Your B&W case is about 4" over regulation, I believe, but I've read that last year many airlines began waiving the oversize fee for bikes (the weight limit still applies, but a Brompton plus the case should easily meet it). So tell the check-in agent there's a bike in the case if they ever decide to measure it.
I'm in the process of building aluminum cases for two Zizzo folders my gf and I just bought. I'm keeping them under the size limit to be safe, but because they also convert into trailers (to haul carry-on) and are relatively beefy, I'm bumping up against the 50 lb weight limit for economy seats. Right now I'm scratching my head as to how to incorporate casters and center stands with only 1 lb left to play with. :|
I have a folding portage cart with light weight removable wheels that attach via pushpin axles into metal receivers. Buy two extra receivers, drill holes in the side of the case, bolt on the receivers, and attach the wheels at the destination.
I haven't used it for this yet but plan was I would just take the wheels in my carry on. I also have not work out how to attach the cart to the bike yet.
Wike sells the individual wheels, pins, receivers (2) and even a diy box trailer kit(1) using these parts with instructions if looking to visualize this.
I'm in the process of building aluminum cases for two Zizzo folders my gf and I just bought. I'm keeping them under the size limit to be safe, but because they also convert into trailers (to haul carry-on) and are relatively beefy, I'm bumping up against the 50 lb weight limit for economy seats. Right now I'm scratching my head as to how to incorporate casters and center stands with only 1 lb left to play with. :|