Hey 
Our neighbours at Bespoked Cycles Steil had a super cute breakaway mini city bike (also the Crust Stupid Tourist uses the same setup… to get a packable touring/adventure bike)
Does anyone know how the downtube break works? Is it a sleeve with pinch bolts?
I can see how the seat tube break works and imagine that could be fabricated.
Tia
Elodie
Ps: this is our non-breakaway mini from Bespoked Dresden
Ritchey breakaway? I’m pretty sure you can buy all the bits so you don’t need to make them.
It’s a hinged clamp that encompasses two brazed in lathed bits. The lathed bits flare out from the nominal downtube diameter so that in the axial direction you have a mechanical joint stretching the hinged clamp rather than relying on just friction grip. It only relies on friction-grip in torsion.
good photos here:
If you want to make a lesser ghetto version then you can absolutely make that work too. I did it just with some seatclamps an angle grinder and an old seatpost (link below). So only relying on friction grip. This was for a polo-bike so a bike that i travelled with a lot. I forgot to do the downtube bolts up properly once and when ridden the bike felt like it was going to collapse underneath me. I imagine the legit ritchey version is a bit more forgiving in that regard.
Oooh that polo bike is cool 
I wrote to Ritchey to ask about getting the parts
but I’m also wondering about doing something like your approach
lol ghetto 
