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The Fahrradbus-Project a Summary

Fahrradbus001

The Fahrradbus is a modular, articulated human powered recumbent bicycle for several riders. Because of its tandem configuration, it has synergetic advantages over a single-rider machine in respect of aerodynamics and the number of bicycle parts per person. The first model is a low-tech-DIY-version. The Fahrradbus was invented and built by a small team in 2014.

The beginning.
The idea was born to build a human powered multi-person vehicle, during a brainstorm session at a Young Friends of the Earth meeting in Stuttgart in January 2013. The first aim was more a political one than to invent a practical bicycle design, but we wanted to show that a group of more or less laypeople can build a futuristic human powered vehicle (HPV).

We asked ourselveswhat is possible?”, and imagined what sort of transport solutions could be invented by the big automobile groups with their financial resources combined with the knowhow and creativity of the universities, if they would apply themselves to bicycles.

First, drawings and concepts evolved on paper, and existing HPV concepts were examined and critiqued. Early influences were the Kettwiesel in the ‘road-train’ formation made by Hasebikes (hase-bikes.com), the Twike (www.twike.com) and the Lizzy (www.dielissy.de). Very similar too is the Thuner Trampelwurm, a project we learned about afterwards (www.trampelwurm.ch). In early 2014 our construction plan was complete but ended up in the drawer because the money wasn’t available for implementation.

Michael, Emil, Diego and Philipp the Fahrradbus-Team (from left to right)

Fortunately, the situation changed by accident, when the Young Friends of the Earth met a group who call themselves Uniexperiment (www.uniexperiment.de) who self-educate and run their own educational establishment. This group had similar ideas and thoughts about modular multi-person vehicles and they brought to the project the necessary courage and knowhow to raise money and realise the Fahrradbus.

Soon, things got on the move – material was bought, a workshop was organised and in October 2014 we built with about 6 people in 6 days the Fahrradbus-prototype – consisting of three modules. The maiden voyage was in November 2014 and since then, the prototype has worked without any considerable problems. In summer 2015 the steering system was upgraded for the second and third module in the bus and following this change, the modules could be used separately or all together.

The simple build process and construction techniques for the Fahrradbus make it suitable for educational workshops as we provide. The second Fahrradbus comprising another three modules was built in Berlin in July 2015 by the Wanderuni (www.wanderuni.de), another educational group who completed the build in ten days, including the paint!

The concept.
Now some facts about the concept and technical details before I say something about ride experience and some of the adventures we’ve had on the Fahrradbus.

The Fahrradbus consists of identically constructed modules, each for two people, connected together with couplings. The result is a multi-person ‘sociable’ HPV that tracks easily around obstacles and features particularly good ergonomic and aerodynamic properties. Within each module, each person drives their own wheel with hub gear and selects a gear ratio to suit, giving every rider full autonomy.

Each module in the Fahrradbus can be driven individually or as part of the train. For running in ‘trailer-mode’, a drawbar is used to connect each vehicle, rather than the front fork itself. The bar is clamped in the fork dropout, locking the steering and a towing eye on the bar locates in a simple hitch on the back of the leading vehicle. The simple transition to ‘solo mode’ requires the removal of the drawbar with two quick releases and the fitting of the front wheel, previously stored behind the rider’s seat. The steering is controlled by a single centre-stick . Braking is always available whether part of the train or running independently, affecting Magura hydraulic rim brakes on each rear wheel, worked from individual levers.

Practical features abound and in terms of cargo, the space behind and to the sides of the riders forms a large and versatile luggage space by the use of a cargo-net strung across the frame between the enclosed wheel boxes. More space is possible if the seats are removed, converting the module into a load trailer with the capacity for a euro-pallet – drawn by the power of the riders ahead in the train.

Further adaptations will include an electric motor to enable the Fahrradbus to compare even more favorably with the car in the urban environment. In terms of storage at home and places of work, if the ceiling height allows, storage of a two-rider module takes only the space of two normal bicycles when stood vertically.

The main aims of the project have been achieved – high maneuverability; a sociable side by side layout; inclusivity, enabling weaker and less able people can ride together with more athletic cyclists and all riders enjoy the advantages due to the recumbent riding position.

Basic concept:

  • Multiperson-bicycle: Synergetic effects, fun.
  • Modular and flexible, allowing a number of modules to connect together as a train or ride independently as a single unit.
  • Multitrack configuration is stable, safer in all weather conditions and easier to ride very slowly.
  • Specified with conventional bicycle parts.
  • Riders benefit from the recumbent position: a good all-round view, ergonomics and aerodynamics.
  • Design has the potential to be equipped as a Velomobile, offering weather protection and aerodynamic efficiency.
  • Low-Tech: From the very beginning of the design the philosophy of the Fahrradbus concept includes the low-tech principle. The use of simple interchangeable fabrications in combination with durable design creates a rugged and repairable machine.

Technical implementation:

  • Conventional bike parts (with the exception of the jackshafts).
  • 2D frame of box-section steel tubes: simple construction meant we needed no frame jig during manufacture. The frame is deliberately adaptable so additions and changes can be easily implemented. Adjustability is designed into the frame, which benefits from features like adjustable seats, adjustable bottom bracket, etc.
  • Easily and quickly adjustable seats suit riders from infants to 2.0 m tall (move the bottom bracket clamp and shorten the chain for people below than 1.50 m)
  • 26″-wheels with balloon tires are comfortable enough so a technically challenging suspension is expendable (20″ wheels would of course be much stronger, but less comfortable and you need more expansive big sprockets, plus a rim brake would be more risky because of thermal buildup)
  • Wheels adjacent to the seats ensure stability and form a sort of crumple zone
  • Wooden wheelhouses are important for the vertical parking position, comfort, keep the transmission cleaner and drier and form a place for information and advertising. The open in the front and back of the wheelhouses enable ventilation of the inner parts.
  • Centered steering lever with its open cockpit creates the simplest indirect steering system.
  • Hydraulic rim brakes: simple, enough power, durable.
  • Luggage net under, behind and between the seats: practical, simple and secure storage.

Specification for the DIY-model:

  • length: 2.42 m (3 modules: 6.91 m)
  • width: 1.34 m
  • hight: 1.01 m
  • weight: ca. 60 kg
  • turning circle: 5.5 m (3 coupled modules)
  • gear shift: hub gears (at least 300% gear ratio necessary)

possible application fields:

  • traveling jointly, bicycle tours
  • disabled and less able people
  • schoolbus”, bicycle for families
  • heavy goods transport, cargobike
  • educational workshops at school, for social work, etc. tourism, bicycle hire
  • political actions and for fun

First experience.

The more we cycled with the Fahrradbus, the more we slowed down and started to love cruising around with a smile and we’ve departed from the velomobile goal for ultimate speed and efficiency.

Although we belive there is big potential in the concept of coupled cycling, as we have proven, for the project to develop further, we require more resources.

 

It’s a new feeling of cycling, when you drive in a group especially in a recumbent position. The group dynamics can be positive or negative when we find some riders are less willing to pedal than others. Maybe that’s an impressive practical way to comprehend this ethical Problem…

Riding the Fahrradbus is quite fun. When you cycle, almost without exception there are smiles, laughing and positive reactions from passers by probably because of the delight of the passengers.

However, there is no joy and delight in going uphill. The conflict between riders and reluctance to ride as a team is a ongoing difficulty.

One challenge for the riders is the combination of a net weight of almost 30 kg per person, because of the proud low-tech construction, with the relatively small 300% gear range. If we had more resources, we would have specified Rohloff gear hubs for each wheel (or Pinion gearboxes for each set of cranks). So if the inventers of these genuine bicycle parts read this article, we would be delighted for a donation! :-). The ability to change gear while stationary combined with a wide gear range is essential for a recumbent-tandem like the Fahrradbus.

There may be some energy lost in the way we power and couple the Fahrradbus. We recognised a slightly escalation and resonance of the coupled bike bus so we used some old bicycle tubes to minimise the clearance in the coupling. So far we haven’t taken any efficiency measurements.

The Fahrradbus can easily be driven half seated – in coupled mode or as a single module. We were surprised positively, because we assumed this would be problematic in terms of tyre adhesion. However, we only had trouble when riding uphill on gravel or sandy roads when the small front wheel with less weight is pushed sideways and complicates or prevents steering. If the Fahrradbus is fully populated with riders, there is no problem with the steering system.

We have only tested a Fahrradbus with a total number of three modules. Because of reasons of security, we recommend a maximum of three coupled modules be used on public roads. The reason lies in the modular braking system, because each module has separate brakes and all brakes are required to act simultaneously for a fast enough stop in a situation of danger. This means all three people on the brake position (the left seated rider controls both brakes of one module) must fully concentrate and always be aware of the situation. Practice shows that’s possible with a maximum of three modules and good communication from the lead rider. The longer the bus, the more difficult it is to see what’s going on at the front… and a coupled hydraulic brake system is beyond the project budget and too sophisticated, going against one of the important points of our concept.

It wouldn’t be difficult to motorize the Fahrradbus within a practical, maybe semi-legal way. It would require two independent pedelec-kits (mid-drive or hub motors). The important thing would be to cross the pedal sensors ensuring a harmonious assistance that also reduce or correct the steering problem when going uphill in one-seated modules.

So far each module has driven between 2000 and 3000 km without considerable problems. There wasn’t even a single puncture, thanks the balloon tyres. We think we have proven the DIY construction model to be a consistant and harmonious concept, yet there is more work to be done!

Fahrradbus-workshops
We offer Fahrradbus-workshops. With our support you can build three Fahrradbus-modules in two weeks for example. It’s a great experience for groups to build their own special bicycle – especially with an additional Fahrradbus-journey after the workshop!

We are very curious to hear your feedback, so please comment and get in touch if you have ideas or can help in any way!

VeloVision Issue 51 June 2016

Many thanks to Howard Yeomans from Velo Vision Magazine!