Re: Extensive article on Rivendell and Grant Petersen

On 9/25/2024 3:26 PM, Wolfgang Strobl wrote:
 <BIG snip>
 

 But I'm quite sure that a simple switch using  a low
power radio signal to communicate with a derallieur that is essentially
reduced to a sealed microcontroller operating a single actuator has a
lot less failure points than a mechanical Rube Goldberg device that has
to fit into a brake lever and has to communicate by a degrading wire
rope running over several corners, merging both control and power into
that single, unreliable channel.

 It depends on how deep you want to go with your root cause failure analysis, or preemptively, your FMEDA.
 (this comparison is ignoring the parallelogram/jockey wheel cage assembly; e.g. the basics mechanics of the derailleur)
 But at the top level they have about the same number of failure points: the points you note above VS a switch, battery, and ECM/derailleur.
 A down-tube system is even simpler - no ratchet mechanism.
 What can go wrong? How easy is it to repair?
 The downtube:
- not much can go wrong, even if it's indexed. You might break a cable. Easy to diagnose, easy and extremely cheap to fix. A failed shift lever isn't likely, at least, in my 40 years of riding, I've never seen a failed downtube shifter that wasn't from abuse.
 The integrated mechanical system - A bit more than the down tube, but still extremely easy to diagnose. If it happens to be the shifter, it's usually a replacement, but sometimes repairable for the Fore mechanically inclined (If the mfr sells part: ratchet, bearing, spring....). The complete assembly might be expensive depending on the model. If you can get parts, relatively cheap.
 The wireless:
- the switch contains a battery, physical switch, microcontroller, and transceiver (latter two likely integrated).
    - The derailleur contains a battery, transceiver, microcontroller, stepper motor, worm gear.
 Lots to go wrong there, none of it repairable.
After replacing batteries fails, It's still not clear. Is it the switch or the derailleur? Considering they're a matched pair, it's irrelevant. You're fucked either way, and need to replace the entire shifter and switch set (unless you're lucky enough to have a firmware bug that can be fixed with a new download).
 If you want to dig deeper into the failure analysis- Is it a mechanical failure (corrosion/breakage)? Firmware bug (how would you tell except to try a new download)? or did the silicon just decide to quit? Lot's more points failure there than a mechanical system.
 So which would you rather have? A system that has easily diagnosable exposed mechanical parts with the likely possibility of a cheap repair, or an expensive system with no replaceable electronic parts?
 There's no right, or wrong answer.
 

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