Lo-bus .co.uk   Lo-bus Ambulance Design Study We all love our cars and lavish lots of money on them, but if we are unfortunate enough to  fall sick, suffer an injury, or grow old, these things change. We are then likely to be transported in a builder's truck with a plastic box on the back, or in a lined -out tin van. There are many  worthy people performing these vehicle conversions, but it is very much an attempt to make a silk purse out of a sow's ear. On balance the tin van will give you a better ride, and will make it easier for you to get in and out, or for you to be lifted in and out. This is because the  floor will probably be lower, as will the centre of gravity.   Furthermore your stretcher trolley will probably ride between the front and rear wheels.  Inside a builder's truck, however, you are likely to be bounced along on top of the rear axle. A recent improvement has been Renault Master option which uses collapsible airbags on the rear axle, and a sloping section in the rear floor, with a drop-out ramp. This addresses the main problem, but with the penalty of reduced ground clearance, and it creates a number of  other problems, e.g. roll-out (lateral instability)   I had felt for some time that as a species we could do better, and in 1989 I filed UK Patent  Number GB2220172, for a tubular steel space frame which would form the basis of an extremely low-floored ambulance. In 1992 I was eventually awarded the patent, but allowed  it to lapse at the millennium because nobody would undertake the research and development costs in view of the likely profit from eventual sales numbers.   The maths to prove this structure was completed by a third party, long ago. The correct engineering term is finite element analysis. This design adopts a simple "kit-car"  approach, without which the costs will be insuperable. Ford for instance, might spend three  figures of millions on the development of just a gearbox, whereas this design would use one off the peg, together with a 200bhp diesel engine driving the front wheels.   The rear suspension requires some work, but not a huge amount. In order to achieve the low rear floor, a lot of traditional ironmongery has to come out-from-under. This includes the  differential, the spare wheel, the fuel tank, the fresh air above any rear suspension cross- member-more of this in a moment-and the second silencer. The rear suspension cross-tube will almost certainly be a torsion bar, or bars, with trailing arms at the outer ends, on which  hang the rear wheel hubs. 17 million beetles and over 2 million tractions avant have proved this system. The arms will move up and down inside the rear wheel-arch boxes, and  the pumped, compensating element of the suspension lives in here too. There should also be space in here for the second silencer, possibly the spare wheel (slim jim), and either the air compressor or an oil tank, depending on which medium is adopted for the compensating element. The boxes are covered by spats to enable easy access to components, to reduce drag,  and to enhance the vehicle's appearance. They may also keep the rear end cleaner.

When in use this vehicle should comfortably achieve a cabin floor height of 14 inches. A  Ford Transit will achieve a floor height of:                                                 24 inches. A Peugeot Boxer will achieve a floor height of:                                              22 inches. A Renault Master will achieve a floor height of:                                             19 inches. With this design study's suspension let down, its floor height will be:                10 inches. A domestic stair riser averages approximately:                                                  8 inches. This design study should achieve a ground clearance of 9 inches with the suspension at  normal height. Access through the rear door is envisaged as being via a drop-down ramp, horse-box style,  but a lot smarter, and much smaller. By my measurements there should be no need for a tail lift.  This should reduce weight and cost, and maximize available space.   The driving position is distinctly "cab-over", camper-style, and cab access has been planned to be via a step, probably a drop-out step, outboard of the front wheel(s). If this is impractical or too expensive (A Scania version of this costs lots), then access may have to be in front of  the front wheels, and the quarter light strut will have to be re-positioned. This strut is a structural part of the space frame, and may not be dispensed with per se. If we don't stack up  the crew over the engine, we stand the risk of an overly long vehicle, because we also wish to  keep stretcher trolleys between the front and rear wheels.   Space Frames should produce lighter vehicles. The all-up weight of this one laden with  8 passengers should be no more than 2500kg. A lot of current vehicles of this size weigh more than this before anybody climbs aboard. Historical precedents for successful space frames include the Cisitalia, early Lancias, the gull-wing Mercedes Benz, the front f the  E-Type Jaguar, and Ginetta. In a bigger vehicle, the cab of the American Seagrave fire engine  uses a space frame, as does the cab of the Renault Magnum truck; without this approach, these vehicles would be hugely heavy in relation to their size and strength.   Citroen's suspension has been refined over 50 years. Both Rolls Royce and JCB have utilized it successfully, and as a mechanic's son with a current Heavy Goods Licence, I would be  anxious that it is made easy for service. The opportunity is there within the design for this to  happen. The rear suspension is intended to pick up off frame tube-ends. In the same mood, I have envisaged the front bumper to come off easily, and consideration should be given to  mounting the engine, and maybe the gearbox, radiator and hoses on a sub-frame. I also see no reason for structural sides to the engine-bay; these can be lightweight pop-fit sheets. Airbags are an alternative to Citroen's suspension system, and are commonplace now on trucks and buses, down to about this size of vehicle, so there is plenty of choice.

The power call for a modern ambulance is so great that 12 volts is beginning to look too  wimpy, so I have specified 24 volts, and I envisage at east one pair of multiplexers. This system I would expect to have a strong German flavour. At some point in the future, the rear wheel arch boxes might house an alternative power source, but this has not been explored.   There has been an unsuccessful bootleg of this design since the patent was published. They Never spoke to me, and built a bigger bus, but I feel that their version was not sufficiently three-dimensional. They also used the wrong tube. The result was too complicated, too  heavy, and too expensive. It was also hopelessly underpowered, but I was impressed with  the use of air. The major manufacturers have varied in their attitude to my design, from not replying at all, through "Not invented here", to "Congratulations but we don't have the money". One actually offered to supply components. However, I have no intention of trying for a loan to start a one-product company, and Her Majesty's Government is reluctant to back anything like this, despite it being just about the only design to fully satisfy their regulations. Any taker would probably see no return, but I can think of many millions wasted down the years on less worthy projects. Euromillions rollover results anybody? John Dobson. 2007   dobson91147@btinternet.com Attachments will not be opened    copyright John Dobson 2007

Get free web stats here.