Carrying a folder on a full-size bike
I've recently bought a Brompton, and can envisage situations where it might be useful to be able to carry it around on my full-size commuting bike.
I'm looking for ideas on how this could be achieved, preferably as cheaply as possible! This has been my train of thought so far:
Bolt a plastic crate onto the top of the rear rack. The dimensions of the folded Brompton are roughly 600mm L x 300mm W x 600mm H and it weighs about 11.5 Kg which is well within the capability of the rack.
If it could be laid on its side, I'd need a shallow crate of 600x600 internally, and could use bungees to keep the bike inside. The platform of my rack is about 300mm long so the crate would overhang by another 300mm. This would probably need some extra struts to support the overhang, but would this amount of weight beyond the back wheel cause instability?
It's a problem finding a suitable size crate as they are mostly rectangular, and anything in the right size range is generally way too tall so would need cutting down (not necessarily a problem, so long as its rigidity isn't compromised too much).
Alternatively, if the Brompton is kept upright then a 300x600 crate would do. I still haven't found anything that's ideal, but something in this sort of range seems easier to find. Again, it would need extra struts to support the overhang at the rear. However, would that make the full-size bike too top heavy and difficult to handle?
From a weight and wind-resistance point of view, a basket might be better than a solid-walled crate if there is anything on the market that could be adapted for this purpose. Another route could be to custom construct something out of wood.
Instead of mounting to the top of the rack, I've also wondered about hanging it off the side. The advantage would be a much lower centre of gravity, but the load would be very lop-sided.
Someone has already suggested that I buy a trailer to carry it in, but I don't really want to be encumbered by a trailer (particularly if I need to park up and lock it) and some of the cycle routes in my area would be difficult to negotiate with a trailer.
Has anyone else ever tried transporting a folder this way? Any feedback and further thoughts on the subject would be most welcome!