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Downtube mounted gear chager question.



 
 
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  #1  
Old January 13th 08, 07:53 PM posted to uk.rec.cycling
vernon[_2_]
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Posts: 258
Default Downtube mounted gear chager question.

It's just about a year since I acquired a Trevor Jarvis Flying Gate replica
in fixie guise. I've had a couple of attempts at riding it and have decided
to reverse engineer the bike back into its geared incarnation - I don't
think that fixed wheel is for me.

One of the things that's puzzling me is that the mounts for the downtube
sufters appear to be just squares of metal with a hole in the middle and the
down tube blanks off the the bottom of the hole effectively making it a
blind hole. There is insuffient metal in the brazed on squares to allow
screw threading to take place. Does anyone have any idea what sort of
mechanism fitted onto these squares? Oh and another refinement is that the
derailleur cables have tubes let into the frame to allow internal routing of
the cables. Will this complicate matters?

Cheers

Vernon


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  #2  
Old January 13th 08, 10:25 PM posted to uk.rec.cycling
Zog The Undeniable
external usenet poster
 
Posts: 487
Default Downtube mounted gear chager question.

vernon wrote:
It's just about a year since I acquired a Trevor Jarvis Flying Gate replica
in fixie guise. I've had a couple of attempts at riding it and have decided
to reverse engineer the bike back into its geared incarnation - I don't
think that fixed wheel is for me.

One of the things that's puzzling me is that the mounts for the downtube
sufters appear to be just squares of metal with a hole in the middle and the
down tube blanks off the the bottom of the hole effectively making it a
blind hole. There is insuffient metal in the brazed on squares to allow
screw threading to take place. Does anyone have any idea what sort of
mechanism fitted onto these squares? Oh and another refinement is that the
derailleur cables have tubes let into the frame to allow internal routing of
the cables. Will this complicate matters?


I wonder if they were standard Campgnolo-pattern DT bosses which someone
has partially sawn off as part of the fixie conversion (does it look as
if a rear mech hanger has been sawn off too?). Internal routing of gear
cables isn't ideal for indexed systems, which like straight runs of bare
inner as much as possible, and was probably designed in the days of
frcition shift.
  #3  
Old January 13th 08, 10:52 PM posted to uk.rec.cycling
vernon[_2_]
external usenet poster
 
Posts: 258
Default Downtube mounted gear chager question.


"Zog The Undeniable" wrote in message
...
vernon wrote:
It's just about a year since I acquired a Trevor Jarvis Flying Gate
replica in fixie guise. I've had a couple of attempts at riding it and
have decided to reverse engineer the bike back into its geared
incarnation - I don't think that fixed wheel is for me.

One of the things that's puzzling me is that the mounts for the downtube
sufters appear to be just squares of metal with a hole in the middle and
the down tube blanks off the the bottom of the hole effectively making it
a blind hole. There is insuffient metal in the brazed on squares to
allow screw threading to take place. Does anyone have any idea what sort
of mechanism fitted onto these squares? Oh and another refinement is that
the derailleur cables have tubes let into the frame to allow internal
routing of the cables. Will this complicate matters?


I wonder if they were standard Campgnolo-pattern DT bosses which someone
has partially sawn off as part of the fixie conversion (does it look as if
a rear mech hanger has been sawn off too?). Internal routing of gear
cables isn't ideal for indexed systems, which like straight runs of bare
inner as much as possible, and was probably designed in the days of
frcition shift.


Thankfully the rear mech hanger is intact. It's a chromed Campagnolo set up
at the rear. I'm wondering if the fixings were a sort of band on
arrangement. I've prepared a few poorly focussed images to try to give a
better idea...

http://picasaweb.google.com/vernonlevy/Gate/

Another verbal attempt is that the mounts are best described as square pads
machined at their rears to accommodate the curvature of the downtube. There
doesn't appear to be any evidence of the blocks/pads being sawn down. The
bike was almost certainly a friction shift machine - I can live with that.

Could it bee that I need new braze ons? The frame needs a respray anyway.


  #4  
Old January 13th 08, 11:24 PM posted to uk.rec.cycling
Mark T[_2_]
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Posts: 525
Default Downtube mounted gear chager question.

http://picasaweb.google.com/vernonlevy/Gate/

Another verbal attempt is that the mounts are best described as square
pads machined at their rears to accommodate the curvature of the
downtube. There doesn't appear to be any evidence of the blocks/pads
being sawn down. The bike was almost certainly a friction shift
machine - I can live with that.


If it's any help, the Frankenstein Fixed had band on levers. The
'mounting' is simply a tringular thingy with the flat bit towards the bars.
It's job was to simply stop the band on shifters from migrating down the
downtube. I'm wondering if your thingies are similar.
  #5  
Old January 13th 08, 11:29 PM posted to uk.rec.cycling
vernon[_2_]
external usenet poster
 
Posts: 258
Default Downtube mounted gear chager question.


"Mark T"
pleasegivegenerously@warmail*turn_up_the_heat_to_ reply*.com.invalid wrote
in message ...
http://picasaweb.google.com/vernonlevy/Gate/

Another verbal attempt is that the mounts are best described as square
pads machined at their rears to accommodate the curvature of the
downtube. There doesn't appear to be any evidence of the blocks/pads
being sawn down. The bike was almost certainly a friction shift
machine - I can live with that.


If it's any help, the Frankenstein Fixed had band on levers. The
'mounting' is simply a tringular thingy with the flat bit towards the
bars.
It's job was to simply stop the band on shifters from migrating down the
downtube. I'm wondering if your thingies are similar.


I'm familiar with the triangular stops. My thingies are massively
over-engineered if their sole purpose is to stop band on shifters from
sliding down the downtube.


  #6  
Old January 13th 08, 11:40 PM posted to uk.rec.cycling
Pete Biggs
external usenet poster
 
Posts: 1,801
Default Downtube mounted gear chager question.

vernon wrote:
"Zog The Undeniable" wrote in message
...
vernon wrote:
It's just about a year since I acquired a Trevor Jarvis Flying Gate
replica in fixie guise. I've had a couple of attempts at riding it
and have decided to reverse engineer the bike back into its geared
incarnation - I don't think that fixed wheel is for me.

One of the things that's puzzling me is that the mounts for the
downtube sufters appear to be just squares of metal with a hole in
the middle and the down tube blanks off the the bottom of the hole
effectively making it a blind hole. There is insuffient metal in
the brazed on squares to allow screw threading to take place. Does
anyone have any idea what sort of mechanism fitted onto these
squares? Oh and another refinement is that the derailleur cables
have tubes let into the frame to allow internal routing of the
cables. Will this complicate matters?


I wonder if they were standard Campgnolo-pattern DT bosses which
someone has partially sawn off as part of the fixie conversion (does
it look as if a rear mech hanger has been sawn off too?). Internal
routing of gear cables isn't ideal for indexed systems, which like
straight runs of bare inner as much as possible, and was probably
designed in the days of frcition shift.


Thankfully the rear mech hanger is intact. It's a chromed Campagnolo
set up at the rear. I'm wondering if the fixings were a sort of band
on arrangement. I've prepared a few poorly focussed images to try to
give a better idea...

http://picasaweb.google.com/vernonlevy/Gate/

Another verbal attempt is that the mounts are best described as
square pads machined at their rears to accommodate the curvature of
the downtube. There doesn't appear to be any evidence of the
blocks/pads being sawn down. The bike was almost certainly a
friction shift machine - I can live with that.
Could it bee that I need new braze ons? The frame needs a respray
anyway.


You could just use band-on levers - either with a band that fits over the
stops (or whatever they are) on the frame, or above or below them.

How large are these "pads"?

I have some old unwanted Simplex band-on levers with 10mm (approx) square
slight recesses on the inside. Not in very god condition, but could be
useable.

~PB


  #7  
Old January 13th 08, 11:57 PM posted to uk.rec.cycling
vernon[_2_]
external usenet poster
 
Posts: 258
Default Downtube mounted gear chager question.


"Pete Biggs" wrote in
message ...

You could just use band-on levers - either with a band that fits over the
stops (or whatever they are) on the frame, or above or below them.

How large are these "pads"?

I have some old unwanted Simplex band-on levers with 10mm (approx) square
slight recesses on the inside. Not in very god condition, but could be
useable.

The pads are about 10mm.....just nipping out to the garage to
check...(7/16)" seven sixteenths.....calculate....10.94mm. The
aforementioned pads are diametrically opposite each other and are in the
positions where I'd expect the lever pivots to be. I'm now wondering if
there were threaded tubes on the pads that have been filed down because in
the harsh LED light of my head torch, I could see the hint of an annulus
around each of the holes.

Pending the results of further enquiries I could be interested in your band
on levers.....

Next question....

What is the OLN dimension of a five speed freewheel hub? Are they still
available?



  #8  
Old January 14th 08, 01:19 AM posted to uk.rec.cycling
Pete Biggs
external usenet poster
 
Posts: 1,801
Default Downtube mounted gear chager question.

vernon wrote:

I have some old unwanted Simplex band-on levers with 10mm (approx)
square slight recesses on the inside. Not in very god condition,
but could be useable.

The pads are about 10mm.....just nipping out to the garage to
check...(7/16)" seven sixteenths.....calculate....10.94mm. The
aforementioned pads are diametrically opposite each other and are in
the positions where I'd expect the lever pivots to be. I'm now
wondering if there were threaded tubes on the pads that have been
filed down because in the harsh LED light of my head torch, I could
see the hint of an annulus around each of the holes.

Pending the results of further enquiries I could be interested in
your band on levers.....


£3 posted, if you are.

I'll take some pictures tomorrow so you can see if you like the look of them
(the levers are resin). Very light at just 72 grams in total. They
incorporate cable adjusters as well.

There is some rotational play in one of the levers that would need fixing to
stop it being annoying. There is a square hole (separate from the recess I
mentioned) that isn't so square any more. Something could be inserted to
shim it.

Next question....

What is the OLN dimension of a five speed freewheel hub?


120mm - www.sheldonbrown.com/gloss_sp-ss.html#spacing

Are they still available?


One on ebay in the States - item 220190887704 - $21 shipping.

~PB


  #9  
Old January 14th 08, 10:56 AM posted to uk.rec.cycling
[email protected]
external usenet poster
 
Posts: 175
Default Downtube mounted gear chager question.

On 13 Jan, 22:57, "vernon" wrote:
"Pete Biggs" p...@pomegranateremovehighlyimpracticalfruitbiggs .tc wrote in
...

You could just use band-on levers - either with a band that fits over the
stops (or whatever they are) on the frame, or above or below them.


How large are these "pads"?


I have some old unwanted Simplex band-on levers with 10mm (approx) square
slight recesses on the inside. *Not in very god condition, but could be
useable.


The pads are about 10mm.....just nipping out to the garage to
check...(7/16)" seven sixteenths.....calculate....10.94mm. *The
aforementioned pads are diametrically opposite each other and are in the
positions where I'd expect the lever pivots to be. *I'm now wondering if
there were threaded tubes on the pads that have been filed down because in
the harsh LED *light of my head torch, I could see the hint of an annulus
around each of the holes.

Pending the results of further enquiries I could be interested in your band
on levers.....

Next question....

What is the OLN dimension of a five speed freewheel hub? *Are they still
available?


  #10  
Old January 14th 08, 11:20 AM posted to uk.rec.cycling
[email protected]
external usenet poster
 
Posts: 175
Default Downtube mounted gear chager question.

On 13 Jan, 22:57, "vernon" wrote:
... *I'm now wondering if
there were threaded tubes on the pads that have been filed down because in
the harsh LED *light of my head torch, I could see the hint of an annulus
around each of the holes.


That sounds likely to me. I would be tempted to mount a band-on lever
set above them, using the stubs as stops.

What is the OLN dimension of a five speed freewheel hub? *Are they still
available?


120mm. Yes, they are still available new, though the quality isn't as
good as the best freewheels of old. You can probably cold-set to a
wider spacing and use a six or seven speed, if you want (or scout for
an ultra-6).

Cheers,
W.
 




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