Compass Folding Bike



P

Peter Clinch

Guest
Tosspot wrote:

> So you can't get an 8-Speed Brompton? Thats bad, I would have thought
> it'd be crying out for that solution.


I was chatting to Darth Ben about a Schlumpf on mine, and he said there
was a good chance there would be a suitable version of the recent
Sturmey 8 in the not too distant so probably wise to hold off on the
Schlumpf for a while.

I hope he's right about this, as it would make a generally available 8
for the Brom which would dig them out of the gearing hole they've dug
for themselves.

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 protected] http://www.dundee.ac.uk/~pjclinch/
 
J

James Thomson

Guest
"Tosspot" <[email protected]> a écrit:

> So you can't get an 8-Speed Brompton? Thats bad, I would have
> thought it'd be crying out for that solution.


The Sturmey-Archer website lists a 116mm oln model of the XRF8 in 28h:

http://www.sturmey-archer.com/hubs_8spd_XRF8.php

That's close to perfect for a Brompton. I don't know whether or not these
hubs are actually being shipped.

James Thomson
 
T

Tosspot

Guest
Al C-F wrote:
> Tosspot wrote:
>
>>
>>
>> So you can't get an 8-Speed Brompton? Thats bad, I would have thought
>> it'd be crying out for that solution.
>>

>
> On this years IoW trip, I met a lady with a Rolhoff-equipped Brompton.
>
> Would that be enough gears for you?


Hmmmm, it would, but I'm trying to avoid a Rohloff collection.
Interesting, I wonder how he got it to fit.
 
T

Tony Raven

Guest
James Thomson wrote on 29/06/2006 09:47 +0100:
> "Tosspot" <[email protected]> a écrit:
>
>> So you can't get an 8-Speed Brompton? Thats bad, I would have
>> thought it'd be crying out for that solution.

>
> The Sturmey-Archer website lists a 116mm oln model of the XRF8 in 28h:
>
> http://www.sturmey-archer.com/hubs_8spd_XRF8.php
>
> That's close to perfect for a Brompton. I don't know whether or not these
> hubs are actually being shipped.
>


6mm too wide so no use at all with a titanium rear triangle and only any
use if you cold set a steel rear triangle.


--
Tony

"Anyone who conducts an argument by appealing to authority is not using
his intelligence; he is just using his memory."
- Leonardo da Vinci
 
J

James Thomson

Guest
"Tony Raven" <[email protected]> a écrit:

> James Thomson wrote on 29/06/2006 09:47 +0100:


>> The Sturmey-Archer website lists a 116mm oln model of the XRF8 in 28h:
>>
>> http://www.sturmey-archer.com/hubs_8spd_XRF8.php
>>
>> That's close to perfect for a Brompton. I don't know whether or not
>> these hubs are actually being shipped.


> 6mm too wide so no use at all with a titanium rear triangle and
> only any use if you cold set a steel rear triangle.


Tony,

There are a number of questionable assumptions in your brief statement
above:

You mentioned 112mm previously as the standard Brompton oln, and now seem to
have swung towards 110mm. My recollection (possibly flawed) is that my own
measured 114mm (which was a standard oln for the Sturmey Sprinter 5 - one of
the hub options Brompton offered before Sturmey went under), but maybe there
is, was, or has been some variation.

What makes you sure that a steel rear triangle cannot not be sprung (rather
than cold set) the 2, 4, 6, or X mm required?

What makes you sure that a Ti rear triangle cannot be sprung the 2, 4, 6, or
X mm required, depending on the value of X?

What makes you certain that if such a hub were commercially available,
Brompton would not seize the opportunity to broaden their gearing options
with a trivial re-jigging of their rear triangle?

So come, why:

6mm too wide so no use at all with a titanium rear triangle and
only any use if you cold set a steel rear triangle.

instead of:

The narrow version of the Sturmey 8 speed hub promises to offer
Brompton users a new range of gearing options with, if required, a
trivial cold setting of the steel rear triangle.

or simply nothing at all?

As I mentioned before, I'm aware that many things in life are impossible. I
don't find it particularly constructive to enumerate them to the exclusion
of the possible.

James Thomson
 
T

Tony Raven

Guest
James Thomson wrote on 04/07/2006 00:06 +0100:
>
> There are a number of questionable assumptions in your brief statement
> above:
>
> You mentioned 112mm previously as the standard Brompton oln, and now seem to
> have swung towards 110mm. My recollection (possibly flawed) is that my own
> measured 114mm (which was a standard oln for the Sturmey Sprinter 5 - one of
> the hub options Brompton offered before Sturmey went under), but maybe there
> is, was, or has been some variation.


112mm was from memory, 110mm is from checking.

>
> What makes you sure that a steel rear triangle cannot not be sprung (rather
> than cold set) the 2, 4, 6, or X mm required?


Have you tried springing a Brompton rear triangle? The tubes are pretty
large and short

>
> What makes you sure that a Ti rear triangle cannot be sprung the 2, 4, 6, or
> X mm required, depending on the value of X?


The Ti one is even harder to spring.

>
> What makes you certain that if such a hub were commercially available,
> Brompton would not seize the opportunity to broaden their gearing options
> with a trivial re-jigging of their rear triangle?
>


Because Steve Parry has been cold setting rear triangles for years to
take normal width geared hubs. It compromises the folding width by a
few mm but that's all. Through all this time and frame updates Brompton
have chosen to stick with 110mm and deal with the problems of restricted
hub choice when they could have made it wider. They clearly think
folded size is more important. Even the SA debacle didn't change their
mind.


--
Tony

"Anyone who conducts an argument by appealing to authority is not using
his intelligence; he is just using his memory."
- Leonardo da Vinci
 
J

James Thomson

Guest
"Tony Raven" <[email protected]> a écrit:

> 112mm was from memory, 110mm is from checking.


.... one example. How do you know yours is typical? How do you know what, if
any, variation exists, or has existed?

> Have you tried springing a Brompton rear triangle? The tubes are
> pretty large and short


No I haven't, though I've sprung other small-wheelers without much trouble.

>> What makes you sure that a Ti rear triangle cannot be sprung the 2, 4, 6,
>> or X mm required, depending on the value of X?


> The Ti one is even harder to spring.


I'm curious to know how extensive your own experience of springing steel and
titanium Brompton rear triangles might be. What have you been trying to cram
in there?

>> What makes you certain that if such a hub were commercially
>> available, Brompton would not seize the opportunity to broaden
>> their gearing options with a trivial re-jigging of their rear triangle?


> Because Steve Parry has been cold setting rear triangles
> for years to take normal width geared hubs.


If one fact should have become obvious to you during this discussion, it's
that there is no such thing as a 'normal width geared hub'. The Sturmey AW
is by far the most common hub gear on the road at between 103 and 112mm +.

103mm, 107mm, 112mm, 114mm, 116mm, 118mm, 122mm, 126mm, 130mm, 131mm, 135mm
.... which have you nominated 'normal', and by what criteria?

> It compromises the folding width by a few mm but that's all. Through all
> this time and
> frame updates Brompton have chosen to stick with 110mm.


.... or 112mm, or 114mm, or 11Xmm.

> and deal with the problems of restricted hub choice when they could have
> made it wider. They clearly think folded size is more important. Even the
> SA debacle didn't change their mind.


Brompton clearly think that folded size is important, and Brompton's
customers clearly think that folded size is important. Compactness of fold
is consistently given as one of the reasons to prefer a Brompton by Brompton
riders on this group. Increasing the rear oln to 135mm from 11Xmm involves
increasing the folded package size by up to 25-Xmm. That might be
significant to some proportion of the ridership. 116mm is a different
proposition.

But in any case, even if Brompton never offers the narrow 8 as a factory
option, even if the titanium rear triangle is impossible to spring, even if
X=0, even if the ISO and Tony Raven arbitrarily declare that Brompton falls
outside hub gear norms, a competent bike shop will be able to fit a 116mm
Sturmey 8 to a steel Brompton with little more than a trivial resetting of
the rear triangle, a small weight penalty, and a negligible increase in the
folded width. What's not to like?

Let me say again, I'm aware that many things in life are impossible. I don't
find it particularly constructive to enumerate them to the exclusion of the
possible.

James Thomson
 
P

Peter Clinch

Guest
James Thomson wrote:

> But in any case, even if Brompton never offers the narrow 8 as a factory
> option, even if the titanium rear triangle is impossible to spring, even if
> X=0, even if the ISO and Tony Raven arbitrarily declare that Brompton falls
> outside hub gear norms, a competent bike shop will be able to fit a 116mm
> Sturmey 8 to a steel Brompton with little more than a trivial resetting of
> the rear triangle, a small weight penalty, and a negligible increase in the
> folded width. What's not to like?


I can't see much. As soon as Darth Ben has some time and says it's a
goer, I'll be getting one... (the pre-XS SON he squeezed into my front
forks hasn't caused any problems to date, and it's been a few years now).

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 protected] http://www.dundee.ac.uk/~pjclinch/
 
T

Tony Raven

Guest
James Thomson wrote on 04/07/2006 08:20 +0100:
> "Tony Raven" <[email protected]> a écrit:
>
>> 112mm was from memory, 110mm is from checking.

>
> .... one example. How do you know yours is typical? How do you know what, if
> any, variation exists, or has existed?


There are other ways to check than measuring you know. For example
http://www.sjscycles.co.uk/product-...0mm-OLN-for-Brompton--BRITISH-BUILT-12011.htm

>
> I'm curious to know how extensive your own experience of springing steel and
> titanium Brompton rear triangles might be. What have you been trying to cram
> in there?
>


Well since I have both a Ti and Steel Brompton and I have cold set one
road frame and two tandem frames myself to take wider hubs I would
suggest I have a reasonable level of experience but nothing to compare
to Steve Parry or Darth Ben I admit.

>
> If one fact should have become obvious to you during this discussion, it's
> that there is no such thing as a 'normal width geared hub'. The Sturmey AW
> is by far the most common hub gear on the road at between 103 and 112mm +.
>
> 103mm, 107mm, 112mm, 114mm, 116mm, 118mm, 122mm, 126mm, 130mm, 131mm, 135mm
> .... which have you nominated 'normal', and by what criteria?


And which coincide with currently manufactured hub gears (other than the
SA 3 speed) and currently available off the shelf frames?

>
> But in any case, even if Brompton never offers the narrow 8 as a factory
> option, even if the titanium rear triangle is impossible to spring, even if
> X=0, even if the ISO and Tony Raven arbitrarily declare that Brompton falls
> outside hub gear norms, a competent bike shop will be able to fit a 116mm
> Sturmey 8 to a steel Brompton with little more than a trivial resetting of
> the rear triangle, a small weight penalty, and a negligible increase in the
> folded width. What's not to like?


The resetting is not trivial with beefy short tubes and strong dropouts
but doable with determination (and care because it needs to be
assymetrical to maintain the chainline). What is not trivial is that
the smallest cog available for the 8-speed hub is, IIRC, 23 tooth. The
largest cog the frame will take is a 15T IIRC. The usual solution for
other hubs for an 18T is to take an angle grinder to the frame and
carefully remove the offending frame material or to crimp the stay out
of the way. You can do that on a steel one but I doubt many would risk
that level of butchery to their frame. And I doubt many bike shops have
the equipment that will do it for titanium frames. Whether you can
actually fit an SA 8 speed with its 23T cog I don't know but you can fit
Rohloff's with 18T cogs that way to steel frames. Retrofitting hubs to
Brommies is a whole science in itself

>
> Let me say again, I'm aware that many things in life are impossible. I don't
> find it particularly constructive to enumerate them to the exclusion of the
> possible.
>


Yes, Steve Parry or Darth Ben will do virtually anything within reason
for you (except I think machining and joining titanium is probably out
of bounds) and Len Rubin will possibly build you a full Ti Brompton if
you have the money. But for a practical everyday solution for most
people 110mm OLN hubs are what you need.


--
Tony

"Experience is the name everyone gives to their mistakes."
- Oscar Wilde
 
J

James Thomson

Guest
"Tony Raven" <[email protected]> a écrit:

> There are other ways to check than measuring you know. For example


http://www.sjscycles.co.uk/product-...0mm-OLN-for-Brompton--BRITISH-BUILT-12011.htm

I assumed you'd measured. But in fact you *Googled*, and posted the first
hit.

Here's something else from the same site:

http://www.sjscycles.co.uk/product-...5-steel-Hub-with-Gear-Control-HSJ839-8035.htm

36 hole Sturmey Archer 5-Speed SPRINTER S5 steel Hub with Gear Control
HSJ839 114mm OLN ideal for upgrading old brompton 3 and 5 speed bikes.

You obviously consider SJS authoritative.

I consider them generally pretty competent, and I'm inclined to trust Len
Rubin, who in 1997 agreed with you. But there's a surprising dearth of
authoritative information on this subject on the web. I'd be happier with a
few measurements, but I haven't had time to get to a Brompton dealer in the
last couple of weeks.

> Well since I have both a Ti and Steel Brompton and I have cold
> set one road frame and two tandem frames myself to take wider
> hubs I would suggest I have a reasonable level of experience


So you've never tried to spring a Brompton frame. And yet you wrote:

> The Ti one is even harder to spring.


Which implies you've experience of springing both.

This is one of those classic Usenet Tweedledum and Tweedledee moments:
neither of us has ever sprung a Brompton frame, yet here we are arguing the
ins and outs.

>> If one fact should have become obvious to you during this discussion,
>> it's that there is no such thing as a 'normal width geared hub'. The
>> Sturmey AW is by far the most common hub gear on the road at
>> between 103 and 112mm+.


>> 103mm, 107mm, 112mm, 114mm, 116mm, 118mm, 122mm, 126mm,
>> 130mm, 131mm, 135mm .... which have you nominated 'normal', and
>> by what criteria?


> And which coincide with currently manufactured hub gears (other
> than the SA 3 speed) and currently available off the shelf frames?


Is that a summary of your criteria for normality? First, exclude the most
common?

Hub gears are sold in bulk to the utility market, and utility bikes are
rarely sold as frames, the Brompton being a good example. Off-the-shelf
frames are sports frames, and sports bikes with few exceptions use
derailleur gears. So by excluding the most common hub gear in the world, and
by excluding the bulk of hub-geared bikes from your definition, you've
arrived at a description of a typical hub gear which excludes the majority
of hub gears produced, sold, and used.

> The resetting is not trivial with beefy short tubes and strong dropouts


Steel Brompton dropouts are soft, and cut from fairly thin plate.

> but doable with determination (and care because it needs
> to be assymetrical to maintain the chainline).


Asymmetric setting is no harder than symmetric, since you're setting one
side at a time anyway, though that obviously precludes springing. There's
also room to vary chainline at the front of the bike.

> What is not trivial is that the smallest cog available for the
> -speed hub is, IIRC, 23 tooth.


There's a 19t sprocket, but that, not the oln, looks like a deal-breaker.

James "Tweedledee" Thomson
 
A

Alan Braggins

Guest
James Thomson wrote:
>"Tony Raven" <[email protected]> a écrit:
>
>> And which coincide with currently manufactured hub gears (other
>> than the SA 3 speed) and currently available off the shelf frames?

>
>Is that a summary of your criteria for normality? First, exclude the most
>common?
>
>Hub gears are sold in bulk to the utility market, and utility bikes are
>rarely sold as frames, the Brompton being a good example. Off-the-shelf
>frames are sports frames, and sports bikes with few exceptions use
>derailleur gears. So by excluding the most common hub gear in the world, and
>by excluding the bulk of hub-geared bikes from your definition, you've
>arrived at a description of a typical hub gear which excludes the majority
>of hub gears produced, sold, and used.


In the context of fitting a new hub to a Brompton as an upgrade, it seems
entirely reasonable to consider only hubs which can be bought new and aren't
already fitted to Brompton's as standard, no matter how many thousands of
3-speed SA hubs have been fitted to utility bikes in the past.

On the other hand, if we consider fitting a geared hub to the Compass
bike in the subject line, including 3 speed SAs makes more sense.
Anyone have any opinions on the practicality of that? (And of adding
a rear brake if using a non-coaster-brake hub?)
 
J

James Thomson

Guest
"Alan Braggins" <[email protected]> a écrit:

> In the context of fitting a new hub to a Brompton as an upgrade, it
> seems entirely reasonable to consider only hubs which can be bought
> new and aren't already fitted to Brompton's as standard, no matter how
> many thousands of 3-speed SA hubs have been fitted to utility bikes in
> the past.


That's true, but that wasn't quite the context.

James Thomson