I'm in the middle of building a tough touring bike. It is basically an unsuspended mountain bike with tons of clearance, long chainstays, and all the touring braze-ons you'd expect, and then some. I wanted to build a bike that would have some bells/whistles like disc brakes but also build in the ability to use find anywhere components for when you're out in the middle of nowhere and the village doesn't carry Avid BB7 Road replacement parts. The bike has a rear disc brake mount in between the left chainstay and seatstay to allow for the use of a rack without the fight for mounting real estate on the seat stay.
For right now it will be disc brake only, but the plan is to add canti studs in case the disc brakes fail and I need to made due with what I can find on the road.
Here it is in all it's semi finished glory. 72 degree angles. 26" tires to allow for a shorter top tube without the pedal overlap being as extreme as it would with a short top tube, fenders, and 700c wheels. Built with double oversized tubing, custom picked to find just what I was looking for. It's a mix of all kinds of stuff, but the top and down tube were the hardest to find in the specs I wanted. I finally was looking through the True Temper catalogue and found that their BMX Supertherm tubing was available in double oversized with 1/7/1 wall thicknesses. The tubes were just long enough to work. I wanted to TIG weld this but in case I wanted to do a lugged version the angles and tubing sizes match up perfectly to the double oversized Slant Six lugset Kirk Pacenti offers.
The seat stays began as straight 19mm single taper stays, but I put an obvious 8" radius bend at the top and a more subtle bend right near the bottom end which I think looks very nice when you combine the two. The way the top was bent and where I positioned the stays meant that I had to not only miter the seat stays to the seat tube but also to the top tube, which is visible in the first picture.
I thought I would try something different so I added in a secret compartment for getting whatever kind of exotic drugs I might find in my travels back home. I kid, I kid. The trying something different part was true but what I really was doing here was trying to spice up the standard dimple your chainstay for clearance proceedure. I thought, what the heck, I'll just chop a bunch out, braze some stainless steel right over the new huge hole I created and for all the new bling I'm getting all I have to do is sacrifice durability and stiffness. Actually I have no idea how the thing will feel. I went too extreme on this one but I think the idea might be plausible in moderation. Next time if I decide I want to go through the trouble and this version didn't fail in 5 miles I'll use round chainstays so the chunk I take out won't be such an appreciable percentage of the whole.
Here's the finished stay. I think it looks great and will be even cooler once the frame is painted and that section is polished up.
Here is the other chainstay with clearance cut in for the crank at the pedal hole.
Here is the effect with the cranks installed. Looks good and hopefully won't ride like a wet noodle. A tip if anyone wants to try this: On the alignment table the stays will bend where you did the surgery. If you need to close the distance between drop outs, which you probably will have to since you were adding all this heat to the outside of the stays on both sides, what can and will probably happen is that you will get cracks in the joint between the stay and the stainless steel. My only thought on how to avoid this is to do the opposite that you would usually do ie space the dropouts a little wide knowing that the bridges are going to suck them in. Maybe space things too narrow and let the patching that gets done pull them out to an appropriate width. If it's too narrow even after the brazing I think the joint would tolerate spreading better than smooshing since it would be like pushing the joint together instead of pulling it apart.
A close up of the seat stay/seat tube/top tube junction. Welds look decent. That part won't break. I guess maybe the chain stays are like the break away derailleur bolts made of aluminum so if your derailleur gets caught you don't break your frame. Maybe I'm saving the rest of the frame by just having the rear triangle snap off at the chain stays. Brilliant and safe!
One last weld shot...
