Trial By Fire Trial By Fire

Trial By Fire

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Wednesday, April 20, 2016

Main photo © BrakeThrough Media

When SRAM set out to develop the world’s first wireless shifting system, it was clear that a system this radically different from existing bicycle drivetrain shifting arrangements would need a number of demanding engineering solutions to be competitive at the highest level and perform on a daily basis for any rider. The challenges faced by SRAM engineers were issues that are not only endemic to cycling, but also to electronic devices in general and wireless electronics in particular. These included resistance to dust, mud, and water ingress, chemical compatibility, vibration, impacts, temperature shock, thermal cycling, signal interference, hacking attempts, and more. Perhaps most challenging of all was developing a process to produce thousands upon thousands of these wireless electronic components that met these demanding criteria. 

In order to give a small glimpse into how this was achieved, we reached out to a few SRAM engineers involved in the development of SRAM RED eTap, – Brian Jordan, Scott McLaughlin, and Kelly McHugh. These engineers worked to develop the shape and functionality of eTap as well as the mechanical and electronic operation. However, in this story we’ll focus on how they ensured through years of rigorous testing that eTap could handle the demands of modern cycling while delivering outstanding ease of use and performance out on the road. 

SRAM Advanced Development Manager, Brian Jordan

Brian Jordan on Shift Logic and Wireless Testing 

From the beginning, Even before SRAM had developed electronic derailleurs or a wireless protocol, the company began testing the shift logic of eTap: Right lever for a harder gear, left lever for an easier gear, both pressed at the same time for a front shift. If this didn’t work, the project couldn’t proceed. The SRAM Advanced Development Team, managed by Brian Jordan, tested this functionality by hotwiring a pair of RED mechanical shifters fitted with electronic switches to a competitor’s derailleurs. Jordan said, “We got racers out on it and the response was amazing. They really liked it. They didn’t want to go back.”  

The next big hurdle for Jordan and his team was developing a robust wireless protocol that came to be known as, AIREA. “This protocol was designed for low latency, high-speed shifting, low power, security, and reliability. That was something that existing protocols didn’t really have. It would have been great to use something existing like ANT+™ or Bluetooth™, but they really didn’t fit our needs,” Jordan said.

Photo © BrakeThrough Media

Throughout the development of the AIREA wireless protocol, the team was committed to ensuring that there would never be a crossed signal or interference created by other wireless electronic groupsets operating in close proximity to each other. So the Advanced Development team created a way to test this. 

Jordan said, “The AIREA system is designed to coexist with all other AIREA components in close proximity and to be unaffected by other wireless devices. Every AIREA system cooperates to interleave messages. We created dozens of little circuit boards with the complete compliment of electronic hardware broadcasting on all 15 available AIREA channels simultaneously, so we could simulate 420 eTap systems all shifting at precisely the same moment, over and over again every second. Then, we made this test rig portable so we could take it to major international bike races and other real and simulated environments with “dirty” wireless airspace to test the robustness of our AIREA communications protocol. We call it the peloton test. All of our wireless shift testing has shown extremely high reliability in this environment.”

SRAM Global Director of Drivetrain Development, Scott McLaughlin

Scott McLaughlin on Lab Testing

Global Director of Drivetrain Development, Scott McLaughlin, and his team were responsible for taking the one-off prototypes made by the Advanced Development group and making sure they could take the abuse dished out by WorldTour riders and to find a way to produce the components on a mass scale. 

“It meant hiring new staff, doing a lot of research, and hiring a lot of consultants that would really get us up to speed extremely quickly on electronic testing protocols.” McLaughlin said. 

Once he had the right people in his corner, McLaughlin’s team produced pilot run after pilot run of eTap components, refining the product further with every run. In the end over 30 pilot runs were made and each one was torture tested in the lab. 

McLaughlin explained, “Vibration is of course very important for electronics. Here we took an automotive standard that is meant to simulate 10 years of hard use on the unsprung portions of an automobile. So that would be, for instance, the ABS sensors down in the wheels that are not cushioned by the suspension. So we use this same vibration testing protocol on our electronic shifting system.”

“Another area was battery security. This is a mechanical test, but we wanted to be absolutely certain that in all but the most extreme crashes, you were going to retain that battery and it’s going to stay with the system and remain functioning. Part of that was making sure that when the battery latches and you hear that little snap, it’s on and it’s working. If you don’t do it properly and you don’t hear that snap, the LED isn’t going to light up and the system isn’t going to shift. There are other systems on the market that you can mis-latch the battery and still get the system to work, but once you go over a bump, you loose your battery.”

Photo © BrakeThrough Media

In addition to withstanding the intense vibration that bicycle components experience, SRAM RED eTap components also had to handle the dust and water found on muddy gravel roads.

Addressing this McLaughlin said, “There are worldwide-accepted standards for dust ingress. We chose to hold SRAM RED eTap to the highest, most stringent standards. It’s the same with water ingress. We use a one-meter column of water and drop our parts into it and let them sit for an hour. One-meter of water is a tremendous amount of pressure. You may not realize it, but that is a very tough test and our parts are passing with flying colors. Another is aggressive power washing. We started off with buying power washers and using them… We eventually made a power washing machine that power washes the components from every conceivable angle.” 

High temperatures and sudden changes in temperature also had to be considered during development testing, so McLaughlin’s team developed machines to test this as well.

McLaughlin said, “We developed something we call a thermal cycling endurance test. We use a climate chamber that creates extremely low and extremely high temperatures and extremely low and extremely high levels of humidity. We cycled the system through these extremes while shifting hundreds of thousands of times over days and even weeks at a time to make sure they could withstand this kind of abuse.” 

“Thermal shock was another test we performed. Thermal shock is different from the thermal cycling endurance test. This would simulate something like having your bike in the back of a car on an extremely hot day sitting there for a few hours at up to 50 degrees C and then you pull it out and hit it with a bucket of cold water to wash it. That is a very tough test for electronics and one that we’ve repeated over and over again.” 

While most of these tests were focused on testing the mechanical and electronic parts within each component, ultimately, wireless performance was the primary concern.

“The wireless portion of the system was the part that we were most concerned about. We wanted it to be completely flawless from the start. In five years and over a million kilometers of testing we can still count on our hands the number of times someone has missed a shift,” McLaughlin said.

SRAM Test Engineer, Kelly McHugh

Kelly McHugh on Field Testing

Even with extensive lab tests, like spraying components in a pressure-washing chamber for hours or days on end, there is no replacement for field testing eTap components in the real world. SRAM Test Engineer, Kelly McHugh was tasked with supervising this testing. McHugh gleaned hundreds of insights from more than 1 million kilometers of eTap test miles and passed those on to McLaughlin’s team for product improvement.

McHugh said, "Field testing identified over 500 issues. These discoveries resulted in changes to component design, manufacturing, assembly processes, and user guides."

"Field testing improves our understanding of how components are used in the real world. This enables us to refine lab tests to better replicate these conditions. Some aspects are tricky to predict or replicate though. We're testing not only for function and durability but also for the whole human/machine interaction. Humans are sensitive to subtle changes, are somewhat unpredictable by nature, and have varying preferences. This is where field testing comes in."  

Photo © BrakeThrough Media

Much of this testing involved working with professional teams. McHugh said, “Testing with pro riders was key. Pros are often more sensitive to subtleties. They ride product longer and harder through tougher conditions than the average user. The bikes see these tough conditions too − daily washing with all kinds of chemicals, high speed bumpy rooftop rides in all weather, and extreme race conditions like Flanders and Paris-Roubaix. We attempt to replicate these in a lab environment but nothing beats the real thing.” 

“During field testing we learned that eTap could take a beating. I saw a post-crash bike where the shifters were all scuffed and askew and the rear triangle of the frame was shattered; yet I pressed the shift paddle and the rear derailleur still made that happy little squirm sound as it shifted with ease. One of the many times where I just thought, huh, no wires… and couldn’t help but smile.” 

The Final SRAM RED eTap Field Test Tally

1,000,000 Kilometers of field test riding

40,000 Hours ridden

3 Pro team test squads (AG2R LA MONDIALE, Axeon Cycling Team, Velocio-SRAM)

2 Amgen Tour of California completions

2 Tour de France completions

1 Tour de France Stage win (2015 Stage 8) 

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