Re: Dual-Chain drive train

Catrike Ryder <Soloman@old.bikers.org> wrote:

On Sun, 29 Dec 2024 12:04:34 -0600, AMuzi <am@yellowjersey.org> wrote:
 

On 12/29/2024 9:39 AM, bp@www.zefox.net wrote:

Zen Cycle <funkmaster@hotmail.com> wrote:

https://www.bikeradar.com/news/buffalo-utility-s2
 
Made for developing countries to allow for easier transportation on
cargo bikes, without the exposure and complexity of an external
derailleur or hand-operated shifting (for an internally geared hub). It
was developed and patented with the help of SRAM.

 
Are derailleurs really that bad? A whole new bike for the sake of a granny
gear seems slightly extreme. Internal pawls at small radius are going to
be more stressed  and harder to build than a rear sprocket of larger radius.
 
I'll admit that the narrower flange of a multispeed rear hub impairs the
lateral strength of the rear wheel, but a hub with flanges spaced to leave
room for a two-cog stack would be vastly stronger. What is the "exposure"
alluded to above?
 
Thanks for reading,
 
bob prohaska

 
 

" Are derailleurs really that bad?"

 
Yes.
 
They last a long while for many competitive events (except
criteriums where concrete abrades right through them).
Derailleurs are the overwhelming choice for tourists, even
of great distances, on roads whether paved or not.
Derailleurs are also usually suitable to commuters although
in salted areas that vulnerability is a factor.  Offroad is
sorta sketchy in that failures are regular but alternates
have some serious tradeoffs so the derailleurs just get bent
back or replaced.
 
[note most offroad is recreation, by riders who can well
afford replacement gear. Among the MTB riders, "I broke that
too!" is not always a complaint, it's often a boast.]
 
Extreme use, where unsupported durability is critical, would
lead one to a not-derailleur design of some type.

 
I've long marvelled at the rear deraileur mechanisms and how well they
function when properly set up. I've never had one fail, but I did
replace one a few years back because the idler sprokets were worn
down. Now, granted, I don't go offroad, and I can see potenial
problems there.

I’ve had 4 failures over 40ish years one from rock strike, as a teen with a
new MTB early 90’s managed to to wrap the rear mech around the cassette
with both the gravel and MTB in filthy conditions ie muddy with lots of
vegetation matter, both a few years ago COVID ish times.

And this year the old ish and probably quite cheap rear mech on the commute
bike spring snapped separating from ie so the cage and parallelogram were
separated made for an interesting commute home!

That rear mech was an upgrade? In that the original had become sluggish
even with new cables etc. so a cheap rear mech ie £20 ish solved that, the
gravel bike had a upgrade last winter with a GRX rear mech as that has what
shimano call a clutch ie keeps the chain off the chainstay etc.

I believe that SRAM UDH

<https://www.sram.com/en/sram/mountain/products/udh> is supposed to be more
robust and some of the more modern rear mech’s are chunky boys and
apparently are more durable.

I only have Cues though I have no UDH compatible frame, nor likely to any
time soon, nor do I tend to bash rear mech’s on rocks!

 
--
C'est bon
Soloman
 

Roger Merriman