Inspired by bicycles and guided by a workshop we’ll be hosting at Small is… festival, on the 4th September, my friend James and I have set about building a pedal-powered blender. The following nugget of information does not explain how to build one of these things – Open-Source plans are in the pipeline – but shows the evolution of the idea. Maya Pedal, the Human-Powered Home, and http://www.technologyforthepoor.com all inspired this bit of kit.
The starting point is that technology is a double-edged sword. It can be used to oppress, or used to liberate. The greatest problems facing people across the world, including poor health, environmental degradation, and poverty have been both tackled and aggravated by technological advances of the 20th century. Antibiotics contributing to superbugs and over-population, cars providing rapid transport to a few, but fumes, traffic jams and resource depletion to everyone, and computers allowing amazing data-handling capabilities while reducing our capacities for calm contemplation are a few pertinent examples. So the challenge is to produce technology that benefits people directly, without any of the downsides that tend to accompany technological advance.
A puny pedal machine may quiver at the size and weight of these problems and it would be pure arrogant if it suggested that it had the potential to tackle them alone. However, trying to tackle intractable problems head-on is not the aim of the game. The point is to provide a stepping stone, a test-bed, and food for thought. The need for better use of human muscle power is obvious in both rich and poor places, as the former is facing obesity, unemployment and anxiety, while the latter struggles under the physical toil of everyday life. Our premise is that pedal-powered machines could tackle both sets of problems. Tackle several birds with one stone. Provide meaningful exercise, employment and increased environmental awareness for the rich, and labour-saving, affordable kit which significantly reduces toil for the poor. Pedal-powered machines can be used by anyone. Perhaps they could also be harnessed to tackle growing inequality. At the risk of dwelling on such conjectures, let’s proceed with key stages in the design process.
- Rear-mounted or front mounted. This is a key point in pedal-powered smoothie design. Rear mounts allow you to hook almost any bike to a blender, leading to simplicity of build, easy of transport, and low cost. On the other hand, they are often unstable, always awkward to use (you have to crane your neck to see the blender), and frequently flimsy. Having looked at both possibilities, we settled for front-mounted, following Maya Pedal, and Fender Blender designs.
- Swapping the pedalling direction. Simply swapping the crank-arms on the bottom bracket allows a cyclist facing the old rear of the bike to pedal forward and power a rear wheel, provided the rear mech is flipped. This is approach used for the bici licuadora. In this design, we saved a bit of time but simply flipping the frame upside down. Originally the dropouts and rear-mech were left intact but eventually it was decided to re-weld the drop-outs to allow easy rear-wheel removal.
- Folding or fixed frame. This was not so much a mulled design point as an inspiration: why not put swivel legs on the thing to provide stability in rough terrain (think festivals and undeveloped villages) and ease of storage and transportation.
- How to transmit the power to the blender. Here (for once) we stuck to the well-beaten path of friction drives. These are simple, small, and already provide the large gear ratio needed to get the blender revving (well over 1000 rpm). Many devices are either on or off. However, James came up with a simple friction-pivot which pushes the friction drive onto the wheel. The advantage of this is that it is modular (anything could be pushed on) and the fiction/torque relationship at the interface between the tire and the friction drive can be optimised: drive slipping? Ease it on more. Too much friction? Ease it off a touch.
- Simplicity and low cost. This went without saying but is worth mentioning. We wanted a design that could be copied around the world, so we tried to avoid expensive parts and anything more advanced than a welder.
So that’s the evolution of the idea, which continues to evolve. James has plans to fit a Magimix food processor on, and the basic concept – of a spinning wheel in front of the user – has many other potential applications. Hopefully the plans will inspire people to build more effective pedal-powered machines.