Have you ever made an adjustable frame?
 

Like to test different fork angles and various chainstay lengths?

I was going to make a fork with many dropout positions but I never got around to it. You can find pictures of forks like that on the internets.

I would say there is no reason to make an adjustable chain stay bike, it's all confirmation bias. A horizontal dropout will get you 1" of positions, and there is no difference between any of them. A fork significantly affects the handling of a bike.

People who I don't remember have done some of this stuff before. The likely most common (for a rarely done thing) is a ft drop out that's horizontal slotted to allow variable rake/trail. Can't say I know of head or seat angles (or BB heights and stay lengths) that are also variable. One possible issue might be that an adjusting frame's stiffness and/or weight could be far more noticeable then steering/stability.

As I typed that last bit I realized that all this, stiffness/stability/handling, stuff is very intertwined any thus any test rig can influence the results if not designed well. Andy

The frame part is easy, just use sliding or rocker dropouts. You could also build it with a 44mm head tube and use an Angleset headset to change the head tube angle a few degrees. In reality, it is only going to feel different for a short period of time, until you adjust to the handling difference. Anything different from your current bike is going to feel weird and wrong at first and then you will adjust to it and that will be the new normal, providing that you don't go too far outside the normal range of lengths/angles/offsets.

I can't figure out how to get it linked here but if you search IG for [MENTION=199133]the[/MENTION]blandbicycle you'll see his recent iteration. There have been many before and likely many after, although i don't know how it would be better than Chris's. There have been frames made with adjustable headtubes as well but i dont remember who did it...Rabbit Fighter maybe?

attempting to link

somebody in the comments mentioned this monstrosity https://www.bikeradar.com/news/the-b...ed_slideshow=1

Yep, that's the one I was thinking of. I've seen forks with the hooded/slotted dropouts as well.

just to be clear, it's a monstrosity, but I love it. The site with the videos on it are dead, I imagine it's out there somewhere. I like the fully mechanical data collection.

Never really thought about making a fork where you could adjust a-c (HTA) and rake independently.

Exactly, It's horrible and yet brilliant. I wonder what it taught him. Both in terms of the building of it and the riding of it. Or was it just a brilliant fabrication stunt for the show?

I feel like the weight and complexity is going to mute out a lot of the differences. Sure would be interesting to try it though

The seismograph-style data drum is just the coolest thing ever.

Some long term builders like Mikkelsen had a size cycle for custom bike customers..

Bike Friday has some adjustable fleet bikes , for various sized riders

being one oval main tube & 2 adjustable height bar & seat masts, they telescope for adjustment..

Yes, I come to the conclusion that the complexity and all of those joints have to introduce flex and slop that will overpower any impressions of the geometry changes.