Re: University frame-flex testing: surprising results

[Tom Nakashima]

> <[email protected]> wrote in message
> news:[email protected]...
?
>>
>> I got a new fork, mine being many miles old. I'm sure there are
>> various good ways of extending the steertube and I'd leave that up to
>> the frame builder. I meet riders who have had this done so it isn't
>> uncommon. I have an aluminum spacer tube to get my stem height the
>> same as before. Be careful and after being sure what fits best cut
>> the steertube to length.
>>
>> You'll like adjusting head bearing with an Allen wrench, removing the
>> bars without untaping and removing a brake lever, removing the stem
>> without a hammer and the solid support. For me it was also getting
>> rid of corrosion stuck stems.
>>
>> Jobst Brandt
>

I just got off the phone with Dale, my bike goes under the knife
tomorrow. He just reminded me I'll need to purchase a new headset,
stem and probably new handlebars since mine are Cinelli 26.4
I haven't even looked at stems for 20+ years.

He also mentioned he would like to do the insert/extension for the steering
column. Save me a paint job, alignment, and new fork.
-tom

 

[Jay Beattie]

On Jan 18, 1:50 pm, "Tom Nakashima" <[email protected]> wrote:
> > <[email protected]> wrote in message
> >news:[email protected]...
> ?
>
> >> I got a new fork, mine being many miles old.  I'm sure there are
> >> various good ways of extending the steertube and I'd leave that up to
> >> the frame builder.  I meet riders who have had this done so it isn't
> >> uncommon.  I have an aluminum spacer tube to get my stem height the
> >> same as before.  Be careful and after being sure what fits best cut
> >> the steertube to length.
>
> >> You'll like adjusting head bearing with an Allen wrench, removing the
> >> bars without untaping and removing a brake lever, removing the stem
> >> without a hammer and the solid support.  For me it was also getting
> >> rid of corrosion stuck stems.
>
> >> Jobst Brandt
>
> I just got off the phone with Dale, my bike goes under the knife
> tomorrow.  He just reminded me I'll need to purchase a new headset,
> stem and probably new handlebars since mine are Cinelli 26.4
> I haven't even looked at stems for 20+ years.
>
> He also mentioned he would like to do the insert/extension for the steering
> column.  Save me a paint job, alignment, and new fork.
> -tom- Hide quoted text -
>
> - Show quoted text -

Tom, say hello to Dale for me. I haven't talked to him in 20 years.
I think I was his second or third paying frame customer when I bought
my frame in '76. Some times, you just have faith in a guy. I think I
had five or six total frames from him (some stolen, some crushed by
cars, one on the wall in my basement) -- all built in the old Taylor
Street shop. I shot a 16mm documentary of him building a frame and
philosophizing about various things in a voice over for a film class
at SJSU, but alas, I dumped that film accidentally many moves ago. It
was pretty cool, it opened with torch flame moving around a dark frame
(an exposure mistake that I declared to be art). -- Jay Beattie.

 

[[email protected]]

Tom Nakashima writes:

>> I got a new fork, mine being many miles old. I'm sure there are
>> various good ways of extending the steertube and I'd leave that up
>> to the frame builder. I meet riders who have had this done so it
>> isn't uncommon. I have an aluminum spacer tube to get my stem
>> height the same as before. Be careful and after being sure what
>> fits best cut the steertube to length.

>> You'll like adjusting head bearing with an Allen wrench, removing
>> the bars without untaping and removing a brake lever, removing the
>> stem without a hammer and the solid support. For me it was also
>> getting rid of corrosion stuck stems.

> I just got off the phone with Dale, my bike goes under the knife
> tomorrow. He just reminded me I'll need to purchase a new headset,
> stem and probably new handlebars since mine are Cinelli 26.4 I
> haven't even looked at stems for 20+ years.

You don't need new bars unless you want to do that. Just put a shim
around the ones you have. An aluminum drink can will do. Oops, my
bars are 25.85mm, I don't know what the threadless stems take. Make
sure you have four screws on the bar clamp and two screws on the stem
clamp. Without redundancy, one screw failure means suddenly no bars.

> He also mentioned he would like to do the insert/extension for the
> steering column. Save me a paint job, alignment, and new fork.

Sounds good.

Jobst Brandt

 

[jim beam]

[email protected] wrote:
> Tom Nakashima writes:
>
>>> I got a new fork, mine being many miles old. I'm sure there are
>>> various good ways of extending the steertube and I'd leave that up
>>> to the frame builder. I meet riders who have had this done so it
>>> isn't uncommon. I have an aluminum spacer tube to get my stem
>>> height the same as before. Be careful and after being sure what
>>> fits best cut the steertube to length.
>
>>> You'll like adjusting head bearing with an Allen wrench, removing
>>> the bars without untaping and removing a brake lever, removing the
>>> stem without a hammer and the solid support. For me it was also
>>> getting rid of corrosion stuck stems.
>
>> I just got off the phone with Dale, my bike goes under the knife
>> tomorrow. He just reminded me I'll need to purchase a new headset,
>> stem and probably new handlebars since mine are Cinelli 26.4 I
>> haven't even looked at stems for 20+ years.
>
> You don't need new bars unless you want to do that. Just put a shim
> around the ones you have. An aluminum drink can will do. Oops, my
> bars are 25.85mm, I don't know what the threadless stems take. Make
> sure you have four screws on the bar clamp and two screws on the stem
> clamp. Without redundancy, one screw failure means suddenly no bars.

hmmm, cast [thixoformed] aluminum clamp vs. cold worked stainless screw...

which is the biggest fatigue risk jobst? take a wild-ass guess since
you're such a fatigue expert and all...


>
>> He also mentioned he would like to do the insert/extension for the
>> steering column. Save me a paint job, alignment, and new fork.
>
> Sounds good.
>
> Jobst Brandt

 

[Chalo]

jim beam wrote:
>
> Jobst Brandt wrote:
>
> > You don't need new bars unless you want to do that. Just put a shim
> > around the ones you have. An aluminum drink can will do. Oops, my
> > bars are 25.85mm, I don't know what the threadless stems take. Make
> > sure you have four screws on the bar clamp and two screws on the stem
> > clamp. Without redundancy, one screw failure means suddenly no bars.
>
> hmmm, cast [thixoformed] aluminum clamp vs. cold worked stainless screw...
>
> which is the biggest fatigue risk jobst? take a wild-ass guess since
> you're such a fatigue expert and all...

Pinch clamps place a large bending load on screws if the support for
the screw head is not self-aligning (and most of them are not). The
bending load is carried by the screw as it rotates when being
tightened or loosened. Furthermore, the screw is covered with stress-
concentrating notches. I have seen a lot more failures of bolts for
pinch clamps than failures of the clamps themselves. I'm sure Jobst
has too.

You are correct, that like for like, cold formed stainless (or often,
chrome-plated cold formed steel) is a stronger and more fatigue-
resistant material than HIP cast aluminum. But you seem to ignore the
fact that part geometry is the driving factor in this case.

I have made stems without redundancy in the clamping bolts, but
because of that I chose to use 8mm fasteners, where I have more
usually used 6mm fasteners redundantly.

Chalo

 

[Chalo]

jim beam wrote:
>
> Jobst Brandt wrote:
>
> > You don't need new bars unless you want to do that. Just put a shim
> > around the ones you have. An aluminum drink can will do. Oops, my
> > bars are 25.85mm, I don't know what the threadless stems take. Make
> > sure you have four screws on the bar clamp and two screws on the stem
> > clamp. Without redundancy, one screw failure means suddenly no bars.
>
> hmmm, cast [thixoformed] aluminum clamp vs. cold worked stainless screw...
>
> which is the biggest fatigue risk jobst? take a wild-ass guess since
> you're such a fatigue expert and all...

Pinch clamps place a large bending load on screws if the support for
the screw head is not self-aligning (and most of them are not). The
bending load is carried by the screw as it rotates when being
tightened or loosened. Furthermore, the screw is covered with stress-
concentrating notches. I have seen a lot more failures of bolts for
pinch clamps than failures of the clamps themselves. I'm sure Jobst
has too.

You are correct, that like for like, cold formed stainless (or often,
chrome-plated cold formed steel) is a stronger and more fatigue-
resistant material than HIP cast aluminum. But you seem to ignore the
fact that part geometry is the driving factor in this case.

I have made stems without redundancy in the clamping bolts, but
because of that I chose to use 8mm fasteners, where I have more
usually used 6mm fasteners redundantly.

Chalo