Re: Extensive article on Rivendell and Grant Petersen

On 9/25/2024 5:00 PM, Zen Cycle wrote:

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.
>

>
>

>
>

 There is an alternate; fixed gear.