A low maintenance bicycle for shared mobility
Often I ask myself, am I using my bike for every occasion I ought to in order to heed my own words to minimise my carbon footprint, e.g. when nipping out to the local shop to get some milk? Not really, because there is always the hassle factor: unlock the bike at home, and once at the shop, find a place to lock the bike to and lock the bike; all in reverse order when going home. It does not take long, but it is a hassle and constitutes one factor that too often keeps me from using my bike and makes me succumb to the convenience of the car to the detriment of the planet.
More in general, the inconvenience of handling the bicycle at the beginning and end of a journey is perhaps a contributing factor that prevents the adoption of bicycles as means of transportation for local mobility. Wouldn’t it be nice if, in an ideal world, you wouldn’t need to worry about securing your bike at the journey end points? What if it does not have to be your bike at all and you do not even need to own one? What if a simple but robust community bike was always available everywhere as a service? Then the threshold would be so low that cycling could possibly become, or would have to become the first choice for local mobility.
Admittedly, bike sharing concepts do already exist. Yet I have the impression that something is missing that enables thorough adoption in most cities. One reason may be that there are simply not enough bikes around to reach a critical mass; another reason may be that rental bicycles are splattered around in town rather than being reliably available on designated areas with a maximum distance between them; this relies on a buy-in by the city planners. Maybe there is a lack of respect for public goods that prevents cities or companies to roll out a service? Perhaps the bikes are not sturdy and robust enough to support such a service and make it commercially viable?
That said, I have been thinking of a concept for a long-lived bike construction based on new technology for a long time, a design which concentrates on the needs of an everyday biker, not the road, racing or mountain bike user. This story presents a concept for a simple and durable bicycle which is easy to maintain, robust and suitable for a shared urban mobility service. The basic design is shown in the following sketch.
This concept can only be understood as draft design, of course, and it will have to be worked out in further detail in due course; the following key elements should be considered:
- Mono-coque frame made in a shell design (1)
The idea is to design the frame in a way that it can be produced and assembled in a simple process and yet is very sturdy, e.g. as several shells that can be welded together like in the car industry rather than welded tubes. The frame and its components could be optimised using finite element methods resulting in a light weight design.
All cables for lights and brakes are guided inside. - All moving parts of the drive train are encapsulated (2)
Cog rings, gear box, chain and bearings are inside the frame or are even part of it. The outside lid of the chain stay is removable for maintenance e.g. for changing of ball bearings or cog rings. The objective is a) no moving parts are exposed, can get dirty themselves and hence worn out too quickly or make the rider dirty, and b) hidden parts cannot be damaged or even stolen. - Brakes are encapsulated (3)
At the front and rear drop outs, brakes are mounted inside the frame and act upon the moving hub pieces (5b), similar to the Shimano roller brakes. Lids are removable for maintenance, e.g. for changing brake pads. On the front axle there are two brakes (3a), one left, one right; on the rear axle there is only one brake on the left (3a); the other rear side, the right is used for the sprocket with integrated free-wheel. - Bottom bracket is motion centre (4)
The bottom bracket and front cog ring are all contained in the frame. This may contain a planetary gearbox to adjust the gear ratio.
An electric motor/generator could be integrated into the bottom bracket, or going further, a continuous velocity transmission using a similar approach as the Toyota Synergy drive, mixing pedal and electric power.
The bottom bracket may also contain some locking mechanism that can be triggered using near field communications (NFC) as a means of immobilisation as simple impediment to prevent theft. - Bearings are part of the frame !
In contrast to ordinary bicycles (bearings are part of the wheel hub) the ball bearings are mounted on the frame (5a). For both front and rear, two hub pieces (5b) are held in ball bearings (5a), left and right, respectively. The axle of the wheels (5), is held between both hub pieces (5b) with a quick release pin (5c). The torque is transmitted by means of a cam on both the wheel axle and the hub pieces (5d). - Front and the rear wheel are interchangeable !
Front and rear wheels are of the same design with 3–5 rigid spokes and a foam filled tyre. They do not contain any bearings.
This construction should make maintenance easy. The design is symmetric with both front fork elements and both chain stay elements acting like two prongs; full stability of the frame for fork and chain stay is achieved once the quick release pins are fastened. As such it should be relatively light weight and as simple as possible.
There is no need to lock the bike to anything as it is immobilised unless unlocked using an app. In case the bike is stolen as a whole, there could be a low power RF beacon that allows tracking the bicycle. This tracking information can also be used to collect information on the distribution of bikes in a fleet and to deploy bikes as needed from estimated demands collected from the user apps.
Note, this concept was first published in 1998 on http://peter.wurmsdobler.org/ideas/nerdbike.html
