German power meter company builds instrumentation by hand
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SRM power meters use spider-mounted strain gages that are attached with copper wires to a circuit board below(Image credit: Ben Delaney / Future Publishing)
Once assembled, each SRM meter is calibrated once both rings with a 20.164kg weight(Image credit: Ben Delaney / Future Publishing)
A completed spider ready to be installed onto a crank(Image credit: Ben Delaney / Future Publishing)
FSA Gossamer are among the least expensive SRM cranksets, along with Specialized S-Works and Cannondale SL Hollowgram(Image credit: Ben Delaney / Future Publishing)
Cannondale was the first company to offer SRM cranks as part of a stock bike(Image credit: Ben Delaney / Future Publishing)
With each type of crank requiring its own spider, O-ring, bolts and more, the small parts bins are densely packed (Image credit: Ben Delaney / Future Publishing)
Copper wires run from each strain gage to the circuit board, and the excess wire is trimmed off(Image credit: Ben Delaney / Future Publishing)
After the circuit board is attached to the spider, the electronic connections from board to strain gages is made by hand(Image credit: Ben Delaney / Future Publishing)
The circuit boards for SRM meters are made in Germany, then affixed to the spider with silicone, which allows them to 'float' on the spider and not add or reduce torque(Image credit: Ben Delaney / Future Publishing)
This work station is dedicated solely for pro team assembly. At the left sit Dura-Ace 9000 spiders(Image credit: Ben Delaney / Future Publishing)
The new four-bolt Shimano Dura-Ace crank design allows for a biggger SRM battery and thus longer life (up to a claimed 3,000 hours), but it also makes for more challenging gage-to-circuit-board connections(Image credit: Ben Delaney / Future Publishing)
SRM staffers may or may not have fun during product testing. But hey, somebody has got to do it(Image credit: Ben Delaney / Future Publishing)
A new project for SRM's Colorado Springs office is the 1x MTB unit, which features a USB recharge port(Image credit: Ben Delaney / Future Publishing)
While new models go out the door every day, older models are still in use, too(Image credit: Ben Delaney / Future Publishing)
Here is a 2.5-year-old unit back in for an overhaul(Image credit: Ben Delaney / Future Publishing)
The Power Control 7 is ANT+, but it captures data four times a second as opposed to the standard once per second for most ANT+ head units(Image credit: Ben Delaney / Future Publishing)
Thousands of Power Control head units bear Ward's initials(Image credit: Ben Delaney / Future Publishing)
Stephanie Ward handles new assembly and used refurbishment of Power Control units(Image credit: Ben Delaney / Future Publishing)
Like the Power Meters, the Power Control head units are intended to be used for many years, and SRM refurbishing many of them every few years(Image credit: Ben Delaney / Future Publishing)
An SRM measures power by measuring torque loads on the spider(Image credit: Ben Delaney / Future Publishing)
Once in the fixture, a technician tightens the stack down before placing in the oven(Image credit: Ben Delaney / Future Publishing)
SRM and Schoberer have long histories with pro and national teams. Schoberer worked with the US Olympic team for Project 96, and was given this bike as a thank you(Image credit: Ben Delaney / Future Publishing)
Uli Schoberer founded the company in 1986 as an engineer and amateur cyclist looking to scientifically quantify his training(Image credit: Ben Delaney / Future Publishing)
SRM now uses the wireless ANT+ protocol, and so can be used in conjunction with a Garmin or another head unit, but the company (and most pro riders) strongly suggest the SRM PowerControl 7 head unit for better accuracy(Image credit: Ben Delaney / Future Publishing)
What began as a single crank in the 1990s has expanded to a deep range of road, mountain and track cranks(Image credit: Ben Delaney / Future Publishing)
Beyond the simple saddle adjustments, the SRM ergometer is adjustable for crank length, too, from 150mm to 190mm(Image credit: Ben Delaney / Future Publishing)
The SRM ergometer can be used in a variety of ways in a lab setting, such as fixing the power and allowing the rider to choose the cadence, or in an isokinetic setting that does the opposite(Image credit: Ben Delaney / Future Publishing)
SRM prides itself on its lab-quality equipment. Here, Mike Hall stands next to a lab system that includes an ergometer, software and hardware plus storage room for a metabolic cart suite(Image credit: Ben Delaney / Future Publishing)
New for SRM is a Dura-Ace 9000 crank featuring a right arm Shimano produces just for SRM(Image credit: Ben Delaney / Future Publishing)
At SRM's Colorado Springs facility, the company illustrates its strong connection to the pro peloton(Image credit: Ben Delaney / Future Publishing)
World time trial champion Tony Martin was an SRM user (his team races with Quarq now)(Image credit: Ben Delaney / Future Publishing)
SRM has fixtures for every type of spider(Image credit: Ben Delaney / Future Publishing)
Under a specified amount of presure in a mold, the strain gage bonding is cured(Image credit: Ben Delaney / Future Publishing)
Some power meters get 8 strain gages; others 16(Image credit: Ben Delaney / Future Publishing)
In Colorado and in Germany, strain gages are attached to the spiders by hand(Image credit: Ben Delaney / Future Publishing)
The heart of the SRM power meter is the spider, onto which the strain gages (shown here in four pairs) are mounted(Image credit: Ben Delaney / Future Publishing)
Besides being "on his bike, 8 hours a day," a certain Lance Armstrong was a longtime SRM user(Image credit: Ben Delaney / Future Publishing)
Amber Neben is one of many riders to earn a rainbow jersey on an SRM(Image credit: Ben Delaney / Future Publishing)
Many pro riders send in tokens of their thanks. Shown here are former T-Mobile and US Olympic riders Dede Barry and Kristin Armstrong(Image credit: Ben Delaney / Future Publishing)
After road, two-ring mountain and BMX cranks, SRM is now further exploring 1x MTB designs(Image credit: Ben Delaney / Future Publishing)
Back in the mid-80s, a young Uli Schoberer created a cycling power meter so he could better measure his training efforts as an amateur rider. Fast forward to 2013, and SRM is an international company boasting a dominant presence among professional cyclists. SRM established an American office in Colorado Springs, Colorado, which first began producing mountain bike power meters, but now also assembles about half of the company's product, according to sales and marketing director Mike Hall. Hall recently gave BikeRadar a tour of the Colorado Springs facility.
Below is an illustrated overview of the assembly process. For more details, check out the photo gallery at right.
The heart of the SRM system is a system of strain gages that is mounted on a CNC-machined aluminum spider. The spiders are made both in Jülich, Germany and in Colorado Springs. In Colorado, SRM moves through about 2,500 units a year.
In Germany and in Colorado, pairs of strain gages are hand laid on the spider, then compressed by custom gigs at a set pressure to be cured inside an oven. Most units get 16 gages, but a few ( FSA Gossamer 130 BCD, FSA K-Force 130 BCD, Rotor 3D 130 BCD, and 3D+ 130 BCD) get eight. "Basically on those models, the chassis provides enough stiffness to get the same accurate measurement as the lighter weight chassis with 110 BCDs," Hall said.
Next, German-made circuit boards are mounted onto the spider with silicone, which allows the boards to 'float' on the spider and not add or reduce torque on the system. All this work is done by hand, again either in Germany or Colorado, to ensure precision, Hall said. While outsourcing to Asia could reduce labor costs and perhaps the end unit cost — which start at $2,045/€1,952 for road and $1,799/€1,892 for mountain — SRM prefers to keep production in-house.
Once affixed to the spider, the circuit boards are connected to the strain gages via copper wire, the excess of which is carefully trimmed off.
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Once inspected, the spiders are then ready to be mounted onto cranks and have chain rings attached.
SRM calibrates its meters on both the large and the small ring with two weights that are themselves carefully measured at a nearby university. The cranks are checked radially, laterally, and for trueness.
SRM meters have internal batteries, which last for between 1,600 and a claimed 3,000 hours. Then they have to be sent back to be recharged, at which time they are overhauled and inspected.
The PowerControl head units are similarly built to last, with refurbishing of old units a standard practice.
Mountain bike power meters are continuing to evolve, and SRM's latest generation features a USB recharge port.
The vast majority of power meters are still road units, and the Shimano Dura-Ace 9000 11-speed version is among the latest from SRM. Shimano's new four-arm spider design gave SRM engineers more room to work with, and they decided to capitalize with a larger battery for longer (a claimed 3,000 hours) life before the unit has to be sent back for an overhaul. Shimano makes a custom Dura-Ace-level crank for this product, but declined to add the Dura-Ace moniker to a product that isn't 100-percent Shimano.
SRM loaned BikeRadar a test power meter for a review, which you can look for soon along with a general comparison of many competitors including Stages, PowerTap, Pioneer, and Garmin Vector. In the meantime, check out the photo gallery at above right for more detail on SRM's Colorado Springs facility.
