A Bakfiets Design

Bakfiets bikes are really cool. They are also really expensive and rare here in Australia. An importer sells these bikes from between $3000 to over $4000 for a motorised version.

http://dutchcargobike.com.au/azor-bike-bakfiets-cargo-bike-classic/

Instructables have a few builds for a Bakfiets style bike

Based on what I have read on the internet, I made up these basic specs for my design:

• The bike needs to be electric - to cope with the large hills of Brisbane and increased weight.
• Disc braking will be required - I have read that caliper rim brakes do not have the stopping force required for these bikes when carrying a burden on a hill. 
• The rear wheel will be a 26'' Mountain Bike wheel - as these wheels are more robust and have provision for disc brakes.
• The front wheel will be a 20'' BMX Bike wheel - Need MTB hub with disc brake. 
• RHS steel box section for the base - I would like this to be a 'jig' for the rest of the bike. ie. the RHS will extend beyond its final position to help support the forming of the other components of the bike. Specifically, dummy hubs will be mounted to temporarly mount the chain stays and front forks will components are aligned and welded. The excess can then be cut off later.

Hand sketch to give some dimensions based mostly on my current bike to give a starting off point. Some notes about design constraints:

• Main RHS bottom tube and top tube are parallel to eachother and the ground (for ease of design)
• the angle to the horizon of the seat and steering tube is 75deg because this is a nice round number :D.
• the seat and steering tube are 500mm apart as this is roughly what I have now and thats comfortable.
• The box will need support underneathe to stabilise the load and stop the box from twisting loose.
• The steering tube will need a bash guard (10mm rod steel) to protect it.  

I drafted the bike in sketchup to get a more scale idea of what it might look like.

More work to be done!