Downtube mounted gear chager question.



V

vernon

Guest
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
 
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.
 
"Zog The Undeniable" <[email protected]> wrote in message
news:[email protected]...
> 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.
 
> 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.
 
"Mark T"
<pleasegivegenerously@warmail*turn_up_the_heat_to_reply*.com.invalid> wrote
in message news:[email protected]...
>> 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.
 
vernon wrote:
> "Zog The Undeniable" <[email protected]> wrote in message
> news:[email protected]...
>> 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
 
"Pete Biggs" <[email protected]> wrote in
message news:[email protected]...

> 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?
 
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
 
On 13 Jan, 22:57, "vernon" <[email protected]> wrote:
> "Pete Biggs" <[email protected]> wrote in
> messagenews:[email protected]...
>
> > 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?
 
On 13 Jan, 22:57, "vernon" <[email protected]> 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.
 
In article <cb166d1c-2bfd-47b6-820e-836905a37f55
@f47g2000hsd.googlegroups.com>,
[email protected] says...

> ...indeed. However the Winner Pro was arguably the best
> freewheel ever made, and we will never see its like again.
>
They were excellent freewheels - hard-wearing sprockets, easy shifting,
smooth reliable mechanism, and serviceable too.
 
<[email protected]> wrote in message
news:aa1ebef6-9bad-464d-a57c-5d93670a66d1@z17g2000hsg.googlegroups.com...
On 13 Jan, 22:57, "vernon" <[email protected]> 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.

Now there's also the matter of the internal cable guides which then might
not be positioned to suit the new position of the shifters. I'm seriously
contemplating new braze ons along with a respray.

> 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).

Cold setting is something that I'll consider. I'm going to have to put a
bit of thought in before moving on with this project.

I could of course persevere with it as a fixie.......oh decisions
decisions.....

Thanks

Vernon





eers,
W.
 
On 14 Jan, 18:08, "vernon" <[email protected]> wrote:

> I could of course persevere with it as a fixie.......oh decisions
> decisions.....

If you've only had "a couple of attempts" at riding it, then it might
well be worth persevering for a bit. Riding a fixie is quite different
from a broken bike and giving youself a bit of time to adapt could
well be worthwhile. In the longer term, of course, if riding it isn't
fun then there's little point: some say it can improve your fitness
and technique but you'd have to be pretty committed to some sort of
training plan to see it through.
Personally, I like the simplicity of the bike and it seems to enhance
the simple pleasure of spinning along the road with the wheels humming
and the wind in your face.

Cheers,
W.
 
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