If you live in a traffic-nightmare city like New York or London or Bangkok, an ultra-compact urban electric car is great. They're so tiny that they fit in the smallest parking space, they're quiet, they're often exempt from congestion charges and they're tailpipe emission free, which is important if you live where the air is so dirty that it's visible. Unfortunately, they also have all the boot space of a glove box and the travel radius of a tortoise in a hurry. Unless you have the ideal lifestyle that allows you to work within the vehicle's limitations, there will come the time when you'll need to carry more than a messenger bag or drive farther than a single battery charge. When that happens, you'll probably wish you had some way to magically add an extra boot or a bigger battery. Rinspeed's Dock+Go concept car looks forward to a day when that may be possible.

Teaser shots of the Dock+Go emerged late last year, but as its appearance at the 2012 Geneva Motor Show approaches more details and images have emerged. One thing is certain - it won't be too hard to pick out of the crowd. The Dock+Go will be the ultra-compact with six wheels. That's not quite true. It's more accurate to say that it has four wheels, but when it needs to, it has six. The reason for this is to provide a way to have your automotive cake and eat it.

Having a minimalist, super-economical electric car and still being able to take longer trips or carry more stuff doesn't necessarily mean having two cars. Nor does it mean hauling around a lot of extra car all the time on the off chance that you'll need it once in a while. Instead, the Dock+Go concept makes all that surplus car detachable. Need more cargo space? Need a bigger battery? Don't get a bigger car, just bolt what you need on when you need it. As Rinspeed CEO Frank M. Rinderknecht put it in a recent press release, "You're not going to take your steamer trunk as if you were going on a lengthy vacation if all you want to do is a little shopping at your local supermarket."

The Dock+Go achieves this by designing a car (in this case, one based on a Smart car) that can accept a sort of module or pack with its own axle that bolts onto the rear. The module mates to the car in such a way that it looks like a metal bustle, or as if someone had grabbed the hatchback by its rear door and pulled very, very hard.

The module, which is seen as being purchased or hired by the car owner, comes in two versions: cargo and power. Either way, the modules aren't very big. At only two-feet long (61 cm) overall, there's not much room. The publicity photos supplied by Rinspeed portrayed the Dock+Go doing duty as a pizza delivery vehicle, as suitable for people going on a skiing holiday or as a portable disco, but given that the Dock+Go is intended as an electric car and the cargo version doesn't bring any extra power with it, these seem a bit on the optimistic side.

The "energy pack", as the powered version is referred to, consists of extra batteries to extend the car's range, but can also be a fuel cell or a hybrid engine. Rinspeed also says that the Dock+Go could act as a "Variohybrid" to turn the car's rear axle, charging the main battery, though this does have a whiff of perpetual motion about it. When it's not bolted to the car, the module could also act as an auxiliary power source for the home according to Rinspeed. Bear in mind, however, that this power pack only weighs 287 pounds (130 kg), so it's not exactly like having your own hydroelectric plant in the garage.

As to performance, this is an tiny electric, so it isn't intended to take on the Nürburgring Ring. Acceleration is 0 to 60 in 13.3 seconds with a top speed of 82 mph (90 kph) without the extra batteries and 132 mph (145 kg) with it.

However, the whole thing with the bolt-on boot or range extender isn't the end of the story. The Dock+Go is a full-fledged concept car intended to showcase the work of Rinspeed's partners 4erC GmbH, AEZ Wheels, AkzoNobel Automotive & Aerospace Coatings, A.T. Kearney, Carl F. Bucherer, Eberspaecher catem, Esoro, Harman, Hornschuch, Lumitec, MBtech Group, Schoeller Group, Brose-SEW, Sharp, Studer Handels AG, Takata-Petri, TE Connectivity, voestalpine, Vollmond Advertising Agency, Weber Fibertech and Zurich Insurance.

Though the Dock+Go is based on the Smart car, it's designed to be much lighter with bespoke alloy wheels and innovative steel frames. This is also a car with the digital/social-networking age firmly in mind. The chrome accents on the bodywork are, in fact, digital displays that turn blue at night and can show logos, advertisements, messages and even Facebook updates for the sort of people who must update they world about what they're doing at all times.

The center of the dashboard is taken up by a 12.1-inch LCD screen that provides access to the car's intelligent infotainment system built by the Harman company. This system can not only do the usual things like tune the radio, but it can also store driver and passenger preferences, has a navigation system that learns from the driver's behavior and it can even read your email to you.

Takata-Petri's contribution was to take this digital theme even further by installing a smartphone dock in the steering wheel of the car. There the phone can integrate with the car's systems, act as a second display screen and even respond to gesture commands, though how that will work out while driving remains to be seen.

Rinspeed also points to a bold, new electric heater for the Dock+Go that can belt out 5.5 kilowatts of heat to the cab with 99 percent efficiency. The Dock+Go is also designed to be charged by wireless induction, so clumsy plugs are replaced by a discrete pad under the Dock+Go's parking space - which is a plus if electrics catch on big and municipalities start installing induction chargers at places like stop lights.

However, a lot of questions remain. Exactly how much extra space does the Dock+Go's modules provide? How far does the "energy pack" extend driving range? How easy are these modules to install? Or to remove? Is this a one-person task? Two? Or is this a garage job? And what about the cost? Does buying the add-on axle make economic sense or would it be simpler and cheaper to hire a car for the day? Then there are the electronic extras. They're fun, but they eat up power. As for cranking tunes out the back, unless that sound system is plugged into the mains, it's going to be a very short party followed by a long walk home.

So does this sort of latch on solution overcome the limitations of the electric car or is something more fundamental needed? If the Dock+Go ever reaches production, we may find the answers ... in the meantime, let us know what you think in the comments section.

Source: Rinspeed

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