Baggage on a Brompton

Carrying two full size panniers.
This is really just a proof of concept for the idea of an upward extension for the Brompton rack with two 10mm rails for mounting a full sized pannier on each side.

 

 

Add-on frame provides pannier rails at the right height.

As you can see, the panniers sit well clear of the road but very likely lower than the combined centre of mass of a rider on a loaded larger wheeled bike. The extension is made of 6mm marine plywood with 10mm aluminium pannier rails epoxied in at an appropriate height and it fastens securely atop the factory rack with four easily released clamps. Modern polyurethane wood glue enables very strong butt joints in thin plywood if the joints are close fitting and glued according to the manufacturers recommendations.
This version is 150mm wide, 215mm high and 330mm long. It weighs 790g and the lightening holes do save a little weight besides looking very technical. It's measured specifically to suit my Ortlieb back-roller panniers.
The cut-outs in the edge of the base let the adjustable hooks on the backs of the panniers fit over the side rail of the Brompton rack. The 10mm rails are placed so the panniers lean inwards by 10°.

It would be even better if it could be folded up and packed flat. That wouldn't be difficult with plywood if the vertical central spine simply dropped into slots to stiffen and lock the whole thing together once the ends were unfolded and the removable 10mm rails inserted. I'm thinking about that. It must have been much harder for Brompton designer Andrew Ritchie to figure out the fold for the original Brompton.
Someone should steal this idea and adapt it to TIG welded aluminium rod, the way many actual pannier racks are made.

Prepared pieces before the end-plate shape was refined.

Bottom view.

Wooden cleats on the base positively locate it inside the Brompton rack perimeter.  They are made just the same depth as the rack rails so that the round clamping devices bear equally on rails and locating cleats. The clamps are simply discs of plywood waste left over from the 50mm hole-sawing binge with bolts and wingnuts added. I smeared them all over with excess epoxy resin from another project to seal the end-grain edges and bond the bolts in place.