The Greenspeed Anura Quad

Why a four wheeler?
The Anura Trike (three wheeler) was built primarily to be easy to to ride, and especially to be easy to mount and dismount, so that even people who are physically challenged can ride it. In fact is has drastically improved the quality of life for a large number of people who were so physically challenged that they believed that they would never, ever, be able to ride again! Yet they are now out riding with their loved ones, and their physical and mental health has improved beyond their wildest dreams. In fact meeting some of them last year brought tears to my eyes....  

Now one of the main features of the Anura is that it is built high, simply to allow easer mounting and dismounting, and to allow a better view in traffic. Plus it is built narrow to allow easer access through gateways and doorways. Thus while it was more stable than expected, some people would like more stability. So how to improve stability without making it wider or lower? Answer - add another wheel! And because there is little weight on the front of the Anura, and the new front wheels are of a lighter pattern, there is not much more drag. Yet the stability is improved by a whopping 50%!

There is also, I believe, an improvement in appearance, in that the machine looks more "complete" and we have had a lot of favourable comments from people who have seen and ridden the machine. They like the look of it, and say it is like riding a Go Kart with pedals.

Technical Specifications:-

Technical Design Features
There have been many attempts to develop quadricycles from tadpole trikes (two wheels front, one rear), but we found that the main problem was lack of weight on the drive wheels, so that when one wheel lifted on uneven ground, traction was lost, unless there was drive to both wheels, and then there was drag on the corners unless an extra one way clutch was used on each wheel, and that increased the gearing on the turns. And even then, there is still only one third of the weight on the driving wheels. So traction is still no better than the standard tadpole. The other solution is add suspension, but this increases the complication, weight, and cost of the machine.

Anura Quad neatly over comes these problems by using the delta configuration (two rear, one front) as a basis. The standard Anura Trike has 75% of the weight on the driving wheels, which means superior traction, plus it means the both drive wheels stay in contact with the ground over uneven surfaces, and the differential balances the drive to the both rear wheels. So like the Anura Trike, and unlike tadpole trikes, the Quad gives good traction in winter conditions on slippery ground.  Furthermore the steering geometry has been designed so that when one front wheel leaves the ground, the other seamlessly takes over all the steering control. Having 75% of the weight on the rear wheels also means that the two rear wheels disc brakes are powerful enough to hold the trike on the steepest of hills, and are adequate for normal, everyday use. So there is no need for front brakes, which saves weight.

Like the Anura trike, the Quad frame is made from 7005 aluminium alloy, so it is light and strong with the same 300 lbs rider weight limit. Leg length adjustment is made the telescoping the front frame inside the main frame, so shorter riders can take advantage of a shorter machine.

Plus, like the Trike, the Quad can be used to tow an Anura Trike, to form a Quad/Trike tandem, but care must be taken, on the corners, as the Quad is more stable than the Trike.

Ian Sims C.E.O. December 2011

Anura Trike

Anura Quad

with optional rear fenders and rack.

Differential for balanced two wheel drive, and optional tandem coupling.