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Rotor Launches Less-Expensive INpower Power Meter

New power meter from Rotor is protected inside axle and runs on an AA battery

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Mountain bikers will particularly like that most of the system is protected from the elements.

Rotor today announced a new platform for its crank-based power meters. The INpower Power Meter’s parts are almost all located inside the crank axle. A discrete antenna, about one centimeter tall, and a battery door are the only visual cues.

Hiding two strain gauges, the battery and the electronics inside the axle centers the weight of the system, and provides a measure of protection, which mountain, ’cross, and gravel riders will appreciate. Rotor chose the common AA battery for INpower, heavier than the 2032 coin cells found in most other power meters. Rotor says it chose AA because that size is easy to find at any time. Claimed battery life is 300 hours of ride time—which is a lot of riding.

Like a Stages or Garmin Vector S, INpower does not measure both legs; rather it doubles the left leg power output. Single-sided power allows Rotor to achieve a lower price than it would with a dual-sided system: INpower starts at $939 for a complete crankset (no rings); Rotor’s Power dual sided power meter starts at $1,594 (no rings). Rotor’s existing single-sided power meter, the Power LT, will be phased out.

One very interesting feature of INpower is that the crank’s rotational speed is constantly monitored. Most crank-based power meters sample rotational speed a few times per crank revolution, 1 to 12 times per revolution depending on platform. From these samples, an average rotational speed is calculated. But this calculation assumes a constant rotational speed until the next sample is taken.

But, says Rotor’s research specialist Christie O’Hara, cyclists never pedal at a constant rotational speed. And when oval rings are used, like Rotor’s Q-Rings, the rotational speed varies even more—if you’re using oval rings with any crank-based power meter except INpower, you’re power data is probably off by 2 to 5%, says O’Hara. Constant rotational speed monitoring provides accurate power measurement with oval rings.

The constant rotational measurement allowed Rotor to create a pair of new metrics dubbed Torque 360 and Optimal Chainring Angle (OCA).

Torque 360 allows Rotor’s new Windows software to display a graph of the rider’s complete pedal stroke, showing where in the pedal stroke the maximum power is generated, and illustrating the dead spots. This allows riders to work on their pedaling efficiency, smoothing out their pedal stroke and reducing negative torque, or how much your rising leg is working against your driving leg.

As for OCA, Rotor’s Q-Rings have several mounting options to tune where in the pedal stroke the fat part of the oval is located. The OCA metric displays the crank angle at which the rider applies maximum force, which helps riders with Q-Rings find their optimal mounting position.

OCA and Torque 360 are ANT+ profiles: Any head unit that implements the profiles can display these new metrics.

INpower is an ANT+ only system: there’s no Bluetooth, and no USB plug so firmware updates must be pushed over the air from a computer or smartphone.

I had an opportunity to ride INpower in the Sequel Demonstration Forest. After a time- and leg-saving lift by Shuttle Smith Adventures we rode Buzzards, Cusacks, Ridge, sections one through five of the Flow trail and took Hihn’s Mill out. I do like riding with power on my mountain bike (I use a Stages power meter at home), so I was looking forward to trying this new option. Unfortunately, my unit quit transmitting on two separate occasions. Rotor sent me home with a different unit to ride long term, so I’ll know by next week if I just happened to grab a bad apple.

INpower cranks use Rotor’s UBB system to navigate the sea of bottom bracket standards. The cranks use an extra long (102mm in the mountain version), 30mm diameter axle that can be adapted to almost any current standard with Rotor’s UBB bottom bracket cups. The one significant exception: BB90 or BB95, which happen to be the standards Trek uses.

Rotor will offer INpower cranksets in both mountain and road platforms. Rotor expects the products to begin shipping from Spain next week and land in US shops in mid-May.

For the road, INpower is offered in Rotor’s 3D 30, 3D+, and aerodynamic Flow cranksets. Prices and claimed weights are:

  • Flow with 110 or 130mm MAS spider: $1,139, 597 grams w/110 spider
  • 3D+ with 110 or 130mm spider: $1,079, 525 grams w/110 spider
  • 3D with 110mm spider: $959, 562 grams.

For the mountain Rotor offers INpower for its top of the line CNC machined Rex 1 crank arms and heavier, lower cost forged and machined Rex 2 arms. Rotor sells cranks a la carte: rings and bottom brackets are sold separately. Rex 1 is $1,079 and 562 grams (claimed) with a dual-diameter 110/60mm spider; with a 76mm BCD spider it is $1,019 and 549 grams. Rex 2 is $959 and 579 grams with a dual-diameter 110/60mm spider; with a 76mm BCD spider it is $939 and 566 grams.

For current owners of the above cranks, Rotor will offer the left arm only. Prices are: Flow, $869; 3D +, $839; 3D 30, $779; Rex 1, $839; Rex 2, $779.

With the launch of INpower, Rotor is launching a free Windows application (download from inpower.rotorbike.com) that reads and displays all the information the crank is sending and provides all the data even the most intense triathlete would ever want, including the new Torque 360 metric. An Android app will also be offered. Apple fans will have to wait: Rotor said Mac and iOS apps are in the works, but offered no timeline.

This article originally appeared on www.bicycling.com.

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