[brian_]

You second question regarding hard braking on ONE wheel due to a malfunction in the regen mode seems to me to be of more interest. But it would be of interest for any bike or automobile using regen.

...

Or imagine my wife's Ford Fusion locking up the regen on just one wheel.

While I agree that the worst-case asymmetric failure is unlikely to occur, this EV with separate motors and controllers is able to (regeneratively) brake one rear wheel while driving the other (or just not powering it). The Fusion is unable to that - even if you tried - because the same engine and the same motor drive both front wheels. It can only apply different amounts of torque to the two wheels by using the brake (not motor regeneration) on one... and any current production vehicle (EV/hybrid, or not) has a stability and traction control system that is capable of braking a single wheel.

 

[CBOY]

Photos of the completed trike.

 

[CBOY]

And a video of the build and the trike on the road.



https://www.youtube.com/watch?v=QwWzzDFrNT8

 

[MattsAwesomeStuff]

Wow, what an awesome build.

So? What was it like? How did it feel? How fast did you go? How much power did it draw? How was the ride?

We don't often see people finish their build, or stick around for the afterparty .

 

[CBOY]

While I agree that the worst-case asymmetric failure is unlikely to occur, this EV with separate motors and controllers is able to (regeneratively) brake one rear wheel while driving the other (or just not powering it). The Fusion is unable to that - even if you tried - because the same engine and the same motor drive both front wheels. It can only apply different amounts of torque to the two wheels by using the brake (not motor regeneration) on one... and any current production vehicle (EV/hybrid, or not) has a stability and traction control system that is capable of braking a single wheel.

My point was more that once you start talking about highly unlikely failures, where do you stop? I believe I could write a doomsday scenario where regeneraton could engage in one wheel of the Fusion and not the other (broken axle comes to mind). Would such scenarios be highly unlikely? You bet. Would a bunch of bizarre things have to go wrong for it to happen. You bet. But I could create the possibility. And the scenarios for front motor, rear motor or front & rear motor two wheelers are even easier to come up with. So I have no quarrel with discussing whether regen might, in some highly unlike set of circumstances, be unwise on an EV. But I see no reason to limit that debate to just parallel dual motor configurations.



The funny part of this is that early on during test drives I DID, in fact, engage the regen on my trike on only one side...totally by mistake. I didn't have the ground wires properly configured so when I applied my variable regen, it only applied on the right rear. So I do have an inkling of what it might actually feel like if this were to happen. And the "grab" was fairly trivial. Granted, this braking didn't come as a surprise, since I was applying the regen via my hand controller and knew it was coming. And more importantly, this wasn't full on total force engagement of regen which one might consider in a doomsday scenario.



But the final point I would add is that if a builder is concerned about using regen, the maximum amount of braking can be adjusted in the user programming software...at least with my kelly controllers it can be adjusted. The maximum is 50%...and you go down from there if you want. And if you REALLY want to test if it is a potential safety issue, just unhook the regen on one side, go for a test spin and mash the variable regen lever (or engage the regen via the throttle release or brake application if that is how you are doing the regen). Then, if you feel the results are a potential danger, just adjust down the maximum braking that regen can apply until you feel you are in your safety zone.

 

[CBOY]

Wow, what an awesome build.

So? What was it like? How did it feel? How fast did you go? How much power did it draw? How was the ride?

We don't often see people finish their build, or stick around for the afterparty .

Thanks for the kind words. It has been quite a learning experience. And I'm still ironing out a few kinks as I get some miles built up.



The next major step is to soften up the front suspension. The front fork is off a Kawasaki Voyager and the weight distribution is far different on the trike vs. the bike. Currently the front fork is very stiff. Fortunately Voyagers use an "air ride" system so I can do some of the adjusting just by altering the front shock air pressure. The second alteration will be using lighter weight oil in the shocks. The donor bike came with a new set of front shock tubes (springs and shocks) so I have to install those tomorrow and start getting them dialed in.



The donor also came with Progressive rear coil over shocks which I used on the trike and they seem to be working great even though my tail end is about 325 lbs heavier than the Voyager (but split between two wheels rather than one so the extra weight per wheel is about 162 lbs). The Progressives seem to handle the extra weight with ease. On the plus side, the trike is not built to carry an extra passenger and I am fairly slim...so I think the rear suspension is going to be good to go.



No all-out speed runs yet. Based on my own testing of the wheel RPMs and the tire circumference, the bike should be capable of just over 60 mph. So far I've only taken it to 40. And I probably won't go any higher until I get the front suspension working a little better to absorb the potholes.


Power usage numbers are not very reliable yet. Trips have been relatively short, speed is being held down, and I'm still tinkering and adjusting here and there. But so far I'm seeing power usage in the 89 - 110 watt/hour per mile range depending on how hard I've pushed the bike. But I'm treating those numbers as very preliminary at this point.



One sort of odd point to report. It takes a bit of getting used to having that wide rear end following along behind you. The chopper is a good deal wider than by 1000W trike and I often forget that as I'm driving into the garage (I've put a couple nice gouges in my garage workbench) and I even put a scratch in the lower rear quarter panel of my wife's car (oops) when I drove around it in the driveway. Maybe I need to invent some sort of radar system out there on my flanks.


I'll be reporting more trip data as it accumulates and becomes a little more reliable.

 

[electro wrks]

My point was more that once you start talking about highly unlikely failures, where do you stop? I believe I could write a doomsday scenario where regeneraton could engage in one wheel of the Fusion and not the other (broken axle comes to mind). Would such scenarios be highly unlikely? You bet. Would a bunch of bizarre things have to go wrong for it to happen. You bet. But I could create the possibility. And the scenarios for front motor, rear motor or front & rear motor two wheelers are even easier to come up with. So I have no quarrel with discussing whether regen might, in some highly unlike set of circumstances, be unwise on an EV. But I see no reason to limit that debate to just parallel dual motor configurations.



The funny part of this is that early on during test drives I DID, in fact, engage the regen on my trike on only one side...totally by mistake. I didn't have the ground wires properly configured so when I applied my variable regen, it only applied on the right rear. So I do have an inkling of what it might actually feel like if this were to happen. And the "grab" was fairly trivial. Granted, this braking didn't come as a surprise, since I was applying the regen via my hand controller and knew it was coming. And more importantly, this wasn't full on total force engagement of regen which one might consider in a doomsday scenario.



But the final point I would add is that if a builder is concerned about using regen, the maximum amount of braking can be adjusted in the user programming software...at least with my kelly controllers it can be adjusted. The maximum is 50%...and you go down from there if you want. And if you REALLY want to test if it is a potential safety issue, just unhook the regen on one side, go for a test spin and mash the variable regen lever (or engage the regen via the throttle release or brake application if that is how you are doing the regen). Then, if you feel the results are a potential danger, just adjust down the maximum braking that regen can apply until you feel you are in your safety zone.

Good points. In this low power design let's hope a failure scenario would not be catastrophic. One point to remember in this case is that a system using typical electronics, generally speaking sooner or later, is much more likely to fail than the tried and trued mechanical system. I'm qualifying this statement because there are electronic built for the military, for example, that have shielding, robust construction, and redundancy built in to reduce their potential failure. I don't think the typical Kelly controllers have this kind of construction.
Many builders and some large manufacturers have come out with separate wheel drives in the past. Most have quietly abandoned the concept because of the safety concerns we are discussing.
Obviously, Tesla is an exception to this trend with their new Semi and Roadster designs. They probably have redundant separate system(s) that monitor the drives and can instantly compensate for a failure. Let's hope they have figured out how to safely do separate wheel drives.

 

[brian_]

Many builders and some large manufacturers have come out with separate wheel drives in the past. Most have quietly abandoned the concept because of the safety concerns we are discussing.
Obviously, Tesla is an exception to this trend with their new Semi and Roadster designs.

As usual Tesla isn't ahead in technology here. The Semi will use separate motors, but so would the earlier Nikola Motor truck, as well as the buses already in production with ZF's AxTrax AVE axle and BYD's similar hardware. This ZF electric axle is used in the Mercedes electric truck (which is not in production, but is ahead of the Tesla Semi). Then there are the even heavier off-highway trucks...

While the new Tesla Roadster is still a prototype, a few production hybrids have used separate left and right motors in one axle for years. Granted, it's the lower-powered axle: the front of mid-engine sports cars such as the Acura NSX, and the rear of front-engine SUVs such as the mid-sized Acura and Honda. On the other hand, in these cases it's the electric-only axle which gets two motors; the engine-driven axle gets only one motor for lower complexity (since the engine drive already requires a differential).

Separate drive (or braking) wheel torque is one purpose of these two-motor axle systems, particularly in high-performance vehicles, so different drive torque is obviously significant to vehicle control. The manufacturers seem to be confident that they can handle issues, although

• as I noted earlier, failures are already a risk with mechanical brake-based ABS, traction control, and stability control systems, and
• as electro wrks noted, the hardware grade and quality assurance / quality control of automotive systems are unlike typical consumer goods and low-speed vehicles.

 

[brian_]

My point was more that once you start talking about highly unlikely failures, where do you stop?

I get that. I'm not really concerned about asymmetric drive due to failures, but it does need to be considered in design.

I believe I could write a doomsday scenario where regeneraton could engage in one wheel of the Fusion and not the other (broken axle comes to mind).

A simply broken axle would leave the differential output of the broken side spinning freely (not constrained by a shaft connection to a wheel), so the other side wouldn't get any torque, due to the open differential. Of course the broken shaft could jam in some way, and that problem - which is unrelated to regeneration and could occur in any vehicle, electric or not - just doesn't happen enough to be a concern at all.

 

[electro wrks]

CBOY, what is the latest on your trike build? Have been able to log any more test miles?