by Olav Naess
Small electric vehicles (like bikes) tend to be designed as a single unit upon which the driver sits or stands. And when the driver decides to become a pedestrian, the vehicle is either left or carried along. At least the battery pack needs to be carried along for recharging.
Such a light vehicle is very easy to steal, so the owner tries to lock it to something, but parts of the vehicle may still be stolen. The owner will then try to carry it along as a piece of luggage, and discovers it is not designed for this. It may be folded together so that it becomes quite compact, and one or both wheels may even be rollable as luggage cart wheels, but the vehicle will still be awkward to carry along.
The best way for the pedestrian to carry along the needed vehicle parts is to have as much as possible in a backpack, and the whole thing will then feel much lighter than when it is an unwieldy structure that might have to be carried away from the body.
Our design strategy is then: Design as much as possible of the vehicle to stay in the backpack. The battery is easy to place in the backpack, and this is most urgently needed there – so that it can be brought indoors for recharging.
The Mechanics in the Backpack
The mechanical parts are not so easy to place into a backpack, as the mechanical energy – unlike electric energy – must follow certain simple paths – preferably a straight line.
The GoPack design follow a simple mechanical principle: The mechanical forces (gravity and propulsion) are gathered in a single force column going down from the bottom of the backpack. The main parts (depicted below) are:
The electric motor (M), surrounded by its battery pack (B). 250 Watts should be legal most places, but a three times stronger GT version with 1 hp should also be quite feasible.
telescopic coaxial pillar (T).
The outer part is a tube supporting the weight of the driver and the backpack. A seat on the middle part of the tube can be turned forwards and locked when the telescopic pillar is pulled down for riding. The seat goes up to the bottom of the backpack when the pillar is retracted into the backpack.
The inner part of the coaxial pillar is a telescopic extension of the motor axle, transmitting the propulsive force down to a wheel below. (A mechanically simpler, but more clumsy solution, is to have the motor in the lower part of the column.)
A remote control, attached to e.g. a thigh, controls the motor speed. Speed reduction should give regenerative braking. A headlight could be placed on a shoulder strap and supplemented by signal lights on the backpack.
The GoPack is carried as a backpack – with three wheel modules
It contains a battery pack (B - outlined), a motor (M), a telescopic non-rotating column (T) containing a rotating axle, and a bike seat (S).
(Optionally also a lamp (L) and signal lights)
Wheel modules etc.
Everything beyond the lower end of the motor axle belongs to the wheel module(s) – or whatever is powered by the backpack.
Various wheel module designs may be available. The first three of these are shown in the picture.
The smallest one, shown in use, has two small wheel modules, with a two-wheel inline skate (or roller ski) for each foot. Steering is done by rotating the front foot, and braking by lifting the front toes. A strap is holding the skates together (for a more relaxed ride). It should easily detach for enabling ordinary skating at low speeds (indoors). It may be possible to put a pair of these skates into the outer (rear) part of the backpack, along with a helmet (- not shown – wooden heads don't use helmets).
Two larger wheels may make up a single bike-like wheel module. Anyway, the wheel module(s) will be small and light, easily carried in one hand – perhaps within a common plastic bag.
Two medium-sized wheels side by side, emulating a Segway. A guiding tube going up from the platform fixates the lower end of the column so that a gravity sensor and a computer in the backpack can do the balancing. (This wheel module has mechanics for turning the wheels towards the side the driver is leaning.)
(toy) scooter can easily be steered with its vertical T-shaped or
(preferably) Y-shaped handlebar. This vehicle is efficiently
collapsible, so that it can fit into a compartment of the backpack.
A wire going out from the top of this compartment could be attached
to the front of the scooter (or to the strap of the skate pair in
alternative 1), and the motor-pulled wire could then pull the
vehicle up into its compartment (or to the outside of the
This wire could also be a cable delivering current to a motor in the vehicle.
Many other energy-receiving module types (with or without propulsion) can be used:
An ordinary bike could be used – with attached mechanics transmitting propulsion force to the drive chain (or to the tire of the back wheel).
There could be a single wheel on the lower end of the column, and the driver could wear ordinary roller skates.
A similar minimal belt traction unit could be used by a skier.
If the backpack is waterproof, a propeller (in a tube) could be used for propelling a diver.
For stationary work, the motor could drive a drill, pump or whatever.
Or the pack battery could simply be used as a power supply. (The headlight on the shoulder can give quite strong light for many hours.)
These small vehicles don't permit muscle propulsion, and give no proper workout in the way an ordinary bike does.
For a human to get a proper workout and provide efficient propulsion, the feet and the body (and stabilizing hands) must be placed in proper position to each other by a strong framework which normally (in a standard bike) wastes much weight and space. Such a contraption might as well stand in the home. It is better to have a shower than e.g. a meeting room nearby after the exercise.
Copyleft Olav Næss 2014