Full-Sized E-Trials

[jojo]

Hi nostroke, really a beautiful conversion!!!

I think also the settings of the Controller etc. are very complicated.

I had tested the prototype of the EM a Long Time ago. Now the Bike has nothing to do with that Bike of the past. Your battery Packs are quiet small. Do you have a BMS on in?

[nostroke]

I don't know much about the EM motor / controller. But the settings on my rig, which uses an Alltrax controller, are way simple. Because its a permanent magnet motor, there isn't much to tune. Only the throttle ramp which I do my best to fully disable. I want instant response. The touchier, the better,

A lot of the newer electrics use brushless motors, which I have used in road going vehicles. Brushless motors are somewhat more efficient in terms of energy consumption. But typically, the motors and controllers are on the heavy side. And further, the last thing I want is an electrical engineer deciding how responsive I should have my throttle. I expect that is why the Scorpa and GAS GAS conversion use that (what I consider) hokey method of using a clutch operated potentiometer to make the bike more gas-like. I can see a need for a clutch when you need massive honks of torque, but it would need a real friction clutch to really do the deed, IMHO. I have modelled a friction clutch that would fit onto the motor shaft directly with no jackshafts or secondary reduction required, but have yet to build it. I am waiting until my riding skills are good enough to use that much launch!

I don't use an on board BMS. I use RC car stuff for monitoring and balancing the cells, but they rarely need it. And as for over-discharge issues, I just quit riding when the power fades, which is usually a bit above the danger zone. I never pull the cell voltage below about 3.7 volts, which is very safe.

Edited February 5, 2013 by nostroke

[gwhy]

You can mimic a mechanical clutch 100% using electronics with a brushless motor / controller , I dont know how Scorpa and GG do it but I have my own method that works. BMS tends to be more trouble than its worth on lower than 60v systems ( I know of more battery problems that has been caused through on board BMS that has convinced me never to go down the BMS route ) all my bm is done manually .

[nostroke]

My concern with doing the whoopee launch electronically is based purely on theory and not experience, so I'm kinda talking out my butt here. But I would think that a 20 pound mass spinning at 5 to 6k rpm would dump a lot more energy than most of today's batteries or electronics would deliver. My gut says that if you could translate maybe 800 to 1200 amps into torque efficiently with your electronics, it could equal the flywheel effects' massive outburst. But I doubt that a normal human could modulate that, even if you could deliver those currents efficiently. Again, this is theory, not observation, although I did ride Scorpa's earliest prototype several years ago with a very early potentiometer set up on the clutch. I expect its been electronically refined a lot since then, but physics is physics. So I still say a flywheel will out-launch most electronics, In theory.

I've heard many call a BMS a battery murdering system, heh. But like everything they are always getting better.

[gwhy]

The torque of a brushless motor is proportional to the BEMF of the 3 phases which tends to be much, much more current than from the battery side. There are many other factors that would also need to be considered i.e motor diameter, motor speed and gearing in working out if a flywheel is going to be better, my controllers are set for around 300A on the battery side and the phase current is limited to 2.5x battery current, I know this do not translate to the 800A+ on your estimated needed but the bike is near on 20kg lighter than a gas version so its swings and round abouts and its all about finding the best setup for the rider. I dont want to start getting into the whole debate of which is better, but I do think you are right as regards the flywheel but at a cost of it will make the bike heavier and less efficient.

[nostroke]

I guess I am sort of obsessed with the idea that at some point a pro rider will whine that electrics can't do the big launches. The design I'm working on is a sort of inside out version of a typical gas bike clutch. So instead of the primary gears being the input and the mainshaft (inner hub) being the output of the clutch, this design would use the motor shaft keyed, splined, whatever, to the inner clutch hub. Then the output would be a countershaft sprocket attached to the outer basket. The crank assy (w/ flywheel) on most gas trials bikes is around 20 lbs, the same weight approximately as the rotor on most electric motors of this scale. I think with the added inertial moment of the pancake motors relatively large OD, you could get more flywheel driven launch than a gas bike. In fact, I think that maybe the electric motor could be even lighter, maybe just 10 to 15 pounds of motor total weight with more inertia from added RPMs if needed. Anyways, this is just kind of a dream of mine, that I could make an electric that out-performs a gas trials bike and still weighs less. I think the technology is here today to do this.

All that said, I really like not having a clutch to fiddle with. At my stage of riding, I'm still working on my basic balance skills, not falling over at a standstill!

[jojo]

The electric clutch of my em 5.7 is for me very usefull as a Kind of emergency Switch, but i have so much Good response from the throttle that i don't use the electric clutch a Lot. Like nostroke Said, this isn't comparable with a real clutch, but i think for 98% of the riders it is ok.

[gwhy]

The electric clutch of my em 5.7 is for me very usefull as a Kind of emergency Switch, but i have so much Good response from the throttle that i don't use the electric clutch a Lot. Like nostroke Said, this isn't comparable with a real clutch, but i think for 98% of the riders it is ok.

I find this interesting, The arrangement of my e-clutch reacts and feels 100% like a real clutch ( including big launches and being able to modulate fine throttle control ) the only down side to the e-clutch is that there is no engine noise/feedback but this is just a matter of getting used to it. I think It really depends on what type of controller it is i.e is it a speed based throttle or a current/torque based throttle. If it was a pure speed based throttle then I found this not the best thing for trials but can be usable if coupled with some throttle conditioning ( maybe how the EM does it using a e-clutch ) but a current/torque based throttle then this is better and can be used out of the box for trials as is but this can also be enhanced with some throttle conditioning ( e-clutch ).

[nostroke]

I once took a piezo buzzer and connected it in parallel with two 2 motor leads (brush motor), so it would increase the frequency based on the voltage supplied to the motor. It was very cheap and simple. And annoying!

Your 3 phase brushless motors have a lot more levels of control, like speed vs torque, that I'm sure let the engineer tailor things way beyond what I can with my garden variety golf car controller, which acts like a current controller. I would love to try one. Maybe in a few years there will be an electric class in comps, or at least a forum dedicated to full sized electrics.

I think I may be suffering from an inferiority complex due to having to post in the kiddie bike forum!

[gwhy]

I was considering using something along the lines of a buzzer, but I have not got round to trying it. Brushless allows a lot more configuration but the cost of the controllers tend to a lot more expensive than a brushed controller. You can play with a brushless set for quite cheap ( not one for a full size trials bike, but maybe something to put on a bicycle , maybe less than $150 for motor/controller). I have PM'ed the site admin to either rename this forum to just 'electric trials bikes' and have a sub forums off that for the different makes but nothing :-(.

[nostroke]

I guess the next feature we need to see on motor controllers is the ability to play .WAV files. I wonder if I could copyright the pop pop pop of a properly muffled two-stroke?

[gwhy]

Would be quite fun, maybe have the sound of a R6 sports bike or maybe a Harley D..

[nostroke]

gwhy-To be clear, with your e-clutch, I take it that the twist throttle, when the clutch is depressed, simply sets the peak available power. The clutch lever, as it is released, modulates power within the limits set by the twist grip? The clutch sort of IS the throttle in this case?

The more I ride with just a twist grip, I can see a need for a more precise control, which I believe the E clutch would provide, once I got used to it. Another approach might be a non-rotating grip on the right and a index finger trigger on the left side. Seems like this would free up the right hand for better front brake wrangling.

I confess, I have as much fun modifying stuff as I do riding. Go figure. Hey how about a foot operated mousetrap suicide clutch!

[gwhy]

The twist grip is a pure speed control and the clutch sets the torque/current limit ( just like a manual gas bike ). When The clutch is pulled in the current limit is set to a level that even at full throttle there is not enough power to move the bike but the more current you allow to the motor the more torque it will start to produce, with the clutch fully out I would compare riding my bike to riding a 280 beta in 1st gear ( but with 3X the top speed ) and not using the clutch at all, it becomes very twitchy and very easy to loop out. I started off by setting up a 2 position switch that changes the resolution of the throttle ( setting 1 would give 0-100% speed and setting 2 0-60% speed for the full range of travel of the throttle) this worked ok but still didnt allow for nice control in the slippery stuff as it still gave 100% torque at any throttle position. And to be honest I like modifying the bikes more now than riding them now..

[nostroke]

So last night I rigged up a clutch pot, using a 5k linear pot with a 12mm stroke, the same as the master cyl piston travel. I think if I put the pot in series with the throttle pot (2-wire), with the low resistance position in the 'clutch out', it would work as normal. But when I pull the clutch in, it will effectively reduce the throttle signal. Due to my dyslexia, I probably have this backwards, so I'll be sure to remove the drive chain while futzing around. It should work similar to your more elaborate scheme, which I cannot do with this controller.