Rotary Powered Christini–A Closer Look

A few years back DARPA (Defence Advanced Research Projects Agency) created a challenge to develop a portable electric power source from a lightweight motorcycle. Recently this video of a Christini motorcycle with a rotary/electric power plant surfaced.

So Dirt Bike Test did a little digging to see what we could learn.  In the initial initiative this was the objective.

OBJECTIVE: Develop the required technologies and demonstrate a lightweight two-wheel drive (2WD) hybrid-electric off-road motorcycle for combat troop use powered by heavy fuels, capable of short periods electric-only propulsion, and usable as a portable electric power source for soldiers in the field.

All-wheel drive or two-wheel drive motorcycles have been experimented with for nearly a century and have experienced limited commercial success. The long-term American product is the small Rokon Ranger with a mechanically driven front wheel. Newer to the market is Christini Corp”s AWD 450. Other current developments include the hydraulically driven Yamaha WR450F 2-Trac, and KTM”s recent patent for an electric front wheel drive. While the various pieces of interest exist in isolation, nobody has successfully combined heavy fuel capability, 2WD, and hybrid powertrains into a useful off-road motorcycle. This is a very challenging component and system design problem. This SBIR proposes to address the challenge through the innovative application of technology to develop a motorcycle capable of improving support for soldiers operating in remote and harsh environments. Desired characteristics of the vehicle include: Silent electric only mode and low noise (<75 dB) during normal operation Production of supplemental power, e.g., for battery charging Two-wheel-drive in support of extreme terrain operations Heavy fuel compatibility>10% improvement in load-specific fuel consumption as compared to existing fielded motorcycles.

The Christini AWD Hybrid Motorcycle was developed as a fully operational mobile charging station with the lightweight capabilities of its current AWD motorcycle but with the charging capacity of a large generator.

Here is what it can do:

Riding/Patrol Mode:

Electric:  The Christini AWD Hybrid Moto can operate on full electric only power with a low sound profile (chain noise) up to speeds of about 25mph.  This is generally considered to be the max rider speeds for patrol or tactical operations. This operational mode is scalable for range based on a multi pack power system using standard Lithium Ion batteries.  

Fuel operations (Gas/Heavy Fuel): Once the bike is up to the max electric speed, the operator can run on full Rotary engine power from a claimed 25-65mph.  The rotary can generate over 42 hp on gas and will have nearly the same power on JP8 or other heavy fuels. The operational speed of the bike is nearly the same standard Christini AWD.

On Board Charging:  The rotary engine is equipped with a large starter/generator that can charge the passive on board battery (or batteries) while riding the bike.  This system acts as a range extender and can increase the overall silent operation of the bike when necessary.

Stationary Charging Mode:

The bike, once stationary, can be “switched” into charging mode.  The multi fuel rotary can be decoupled from the drive of the bike and run the DC brushless motor as a genset.  The rotary makes 12 HP in idle mode and will power the electric motor to an output capacity of 10,000 watts of usable power with the potential to do more.  This system will allow operators to charge communication equipment, drones, robotics, etc. in a forward operating position.

Entered into the evaluation were two other vehicles. DARPA has funded both to phase two development under a small business innovative research award, essentially two non-competing grants to develop the technology. The lighter of the two, the Silent Hawk, is built by Logos and based on an Alta electric motorcycle with a hybrid powertrain that combines a battery-powered electric motor with a small Wankel rotary engine supplied by Cubewano that works as a range-extending generator and can power electrical equipment in the field. It will have obviously run into some issues, not the least of which is Alta’s recent ceasing of production and closing up shop looking for further investors.

The Nightmare from LSA Autonomy is a larger heavier version of the Silent Hawk a larger horsepower rating, 17 in front and 135 in back. The Nightmare averages around 13 kilowatts in generated power, versus 7.5 kilowatts for the Silent Hawk. Both have the ability to run external devices, too.

The larger issue for these two entries is the adaptation of using a front electrical hub as a motor. So far there is not the technology to control the spinning and torque of the front wheel in off-road conditions, something that seemed to even stymie motorcycle giant KTM who have held patents for driving the front wheel through electrical energy with a normally powered (gas engine) driving the rear. The Christini’s mechanical system is proven and simplistic as well as much more durable and performance oriented than the hydraulic systems that were popping up for a while. If ABS took a long time to develop and get as good as it is now on motorcycles, electric AWD could be in for a long haul as well.

It is rumored that Christini will be selling a limited number of rotary powered bikes in the configuration shown here (but not heavy fuel capable) in the near future to consumers looking for something a lot different than a regular electric or AWD bike. The machine would be ideal for hunting where silent approach (all electric) is best but range (getting most of the distance on rotary) is a factor. In Military operations the bike is more of a mobile power generator in extremely difficult to reach locations. It is ridden into the remote location and then used to power something, more than the necessity of silent operation.

Both the Nigtmare and the Silent Hawk are currently in a second round of development through a DARPA grant and we’ll see if anything like this comes to a consumer marketplace. And in investigating info for this story Dirt Bike Test has secured a 2019 Christini AWD 450 for a full test so stay tuned for some two-wheel drive dirt biking in the near future.

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