at all power levels.	We commonly need to feed power in or gradually cut power using clutch as we progress through a maneuver.	eg on ICE you wind up the motor, then feed out the clutch as you roll off the throttle. This reduces the chance of wheelspin, ensures that for longer duration moves there is ample power throughout but all accurate power delivery is via the clutch finger not the throttle.
Power can be delivered with a falling RPM profile, irrespective of load on the drive.	If a wheel accelerates when it bounces into the air in low traction situations it's pretty much game over - it wont regain traction when it contacts the ground again. Sliding friction is lower than static friction.	ICE bikes - rev the bike, close the throttle and release clutch. Wheel will now only ever slow down. Typically the clutch release (fast or slow) is done with a heavily loaded tyre on points of higher traction. The bike then 'coasts' on flywheel.
Delivered power and RPM fall as a factor of load.	For trials riders think splat-to-stop. For others, we often want to pop forwards, but land on an obstacle with very little forward speed and with the tyre hooked up on the obstacle.	ICE bikes - once again, rev the bike to put energy in the flywheel. Pop the clutch with closed/closing throttle and the bike will accelerate & rotate fast, but it's forward speed will end up very low because by the time the energy in the flywheel is used the rpm is now quite low, so wheel speed is low. It's up to the rider to judge how much excess energy they want in the system when they land. Sometimes it's lots, sometimes none, sometimes it's land with none but be already setting up the available energy for the next pop eg winding on throttle/rpm with clutch slipping.
Rider feedback for available power should be non-visual. Probably audio.	If you are setting the available power before applying it with 'clutch', you need to know where you've set it.	Audio works really well on ICE bikes. I don't see any reason to change.
Asymetric motor "inertia"	Allows for quick response in preparation for a move, but then the drive acts as if it's got lot's of momentum.	In flywheel terms - quick to spin up, but slow to spin down. A light flywheel effect when spinning it up, but heavy when it delivers energy. This needs to be isolated from the normal throttle response when riding on throttle. eg. when the clutch (lever) is in, motor response is very quick, but when the clutch is out it's considerably slower. No clue how this would feel to the rider - maybe terrible? EDIT: It's been pointed out to me that the Stark Varg has this implemented in it's user settings "Virtual flywheel." Accelerate and Decelerate. Patent Pending apparently, but I can't find the patent to investigate.
Motor locks when stalled	Prevents dangerous rollbacks on big steep slopes.	If things go bad on a big steep slope the best course of action on an ICE bike is to just stall the motor and let the bike hold on compression. Getting to the rear brake is usually impossible, and the front does nothing (except make you lose steering too) in this situation. Trying to manipulate clutch on a scary big slope while holding the bike and trying not fall over is often waay too hard! When current e-trials 'stall' or the lanyard is pulled they go into freewheel - terrifying and dangerous. Your best option is often to jump out of the way and watch the bike cartwheel to the bottom!
more to come as I think of it.

 

[DingusMcGee]

bikerpete,

Thanks for compiling the chart on e-trials bike control suggestions. I will study it more as

I am gathering parts from retired ebike items to begin a table mock-up.

 

[speedmd]

Looks like a great list pete! Important to qualify the real world experience - understanding levels so we are feeling out the direction of mods congruently. We are all somewhat prisoners to our own cache of the human experience.

DMG, you may have a great idea here with the second controller integrations.

I could see it a bit better now linking the clutch lever to allow forward impulse's as well as release to even braking functions; and continue to the "all the way in" position to even reverse direction enough to hold balance on the static wheelie. Mind blown! Goes full segway for you. Sorry pete, had to go there. LOL

Have to admit, that I am liking the idea of a super light, super high torque motor with super responsive controller setup. Can not think of anything I don't like about it. I also like the multi path trial method of incremental improvements. As with most development, "it's often easier doing it the hard way".

 

[bikerpete]

bikerpete,

Thanks for compiling the chart on e-trials bike control suggestions. I will study it more as

I am gathering parts from retired ebike items to begin a table mock-up.

It's a bit of a grab bag at present. I'll have to work on it in a spreadsheet and get it into some sort of priority order or groupings. Also make sure what I've jotted down there is actually what I think I intend.
But maybe it'll help keep pulling things back into an integrated direction - it's easy to go down a path and then realise you've been so focused on one aspect you've completely forgotten something else that's quite contrary.

I'll be keen to see what you come up with. I suffer from paralysis by analysis too often.

Important to qualify the real would experience - understanding levels so we are feeling out the direction of mods congruently. We are all somewhat prisoners to our own cache of the human experience.

For sure.
There's also a big span of what different level riders want a bike to do.
If you're riding pretty much always on two wheels it's a very different game to when you're on one.
Many riders never really learn to use the clutch and can ride incredibly well - just look at some of those blokes who grew up on cable clutches and are still riding twinshock or classic bikes - never touch the clutch between start & end gates but never put a foot down either.
And then the other end, the Expert/Pro/T1 class who only seem to have front wheels to get between sections or to hop the rear into place, and who use the throttle almost like an on/off switch and everything happens via clutch.

I look at all this from the perspective that current ICE bikes are state-of-the art, pinnacle of engineering excellence for the job.
I love riding my 2021 TRS RR 300 - it's such a good machine! I dislike the noise. And I'm just not really interested in riding an electric bike that isn't as good.
Life's too short to ride shit bikes!

EM just isn't there yet as far as I'm concerned. I held out hopes for the Dragonfly but they dropped the gearbox and didn't give it a flywheel at all. Neither of them have sufficient power when you're up in the higher RPM - I can't talk to that, but I've heard that from some extremely experienced riders. It remains a bit of mystery to me why that's the case.
GasGas have just shown a teaser of their new electric prototype - similar to the first one with the motor buried into the ICE crankcase, so they have their normal clutch and 6 speed gearbox. Unfortunately no flywheel.
I bang on about flywheel, but I've never, ever seen a bike without one do what a bike with one can do. So I'm just not interested in not having one. Look at videos of 'Stuffs' - I've never seen an EM or Dragonfly do a convincing rendition. My Dob wouldn't either until I threw a whacking great flywheel on it and beefed up the clutch, then we were away.
As I said, life's too short for shit bikes.

That said, I do enjoy my little electric DOB. It's not really comparable to the TRS, it's quite a different game playing on it compared to a full size trials bike. And it lets me ride places I could never ride a full size bike, even electric. It looks a bit like a toy so people seem to treat it like it's just someone playing with a toy, rather than a damn motorcycle rider. But it's a lot more fun the closer I get it to the sort of response the TRS gives, albeit in a scaled down manner.

Bottom line for me is I want something that performs as well as an ICE bike at my skill level.

I occasionally twist the throttle to WOT, let it build, then drop the clutch, but I scare the crap out of myself when I do! Half throttle or full throttle for a short time - no problems, do that regularly.
I can gap across obstacles on the rear, but can't (yet) really stop and balance on one then hop to the next.
I can hop front and rear more or less consistently.
I ride the clutch almost constantly.

So that's a rough idea of where I'm at and what I'm after.

 

[speedmd]

Like the idea of a graded skills list. I also am a old cable clutch rider that took a long break before getting back into it a bit. New for me is a 2012 sherco. I catch myself going back to the old methods and can clear novice stuff but need much work on clutching. Brakes are much better than the old plunker also. Balance points are a work in process given the relatively hyper sensitive controls.

Front hops are good so far, but the rear is a timing issue for me most times. It's getting there. Smaller blocks, I can wheelie onto and stop but the bigger ones I find myself needing to adapt a route off depending on the trip up. It gets ugly quick at times on the bigger stuff. I ride very little so its taking extra long to develop.

Balance point wheelies in higher gears are no problem, so working on stop - hoping in lower gears now. Balance is not what it was years back. One thing I am finding is that my balance on the pedal bikes has improved drastically since getting back on the moto. Sure it will pay off long term preventing bad falls while in lycra. Amazing how much better I can hop the mountain bike these days.

 

[bikerpete]

Balance is not what it was years back. One thing I am finding is that my balance on the pedal bikes has improved drastically since getting back on the moto. Sure it will pay off long term preventing bad falls while in lycra. Amazing how much better I can hop the mountain bike these days.

Just another of the inevitable declines with age. That's a part of my motivation to keep riding trials - slow the decline in balance with age.
Bicycle and moto trials give each other a nice feedback loop - some things are easier to learn on one or the other, and then transfer to a degree.

The 'moderns' really do respond well to a dramatic change in approach - throttle as available power, clutch as applied. Totally different from the old bikes and really hard to break the old habits!
Best exercise ever - R.S.G. - Rev Squat Go. Roll slowly toward 3 markers each about 1.5-2m apart, ideally very slight uphill slope. First mark increase throttle but keep speed at slow walk (clutch slip). Second mark squat down into the bike, keep speed & rpm constant. Third mark Go - stand up, release clutch & close throttle.
Important - you are NOT aiming to lift the front wheel! If you do it accurately and with good RPM the front will lift, but that is NOT the goal, it's a result of making the right actions.
If you even think about lifting the front you absolutely will start adding in a litany of errors that demolish the goal.
When you get it right it's nuts how much RPM you can start with. WOT, engine peaking until it starts 4-stroking and wont go any faster, then GO, even on a 300. The bike will leap vertical, but immediately settle and start to drop back down (maybe a touch of brake at that sort of rpm). If there is any, repeat, ANY, throttle on by the time the clutch is fully out you're looking for a loop out. Potentially a very exciting one if you've got any significant revs up.
I'll about guarantee that you wont be able to cleanly Go without giving it a little tweak of throttle - force of habit.
Video it to check and listen to the motor noise.
There's a heap of other stuff to work on in that exercise too. This one exercise is the key foundation to all modern techniques.

Here's the guy who coined the phrase and a couple of applied examples. You can easily see the 3 parts.
These slowmo's also let you really see the throttle wind on, the stand, the timing of clutch and the closing throttle. You can see the back wheel snap into action but quickly slow down. On the concrete wall it's obvious how when it hits the face the wheel is only spinning at about the speed it's travelling up the face. Hooks up instantly.
A little before the first one he does the same wall on an enduro bike - you really hear the RPM on that one because their flywheels are so small you need to rev the guts out of them to get any energy into it.

 

[speedmd]

Thanks Pete. Great explanation of the hop. Need to practice, practice, practice!

 

[DingusMcGee]

bikerpete,

I have watched the video of Neil Price and must comment on the observation that his real wheel does break traction on the dirt. Some post back You emphasized that the wheel must never break traction — maybe not so?

The breaking of traction in the video happens both while climbing the cement blocks and the big log climb.

 

[speedmd]

Breaking traction as I understand Pete is when the tire slips to the point of failing to supply the needed thrust. All dirt bikes work in a way that the tires will slip "x" amount of degrees of rotation on normal riding surfaces but still deliver the thrust to do the job the best it can given the traction of the conditions. Anyone riding trials, knows full well that loading the contact surface is a main ingredient and when you unload it, all hell breaks loose. Just trying to move a running bike over a small obstacle while your feet are on the ground shows this very clearly. Something as small as a railroad tie can stall the motion most times if your off it. Keeping the tire close to the speed of motion and loaded is the trick.

Watching xtrials last night and it was quite the show. The 180 degree hops from a stand still just blow me away. Determined to learn that one. LOL

 

[bikerpete]

bikerpete,

I have watched the video of Neil Price and must comment on the observation that his real wheel does break traction on the dirt. Some post back You emphasized that the wheel must never break traction — maybe not so?

The breaking of traction in the video happens both while climbing the cement blocks and the big log climb.

Maybe a misunderstanding between us.
As @speedmd said, on dirt there is always a degree of slip as the surface breaks down. We use that all the time but have to work within it's limits.
I haven't gone back to look, but I'd expect that on the concrete the tyre grabs pretty strongly as it flattens onto the surface, but then slips as the load comes off and the tyre opens up again. At that point it is just the rider & suspension actively trying to press the tyre onto the surface that provides load & so traction. That's unlikely to be enough to keep the tyre totally gripping, but it's enough to provide sufficient drive to complete the climb. That part is what sorts the experts from the wannabe's!

Where things go totally pear shaped is when there is not enough load on the tyre to overcome the acceleration from the motor - then the wheel spins up, very, very quickly on e-bikes. It is this part that a flywheel and closed/closing throttle mitigates against.
In Neil's videos I would expect that at the point that you see a little slip between wheel and wall you currently see a relatively small slip speed, and one that certainly does not increase. If throttle was still open at that point the slip speed would increase to the point the tyre completely transitions to sliding friction and the consequent loss of drive, not to mention other effects causing the bike to tend to rebound off the wall etc.
That may not be exactly accurate to the physics of it, but I think it's a reasonable sketch of what's going on.

There's a huge difference between slip and spin. In Neil's video just look at the acceleration and rotation he generates as he releases clutch - it's big! If he mis-judged the power release too much the back wheel would actually spin and the bike would go almost nowhere. That's what we (usually) can't afford to do. That's where trials riders so often laugh at trail/enduro riders who just keep adding more and more power and just dig deeper and deeper holes instead of finding the limits of traction and working there.

So bottom line we can't break traction to the point of spinning the wheel up, but we are often working in that transition zone where there is some slip. This is where traction control could become a double edged sword, sometimes we embrace a certain amount of slip, other times not so much, and those times are occurring moment by moment.

 

[bikerpete]

Watching xtrials last night and it was quite the show. The 180 degree hops from a stand still just blow me away. Determined to learn that one. LOL

I've been working on flick turns the past weeks - I'm happy if I can get 45 degrees off a little lip! Like so much in trials, the timing is just so precise for it to all come together. Nothing another few thousand hours wont fix.