Passoni Welding
 

In a recent thread that was shut down, there was a discussion of fillet brazing. One of the posts was from member Dan Chase , who I haven't previously met. His post, which I am editing below so as to avoid the prior conflict, as well as to focus on the topic I wanted to discuss, mentions fillet brazed Passonis. I am not a metallurgist, or a welder, but I am very curious about Passoni and their construction. I wanted to delve deeper on this post, unfortunately the thread was closed. Hence this thread.

I acquired mine from a former member (Citoyen Du Monde). I am deeply grateful to him for choosing me as the recipient. Those who know him are aware of his knowledge of the industry and builders...

Citoyen had told me, and I'm hazy on details because it has been a while since we discussed this bike, that the tubes were each rolled individually from ti sheets. My understanding of ti frame building is that it would have been puddle welded, and the welds were then very carefully polished out by the builder. I'd assume that was the method used here. The original Passoni was built by Riva for himself...and he had been asked by people over the years to manufacture/sell them. I found one link that mentions some of the details I recall from that conversation:

https://www.cyclist.co.uk/in-depth/1...-factory-visit

My recollection is somewhat different than the link on a point or two - I recalled the son having formed a partnership with Riva some years later, and learning how to fabricate the bikes. He had an early death, and the brand was sold.

I was hoping that Dan may know more, or discuss the gap in our understanding. I don't think fillet brazing would really apply to construction of titanium, no?

The post I wanted to respond to:

...Redacted...

I`d put a 1989 Passoni Animus Titanio TT in the mix for filet work - I`m working on a 1989 TT made by Luciano Passoni himself and it is incredible.
I`d also put my 1980 Moser Sanson team bike in mix for lugged brazing - the frame built by Ugo De Rosa himself was a masterpiece when inspected bare metal - an exceptional ride.
If we need to put credentials on the table (WTF happened in this thread????) I`m a professionally trained gold/silversmith so understand a thing or two about brazing/soldering and finish (though engineers are much better at understanding the mechanics of a good joint - I see the finish)

"Redacted"

Dan.

I’ll post some photos of mine as well, including the integrated bars/stem.




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That looks like a ton of work to polish all those welds smooth.

The titanium version of a Barra.

not sure I buy the tube from sheet- except
for the tapered elements.
the cost to tool up to make ti stays and blades would be significant.

the Ti welding... wonder how they kept the oxygen away?

I got to see the ti-22 CanAm car take shape
Everything, complete chassis, roll bar, suspension elements were all titanium
this was in the late 60's!
Thousands of ti pop rivets and the suspension parts welded up in an inert tank with windows, flood it with argon, looked like a sandblast case with a pressure door.

Bryant, the designer had worked out the early version of ground effects, under the car was a wedge of open space. Lots of downforce when un -disturbed air flowing, and that was part of its demise, dirty air behind another car, modest hill, and car did a backflip.
end of that tub.

not really enough cash to build another
probable cost $250k in material back then

I tend to trust CDM on this point, and it also is repeated in the link I posted. The engineer, Riva, was involved in aerospace and probably had some access to work equipment.

I trust what I learned in school and in the school lab. Not stating it cannot be done.

kind of like Pino claiming his titanium tubes were bored out of titanium rod. Sure.
the fact that they were Brazed together somehow was not in visual dispute and amazing in of itself.
someone would have to hold a seance with Cecil to get the lowdown.

if one reviews a Speedwell fork- that was a wild amount of work also

Beautiful bike. I remember when you first acquired it. Glad to see it's still around. The work sculpting those shifters is quite something. And the bars/stem combo! :love:

Yes, I believe this would be considered fillet brazing. It does remind me of my Speedwell Titalite (album link), though the Passoni is more elegant and carefully constructed. My Speedwell seat cluster looks crude by comparison.

Thinking out loud...If it was rolled, seamed, and polished smooth, shouldn't you be able to see the seam on the inside of the tubes? You could pull the post and stem and have a look inside, right? Surely, the inner part of the seam would not have been polished. Even if the tubes were reamed, there would still be some visible trace.

As is so often the case, I don’t know enough to argue the point intelligently ;)

Good point - I’ll take a peak at some point.

I've heard from multiple sources over the years that Passoni tubes were all rolled from sheet and welded along the seam. Maybe each source was quoting the other one and it all started from a misunderstanding? Possible I guess, but I'm inclined to believe it's actually true. That dude was nuts (or maybe still is?)

Probably similar to how all Ti frames are welded, in the atmosphere with an argon purge inside, and a really good gas lens on the welding torch. It's not really that hard.

Having done both, I do see a strong resemblance between Ti welding and fillet-brazing of steel. Hard to explain but basically the behavior of the molten puddle. The Ti puddle acts more like a brass ("bronze") fillet's puddle than like a steel TIG weld. I friggin LOVE the molten Ti puddle, it's one of the most beautiful things I've ever seen. Fillet brazing is pretty cool too, but nothing beats Ti for me, while I'm actually doing it. (For riding, it's a toss-up. Other factors are more important than what material it's made of)

<brag> when I took Gary Helfrich's UBI class (early-'90s), my very first test weld in Ti, less than an inch long, came out awesome. It looked just like a Merlin/Seven/Moots/whatever. </brag>
Gary was surprised at first — it was literally the first time I had tried welding Ti, and I wasn't even a good TIG welder in steel, I was a TIG beginner. But then he remembered that most of the people he'd taught who'd picked it up the fastest were brass fillet brazers. The ones who were the worst at Ti were guys who were experts at welding aluminum, which is so different that all your reflexes are wrong! Un-learning wrong reflexes is hard. But even TIGging steel doesn't prepare you for TIGging Ti as well as brass fillet brazing on steel does.

Gary also taught us how to smooth the welds, like on a Passoni. I signed up for his class after seeing a 1.0 kg Ti frame he made and brought to the Interbike show, it was fantastic. It looked so organic with the tubes just flowing into each other. I didn't make a whole frame in the class — you didn't build a frame in that first class of his, though the class changed, and later editions you did build a frame. But in this class of maybe eight? guys, I was the only one who made something rideable, a Ti stem in the style of an Arctos or Ibis, welds all smoothed and polished. Came out truly excellent. (Gary also taught Ibis how to make stems, so the family resemblance between an Arctos and an Ibis is no coincidence.)

Suffice it to say, the equipment needed was pretty minimal, and I went back to Davidson after the class and started making Ti frames there after collecting a pretty minimal set of Ti-specific tools. Mostly just some purge fittings to go in the openings of the frame, a couple small purge boxes for things like stay-end "bullets", and the argon plumbing to those fittings. And a really big gas lens for the TIG torch. Making Ti frames is easy! :lol:

Too bad they're totally obsolete these days. If it ain't carbon, it's worthless, right? :50:

Mark B

I wish I had the background to understand more of this post, but I appreciated the parts I did understand, and appreciate your insight. Even if I didn't understand all of it ;)

pretty bike no matter if the tubes were rolled, drilled, conjured by magic or furnished by an alien :)

Awesome pragmatic post demystifying frame building. I find welding titanium, once set up is easier than tig welding especially high-strength alloys such as 853 or 953. As I have started before the ultimate indication of a frame builder's skill is in a simple tig welded air-hardened steel frameset. You only get one pass through it and any errors are there for everyone to see.

Hi Guys,
Sorry to be slow in responding - have been away for a few days.

I have an `89 Animus TT being re-built at the moment - I`ll have a look inside the tubes and see if I can determine the construction method - I can confirm the downtube is 30mm o/d and I don`t think that is a stock seamless titanium 3al-2.5v - though if they rolled and welded the tubes then who knows what the original titanium specs are. The welding and forming on the early Animus is exceptional, especially around the area of the TT position mounted down tube shifters and internal cable entry points.

Yep, pretty sure its double/triple passed puddle welded so maybe not classed as fillet brazed - that previous thread mentioned was a bit hot under the collar rather...

Pics and details of the bike coming soon, Dan.

Just a friendly tap on the shoulder Dan - looking forward to your post ;)

I'm only going to repeat what I've heard from others (over on the Paceline forums), but yes -- Passoni are welded, then smoothed out. Second pass? Ground and polished? I'm not sure.

But it's not fillet brazing.