Awesome! And even if it was, I just remembered I’ll be saving some weight near the center/back of the bike by having an external BB with GRX 800 cranks instead of my current square taper and classic SL6400 cranks. Also a lighter seatpost.
Someone on Reddit recommended I look for OEM replacement forks and I found that I can find a fork for a 2022 Giant TCR for about €300. It has a 1 1/4 tapered steerer, not the massive 1 1/2 so I’ll be able to integrate that with a bigger head lug no problem.
I can “spend” a bit more weight on my head lugs now anyway since I’m saving so much weight in the fork. (Internet says the fork weighs somewhere around 380g as opposed to ~950)
It’s a bit more road-oriented than I was going to go but I’m fine with that, it still has more clearance than my current bike and clearance is already not the biggest issue on that bike.
Edit I found that giantbikespares also has Liv forks, and found one with the same lovely slim look for an even slightly lower price and that does have room for 38mm tires hooray!
Alright so I know some of you advised against building a jig but I do have an idea for a very very simple fixture that’s similar to something I’ve seen others use and it’s very affordable!
The bulk of it in my version is standard 40x80mm extrusions, an 8080 extrusion as the main spine and mostly standard brackets and mounting plates, all very affordable. Only a few cones (BB & head tube) and 2 custom L brackets are needed for the head tube.
Checking angles will be done with a spirit level and an app on my phone! My phone has a nice flat side with no buttons and I have calibrated it to be within about +/- 0.1° accurate.
Total cost without dummy axle because I’ll need that either way is about €360.
Seeing as I don’t have any sort of flat reference surface and I’d have to buy that anyway it makes more sense to me to build this fixture to keep things roughly lined up. I’ll be able to position everything relatively precisely by using my CAD sketch of my frame and a CAD sketch of the jig.
This style also allows for good access with the torch for brazing in the jig.
Just remembered I should post some of my previous little silver brazing test pieces I’ve made so far to see if anyone has any advice to add, nothing with lugs yet but just getting a feeling for the heat and flux.
Test parts in chronological order I made them in:
Very first test: two bits of 0.5mm stainless steel
Appreciate your pics! I am getting ready for frame #3. My Ceeway order arrives next week.
I am going to jig the frame up on a flat surface with the appropriate tube holders and the tack braze it. Since I am a woodworker I have a large cast iron table on my shaper with a BB post for doing alignment. It worked great for my wife’s mixte.
This frame will be a mixture of lug and fillet brazing.
I’m contemplating whether I should use 12.7x0.8mm seat stays instead of 14x0.7mm because I really like the look of skinny seatstays and it would allow for a less bulky, lighter dropout design because my chainstays are 12.5mm at the tip which matches nicely.
Would 12.7x0.8mm seatstays be too flexy? My current bike has columbus air teardrop stays that feel slightly too flexy to me, they start and end at about ~11mm diameter and have a roughly 11x15mm section in the center, but I can’t find the wall thickness. I think 12.7x0.8 would be slightly stiffer? Maybe if I add a sturdy seatstay bridge or something.
I would suggest, the thing that you want to focus on at this point is assembling the tubes into a bike. You might get more of a feeling for which tubes you like once you have more experience with a wider range of options, but preference and differences in perception play a huge part in the answers to the question you’re asking.
I would say the tubes you’ve mentioned could easily both make a great bike, it’s not going to be the difference between those two which causes any notable difference. I have bikes with normal road stays, 19mmx0.9 round seat stays, “aerofoil” shaped 55x13mm stays with a 1mm wall, and 8mmx0.7 stays, I don’t think I could tell you if they rode any differently because of the differences in those tubes.
Heh you’re probably right, I’m out here thinking I’m gonna feel the difference between one tube and another when in reality I’ve barely ridden any quality frames. I’ll just pick whatever seatstays fit the best with the design.
Worked on the seat lug today, I’m happy with the result! I think I’ll settle for the 14mm stays, they fit nicely.
I want to have a 28.6mm seat tube and an oval ~25x32 (ovalized 28.6) top tube so I figured having the lug slot over the seat tube and into the top tube would give me the nicest smoothest transition and I’m quite pleased with the result.
Edit: looking at the pictures again I’m gonna take a few millimetres off the bottom and add a bit to the top because it looks a bit too bottom-heavy right now. Also still a little work to do on the insides, the section after the top tube right now has a straight wall on the inside which means excessive wall thickness on part of it. Will change my surface construction a bit to fix that.
That’s more like it! Weight is also reasonable, Fusion estimates 92g, I’m happy with that considering I gave it a pretty decent wall thickness of 1.7mm around the seatpost.
I cut 50mm long sections from the 0.7mm ends and 0.5mm center and squished them between a 3D printed die to compare springback. As expected, the 0.5mm section has significantly more springback than the 0.7mm section.
The tube before squishing is 28.6mm and the goal is to achieve approximately a 25x32 oval. By squishing between a 21x35 die (bit too much extra clearance though) the 0.5mm section became 25.5x31.9, so very close to what I want, and the 0.7mm section became 24.4x32.9 so a bit too flat.
For my real top tube I’ll be 3D printing a full length die in 4 pieces, then using 2 pieces of wood as a backing to provide extra stiffness and so I can drive long screws into them for alignment and to pull the dies together. Hopefully by varying the flatness of the oval in the die, matched to the butting profile of the tube I’ll be able to get a nice consistent oval.
How are you joining these? are you welding or brazing? If you’re brazing, I would add the rib back as it will help draw the filler up to the surface so you don’t end up with a small seam there. I see you removed it from later drawings. Think about how you’ll add filler to the joint. Adding it in at the seam won’t be ideal. Using a pre-form inside the joint and melting it from inside out would work but you’ll want to do some testing to make sure you’re getting the whole joint filled. Drilling a small hole in the tube to feed the filler in through is another option.
Philosophically, if you can set whatever shape you want, why not do external lugs to add interest? OR, why not just fillet braze this and skip the 3d printing costs?
Yes I’ll be brazing this with silver. I’ll have it printed with the ribs indeed to have a surface to melt my filler on, just didn’t put them back yet before I took the screenshots.
I also thought about whether a small hole in the tube would be a good idea, would this make it easier to feed filler into the joint?
The original plan was external lugs and I’ll be keeping that for the head lugs, BB and dropouts but as I want to join a 32mm wide top tube to a 28.6mm seat tube, having the top tube side be an internal lug is currently the best way I could find to have a nice clean connection.
I could design a fully external lug for this too but I’m afraid it would be very difficult to get it to look right. This way it’s a smooth and clean connection but I get to keep the nice little tips at the top and bottom at the seat tube side.
Well, I studied product design and I’m currently in a job where I don’t really get to use the creative artistic side of design, so designing this frame around these lugs is a nice way for me to sharpen my design skills and a good creative outlet.
Having made a 3D printed seat tube binder lug like this before, one thing I would recommend is cutting the slot as a secondary operation instead of having it as a printed feature. The heat distortion from printing will cause the binder slot to “peel apart” and it’s tough to smoosh it back into shape.
You know what it may sound silly but I didn’t really think about that being an option because I haven’t found an EU supplier yet that stocks that.
I do see Ceeway carries 31.7x28.6 tubes which would be very nice but I only see Spirit HSS which is probably a bit pricy for me and Zona in 9/6/9 which is a bit too heavy for what I’m looking for.
Either way I’ll try ovalizing the 28.6 7/5/7 Zona top tube I have laying around, it should work alright with the dies I’m currently printing. If it fails anyway I can still resort to that Spirit top tube I suppose.
Edit: hey wait a minute biketubing does have that Spirit 31.7x28.6 top tube! And it is pricy indeed!
I’m sure it’ll be rewarding to make the oval yourself but the tooling and design cost seems like it would make the extra $20 for a fancy tube a bargain.
Also since you’re in Europe, I’m pretty sure you can get reynolds tubes direct from the source.
Ah crap yeah now I remember why I never gave those tubes any thought, I forgot they were tapered and not oval haha.
Design and cost of the dies isn’t too bad to be honest, some PLA for my 3D printer and wood scraps, also a fun side project. I already bought the top tube before I decided to have an oval top tube anyway so it’s cheaper to squish that than it is to buy a new oval one.
If I ever want to build a really fancy “forever bike” after learning from my first frames, I might want to put in the effort to get my hands on that Tange tubing, I don’t know why but I find Tange prestige tubing cool as hell. Probably because I rarely ever see it around.
Yes, or a small notch at the end of the tube. I wasn’t ever very satisfied with that approach though. I worried that I didn’t get it to flow to the end of the plug. I spent a lot of time working on using internal pre-forms. I made a bunch of plugs on my lathe and then brazed them into tubes and cut them up to make sure I was getting full penetration. Essentially, there is a ring of filler that is pressure fit into the tube and as you insert the socket to the tube, it seats against the socket end and the tube. Then you heat the whole thing up until the filler melts out from the inside. Once the filler wicks up onto that rib you have, you know you have a full joint. I have found that to be a very nice way to do joints like this:
