Jobst Brandt's Peter Johnson frame and fork
Joss Winn
Hello,
I came across pictures of Jobst Brandt's Peter Johnson frame and fork
the other day
<http://www.bikecult.com/works/archive/04bicycles/pjohnsonJB04.html> and
am hoping someone might be able to explain the photo caption that says:
"All filet brazed construction, with butted headtube,
and a gorgeous flat-top fork crown with seamless blades."
I know what filet brazing is when I see it, but am interested in the
method of construction of the fork crown and blades. Can anyone (Jobst
Brandt?) explain this in more detail to someone who has no experience of
frame building.
Jobst, if you care to, would you mind offering more info on the
construction and design of your frame? I've been able to pick up bits
and pieces from searching the archive, but have not found any detailed
description.
Thank you very much,
Joss
My Robin Mather frame for those interested in lugged steel:
http://jlw.freeshell.org/fixie/mather/build/images.html
--
Zog The Undeniable
> I know what filet brazing is when I see it, but am interested in the
> method of construction of the fork crown and blades. Can anyone (Jobst
> Brandt?) explain this in more detail to someone who has no experience of
> frame building.
Apart from the flat top, it looks like the "aero" fork crowns that were
popular before carbon forks took over. These have long plugs which
exactly fit into the fork blades, so effectively they're internally lugged.
philcycles
While I can't speak for either Peter or Jobst I'll bet the caption
refers to the fact that the crown and blades look to be one piece, ie:
no seams. Peter is a world class machinist and may have made the crown
himself.
Phil Brown
Qui si parla Campagnolo
Joss Winn wrote:
> Hello,
>
> I came across pictures of Jobst Brandt's Peter Johnson frame and fork
> the other day
> <http://www.bikecult.com/works/archive/04bicycles/pjohnsonJB04.html>
and
> am hoping someone might be able to explain the photo caption that
says:
>
Man oh man is his big ring worn out!!
Bill Sornson
I was wondering when someone would comment on those teeth! (They match the
bike, at least.)
Tom Nakashima
>>> the other day
>>> <http://www.bikecult.com/works/archive/04bicycles/pjohnsonJB04.html>
>>> and am hoping someone might be able to explain the photo caption
>>> that says:
For a second or two there, I thought the last photograph was Eddy
Merckx...Naaaaa.
-tom
JH
Not to start a flame war here, but I'm just wondering . . . . . where
are the helmets?
Benjamin Lewis
>
> Joss Winn wrote:
>> Hello, I came across pictures of Jobst Brandt's Peter Johnson frame and
>> fork the other day
>> <http://www.bikecult.com/works/archive/04bicycles/pjohnsonJB04.html>
>
> Not to start a flame war here, but I'm just wondering . . . . . where are
> the helmets?
What helmets? (I find it difficult to believe you're not trying to start a
flame war. If you look at any of Jobst's archived photos you'll see that
he does not wear a helmet.)
--
Benjamin Lewis
Although the moon is smaller than the earth, it is farther away.
Joss Winn
> JH wrote:
>
>>
>> Joss Winn wrote:
>>> Hello, I came across pictures of Jobst Brandt's Peter Johnson frame and
>>> fork the other day
>>> <http://www.bikecult.com/works/archive/04bicycles/pjohnsonJB04.html>
>>
>> Not to start a flame war here, but I'm just wondering . . . . . where are
>> the helmets?
>
> What helmets? (I find it difficult to believe you're not trying to start a
> flame war. If you look at any of Jobst's archived photos you'll see that
> he does not wear a helmet.)
>
Before this thread moves over to helmets, are there any more thoughts on
the construction of the Jobst Brandt/Peter Johnson fork?
Joss (propping up the thread) Winn
--
jobst....@stanfordalumni.org
> I came across pictures of Jobst Brandt's Peter Johnson frame and
> fork the other day:
http://www.bikecult.com/works/archive/04bicycles/pjohnsonJB04.html
> and am hoping someone might be able to explain the photo caption
> that says:
> "All filet brazed construction, with butted headtube, and a gorgeous
> flat-top fork crown with seamless blades."
> I know what filet brazing is when I see it, but am interested in the
> method of construction of the fork crown and blades. Can anyone
> (Jobst Brandt?) explain this in more detail to someone who has no
> experience of frame building.
> Jobst, if you care to, would you mind offering more info on the
> construction and design of your frame? I've been able to pick up
> bits and pieces from searching the archive, but have not found any
> detailed description.
As you can see in the shots of the head/downtube joint. This is the
classic style in which Peter builds steel frames. The bottom bracket
is a lug and has stiffeners up the sides of the seat tube to restrain
bending loads. Peter is aware that I had frame failures there in the
days of my Italian frames.
The fork is a derivative of a Masi fork crown filed and fillet brazed
to have a smooth transition because here also, I have had failures
from Cinelli internally lugged crowns that cannot be feathered to
avoid notch stress concentrations. This bicycle is over 15 years old
and has at least 10,000 miles per year on it.
The chainrings still work fine with new chains but I have a couple of
new ones whose day will come one of these days.
> My Robin Mather frame for those interested in lugged steel:
Tom Nakashima
<jobst....@stanfordalumni.org> wrote in message
news:J97ie.718$W51....@typhoon.sonic.net...
>
> http://www.bikecult.com/works/archive/04bicycles/pjohnsonJB04.html
. This bicycle is over 15 years old
> and has at least 10,000 miles per year on it.
>
Pretty awesome Mr. Brandt, that would be over 150,000 miles on a steel
frame.
Frame builders of all material, take note.
Have you ever calculated how many miles on a bicycle you have accumulated
since you started cycling? I was wondering if you have a shot for the
Guinness Book of Records.
-tom
jobst....@stanfordalumni.org
As I mentioned, the sloping (solid steel) fork crown was a great
disservice to bicycling in that it is heavy and failure prone for its
internal and un-feathered internal lugs. I had two failures and have
seen others.
jobst....@stanfordalumni.org
http://www.bikecult.com/works/archive/04bicycles/pjohnsonJB04.html
>> This bicycle is over 15 years old and has at least 10,000 miles per
>> year on it.
> Pretty awesome Mr. Brandt, that would be over 150,000 miles on a
> steel frame.
I'm still riding hubs and spokes of wheels that I built in the early
1970's and just replaced the rims as they wore through. I find that
more interesting because in that time I have seen many bicycles with
spoke failures from poorly built wheels but with good spokes.
> Frame builders of all material, take note.
> Have you calculated how many miles on a bicycle you have accumulated
> since you started cycling? I was wondering if you have a shot for
> the Guinness Book of Records.
I don't care for such records. For me it is the enjoyment of the
places and people I see riding my bicycle ,be that a weekend ride in
the Santa Cruz mountains, the Sierra Nevada, or the Alps. The British
are great for endurance records where I have read of bicyclists who
put in their 100 miles per day, rain, sleet, hail, or snow to set some
record. That strikes me as a wasted effort in a useless pursuit.
On the other hand, this seems to be a human foible judging from the
ride reports I see on wreck.bike.rides that are all about suffering
and death (rides) that they survived. I don't think these riders see
much or at least they keep it secret in their reports that mainly
reach out for merit badges. As I have often written, "If you didn't
like it, don't tell me about it!"
Ride bike! It's a lot of fun if you keep your eyes open.
Alfred Ryder
>
>
But that is why his two rings are the same size. The other one is his spare.
c...@nospam.net
The chainrings are so close in size it looks like a 1/2 step setup. What is
the size of the two chainrings?
cel
"Qui si parla Campagnolo" <pe...@vecchios.com> wrote in message
news:1116258768....@o13g2000cwo.googlegroups.com...
Jay Beattie
<jobst....@stanfordalumni.org> wrote in message
news:2W8ie.795$W51....@typhoon.sonic.net...
You live in a Mecca for cycling. Please tell me the traffic is
dreadful so I don't feel so bad about moving away 20 years ago.
> On the other hand, this seems to be a human foible judging from
the
> ride reports I see on wreck.bike.rides that are all about
suffering
> and death (rides) that they survived. I don't think these
riders see
> much or at least they keep it secret in their reports that
mainly
> reach out for merit badges. As I have often written, "If you
didn't
> like it, don't tell me about it!"
Good luck changing that. There is a pathological need for heroic
events, or events that we can claim are heroic. I could tell you
stories about my commute to work that would rival Homer (Simpson,
that is). Or should I say my training ride into work. -- Jay
Beattie.
carl...@comcast.net
jobst....@stanfordalumni.org wrote:
[snip]
>As I have often written, "If you didn't
>like it, don't tell me about it!"
[snip]
Dear Jobst,
Cognitive dissonance?
Carl Fogel
jim beam
> Tom Nakashima <t...@slac.stanford.edu> writes:
>
> http://www.bikecult.com/works/archive/04bicycles/pjohnsonJB04.html
>
>
>>>This bicycle is over 15 years old and has at least 10,000 miles per
>>>year on it.
>
>
>>Pretty awesome Mr. Brandt, that would be over 150,000 miles on a
>>steel frame.
>
>
> I'm still riding hubs and spokes of wheels that I built in the early
> 1970's and just replaced the rims as they wore through.
er, you forgot to mention the hubs that broke flanges & ruined bearings,
oh & the spokes that you've replaced because they broke...
"this hammer's 30 years old. it's had 3 new handles and 2 new heads,
but it's still the same hammer". right jobst? don't let fact get in
the way of a good story.
jobst....@stanfordalumni.org
>>> I came across pictures of Jobst Brandt's Peter Johnson frame and fork
>>> the other day
http://www.bikecult.com/works/archive/04bicycles/pjohnsonJB04.html
>>> and am hoping someone might be able to explain the photo caption
>>> that says:
>> Man oh man is his big ring worn out!!
> Jobst must have some powerful legs to push that gearing in the
> Italian alps! The chainrings are so close in size it looks like a
> 1/2 step setup. What is the size of the two chainrings?
They are left over from the days of half-step gearing and five speed
clusters of old. I use the 46-21 or 46-24 for the long hills. It
works.
Father and son photo:
Antti Salonen
> I'm still riding hubs and spokes of wheels that I built in the early
> 1970's and just replaced the rims as they wore through. I find that
> more interesting because in that time I have seen many bicycles with
> spoke failures from poorly built wheels but with good spokes.
I guess that should make it more than half a million kilometres for the
hubs and spokes? I'm assuming that these are early 70's top-end Campagnolo
hubs. Have you had to replace the cups and cones often? Can you estimate
how many individual spokes you've had to replace during these 30+ years?
-as
Dan
"jim beam" <nos...@example.net> wrote in message
news:l4WdnWsK-Mt...@speakeasy.net...
>> I'm still riding hubs and spokes of wheels that I built in the early
>> 1970's and just replaced the rims as they wore through.
>
> er, you forgot to mention the hubs that broke flanges & ruined bearings,
> oh & the spokes that you've replaced because they broke...
>
> "this hammer's 30 years old. it's had 3 new handles and 2 new heads, but
> it's still the same hammer". right jobst? don't let fact get in the way
> of a good story.
>
I suspect that the tall man has more than one set of wheels.
jim beam
Tom Nakashima
<jobst....@stanfordalumni.org> wrote in message
news:2W8ie.795$W51....@typhoon.sonic.net...
>
> I don't care for such records. For me it is the enjoyment of the
> places and people I see riding my bicycle ,be that a weekend ride in
> the Santa Cruz mountains, the Sierra Nevada, or the Alps. The British
> are great for endurance records where I have read of bicyclists who
> put in their 100 miles per day, rain, sleet, hail, or snow to set some
> record. That strikes me as a wasted effort in a useless pursuit.
>
> On the other hand, this seems to be a human foible judging from the
> ride reports I see on wreck.bike.rides that are all about suffering
> and death (rides) that they survived. I don't think these riders see
> much or at least they keep it secret in their reports that mainly
> reach out for merit badges. As I have often written, "If you didn't
> like it, don't tell me about it!"
>
> Ride bike! It's a lot of fun if you keep your eyes open.
>
> Jobst....@stanfordalumni.org
There is much truth to this Jobst. I do have Death Ride Pins, and Mt.
Hamilton Challenge patches from years ago, but nobody really cares. They're
actually in a box somewhere, and when I do think of them today, I think of
the cost I had to pay to enter the event when I could have rode the same
roads for free. After while the novelty wears off.
Question about one of your photos; Peter Johnson is indeed a great frame
builder, as I got to speak with him on a few occasions. I noticed his
personality is different from yours. The photo of him on his Faema Masi,
all decked out in his Merckx colors doesn't strike you as odd? I was
wondering why he isn't riding one of his own built bikes?
http://www.bikecult.com/works/archive/04bicycles/pjohnsonJB04.html
-tom
philcycles
Tom Nakashima wrote:
> Question about one of your photos; Peter Johnson is indeed a great
frame
> builder, as I got to speak with him on a few occasions. I noticed his
> personality is different from yours. The photo of him on his Faema
Masi,
> all decked out in his Merckx colors doesn't strike you as odd? I was
> wondering why he isn't riding one of his own built bikes?
> http://www.bikecult.com/works/archive/04bicycles/pjohnsonJB04.html
> -tom
Peter is a Masi collector.
Phil Brown
Matt O'Toole
> <jobst....@stanfordalumni.org> wrote in message
>> I don't care for such records. For me it is the enjoyment of the
>> places and people I see riding my bicycle ,be that a weekend ride in
>> the Santa Cruz mountains, the Sierra Nevada, or the Alps. The
>> British are great for endurance records where I have read of
>> bicyclists who put in their 100 miles per day, rain, sleet, hail, or
>> snow to set some record. That strikes me as a wasted effort in a
>> useless pursuit.
>
> You live in a Mecca for cycling. Please tell me the traffic is
> dreadful so I don't feel so bad about moving away 20 years ago.
The traffic is terrible. The thing to feel bad about is what your old house is
worth now!
Matt O.
jobst....@stanfordalumni.org
These hubs have some features that would not make them my choice
today. These are that the rear axles are overextended with my 129mm
spacing and easily break at the inner end of the right bearing cone.
The quality of cones is such that they look almost brush finished and
run rough even when new. I think the finish is consistent with their
material quality which allows them to spall after a few 10k miles.
I have plenty of broken axles and a fair collection of old spalled
cones. Riding with an 8-speed derailleur with a 6-speed cluster means
that the derailleur limit screw cannot engage the stop for shifting
into the lowest sprocket, so that must be done with care. On occasion
I have missed and kinked a spoke in the process. This has caused a
few outbound-spoke failures.
Considering that these flaws are spread over many years of service,
they don't amount to much intervention. I grab the bicycle, bounce
its front and rear wheel on the floor to see if the tires are hard,
and go for a ride. I get to inspect the wheels closely when I get
a flat, as is seen in various pictures shown in this newsgroup.
jobst....@stanfordalumni.org
>>> I'm still riding hubs and spokes of wheels that I built in the early
>>> 1970's and just replaced the rims as they wore through.
>> er, you forgot to mention the hubs that broke flanges & ruined bearings,
>> oh & the spokes that you've replaced because they broke...
>> "this hammer's 30 years old. it's had 3 new handles and 2 new heads, but
>> it's still the same hammer". right jobst? don't let fact get in the way
>> of a good story.
> I suspect that the tall man has more than one set of wheels.
I have two and the "other set" is in fact the other one that stands in
reserve. I don't see the need to wear out two sets at once. I grab
one of these wheels if I discover a low tire when I want to go
somewhere and don't care to mess with patching at the moment. The
hubs on those wheels have the curved QR levers that came after the
original straight Campagnolo QR on regular wheels.
Sheldon Brown
> Riding with an 8-speed derailleur with a 6-speed cluster means
> that the derailleur limit screw cannot engage the stop for shifting
> into the lowest sprocket, so that must be done with care. On occasion
> I have missed and kinked a spoke in the process. This has caused a
> few outbound-spoke failures.
Ouch! A couple of easy fixes for that:
A. Install a longer low-gear stop screw.
2. Install a 10 mm spacer washer betwixt the derailer and the dropout
hanger.
You're tempting Murphy's Law riding with an improperly adjusted low-gear
limit stop.
Sheldon "Murphy Bites!" Brown
+---------------------------------------------+
| Television: |
| A medium. So called because it is |
| neither rare nor well done. |
| --Ernie Kovacs |
+---------------------------------------------+
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com
jobst....@stanfordalumni.org
>> I don't care for such records. For me it is the enjoyment of the
>> places and people I see riding my bicycle ,be that a weekend ride
>> in the Santa Cruz mountains, the Sierra Nevada, or the Alps. The
>> British are great for endurance records where I have read of
>> bicyclists who put in their 100 miles per day, rain, sleet, hail,
>> or snow to set some record. That strikes me as a wasted effort in
>> a useless pursuit.
>> On the other hand, this seems to be a human foible judging from the
>> ride reports I see on wreck.bike.rides that are all about suffering
>> and death (rides) that they survived. I don't think these riders
>> see much or at least they keep it secret in their reports that
>> mainly reach out for merit badges. As I have often written, "If
>> you didn't like it, don't tell me about it!"
>> Ride bike! It's a lot of fun if you keep your eyes open.
> There is much truth to this Jobst. I do have Death Ride Pins, and
> Mt. Hamilton Challenge patches from years ago, but nobody really
> cares. They're actually in a box somewhere, and when I do think of
> them today, I think of the cost I had to pay to enter the event when
> I could have rode the same roads for free. After while the novelty
> wears off.
> Question about one of your photos; Peter Johnson is indeed a great
> frame builder, as I got to speak with him on a few occasions. I
> noticed his personality is different from yours. The photo of him
> on his Faema Masi, all decked out in his Merckx colors doesn't
> strike you as odd? I was wondering why he isn't riding one of his
> own built bikes?
That is one of his many antiques that he owns and a fine replica of a
jersey of that era.
> http://www.bikecult.com/works/archive/04bicycles/pjohnsonJB04.html
You didn't see why I am wearing a faded wool turtle neck Pedale Alpini
jersey and many of the other riders at this gathering are wearing
similar jerseys of long defunct bicycle clubs or teams. This is an
old timers ride where we get together and recall great rides and races
of the past. Tom Hardy puts these meetings together at various times.
On such occasions we also realize our mortality when noticing that
some of our best racers are no longer here and we miss them.
jobst....@stanfordalumni.org
>> Riding with an 8-speed derailleur with a 6-speed cluster means that
>> the derailleur limit screw cannot engage the stop for shifting into
>> the lowest sprocket, so that must be done with care. On occasion I
>> have missed and kinked a spoke in the process. This has caused a
>> few outbound-spoke failures.
> Ouch! A couple of easy fixes for that:
> A. Install a longer low-gear stop screw.
Oops, the screw is long enough but it isn't aimed at the place where
it is intended to bear. It is pointing off into thin air yet.
> 2. Install a 10 mm spacer washer betwixt the derailer and the
> dropout hanger.
That has greater possibilities but I'm not so hot on machining a
special derailleur anchor bolt and having it stick out there along
with the other hardware.
> You're tempting Murphy's Law riding with an improperly adjusted
> low-gear limit stop.
I'm aware of that but as I said, there isn't a clean solution. My
older 7-sp SunTour derailleur could do that but then while riding in
the redwoods a derailleur stick killed it and I rode home on a fixed
length chain bicycle.
Jay Beattie
<jobst....@stanfordalumni.org> wrote in message
news:diqie.929$W51....@typhoon.sonic.net...
Why do you spite yourself? Is this some odd ascetic thing. We
have cassette hubs that cost little more than you are spending on
cones and axles. You could build a wheel using one. -- Jay
Beattie.
Tom Nakashima
<jobst....@stanfordalumni.org> wrote in message
news:oVpie.923$W51....@typhoon.sonic.net...
>> http://www.bikecult.com/works/archive/04bicycles/pjohnsonJB04.html
>
> You didn't see why I am wearing a faded wool turtle neck Pedale Alpini
> jersey and many of the other riders at this gathering are wearing
> similar jerseys of long defunct bicycle clubs or teams. This is an
> old timers ride where we get together and recall great rides and races
> of the past. Tom Hardy puts these meetings together at various times.
>
> On such occasions we also realize our mortality when noticing that
> some of our best racers are no longer here and we miss them.
>
> Jobst....@stanfordalumni.org
Jobst, I enjoyed reviewing your 40-years in the Alps link, looks like you
put in some new photos, or it's been too long since I've last seen. I don't
think I would have recognized the young Bill Robertson as we sometimes use
Robertson's Machine Shop services. I asked him a few years back if he
remembers riding in the Alps with you, and he replied; "Those were the good
ol days".
btw: John Grant says hello, I lent him my copy of the Bicycle Wheel years
ago, said it came in handy.
-tom
currie...@yahoo.co.uk
fillets on top of lugs?
What's the chainstay bridge on your bike for? I thought they served no
purpose.
Thanks,
Thomas Hood
jtaylor
<currie...@yahoo.co.uk> wrote in message
news:1116414465.1...@g14g2000cwa.googlegroups.com...
> What's the chainstay bridge on your bike for? I thought they served no
> purpose.
>
Not _no_ purpose - it'll keep the tyre from jamming in the stays when you
hit it hard to knock it out of the dropouts.
currie...@yahoo.co.uk
Tom
jim beam
the bb/chain stay junction.
avarc...@gmail.com
>How does that happen with vertical dropouts?
It doesn't.
I found this in the archives:
http://tinyurl.com/bfopt
Joss
Dave Larrington
None of you lot use mudguards then...
--
Dave Larrington - <http://www.legslarry.beerdrinkers.co.uk/>
The sixth student said, "I ride my bicycle because I want people to
look up to me and say 'Wow! He looks really good up there!' The
teacher replied: 'Go away, Fabrizio!'"
jtaylor
Leading to this:
http://pardo.net/bike/pic/fail-009/ccf12_2.jpg
Please, no comments from "mb" about how brazing temperatures will not
produce a heat-affected-zone.
jobst....@stanfordalumni.org
>>> Is your frame like this
http://tinyurl.com/drbrq ? What's the idea of
>>> fillets on top of lugs?
>>> What's the chainstay bridge on your bike for? I thought they
>>> served no purpose.
>> tube manufacturers generally recommend them to help mitigate
>> fatigue at the BB/chain stay junction.
> Leading to this:
> http://pardo.net/bike/pic/fail-009/ccf12_2.jpg
> Please, no comments from "mb" about how brazing temperatures will
> not produce a heat-affected-zone.
We only have that picture of a badly cared for frame with rust coming
through the paint. I don't know what else on this frame was wrong but
just a vignette like this does not support having or not having a
chainstay bridging tube near the BB.
Meanwhile, consider what forces this bridge possibly could support,
what causes them, and how the bridge can do this when located so close
to the more massive and rigid BB. In all, the additional brazing and
cross section discontinuity probably weakens the chain stays. Such
considerations are what evoked the item in:
jim beam
quoting your own misunderstanding "probably" doesn't help the situation.
fact is, manufacturers like dedacciai /specifically/ recommend
chainstay bridiges & /specifically/ cite fatigue mitigation as the
reason to use them.
jim beam
if anything, that proves my point - there /is/ fatigue loading in this
area. i've seen more bridgeless frames fail at the bb/chainstay
junction, both lugged & lugless, than i've seen bridged frames fail.
regarding heat affected zone, yes, that can be a problem depending on
tubeset & builder, but the same problem exists for the bb, so again,
it's a migration to a point with less leverage up the chainstay rather
than at the maximum leverage, the bb junction.
Jim Smith
> jtaylor wrote:
>> "jim beam" <nos...@example.net> wrote in message
>> news:H7-dnfpo8_1...@speakeasy.net...
>>
>>>currie...@yahoo.co.uk wrote:
>>>
>>>>Is your frame like this http://tinyurl.com/drbrq ? What's the idea of
>>>>fillets on top of lugs?
>>>>What's the chainstay bridge on your bike for? I thought they served no
>>>>purpose.
>>>>
>>>>Thanks,
>>>>
>>>>Thomas Hood
>>>>
>>>
>>>tube manufacturers generally recommend them to help mitigate fatigue at
>>>the bb/chain stay junction.
>>>
>> Leading to this:
>> http://pardo.net/bike/pic/fail-009/ccf12_2.jpg
>> Please, no comments from "mb" about how brazing temperatures will
>> not
>> produce a heat-affected-zone.
>
> if anything, that proves my point - there /is/ fatigue loading in this
> area.
Of course it does not. The bridge obviously changes the flow of
momentum in that area, but there is no reason to come to the
conclusion you do based on that picture.
> i've seen more bridgeless frames fail at the bb/chainstay
> junction, both lugged & lugless, than i've seen bridged frames fail.
That would be a correct ivestigative approach. Of course,
recolections are notoriously unreliable.
Doesn't anyone have a model of this?
jim beam
> jim beam <nos...@example.net> writes:
>
>
>>jtaylor wrote:
>>
>>>"jim beam" <nos...@example.net> wrote in message
>>>news:H7-dnfpo8_1...@speakeasy.net...
>>>
>>>
>>>>currie...@yahoo.co.uk wrote:
>>>>
>>>>
>>>>>Is your frame like this http://tinyurl.com/drbrq ? What's the idea of
>>>>>fillets on top of lugs?
>>>>>What's the chainstay bridge on your bike for? I thought they served no
>>>>>purpose.
>>>>>
>>>>>Thanks,
>>>>>
>>>>>Thomas Hood
>>>>>
>>>>
>>>>tube manufacturers generally recommend them to help mitigate fatigue at
>>>>the bb/chain stay junction.
>>>>
>>>
>>>Leading to this:
>>>http://pardo.net/bike/pic/fail-009/ccf12_2.jpg
>>>Please, no comments from "mb" about how brazing temperatures will
>>>not
>>>produce a heat-affected-zone.
>>
>>if anything, that proves my point - there /is/ fatigue loading in this
>>area.
>
>
> Of course it does not. The bridge obviously changes the flow of
> momentum in that area, but there is no reason to come to the
> conclusion you do based on that picture.
excuse me, but the presence of fatigue cracking is about as conclusive
an evidence of strain as you can get. fatigue fundamentally cannot
happen without strain cycling.
Jim Smith
Sure, but it tells you nothing about what the strain would look like
without the bridge. You seem to be claiming that it does. Maybe I
misunderstood you, maybe you were only claiming that there is some
strain somewhere in the chainstays somewhere around the bottom
bracket. Sure, the photo proves that.
Matt O'Toole
> Meanwhile, consider what forces this bridge possibly could support,
> what causes them, and how the bridge can do this when located so close
> to the more massive and rigid BB. In all, the additional brazing and
> cross section discontinuity probably weakens the chain stays. Such
> considerations are what evoked the item in:
>
> http://tinyurl.com/bfopt
Besides the tire jamming issue, I always thought the bridge tradition came from
fender mounting.
Matt O.
Richard Sachs
"jim beam" <nos...@example.net> wrote:
> quoting your own misunderstanding "probably" doesn't help the situation.
> fact is, manufacturers like dedacciai /specifically/ recommend chainstay
> bridiges & /specifically/ cite fatigue mitigation as the reason to use
> them.
i am a dedacciai user for a decade, using mainly zero series
tubing. i use the 30x17 oval c'stays and no bridge. i have never
read or heard that dedacciai recommends bridges...
e-RICHIE
jim beam
ago. wish i'd kept it. but even if i hadn't read it there, the fact
that, in the event of failure, the fatigue cracking point "migrates"
from the bb to the bridge tells you there's something significant going on.
my personal favorite bb bridge is this:
http://www.dellasanta.com/index.php?do=photos&which=Pearl%20White&image=white-red-bb3.jpg
the teardrop is a nice touch that can mitigate stress risers just like
the pointed tangs on the tube lugs.
richar...@juno.com
ovalized 30x17 pipes. i feel that adding heat there is
courting disaster, regardless of who adds the heat and/or
for what reason the bridge is added.
the jpg shows a bridge with a fender mount; i wouldn't choose
"modern" fully-ovaled c'stays for an application like this.
e-RICHIE
richar...@juno.com
i would only add a bridge with 22.2mm round pipes. on
ovalized 30x17 pipes, i feel that adding heat there is
jim beam
shouldn't be any more disasterous than brazing the tube to the bb shell,
particularly if the butt section extends beyond the bridge, which it
usually does. i haven't done any metallography on the modern tube
steels, but allegedly, they resist recrystallization very well. if
that's the case, particularly if you're using a lower temp silver
solder, you'd be fine. and if you used a tube set made of an air
hardening steel it should be /made stronger/ by the heat, not weakened.
richar...@juno.com
there is no "butt" section.
i haven't done metallography either, but i've brazed
frames since 1973. whether it's silver-alloyed rod used
for brazing (not soldering) or brass, the bridge has an
effect of the shape of the pipe, leaving its footprint
embeded into it. take apart some assemblies and you'll
see how the area "inside" the c'stay compresses a bit
once the expanding/contracting occurs. a round section
c'stay has proven over time to accept this with no
disasterous consequences. i don't believe this will be
the case if bridges are added to flatter "ovalized" c'stays.
yes-you are correct: the fact that the jpg shows a fender
mount is not part of the equation.
e-RICHIE
Luns Tee
<jobst....@stanfordalumni.org> wrote:
>> 2. Install a 10 mm spacer washer betwixt the derailer and the
>> dropout hanger.
>
>That has greater possibilities but I'm not so hot on machining a
>special derailleur anchor bolt and having it stick out there along
>with the other hardware.
But also, this would sacrifice adjustment range on the high-gear
limit stop. Maybe there's enough range available for this to work. Or
maybe you'd end up with neither stop functioning instead. But, the
high-gear limit stop may be less of an issue given the shift lever has
its own stop on this end.
>> You're tempting Murphy's Law riding with an improperly adjusted
>> low-gear limit stop.
>
>I'm aware of that but as I said, there isn't a clean solution. My
>older 7-sp SunTour derailleur could do that but then while riding in
>the redwoods a derailleur stick killed it and I rode home on a fixed
>length chain bicycle.
I imagine I'd try cutting a length of thick-wall aluminum
tube to slip over the cable between the derailleur's housing stop and
cable clamp, and file that down to the right length to act as a travel
stop. How the tube ends bear on the derailleur might need a little
creativity though, depending on the particular derailleur.
-Luns
jim beam
> jim beam wrote:
>
>>richar...@juno.com wrote:
>>
>>>i would only add a bridge with 22.2mm round pipes. on
>>>ovalized 30x17 pipes. i feel that adding heat there is
>>>courting disaster, regardless of who adds the heat and/or
>>>for what reason the bridge is added.
>>>the jpg shows a bridge with a fender mount; i wouldn't choose
>>>"modern" fully-ovaled c'stays for an application like this.
>>>e-RICHIE
>>>
>>
>>the fender mount is not relevant. regarding the effect of heat, it
>>shouldn't be any more disasterous than brazing the tube to the bb
>
> shell,
>
>>particularly if the butt section extends beyond the bridge, which it
>>usually does. i haven't done any metallography on the modern tube
>>steels, but allegedly, they resist recrystallization very well. if
>>that's the case, particularly if you're using a lower temp silver
>>solder, you'd be fine. and if you used a tube set made of an air
>>hardening steel it should be /made stronger/ by the heat, not
>
> weakened.
>
>
> there is no "butt" section.
no butt? that's not what's indicated by the tube data you can check at
the dedacciai or reynolds web sites. /some/ are plain gauge, but butted
section chain stays are most definitely available.
http://www.dedacciai.com/download/prd_eom
[this is a pdf. do a "save as", then add the file extension so it will
open properly.]
http://www.reynoldscycles.co.uk/downloads/PARTLIST.pdf
richar...@juno.com
oh. in building jargon that is referred to as
taper-guage, not "butt". however, this information
doesn't change my p.o.v. that the bridge affects
the chainstay (as described above) and that round
c'stays have proven to remain virtually unaffected
by this, whereas the shape of an oval-ized stay
of similar guage - well, let's check back in a decade
or three to ascertain whether the bridge helped or
hindered the life span of these frames.
e-RICHIE