This has to go down as one of the most inventive and ambitious motorcycle designs I’ve seen in nearly 20 years following two-wheeled innovations. That doesn’t mean I’d have the cojones to ride it, especially given its eye-popping steering setup!
The Kejashi tilt-wing motorcycle came about as creator Kent Shillitoe contemplated the reasons why Formula One cars can get around a track so much faster than MotoGP bikes. Sure, they’ve got more rubber on the road for grip, but they also smash that rubber into the tarmac with extraordinary amounts of downforce. Not quite as much as this crazy jigger, but extraordinary nonetheless.
MotoGP bikes run miniature ‘winglets’ these days, of course, but they’re tiny in comparison, and since they’re fixed statically to the bike, they create a problem that F1 cars don’t have to deal with: when you lean a bike right over in a fast corner, those winglets lean at the same time.
The result: when the bike goes beyond 45 degrees, it starts creating more force pushing the bike to the outside of the corner than downforce. Given that the GP aliens are now routinely dragging their shoulders on the ground at lean angles beyond 65 degrees, it’s no wonder those winglets are small.
But what if you could keep the wing level? You’d get all the downforce and nothing pushing you towards the gravel trap. You could run a really big wing, too… Although you’d have to put it on the front of the motorcycle, because that’s where you’d want the extra grip.
Kent Shillitoe
Shillitoe, a South Australian motorcycle mechanic, clearly isn’t a man to just sit and wonder, because he went and built the thing to see if it would work. “Tony Foale wrote a book on motorcycle handling and dynamics,” he tells me over a video chat from the bike dealership where he works in South Australia. “He thought about this, but yeah, nobody’s actually been able to create a tilting wing that works. I’m always thinking while I’m working on bikes, and just came up with the idea and thought, well, if no-one’s tried it, it’s up to me to give it a go!”
So he pulled the engine and front end out of his little Honda CB125 commuter bike, plonked in a 50-horseower 2-stroke dirtbike engine (complete with his own custom-built ‘bellystinger’ expansion chamber), and then set about creating a truly mind-boggling steering and downforce system, hanging off the front of the bike in a large steel cage.
The offset, trailing steering system
It takes trust and faith to ride a motorcycle round a corner. Part of that trust and faith for me has always been based on the idea that even when the steering angle changes, the front and rear wheels will still be in line with one another.
Kent Shillitoe
Not on this thing. Shillitoe’s Kejashi system, which sounds Japanese but is just a nod do his own name KEnt JAmes SHIllitoe, disconnects the forks and handlebars from the normal steering head, and mounts them on a trailing arm coming back from a point well out in front of the fairing. As a result, when you push the left bar to initiate a left turn, the entire steering column, wheel included, swings more than a foot out to the right of the bike’s center line.
That means you don’t have to lean it as far, for one thing. “Offsetting the weight toward the inside of the turn, that’s what the GP guys are trying to do with their bodies,” says Shillitoe. “But moving the wheel toward the outside of the turn naturally offsets the weight of the bike and the rider toward the inside, and reduces the amount of lean angle required. It’s a bit like a Can-Am Spyder – on those things, if you corner them hard enough you can pick up the inside wheel, and then it’s kind of just acting like my design.”
It also gives you a new party trick. “I sneakily rode it home from work once,” laughs Shillitoe, “through the country, I took the back dirt roads. And there was a bit of a boulder on the road, and without thinking, I’ve just gone ‘whoop’ and it’s gone between the wheels. I was like, ‘what the…'”
Kent Shillitoe
So how does it ride? “Yeah, it felt all kinds of wrong to begin with,” he grins. “But once you get used to it and trust it – and not look at it – it starts feeling very natural. It steers sort of like a normal motorcycle, but it feels disconnected to begin with. But it’s stable; you can take your hands off and it just trails along, no worries!”
“If you ride the rear brake, it wants to fall down even more into the turn,” he continues, “and you can roll on the throttle and it’ll start to pick back up a little bit. It feels all kinds of weird, but it works. I don’t know how!”
The tilting wing
That remarkable steering head also tilts the wing arrangement, which pokes up rather inconveniently in front of the rider’s face if they’re not tucked down. “Ah, it’s sort of like a Formula One car with the HALO,” says Shillitoe, “it’s just got that single beam in front of your eyes when you’re going dead straight. The main wings are up above your eyesight. And when you’re cornering, you’ve got totally clear vision.”
Kent Shillitoe’s tilt-wing motorcycle steering system
How’s the weight? “Well, it turned out not too bad, because I stripped a lot of the road-going gear off,” he tells me. “The standard weight of the bike is 128 kg (282 lb), and even though this prototype’s built from steel, the whole bike still only weighs 130 kg (287 lb).”
There’s a notable amount of drag approaching the bike’s top speed of around 150 km/h (~93 mph), but the downforce is also apparent. “When I get up to that speed,” says Shillitoe, “you can see the front forks compressing a little bit. According to my calculations, at 150 km/h, there should be about 60 kg (132 lb) of downforce. You do notice a bit of drag… In the future, I’d love to run something like the DRS system in Formula One, and just tilt it up to reduce drag.”
And what about the cornering? Well, a little hard to tell at this stage, since he’s mainly banging it around back-country dirt roads where downforce isn’t going to make a huge difference. But the feel from between the wheels is encouraging, he tells me. “It’s totally stable, and you just swing the front out, it leans in, the wing tilts… And then it feels like it just pushes you around the corner like nothing else.”
Check out a video:
Crazy New 2 Stroke Motorcycle Design
Where to from here?
Shillitoe wants to take the Kejashi bike to the track and experiment with higher-speed cornering in an environment where grip is paramount, but he’s waiting until the cold South Australian winter abates. Ultimately, this design is wildly inappropriate for the street, and it won’t be any good in head-to-head racing, either. “It’s more designed for one-lap time attack type racing or hill climb events,” says Shillitoe.
He’d love to see somebody with better manufacturing gear at their disposal take the idea up a notch or two from his 12-month shed-project prototype. A super-rigid, lightweight carbon frame could work really nicely, he reckons, since the offsettable front wheel could potentially act like a secondary suspension system when the bike’s leaned right over.
“I remember when Ducati went to their carbon frame, and it was just way too stiff,” he says. “I think the Kejashi system could go to that carbon frame because it’s got that lateral bump absorption built in… Look, I’ve got dreams that it’ll go somewhere, but I don’t know! I can’t hype it up too much ’til I’ve actually proven it properly. But I’ve ridden it plenty hard on the road, it’s capable.”
Kent Shillitoe
I’ve asked Kent to promise he’ll tell me when he takes this thing to the racetrack, because I’d love to see it in action. It’s such an out-there idea and such an audacious approach that I’d love to see it work. The closest thing I’ve ever seen on the tarmac would be the Zenvo TSR-S hypercar, which takes active aeros to even greater extremes, including tilting its rear wing to push the back of the car into the corner.
I guess if the whole downforce thing doesn’t pan out, Shillitoe can always turn that wing upside down, see if the Kejashi flies, and ask Guinness if it’ll qualify as the world’s fastest hang glider? Either way, godspeed, you magnificent bastard, you’re a braver man than I!
Check out the gallery for more images of this unique bike, and some diagrams Kent’s put together showing some of the physics concepts behind the design.
Kent Shillitoe
Source: Kent Shillitoe
