Mixte Question

[cmsanford88]

Hey guys! Still plugging along with classes and practice and starting to daydream a bit about the future and inevitable girlfriend bike. Would love to take a crack at a mixte and have been perusing assorted details. I came accross this detail and liked it a lot, but was curious how it was accomplished. I'm assuming these stand-offs were brazed to the thin section of the seat tube, is this a super low-stress joint or did he likely use a beefier tube? Maybe a 9/6/9 top tube for the extra butt length?

Bike is by Royal H by the way, here's a link to more info:

The One and Only 'Constance'! a Mixte by Royal H. Cycles

5079916583_aabfa1b5ff_o.jpg

Thanks!
Chris

[Blacklabbikes]

There's a lot of reinforcing plate there for what is a relatively low stress joint, you're probably good to go with whatever. Personally I would use something from the touring end of the spectrum on a mixte that will be used (presumably) for day to day transport. that gives it the robustness for steps, curbs, pubs and the towpath/gravel out of town.
As for how - these look like plate sections with some 1/2 inch tubing all joined together.

Some of these on the other hand are lugs like the one half-way down this page Lugs. I think I would use the lug.

[Chauncey Matthews]

Plus the top set of seatstays are whats really supporting the seat tube.

[cmsanford88]

Thanks for the input guys, also occured to me there are 2 or 3 other bridges between those tubes, so it's probably a relatively redundant joint. Might still go with a lug eventually, as you said Joe it'll be an around town bike so better safe than sorry.

[Blacklabbikes]

Most of the bridges on a mixte are about protecting the long run of tubes from knocks, kicks and other abuses - and stopping them from thrashing around.
One of the nicest minimal reinforcing that doesn't use a lug is on this: 196s Oscar Egg Junior Mixte | The Online Bicycle Museum

[Andrew R Stewart]

IMG_1399.jpgMixte frames never really did it for me. I think they are far better conceived then 4 stay "ladies" frames, having a 3rd set of stays to best brace the seat tube from bending forces. But the thin diameter head tube to rear drops tubes really lack torsional stiffness, granted most mixtes are not about performance but still... And as a life long shop wrench having more surfaces to sneak a rag around to clean isn't the way to an easily serviced bike. But that's why we do this building thing, so we can create out view of what's right.

When I was first starting out I did like the look of many shorelines. Bottle boss diamonds, stay bridge end plates, blade reinforcements along the insides. Kind of like glittery bling. But as I aged and evolved in my visual and building tastes I now feel quite the opposite, give me a filleted all over frame these days.

Here's a shot of a recent bike I built for a long time friend. When I built her first Stewart in 1979, and if that were to have been a no top tube design, this bike would have been much like what Chris showed. But almost 40 years later this bike is what I did and like more then shorelines glitter. Andy