2_i 

My feelings about alu front derailleur adapters, typically off AliExpress, have been mixed, to say the least, even when I made some of them work. I had one solid steel adapter for Brompton, purchased from fietsbob and offered in the past by Channell Wasson, a colorful Brompton dealer in Palo Alto, CA. (Here are some links for C.M. Wasson: one on him driving a steam automobile, one showing a bike with three rings and likely his adapter used there, and one for his Foldabikes store.) The problem with a single adapter is of it being one off, not possible to port onto another bike, etc. With this I looked whether I could produce a CM Wasson replica, tweaking it a bit to my own circumstances where I need w wider gear range.

The photos of the outcome are below. Mine is the stainless steel version, while CM Wasson is the one painted black. It is my 2nd brazing project only, so it is kind of messy. I used a MAP torch kit from a hardware store, Stay-Silv 45 filler and pieces from framebuilders' supply stores. I worked intermittently over a weekend day with the activities summing up to 2-3 hours. Besides the torch, the tools included a saw and a grinder.

One question might be why not do it directly on a steel bicycle frame. I do not trust my abilities this much. If I mess up an adapter, I can just toss it.

Schwinnsta

Nice work. Let us know how it works out.

2_i 

I am eager to test myself and use it to streamline my front drivetrain. However, I also have a trip in the company of Brompton scheduled for 10 days from now and I do not want to throw something not fully tested in. The testing and tweaking will have to wait till afterwards .

Schwinnsta

How did you make it. What did you start with?

2_i 

I bought a piece of SS 1.5" tube, 0.065" thickness. I bought 2 SS seatpost clamps, an SS derailleur boss and an SS cable stop.

First I measured the geometry and made a 1:1 drawing, deciding the working position for the mount and its angle. My subsequent steps were not optimal and I will rather describe the order of actions I would carry out after the experience I gained. Specifically, with a nimble torch it is easier to properly heat small pieces than large, so you need to shrink pieces you work with as soon as possible. Now I would cut the length of the tube needed for the adapter, then halve the piece along its length. The tubes are sized according to the outer diameter, while the inner diameter must match 1.5" of Brompton. The half for the adapter needs to be spread out for this a bit.

The derailleur boss is meant to work with a smaller diameter tube and oriented along it, while you generally have a different situation on the folder. For brazing, you need to shape the boss so that it adheres well to the tube. Quite a bit of effort is needed to shape the boss to the tube. Then you work on brazing the boss and make sure the angle and position is where you want it. It is better to work on that piece first, because it is the largest and requires most heat.

Next you can do cable stop and make sure its angle is good enough. From the other half of the tube you cut off a narrow strip for the back band. From the two seat clamps I cut off the ends and brazed them to the clamp and the adapter for the sake of mounting the adapter with the screws. In the last stage, I cut off redundant metal from the adapter.

For manipulations I got myself a cement block from garden supply section of the hardware store on which I could put all the parts I worked with. I held the parts with vise grips and steel wire, at least in the later part of the project, after I gained experience. This is about it.

Schwinnsta

Thanks for the description. I have yet to try brazing. On another of your projects, you routed aluminum. I have not had the nerve to that, either. I did use the torch to remove the heat treat from aluminum for the purpose of bending it.

2_i 

My first brazing project was to make a mount where I brazed together 2 steel strips. Normally I would rivet, but one of the strips was thin and narrow so I felt that the riveting would not be secure. Given the threshold for declaring success, this kind of project is good for the start. Prior soldering experience helps, but brazing is well less forgiving. You must be better prepared ahead, because handling of the items is tougher. Also heat delivery is quite a challenge though this may get easier when you have a better heat source than a torch.

2_i 

Just a follow-up. As I have some time till the next major use of the bike, which is good for trying things out, I finished and mounted my adapter. I needed still to adjust the angle for derailleur boss and remove excess brazing alloy. In the process I learned how to protect the work the areas that are deemed already good enough. On the way, the brazing process started getting more predictable for me. Moreover, I painted my adapter to match the frame.

After replacing a tweaked Litepro adapter with this one, shifting improved, got more precise and easier I think largely due to the better positioning of the cable stop relative to the derailleur's arm. The replacement is also important for me psychologically, as I take my bike to places where can only rely upon myself and I hate having parts that may fail at any moment and I cannot help that.

Schwinnsta

I am thinking of making one of these. I would like to add a couple of speeds to my B. I can drill out concentric circles and bandsaw them. I can heat them up and bend them. I lack brazing skills, but have tools to do it.

What tooth chain rings does yours have?

Had you tried one of these?

2_i 

The hardest in brazing is that you operate at a very high temperature. With this, there is not a lot of room for correcting when things are hot. You basically need to prepare very well the ground ahead and use the temperature to create the joint. The good thing is that the joints you create are incredibly strong.

I have now 50-34-20. Getting two rings to work under the space constraints is much easier than three, so, when moving ahead, I would suggesting trying to conquer first that more modest territory and seeing whether it might be enough.

The adapter you link is marginal, in design and execution. The best one I found in the market is the Litepro for Birdy. You have to add a shim to fit the diameter, you better secure the boss with two screws rather than one, use Loctite, even red, and adjust the derailleur angle with Sram or other brand asymmetric washer.

Schwinnsta

It seems strange that there are not after market ones specifically for Brompton by for instance Bikegang.

Which filler and flux? Please link.

2_i 

I know, especially that all kinds of other add-ons are produced for Brompton and I doubt there are more Birdies in the market than Bromptons. Ridea now actually now offers an adapter for Brompton, but it runs at $140 and I see no reason for buying that adapter, irrespective of the price. t is just an OK design. I have both Ridea and Litepro adapters for Birdy and Litepro is in my eyes a tad superior.

For stainless I used Harris Silv 45, both rods and wire, and Harris Stay-Silv Flux. I also found Solderweld Hot Block Putty useful. It is not cheap.

brommiephillip 

Hey guys, I’m starting this project now too. And I couldn’t see if the litepro adapter for birdie lets you angle the mounting post? To accommodate angle

you said to use some kind of asymmetrical washer from sram? Can you explain that part