"Laser Spoke has developed a unique optical power monitoring system for cyclists. Easily installed on the rear hub, Laser Spoke measures deformation of the wheel under applied torque using a system of lasers and optical devices. By detecting deformation in the final element of driving system Laser Spoke records actual power output showing an integrated performance of the rider and the bike."

Interesting. Makes one wonder how they'd calibrate? Every wheel is different and they can't control that. Such a laser system (interferometer probably, yeah?) can pretty easily measure deformation and by proxy measure relative power, but easily/accurately calibrating for watts of power output will be a challenge they'd need to overcome.

I guess something similar to Qalvin calibration. Hang a weight off the crank with the bike fixed in a trainer or something. And assume a linear response across the range of torques. Or have multiple weights?

Things I wonder about:

1) Doesn't hard cornering also cause relative twist between hub and frame?

2) Mud, dirt, water. This doesn't sound like a CX or MTB sensor. Laser lens and retro-reflector are down low in the back of the bike. Not ideal from a keeping-it-clean perspective.

Interesting. Making the big assumption that this will actually work properly (in all conditions), and can be calibrated properly...you might have yourself a power meter that can truly work across any bike (commuter, track, road, tri, mtn, cx, etc), using almost any wheel (race wheels, training wheels). Regardless of your pedal preferences, bottom bracket, crank length, or BCD preferences.

Count me as extremely skeptical, but also extremely hopeful at this point.

They'd need to hang the cal. weight on the wheel itself. With a weight on the crank they'd need to input the crank length, the ring size, sprocket size (or probably number of teeth) and assume that the chain isn't stretching. Maybe that's what they are doing? And maybe multipoint calibration (for an accurate curve) is accomplished by stepping through the gears and letting that same weight on the crank apply different force at the rear hub?

Agreed. If this works this will be da bomb. I'd be getting one. If it works. It will no doubt measure what it's designed to measure wheel deformation. However that's just a proxy value for what we really want (power output). How well it's calibrated so the watts are accurate, and how well it holds the calibration, will make or break this product.

1) Doesn't hard cornering also cause relative twist between hub and frame?
2) Mud, dirt, water. This doesn't sound like a CX or MTB sensor. Laser lens and retro-reflector are down low in the back of the bike. Not ideal from a keeping-it-clean perspective.

1) I don't think cornering would be an issue. This will be measuring the relative rotation between the hub and rim which will only occur if there is torque being applied.

2) Mud, water and dirt could certainly mess it up.

This design has been kicking around for awhile. I didn't click on the link so I'm not sure what the current configuration is, but previously it was going to be only built and calibrated wheels. Obviously that isn't ideal, but neither is forcing the buyer to calibrate, so having both seems like the best way to go.

One aspect I'm skeptical about is how consistent the calibration will be. A wheel is a discontinuous assembly of parts that will have some degree of friction and relative motion. It isn't an ideal place to measure strain and predict stress.

Anyway, it's an intriguing concept, and may find a place as a low budget PM option.

Hello rruff and All,


Developer discussion here on Wattage: https://groups.google.com/.../wattage/94xvrvTs71M

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Cheers, Neal

+1 mph Faster