Baggage on a Brompton

Making a saddlebag mount. 
The remarkable Heinz Stücke tours this way on a Brompton. A capacious Brompton T bag on the front and a hikers backpack perched on the rear rack. Heinz left home to see the world on a bicycle in 1962 and fifty-three years later he is still traveling. The Brompton was supplied by the company in 2009 to help him achieve his plan to cycle in every single country of the world.

Heinz Stücke and his Brompton M6R

The backpack on the rack seems to be quite common among Brompton tourists, usually attached at the top to a bar fastened to the bag loops on the saddle and bungeed to the rack at the bottom.
I thought I could adapt pannier bags that I already use on conventional diamond frame bikes.
My first goal was to mount one bag behind the saddle for around town shopping and short tours. The bags I have are Ortlieb back-rollers. When carried  athwartships, I think they look better without the angled "front" some bags have to avoid heel strike when clipped fore and aft on a pannier rack. These bags would be symmetrical and identical, no "left" or "right" bag except that I retro-fitted one Ortlieb outside pocket to the "rear" of each one. The bag loops on the Brooks B67 saddle are steel which seem more trustworthy than the moulded plastic loops provided on many other saddles.
Here's what I came up with.

Pannier mounting loop

It's a simple rectangular metal loop attached to the bag loops with ultra-strong nylon zip-ties. At 270mm wide, it suits the widest spacing of the two adjustable attachment hooks on the bag.

Bag sits on the rack. Stabilized by a cord lashing.

The depth of the loop is 145mm. This allows the bottom of the bag to rest on the rack. It also allows room for a big load crammed in under the roll-top bag closure to still be below the saddle. If the cord lashing was replaced with a loop of strong shock cord the bag would be almost  as quick to unclip as on a conventional rack. The loop does not get in the way when the bike is folded.
A different bag or a different seat height will probably need to have the loop dimensions adjusted.

Side view

Materials list:

1 metre 6.3mm galvanized steel rod

250mm 10mm OD aluminium tube.

120mm 8mm OD aluminium tube

JB Weld epoxy steel adhesive/filler

I considered using 6mm aluminium rod for the loop but decided that the steel would be stronger with only a small weight penalty.

The bending jig

The bending jig wasn't too much trouble to make considering the neat result. Just a 50mm thick slab of wood with bits of 25mm broomstick in holes drilled to suit. The 10mm aluminium tube is just the right size to accept a bag hook. Many racks are made of similar diameter material. It was centered on the metre length of steel rod and I glued it in place with JB Weld, though leaving it loose would create no problem. The bottom two broomstick pegs were initially left out to permit bending of the rod well beyond 90 degrees at the top two corners. This created nice tight radius bends. The nails and later the clamped on wood blocks were progressively added to maintain the tight radius when the rod was bent back to 90 degrees. The one metre of rod stock was more than enough for this job. It's easily bent by hand using a short length of steel conduit slipped over it for added leverage. When I was pleased with the bends, I trimmed off the two rod ends with a mini hacksaw.

Job completed.

Finally, the 120mm piece of 8mm tube was buttered up well internally with JB Weld on a bamboo skewer. It is a close fit and just the right length to be slid fully over one of the rod ends, then slid back over the other end and centered to securely close the loop of rod. The loop has since been given a couple of coats of rattle-can black lacquer.

Next in this blog: A device for carrying two Ortlieb bags on a Brompton rear rack.