Extreme Electric Motocross Bike
September 23, 2006 The recreational vehicle industry and specifically trail bikes look to be set for a whole new range of possibilities in the near future as electric motorcycles become viable. Electric dirt bikes offer several compelling advantages over their current petrol-burning brethren, the most significant being they are completely silent. There is nothing more out of place in the forest than the bark of a four-stroke or the staccato rasp of a two-stroke – at complete odds with the tranquility of the wilderness and quite capable of spoiling the experience for those ten miles away, motorcycling without the noise is long overdue. For this reason, bikes are essentially banned from suburbia. Proof of just how far electric dirt bikes have come is the US$5,500 Drift XC bike from Electricross.
Though it only develops 19 bhp, the linear, predictable power delivery has broad torque available from the very bottom of the rev range and is absolutely ideal power for loose surfaces. The trick is in the weight though as the Neal Saiki designed bike is ultra light – just 140 pounds ready for riding compared to 240 pounds plus for a petrol engined bike of similar output.
There is no wet weight for an electric bike as there's no petrol to burn, engine oil or even a gearbox. Saiki's cross country bike designs have won numerous World Cup mountain bike titles and he recently landed Mountain Biking magazine's 2006 X-Country Bike of the Year, so he knows his stuff . Before bikes he designed the first successful human powered helicopter (pictured), claiming one of the plumb aviation design firsts in history.
Inspired by the potential of the electric motor, Saiki has spent the last couple of years designing and building an electric cross country bike. Saiki found that motorcycle parts are generally too heavy (without the vibration, an electric bike can be built lighter) and bicycle parts were too weak for the forces he wanted to direct. The frame parts are all made from American-produced aluminum. Accordingly, every part had to be uniquely developed using computer analysis to optimize every component, such as the patent pending double diamond design that is lighter and stiffer than conventional swingarms.
Most of the parts such as the hubs, spokes, rims, chain and sprocket are custom-made, so almost everything had to be uniquely developed. Weeks of and all of Neal's mountain bike experience was brought to the Drift's frame design in order to create the lightest and most advanced electric motorcycle frame possible.
Despite it's weight, this is no toy bike - it is full powered motocrosser without noise and opens up all kinds of backyard and semi-urban riding opportunities where noise is an issue due to impinging on the amenity of neighbors. If there were no noise, surely there could be no reasonable complaint providing permission was available to ride on the land being used. The noise issue could also impact where bikes can be used, enabling them to be given a section of inner-city parkland just for silent motorcycles.
It is an intermediate sized bike, but weights only 140 pounds with the power pack and 80 pounds without. The power pack is easily removable for transporting. The off-road suspension features 7 to 8 inches of suspension travel in the front and 8 inches in the rear. The fully tunable motor controller allows a custom power and speed map to be loaded to tailor the throttle response from "trail riding" to "racetrack" or anywhere in between. The power can be easily turned down for younger riders making the Drift suitable for a wide range of abilities. The controller is adjusted by hooking a cable up to your computer and running a software program that is provided. The software is easy to use and the controller can even record data as you ride so you can see where you've got the throttle open and where you haven't.
A half power switch is also an option. At the flick of a switch the top speed and power is cut in half. This is perfect for beginner riders or for the occasional ride down the street in the bike lane. The switch extends the life of the battery considerably. With the reduced top speed the bike can technically qualify as a motorized bicycle and be ridden in the bicycle lane for commuting in most states. Check your own state laws at the DMV.
The quick-change power pack is the most unique feature of the Drift, because it can deliver up to 600 amps and yet a spent power pack can be replaced in seconds. Without this unique feature, the Drift would be totally impractical. Nobody wants to wait around for a dead battery to charge and with the Drift there is no waiting. In a few seconds you can slide in a fresh power pack and you are tearing it up again or letting your buddy have a turn. The unique modular power pack and protective frame design are patent pending. The power packs and chargers can be either fast charge or slow charge. The slow charger works in 2.5 hours and the fast charger works in 40 minutes. The power packs are priced so you can have a couple of them on hand for a full afternoon of riding.
There are power upgrades, suspension upgrades, and even charger upgrades to make the bike fully customizable. The controller, which limits the power from the power pack, can be either a 300 Amp controller or 400 amp controller. The higher powered controller makes the bike faster, but it also drains the power packs more quickly. Hydraulic disk brakes are standard with the choice of single or dual piston calipers. There are also two front fork choices including a very advanced unit from Fox. The rear suspension is handled by custom valved rear shocks from Fox. Fox and Electricross Inc are located near to each other and share years of experience working together. Fox rear shocks are 2 way adjustable with an optional air assist for bottom out tuning.
Not stopping there, Electricross Inc. has engineered the future right into the Drift, allowing for new types of batteries, controllers and motors to be adapted into the universal frame and modular power pack design. This sets up the Drift to handle any new technology as it develops. Electricross Inc is currently developing Lithium Polymer power packs that have incredible power and increased range. Unfortunately the price of these packs is going to be incredibly expensive to go with the incredible power. For the near future, the Drift uses the most advanced lead acid vehicle batteries in the power packs and they are the best balance between power and price.
Riding the Drift is smooth and deceptive. The lack of noise makes the bike seem less powerful than it really is. It's not until you race a gas bike that you realize how fast you are going. Great care has to be used not to give it too much power from a standstill or you will instantly be looking at nothing but sky. Electric motors produce huge amounts of torque at low RPM. Once you are rolling it's pretty easy to keep the front wheel on the ground, but you do have to get your weight forward under full power or the front wheel gets very light. You definitely have to ride this bike, not just sit on it.
The power is instantaneous and everywhere. There is no clutch and there is no need to be in the powerband. Just twist the throttle and go. In fact, there really isn't a powerband since electric motors produce maximum power across their entire RPM range. The Drift leaps out of corners like a spring and nothing gets the holeshot like the Drift. The gearing is set low for track use with a top speed of about 44 MPH, but the sprockets are easily changeable to increase the top speed. The range is about 10 miles or about 45 minutes of riding per power pack on high power. When the half power switch is enabled on the bike the range increases to about 15-20 miles or more than an hour of riding at moderate speeds.
The stock tires are lightweight all-purpose tires with lots of small knobs. It's a good tire for general trail riding with the occasional paved section. The knobs are closely spaced and small in order to leave a barely noticeable trail in soft dirt. For track use, full knobby dirt bike tires are available and so are street tires for super motard.
The Drift has many unique safety features. The power pack is removable, but also completely perimeter protected by the frame in a patent pending safety design. In the event of a crash the power pack is retained in the frame and protected from damage. Each power pack is individually fused to protect against shorts. The main power switch has a plastic key that is tied to a wrist strap. The main power is turned completely off as soon as the rider's hand comes off the throttle.
Neal is seeking international interest for distribution of his motorcycle. He can be contacted here.