I was thinking the fork crown would be machined, if it matters. Not many thin walls.

[MENTION=128980]Catnap[/MENTION] - I agree. I am going to prototype nearly the entire bike. I think showing the prototypes to the builder will help in the relationship. I don't think throwing drawings over the fence will end well in any way.

I did print (in plastic) and earlier version of the stem and brake levers. The stem changed and I need to reprint. I have bought some different aluminum bar (6061, 3003) in different wall thicknesses and I have made the bending mandrel. I haven't gotten to bending the bars yet. I'm thinking about hacking a Light and Motion 360 to use in the bars.

I think I'll also take a swag at the rack and lock combo. I will definitely fabricate the lock. I don't have the brazing experience for the final build, but I certainly can weld and bend stainless. I make that sub assembly, the rest of the bike is pretty straight forward. A couple of screw bosses in odd places.

I will print the rear dropouts in plastic first as a proof of principle. I am curious about attaching the stays. All of the videos I have seen have the straight slots cut into the stays. But then I never see how the builder bends the stays. If they go in straight, that would require to bend the stays. On the other hand, if you angle your slot cut, the stays can remain straight. Is one method prefered over the other? And then why is that?

And [MENTION=57478]repechage[/MENTION] - Yes, this is an Italian city bike using modern tech. There is nothing new under the sun with regards to bikes. They are too simple of a mechanism to have anything "new". And while the geometry maybe from a city bike of the 50s and 60s, it is also a race geometry from the 30s.

I missed the machining of the crown. The CNC shop will love you making their next boat payment unless they owe you a favor.
With a 3.5 mm thick face plate for the dropout, why not divide all thicknesses a bit and just trap the segments from both sides?
When I was messing around with a few frame designs, one solution I used was to introduce bends to the dropout to match the center lines of the stays. (Typical Campagnolo ends have some pre bend) That way the slot the dropout inserts to will be aligned with the center lines of the stays.
Much later I see now a few builders design slots in the dropout so that the stays do not get slotted, the thicker dropout traps the undisturbed "tube".

David Kirk created a dropout that has a ball on the end...it fits into the tube like a ball and socket joint

I couldn't find s simple picture on his site but you can see it on the table of parts and in build mode here Build | Kirk Frameworks

it might be something you could do in similar manner

I had this printed a few years ago in 17-4 stainless through Solid Concepts (now Stratasys) in a laser sintering process. I see they now have 316LI wanted a prototoype to test that I could possibly do a lost wax casting. The cost was ~$200 as I recall. The surface was fairly rough, it would take a significant amount of sanding and polishing to get that mirror finish you're looking for.



BTW, this is the decaleur I made with it:



This project has been on the back burner, I'll send it in to Waterford to see if they'd make it for me.

Really like the split dropout solution for belt drive.

in the frames I've built, i brazed the dropouts into straight slots cut into the stays. then after they have cooled, I cold-bent them in a vise to the correct angle. it's an easy tweak and doesn't affect the joint.

to add to this one - another framebuilder I share my shop with had a whole lot of biplane fork kits made for him by a CNC shop. If you want to buy a set from him, I'm sure he'd be willing to hook you up cheap. you can email me at mechastudios *at* usa *dot* net. It's basically two steel plates: the lower plate has ovals cut into it for the fork blades, the top plate has similar recessed divots for the blades and a hole in the center for the steerer tube.

What bends? The dropout? The tubing? Both?

Stainless?

sorry if it wasn't clear - the dropout bends.

as for the fork crown, it's not stainless. Not sure what grade steel it is, actually, but def. not stainless.

@iab I had occasion last night to take the belt off my Priority (the same one in post 72), and discovered the fasteners were chain ring bolts. It reminded me of your project here.

Aluminum?

That would be interesting. They don't have nearly the strength of stainless. I think it would also show there is not a huge amount of stress at that point.

The frame and dropouts are aluminum, the bolts were some kind of steel, probably. It's not an expensive bike.

Always an honor to be thought of.

You sir make a fine looking hub. It should always be on the top of the list for hubs to use.

Let's dust off this thread. 3 years in. 5-year timeline may be a bit aggressive, we shall see. Latest and greatest refinement is here (up to image 54, the rest is old stuff) - https://www.flickr.com/photos/681231...57656681474954


Gregario_Dims_10-05-18 by iabisdb, on Flickr



02_Gregario by iabisdb, on Flickr

I think the stay ends are asking for trouble, frightful to fabricate.
Much is possible, but at what cost?

Why is that? The program I use enables me to "unroll" any surface created to 2D. I print it, wrap it on the uncut stay, cut and bob's yer uncle. That will take decidedly less time than bringing a printed part to a fine polish.

Pure curiosity and knowledge question: what is the state of the art for for printed metal, what materials are printed and are they malleable enough to wrap?

I think you misunderstood. I will have the lugs, dropouts, BB shell and some plugs for the chain stay bridge and rear rack printed in stainless steel. The tubing is Columbus xcr stainless. From the picture below, you can see the internal sockets I'd like to use on the rear dropouts in a fishmouth design.

repachage pointed out aligning the cut end of the stays could be difficult to match the dropout sockets. But I can virtually "unroll" the stay ends to a 2D pattern. That 2D pattern can then be printed on paper or a thin film. I can use that as a template for the uncut tubing end.

10_Gregario_Rear_Dropouts by iabisdb, on Flickr

Or I misunderstood your question.

You can print aluminum, titanium, stainless and most every precious metal. The stainless can be annealed to be malleable. Precious metals are just naturally soft.

Shear strength is about 85%, tensile is about 90% and compressive is about 95% of the "natural" material

If you are printing the dropouts, from a fabrication perspective it would be easier and stronger to print the stays' lug points directly on the dropout and then have a more traditional stay-to-dropout interface where the dropout has a round end that fits into the end of the stay tube.

After brazing it will look the same as what you have in the drawing, but you wouldn't have to cut that lug pattern in the interfacing parts, and the joint would be stronger because you would have more contact surface area at the braze joint. The round-end style I'm talking about looks like this, where those round ends fit into the seatstay and chainstay tube ends.




Let me know if that doesn't make sense. Fairly hard to put into words an idea about a complex 3D drawing

I thought about that. I have a question to a couple of folks who haven't provided an answer.

In the example you posted, the socket diameter is the same end to end. Just eyeballing it, I'd say the length is 20-25mm. My question is that chainstays, and seatstays to an extent, are tapered. Over the length of that socket, the ID of the chainstay increase by 1.0-1.2mm. I have been told when using silver solder, your gaps should not exceed 0.3mm, where the gap at the end of that internal plug will be 0.5mm. I don't know if that is acceptable.

By cutting the stay, the metal can flex over the undercut. At least, that is my theory.

The heat, even to only heat up silver will make for treachery. 6 joints. 24 points.
The other item to knock down in my view from here, the stays are of course tapered, the dropout plug won't be without an interference fit.
You could ream the stay to create a straight bore but that will in my view intensify the problem as the tips of the stays will be very thin.
Alternatively, you can depend on the silver to fill a gap, some formulas will do this better than others

I would suggest not to slot the top and bottom of the stay but slot the dropout, that will reduce the fragile-ness of the stay end. you can keep your side to side detail.
I really think prototyping a joint and "brazing" it up will reveal much and cause a rethink here from the original assembly scheme.
A case that the math can be correct, but the physical will push an alternative.

As TenGrainBread posted, internal sockets are commonly used on tapered stays. Obviously, the socket cannot follow that taper, it must be straight. So is it safe to assume that 0.5mm gap at the end of socket is acceptable? The couple of builders I have talked to haven't used sockets, but agree with my assumption the gap is OK. What do you think?