Linearc's geometric bicycle single-speed prototype, 4/07

We're developing a reciprocating-lever propulsion system for bicycles, handcycles, wheelchairs, whatever you want to move. No pedal 'dead spot,' much easier on the knees, variable pedal stroke lets you power through turns and among deep obstacles. A continuously-variable-ratio version is in development, but the single-speed is very slick to ride. The design is protected by U.S. patent application, but anyone may license it for one-off or volume production. For more info see www.geometricbikes.com

Category:

Autos & Vehicles

Tags:

• Linearc
• geometric
• bike
• bicycle
• CVT
• HPV

[Linearc]

Been using sprag clutches, BB-30s, and they work great but knew from the beginning they're undersized for the torque input. Will be experimenting with separate, smaller bearings and larger sprag sets, with ceramic races to save the weight.

[Linearc]

Been using sprag clutches, BB-30s, and they work great but knew from the beginning they're undersized for the torque input. Will be experimenting with separate, smaller bearings and larger sprag sets, with ceramic races to save weight.

[angliru23]

how on earth does that work?

[Linearc]

Really simply, actually. A double-sided, mirror-image freewheel (a flip-flop hub works OK with LH & RH freewheels) and the cable/chain combo connecting the two pedal levers saws back and forth. Feels more like skating than cycling, as at any speed, you have a choice of cadence/stroke combinations. For climbing, shorter strokes/higher cadence helps.

[IsaacBickerstaffEsq]

Yeah, that's what I hacked up for an HPV back in the 70s. I did it so I could put the pedals on a sliding rack to keep the frontal area minimal and a full floor under the rider.

[Linearc]

One innovation (I think) is the carbon/thermoplastic leaf springs that return the pedal levers to center, rather than to one extreme of their travel. I've read about other lever bikes on which, if your foot slipped off a pedal, it could give you a very painful thwack. Unlike metal springs, it doesn't seem to unduly stress the carbon ones to flex in both directions. On an HPV, using this hub as an intermediate jackshaft, you could easily add whatever kind of gearing you like.

[pisoiorfan]

So how is this transmission going after three years? How do the freewheel clutches behave? I ask this since they are subject to alot more cycles than in a normal hub.

[pisoiorfan]

So how is this transmission going? How do the freewheel clutches behave? I ask this since they are subject to alot more cycles than in a normal hub.

[vivoslibertos]

It doesn't cycling but more like stepping. Pretty interesting and cool.

[IsaacBickerstaffEsq]

"Competitive advantages?"

None. As has been well understood for over 100 years. You canna change the laws of physics. The advantage is to be found in specific cases (like my HPV) where range of motion is restricted for some reason.

Assuming an equally matched opponent I'd kill that thing up Smuggler's Notch or Equinox - on a fixed gear.

In fact I'd be rather interested to see if it could make it up at all without coming to a dead stop.

[IsaacBickerstaffEsq]

Return spring? Oh my.

". . .there's no longer any pedal 'dead spot'!"

Nonsense. As is inherent in all linear systems there are dead spots so extreme that they are clearly visible in your video, where the motion of the feet is completely and utterly, well; dead. Motionless. Both at the same time. No drive at all.

[EmeriLizzie]

I actually had a bike similar to this when I was a teenager. I can't remember where/when my mother bought it for me, but I remember I was the talk of the neighborhood! Now no-one believes me when I tell them I had a bike that the pedals went up and down instead of around (rotary). I am actually trying to find one as it was easier on my knees then a conventional bike.