I've been on the lookout for some sort of hard case to stuff my Brompton in, and not having much luck. The B&W hard case is the best, but it seems that it might be too heavy when combined with the Brompton. Thanks to other members, like Scooper, who have checked weights, measurements, etc. for me.
I decided to head over to the local mall and scope out a few luggage shops, but came up empty in terms of hard cases. Most are just too narrow - I wish they would make wider luggage. However, I did come across a 29" (?) upright by TravelPro that measured about 21" across. It was about 62.5" to 63" linear inches in total: would probably just make it through as regular checked luggage.
The Brompton would definitely fit, if I took off the seat (see photo). It's a softsided case however: it has a minimal, flexible frame. It would not offer much in the way of impact protection. It is light however (9 lbs) and has the advantage of obviously being standard looking luggage and offering a better structure to place extra padding along the sides (plastic sheets, foam, etc.). The sales associate and my wife were skeptical however; all it would is one good whack - particularly in the corners - and a wheel, locking bolt, handle, etc. would probably deform or break: there's not much clearance to put a lot of padding. I'm not sure if this is better or worse than padding up the Brompton soft-sided case, which has less support, but might be handled better than regular looking luggage.
Brompton in TravelPro Pullman.jpg