The most complicated KERS in the world

Dailies, Galleries -


Kinetic Energy Recovery Systems, more commonly known as regenerative braking, work by applying resistance to the electric motor, thereby slowing the bike down and turning the motor into a generator. The relatively small amounts of electricity generated are used to put a little bit of charge back into the batteries. On electric motorcycles the motor drives the rear wheel so, until now, KERS setups have been limited to putting resistance on the rear wheel, which is obviously limited by traction as the bike slows down and shifts its weight forward. By using an incredibly complicated arrangement of in-wheel clutches, telescoping drive shafts, chains hidden within the top yoke and bevel gears — a system that’s remarkably similar to the Christini mechanical two-wheel-drive system —  Chip Yates has managed to connect the front wheel to the electric motor to boost the capacity of regenerative braking onboard his Swigz Pro Racing TTXGP competitor. Something he claims will allow him to use the same battery capacity as competitors while making nearly twice the power.

Chip explains the system best:

“The process of electrical regeneration is initiated when the rider squeezes the KERS brake lever, located on the left handlebar. This level sends a signal to our MOTEC ECU, which runs a number of calculations from our KERS control software, and then outputs a regeneration command to the UQM motor controller. The UQM controller then initiates regenerative braking torque in the motor by creating an electromagnetic field in front of the spinning rotor that acts to slow the motor down and feels like front wheel braking.”

“The front wheel is equipped with special one-way clutches housed in custom CNC machined wheel hubs that allow the front tire to transmit energy back to the electric motor, but do not allow the electric motor to drive the front wheel; our bike is rear-wheel drive only. These clutches have the capability of transmitting more than 500 ft/lbs of braking torque from the front wheel, although we currently software limit the regeneration levels to less than that amount based on a number of factors. The clutches mate to a ring and pinion gear set located on each side of the wheel, on the front axle centerline. The pinion gears turn two counter-rotating and telescoping driveshafts that can be seen running along the outside of the Ohlins front forks.”

“The driveshafts share the torque load and so can be smaller diameter than if we only used one big shaft. They enter into the lower triple clamp and each has its own sprocket at the top end to drive a chain inside the hollow triple clamp. The two chains coming from either side are positioned one above the other to avoid interference and they drive an inner and outer shaft in the center of the triple clamp that rotate in opposite directions as they head up to the custom steering head in the frame of the bike. Once inside the steering head, one of the shafts turns a lower bevel gear and the shaft rotating the other direction turns an upper bevel gear. Between these counter-rotating bevel gears is an output bevel gear that exits the steering head and turns a KERS driveshaft that runs inside the frame rail of the bike. The counter-rotating driveshafts and bevel gears act to counteract torque steer felt through the handlebars.”

YouTube Preview Image

“The KERS driveshaft runs from the steering head down to a KERS gearbox located inside the frame rail around the area of the rider’s knee. The gearbox turns the spinning KERS driveshaft into a rotating drive sprocket, and the sprocket turns a KERS chain that runs down to the UQM electric motor shaft where it can be used to generate electricity for recharging our on-board battery pack. There are a few additional elements to this system that we can’t elaborate on for confidentiality reasons but this gives a pretty clear picture how things work.”

“Our proprietary and patent-pending KERS control software has features that smooth out the front wheel braking, limit braking based on factors such as lean angle for safety and also based on battery pack voltage to guard against overvoltaging the pack.”

“Our system can be coupled to the hydraulic front brake for seamless control and activation, but for our testing and first races, we have decided to split the front braking controls into a left handlebar KERS brake lever, and a right handlebar hydraulic friction brake lever to give me more control over how I trail brake into corners.”

“With this system on our bike at a representative track such as Laguna Seca, we can use the same size battery pack as our electric competitors, but make about twice the horsepower over the course of an entire 12-lap race. Our analysis indicates a lap-time approximately 10 seconds per lap faster than the fastest electric racebikes have recently accomplished at Laguna Seca making it a worthwhile development.

This setup sounds so identical to the Christini AWD system that we’d be surprised to learn that Chip hadn’t adapted it for this application. Christini developed a mechanical rather than hydraulic drive system because the the power losses are less, we’d expect Chip chose it for the same reason.

The bike this system will be operating on is the somewhat ungainly modified GSX-R750 you can see in these photos. In addition to the novel KERS solution, the Swigz bike uses an all-in-one power management/traction control system that will meter out the peak power of 194bhp and peak torque of 295lb/ft not just to prevent wheel spin, but with a constantly adjusting algorithm, it’ll make sure the energy stored in the battery packs will last the full race distance too. All the rider has to do is crack open the throttle and he’ll get the maximum power that traction and charge/remaining distance allows.

It’s sort of hard to think of revolutionary technologies like that fitting into a package that looks like its been created without sympathy for motorcycle physics. Those huge battery packs appear to shift a significant portion of the weight into non-ideal places like that huge tail section. Chip, a successful AMA Pro racer plans to ride this bike in TTXGP races himself, somehow we’re sure that, despite appearances, he wouldn’t set out to do so on a machine that was fundamentally compromised.

Swigz Pro Racing via Autoblog Green

  • 2ndderivative

    Exciting stuff. At least in the case of electric motorcycles, racing definitely does improve the breed. I’d guess that within ten years we’ll have very well sorted electric sportbikes that are functionally equal or superior to gas-powered bikes of today.

  • Glenngineer

    I think the weight, inevitable inefficiency, and less than completely automatic control will prove this to be a dead end in electric bike design.

    • Grive

      At least the “less than completely automatic control” part is a nonissue.

      Chip states in the article that it can be seamlessly integrated into the front brake lever, but for testing he wanted it to be separate.

  • GGno

    Is this THING able to turn???

  • quentin wilson

    Successful AMA Pro Racer? His best finish is 21st. That is not success, it is abject mediocrity. Believe me I know from experience.

    Those fork lowers are _identical_ to the ones on my Christini 250X, I am sure if you called Steve Christini he would verify. That would be very journalistic of you. Why else would you engineer dirtbike forks for a roadrace chassis? The unfortunate part of that is that the chain mechanism in the lower triple clamp prevents the fork offset from going far back enough to get good trail numbers. You gotta start somewhere though, and using the rear brake for re-gen isn’t necessarily the best way to go.

    • seanslides

      “…the chain mechanism in the lower triple clamp prevents the fork offset from going far back enough to get good trail numbers.”

      I’ve wrenched on a few christinis, and I’m sitting here scratching my head on this one. If you machine custom triple clamps, you should be able to put the forks wherever you want them. The only problem I can foresee is that of chain tension between the driveshafts and the center sprockets. Even then, there’s still quite a bit of fudge factor to work with.

      Am I missing something here?

      • quentin wilson

        The driveshafts dictate axle position, which as you have seen first hand forces the axle quite far out relative to the fork centers. In order to get close to the trail numbers of a roadbike, the triple clamp would have to be machined inverse and would then limit steering lock along with a few other issues involving the gear ratios and component strength. I have a feeling Steve is working on it…

        • seanslides

          Steering lock is basically a non-issue on a road racer. I think the easiest solution would be to flip the forks around backwards so that the driveshafts run down the back. You’d have brakes hanging out in the wind, which isn’t the most aerodynamic thing, but on that bike, I don’t think it’s really gonna matter.

          I think that ditching the chains in the lower triple for a gear drive would be nice too. Actually, ditching all the chains in the system for gear drives is probably a Very good idea. It doesn’t matter as much on a dirt bike, but the lag from chain slack would be pretty nasty if you’re using it for braking. I bet it’s the equivalent of having brake lines made of old condoms and an extra sloppy lever with those chains in there.

          Oh well, I’m sure they’ll figure it out. They pretty much have to. This is the only way electric bikes are going to have real regenerative braking.

          If Michael Czysz was feeling a little crazy, he could probably adapt his strange and flexy front suspension to accommodate driveshafts inside the sliders seeing as there are no springs or hydraulics in there. Something to think about…

  • Les

    Seems a bit complicated without much reward. Reminds me of a goldberg machine.

  • cadbury64

    I salute Mr Yates for his original thinking, and given one of the biggest limiting factors in electric vehicle acceptance seems to be range, this is a good place for innovation and development. However the system of shafts , gears and chains sure sounds like a complicated way to achieve it. It makes me wonder if there is not a more elegant way to skin this particular cat, like putting a purpose-designed regenerative braking “motor” (or is that “generator”?)into the front wheel hub. Or can the whole front-wheel assembly become the generator? There ought to be some acceptable trade-off between the extra weight in the wheel, and the additional braking force generated, that would allow dropping down to one caliper and disc?

  • zipp4

    I think I may be the only one that thinks this is significant progress…

    Although I’m not an expert designer/engineer/racer, like everyone else who reads this site.

  • Darth Lefty

    Yeesh! Just put a generator in the front hub. Against the rules?

    • seanslides

      Just a bit too much stuff spinning around. It’d take five minutes to change direction with a generator big enough to have any significant effect.


    I just trew up in my mouth a little.