On 4/15/2021 9:00 PM, AMuzi wrote:
On 4/15/2021 7:49 PM, Frank Krygowski wrote:
On 4/15/2021 8:30 PM, jbeattie wrote:
On Thursday, April 15, 2021 at 4:31:19 PM UTC-7,
wrote:
There is serious cost in building a massive frame
fixture. You need to produce and sell
a large number of frames to amortize that cost. For a
very low production volume it's not worth
doing and absolutely not necessary.

I've known several people who have built steel frames, At
least two of those guys were
mechanical engineers, including a good friend of mine
whom I consider to be the smartest
engineer I ever worked with. (We were in grad school
together, and later I hired him to teach in
our program.) He did workshops on frame building at LAW
conventions, back when they had
LAW conventions.

That guy built absolutely beautiful (concours d'elegance
winning) single frames, plus several
tandems. Others built recumbents from instructions or, in
one case, from the builder's own design. None of them
used massive frame plates.

Tom's made it very clear that in addition to being a
bumbling mechanic, he has little
understanding of the economics of manufacturing,

...Â*Â* You never really know what's under the paint -- or
whether the joints are filled and not over-heated.Â* I've
seen beautiful bikes fall apart -- and bikes that were not
so beautiful after you stripped off the paint (e.g.
dynafile dings filled with brass in '70s Ritchey frames).

That brings up an interesting point: We can assess the
beauty of a frame according to our individual taste. But how
do you know any particular frame is really good? What
matters in that evaluation?

If I stripped the paint off a well-used frame and saw a ding
filled with brass, I don't think it would bother me,
assuming it hadn't caused a failure. OTOH, overheating tubes
can lead to failure - but how does one tell before the
failure occurs?

I'm the guy whose custom tandem had its fork blades suddenly
break off. The builder, Jim Bradford, substituted track gage
fork blades in place of tandem gage blades. I never bothered
to weigh the fork, let alone X-ray it, so that defect was
hidden from me.

The blades broke maybe half an inch below the fork crown. I
can't say if that was evidence of overheating as well. Given
that the wall thickness was 1/3 what it should have been,
any overheating was probably just icing on the cake.


I don't know either.

Sprint track blades were the same beefy 1.2mm gauge as tandem blades
then.Â* On a tandem though, round blades are not ideal as the blade flex
is against a smaller section (22mm? 24mm?) than a 29mm classic oval
blade. Riders here are already familiar with normal fork flex and
tandems have a lot more of that.

Pursuit blades at 0.8mm (or even 0.9) would not be a very good choice at
all in vintage material for a road tandem.

I just measured the broken fork blade's wall thickness. I get 0.7mm. And
these were 22mm round, not oval.

After the crash, I was on the phone with Jack Goertz of Tandems, Ltd. He
said he had told Jim Bradford his forks were too flimsy, but Bradford
didn't listen. I assume Jack was talking about ones with normal wall
thickness, not this stupid-light version.

--
- Frank Krygowski