If you're looking for visual interest in a custom motorcycle, the RK Concepts Bearing Cycle offers a lot of it. I noticed this bike for sale and can't remember seeing it before, though it's not the type of build I usually follow so that's not surprising, but it's kinda neat. The entire center frame of the bike is a large diameter functional ball bearing and the suspension is based on the movement of the bearing, controlled by a single shock mounted horizontally on top. Hmm ...
The engine comes from a Honda CR500. The wheels themselves have large diameter bearings in the center with perimeter disk brakes. The front suspension seems to be mounted to the outside bearing race and the rear is mounted to the inside race.
Does the suspension travel in an arc? Does the wheelbase change as it moves? Does ride height change? I didn't find a video anywhere to show it in action so your guess is as good as mine unless you've seen it and can shed some light.
The bike is certainly not practical, the seat I'm not even going to mention, but you have to give the builder, Rafik Kaissi, high marks for originality. Interesting.
Link: Bearing Cycle on eBay
Clive says
Im sorry but that looks like an ass slicing nipple pincher.
But yeah id like to know what happens when it moves.
Paul Crowe says
As I said, the human machine interface needs work, but I think it’s fascinating, in a moving mechanical sort of way. Better yet, since you wouldn’t go very far on this anyway, put batteries in some kind of circular arrangement in the center and replace those huge wheel bearing sections with electric motors and you have a custom electric motorcycle.
Clive says
A two wheel drive one at that!
todd says
The steering head and front forks don’t look up to handling the torsional and bending loads but is really interesting.
They could have used a bed of nails for a seat.
Sebastian Wiers says
“your guess is as good as mine unless you’ve seen it and can shed some light.”
I don’t think it takes any special analysis to figure out. As described, its equivalent to a bike that has a rigid fork and an engine mounted swingarm which pivots at the center of the large bearing. AFAIK, that isn’t a combination that would result in good bump compliance- the unsprung / sprung mass ratio is VERY high (1-1, or even worse on one end).
Paul Crowe says
In my mind I was imagining more suspension travel than this probably has, but within the limits of movement that likely apply, the result isn’t as radical as it first appears. Calculations of loads and forces might be the real issue as you and todd both mention.
joe hacney says
thanks kneeslider for all the fun stuff you send me.please dont stop,i have a kz1300 that i am going to chop.maybe you could send me some concepts thanks.joe hackney l a recording artist
blackbird says
I see a big pocket watch looking thing and a wasted CR500 motor.
loggerjack says
I see a cr500 engine that will never run right without a pipe, if it will run at all !
Lostboy says
I was thinking the same thing. Cool design on the bike tho.
Mircea Andrei Ghinea says
cool concept!!
basically the entire back wheel and what’s inside of the big round circle act as ONE PIECE. one piece which has the pivot point in the middle of the big circle. is like having a biiig swing arm that starts from the axis of the back wheel til the middle of the big circle; and on that big swing arm is also fixed the engine, the fuel tank and other smaller things; all acting as one piece.
very interesting! 😉
regards from Romania,
Mircea