I've built two (three if you count my folding tandem); I'm about to cannibalize my suspended folding Cruzbike and put it on another folding frame.
The problem with Birdy is the front fork. But if you swap out another fork, I think it would make a lovely folding Cruzbike.
On my Sofrider and conversions, I am able to ride below 3mph spinning up big hills. My bikes are geared down to under 17".
Does everybody need this? Can everybody ride every Cruzbike this slow? Probably not.
Is it what you need? I don't kinow.
Yes, I think it could be done, but might not be perfect. Getting something that's a little less steep (and not too high) might work better.
Bike Friday would be the ultimate:
Something like the
Afar 20" 24 Speed Dual Derailleur System Drive Family Foldable Tandem Bicycle
would work well, too:
I don't ride as much as I used to, but I do ride 4 miles every day to and from the train station. Rain/sleet/snow I ride.
When it is snowy/icy, I ride my upright folding bike with studded tires. I could mount studded tires on my commuting Cruzbike, but given my angle, I think balancing on icy...
It's almost certainly true.
Aerodynamic drag adds a force proportional to speed squared. So increasing the wind you hit by 2 mph is going to have a larger effect than decreasing it by 2 mph.
This is why I like having very low gears. I don't get up hills quickly, but I generally get up them.
I find the exception to this is very steep hills where I find I need to sit up to move my weight over the front wheel to help with slippage. I can only do this for short hills, but I've made...
1) The picture is right. But not really helpful.
2) Yes, you can pedal in such a way that you don't turn the bike. But actually pedaling that way is likely to do bad things to your knees, etc.
3) There are lots of reasons you are more stable when you are clipped in. Your feet being attached...