Bakfiets - a Dutch-style cargo trike

Since I started doing my grocery shopping by bicycle, I've been inetrested in ways of carrying more stuff per trip. The shop is only about 1.5km away, but my shopping bike tops out and develops wobbly steering if you put more than about 10kg in the basket:

After looking at various types of trailers, racks, sidecars and such, I decided that a Dutch-style Bakfiets seemed just about ideal for my needs (a relatively short, non-hilly trip to the shops returning with a 40kg load). Unfortunately most suppliers of such desirable equipment are located in Europe, and with prices starting at around 2399 (before delivery to Australia) it just wasn't going to happen.

While the Gustav W above is undoubtedly a splendid machine, I needed something cheap to try out the bakfiets concept (so that if it turned out to be utterly crap it wouldn't hurt me too much to scrap it and try something else). Armed with a backyard full of scrap bikes, a stick welder, and excessive confidence in my own abilities, I cobbled together the abomination you see below from a 26" mountain bike and a 20" BMX.


Loaded with about 20kg of ballast for test riding. It's a very scary machine to ride unladen.

26" rear wheel, fited with an ancient 1970s 5-speed freewheel and the smallest set of Ashtabula chainrings I had on hand. It'd be massively overgeared for a 40kg load, so I'm going to search for a smaller granny gear.

Alloy caliper brakes on the front wheels only, sourced from the donor BMX. Obviously the BMX rear wheel ended up on the right.

The main spar is constructed from 40mm square hollow section, welded directly to the bottom-bracket shell. This is going to be braced significantly prior to the trike being put to serious use.

The steering pivot bearing is constructed from the BMX's bottom bracket and chainring. Both donor bikes were chosen for their 1-piece-crank construction, as the bottom bracket shells are significantly thicker and stronger than those from bikes with 3-piece cranks.

The support strut and "side-to-side" tubes of the platform are made from pipe with a much heavier sidewall than the red-painted tubes supporting the wheels. Note that the platform is welded to both the upper crank and the chainring of the pivot bearing.

Main spar welded to the BMX's bottom bracket to form the steering pivot. This weld will be given some significant bracing prior to carrying real loads on the trike.

Front view. The handlebars came from an old lawnmower, and could do with being a bit wider. Note that the central pipe on the platform is offset so that the pivot point is centred.

Pros

It only cost $25.

Cons

It's not very stable on corners. This is partly because it's a trike, and partly because I made it relatively narrow so that it could fit through the gaps between the various bollards on the local cycle paths. The brakes are nasty, and would be a lot worse if you were carrying a 50+kg load. It's geared far too high. The handlebars are too narrow. There's no reverse gear. It's hideous.

The verdict

It has potential. Clearly it would be a much better machine with self-balancing hydraulic brakes at the front, and an internally geared hub with pedal-operated brakes at the back would be a significant improvement too. Of course, adding either of those things would bump the price up well above the $25 I've invested to date.

Did I mention that it only cost $25?

23 March 2008 Update


Side view - I made the box quite sturdily (i.e. heavy) since this trike seems to need some ballast weight up front

Improved gearing with a pair of little chainrings, extra bracing strut

Parking brake

...and finally, a name. "MkI" seemed less intimidating than the alternative "Scary Unstable Mongrel Bastard".

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