Possibly silly idea: urban bike

Roger Burton West said:

So what I'd like to do is combine that with a multi-chainring front
derailleur system. Then I can sit on the middle ring while going around
town, shift down for uphills, and shift up for going fast out of town.

However, a derailleur system means jockey wheels so that the chain
length can vary, and I'm not quite sure where they'd go.

Where they'd normally go: close to the back, which is what's done when
using a tensioner for hubs because either the dropouts are wrong/there's
no eccentric BB and/or rear suspension changes the change length when it
deflects anyway.

http://kinetics.org.uk/assets/images/Infiniti_med.jpg is an example of
an 8 speed hub bike with a tensioner. But it is a shame to do this sort
of thing to a bike that works better without that.

Quoted message said:

I believe some of the Bromptons have a multiple gear system like this
(with a 3-speed hub)

Up to a point: the derailleur in the Brom 6 is actually part of the
tensioner/hub drive system giving you a choice of two sprockets to drive
the hub, not separate chainwheels at the front.

if you put a tensioner on you lose some of the advantages you already
have, if you put a derailleur on you lose even more, so while it's
possible you'll be throwing out the baby with the bathwater to some
extent. A more expensive by vastly neater solution would be to put on a
Schlumpf [High]Speed or Mountain Drive, see
http://kinetics.org.uk/html/mountain_drive.shtml for some details.

You keep your gears nicely enclosed so less maintenance, you keep a
straight chainline so there's less wear, you have fewer exposed bits to
get damaged or covered in muck, you maintain the ability to switch
between your whole range of gears at a standstill and, if this sort of
thing bothers you, you maintain a simpler aesthetic. And you'll
probably end up with a bigger effective range of gears, at least with
High Speed or Mountain drive with their 2.5 ratio change

Pete.
--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net [email hidden] http://www.dundee.ac.uk/~pjclinch/

Roger Burton West said:

[W]hat I'd like to do is combine that with a multi-chainring front
derailleur system. Then I can sit on the middle ring while going around
town, shift down for uphills, and shift up for going fast out of town.

However, a derailleur system means jockey wheels so that the chain
length can vary, and I'm not quite sure where they'd go.

[D]oes anyone have practical experience of it on a more normal bike?

In the stupidity of youth, I entered the "Schoolboys' National"
(the Brands Hatch heat) using a bike very much as you describe,
except that I wasn't rich enough to afford a double clanger at
the front, so I put a three-speed block on the side of a three-
speed Sturmey-Archer (with an overlength axle and toggle chain)
at the rear. Needless to say, I came last, but it worked !

** Phil.

Peter Clinch said:

A more expensive by vastly neater solution would be to put on a
Schlumpf [High]Speed or Mountain Drive, see
http://kinetics.org.uk/html/mountain_drive.shtml for some details.

You keep your gears nicely enclosed so less maintenance, you keep a
straight chainline so there's less wear, you have fewer exposed bits to
get damaged or covered in muck, you maintain the ability to switch
between your whole range of gears at a standstill and, if this sort of
thing bothers you, you maintain a simpler aesthetic. And you'll
probably end up with a bigger effective range of gears, at least with
High Speed or Mountain drive with their 2.5 ratio change

Ooh; just think about a Schlumpf X Rohloff
drive system!

If nothing else, the price tag is impressive!

BugBear

Peter Clinch said:

if you put a tensioner on you lose some of the advantages you already
have, if you put a derailleur on you lose even more, so while it's
possible you'll be throwing out the baby with the bathwater to some
extent. A more expensive by vastly neater solution would be to put on a
Schlumpf [High]Speed or Mountain Drive, see
http://kinetics.org.uk/html/mountain_drive.shtml for some details.

Fair point. That doesn't get me the flexibility of three separate
chainrings, but to be honest I'm not sure I'd need the extra-high-speed
bit anyway.

R

--
You get a feeling on certain trails, when you're reacting like you and
your machine are just one thing. It's the feeling of physical exertion
and speed and technique all wrapped into one.
-- Ned Overend

In article said:

Roger Burton West said:

So what I'd like to do is combine that with a multi-chainring front
derailleur system. Then I can sit on the middle ring while going around
town, shift down for uphills, and shift up for going fast out of town.

However, a derailleur system means jockey wheels so that the chain
length can vary, and I'm not quite sure where they'd go.

Where they'd normally go: close to the back, which is what's done when
using a tensioner for hubs because either the dropouts are wrong/there's
no eccentric BB and/or rear suspension changes the change length when it
deflects anyway.

But if the frame is designed for a hub gear, there may be no provision for
a derailleur/tensioner hanger. No doubt you could clamp something on if
necessary though, if the budget won't allow the neater solutions.

Quoted message said:

A more expensive by vastly neater solution would be to put on a
Schlumpf [High]Speed or Mountain Drive, see
http://kinetics.org.uk/html/mountain_drive.shtml for some details.

Quoting Philip TAYLOR <[email hidden]>:

Quoted message said:

the front, so I put a three-speed block on the side of a three-
speed Sturmey-Archer (with an overlength axle and toggle chain)
at the rear. Needless to say, I came last, but it worked !

The "Torpedo" 3-speed hubs use this principle today - space for fitting an
ordinary cassette. Recumbents use them for gigantic gear ranges.
--
David Damerell <[email hidden]> Oil is for sissies
Today is Olethros, June - a weekend.

Roger Burton West roger said:

I'm not planning to do this any time soon, just wondering how practical
it might be.

My usual mount for riding around in town uses a Nexus-8 hub gear. It's
utterly wonderful (as I have gone on about at some length here) to be
able to shift when stationary. What it's not so great for, however, is
going up steep hills or getting a really high speed on a long run.

So what I'd like to do is combine that with a multi-chainring front
derailleur system. Then I can sit on the middle ring while going around
town, shift down for uphills, and shift up for going fast out of town.

However, a derailleur system means jockey wheels so that the chain
length can vary, and I'm not quite sure where they'd go.

I believe some of the Bromptons have a multiple gear system like this
(with a 3-speed hub), so it must be possible, but does anyone have
practical experience of it on a more normal bike?

Roger

--
It never gets easier, you just go faster.
-- Greg LeMond

Have you thought about a speed/mountain drive in the cranks?

Regards,

Duncan

Roger Burton West <[email hidden]> wrote in
news:[email hidden]:

Quoted message said:

I'm not planning to do this any time soon, just wondering how practical
it might be.

If you're old enough 🙂 you will remember just these sort of
adaptations made by Cyclo. Generally for use with Sturmey Archer real
gears.
You could get triple sprockets for the rear or tensioners to use double
chainrings (and I've got one of those in my bits box - and no, you're not
having it!)

Roger Burton West said:

Peter Clinch said:

if you put a tensioner on you lose some of the advantages you already
have, if you put a derailleur on you lose even more, so while it's
possible you'll be throwing out the baby with the bathwater to some
extent. A more expensive by vastly neater solution would be to put on a
Schlumpf [High]Speed or Mountain Drive, see
http://kinetics.org.uk/html/mountain_drive.shtml for some details.

Fair point. That doesn't get me the flexibility of three separate
chainrings, but to be honest I'm not sure I'd need the extra-high-speed
bit anyway.

All you'll get from extra a triple is an ability to jump about 2-3
effective gears in one, but since the hub makes that a non-issue (since
you can change all you want at any time) in any case you're not really
ahead, so it's really just an ability to fine tune the individual
chainwheel sizes that you'll lose. Since you've already surrendered
that at the back I'm guessing it's not actually that big a deal...

A Sclumpf should actually work better with a hub than a derailleur rear
because it's trivial to dial back through the gearing when you do the
Big Change at the front.

Pete.
--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net [email hidden] http://www.dundee.ac.uk/~pjclinch/