Limits system, which will launch this week on Indiegogo, calculates power output from a device mounted between the pedal and crank arm

The world of power meters will be shaken up this week when an inventor seeks crowdfunding for a novel system called Limits, which promises breakthroughs in price, simplicity and technology.

Inventor Ken Norton, technologist and keen cyclist, says the first models will cost just £260 (US$385), which would make this one of the cheapest power meters available.

The meter is unusual in calculating the rider’s power at the pedal spindle. The small cylinder fits between the crank and the pedal; it screws into the crank and has a threaded hole to accept the spindle.

>>> Garmin Vector power meters unveiled

Limits can be swapped from bike to bike with a 2mm Allen key and will fit all standard 9/16th x 20tpi threaded pedals. Norton says it weighs 47g, is accurate to ±2 per cent and the cro-moly housing is waterproof to a depth of 1.3m.

The first development of Limits is left-pedal only; a two-pedal system is in the pipeline

The first development of Limits is left-pedal only; a two-pedal system is in the pipeline

Like most power meters, it’s a strain gauge. In fact, the Limits cylinder contains four strain gauges which measure the electrical resistance in the spindle as it changes in response to the force applied by the rider.

The rider’s force multiplied by the length of the crank is a measure of the torque. The device can be programmed wirelessly for cranks from 165-180mm in length in 2.5mm increments.

>>> Powertap unveils pedal and chainring-based power meters

The Limits cylinder also contains an inclinometer, a sensor that detects the angle of the crank. This means it can calculate cadence without needing any other components.

The unit multiplies the torque data by the cadence to produce the rider’s power output data. The data is transmitted to a bike computer using the ANT+ wireless protocol or to a smartphone via Bluetooth.

Data is stored in the Limits unit so performance isn’t disrupted if there’s a break in the wireless connection, and its replaceable coin cell battery is said to last for one year.

>>> Power meters: everything you need to know

The first production model will fit only the left pedal, and the total power output into both pedals will be extrapolated from that. Future versions will independently measure power from each leg and report total power as well as the balance between right and left leg, says Norton.

He came up with the new solution when working out how to make an e-bike motor’s output change according to the rider’s pedal power. Then he realised it could be used for human-powered bikes too.

Now he’s going to fund production by crowdsourcing support, with a campaign going live on Indiegogo here on Monday April 20. The company is also running a half-price campaign via its website for people who sign up by April 19.

  • That is really wonderful and many people would totally going to love that little thing. They could also attain some specific ideas on how could they improve that little thing to make it more useful.

  • PhotoRestoration

    Not to mention hip rotation angles, knee angles etc….

  • Chris Hughes

    Looks good, but won’t this mean the pedal is further out than usual, requiring cleat adjustment?

  • BikeRideMike

    To say so much emphasis is put on positioning these days, especially cleat position, I wouldn’t entertain this as suddenly my left left is out by half an inch.

  • Richard Braginton

    slightly worried about the amount this moves the pedals out wards

  • KarlRoche

    Really clever and a good price but the positioning is a problem.

  • Mike

    Surely this will mean pushing the pedal out by the size of the device. As a cyclist who has struggled with knee pain i can see this being a problem when setting up the bike.

  • harrydevlin

    Not true that it’s the first meter to calculate power at the spindle, though perhaps the first one to do so using a strain gauge.

  • Ed

    Does it mean that the pedal is moved further away from the crank?

  • Cycling Science

    It looks like the special half price offer has been extended by a day to 20 April.

  • Elton

    Where is a link to a website? Google search turns up nothing. Just this report…

  • Dan

    you misunderstood what they are saying, its first to fit between spindle and crank not first pedal based system.

  • Jordan

    That is how vector works, all the guages are inside of the spindle.They just built a knockoff look pedal around that spindle.

  • Dan

    Why is it false?

  • RG

    “It’s the first meter that calculates the rider’s power at the pedal spindle.” The statement is totally false. Sounds like you don’t know much about the power meter market.