Five Ideas Worth Revisiting

Back to the future

by Julian Edgar

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This article was first published in 2009.

Cars and car technology have been around for about 120 years. Over that time, many ideas and philosophies have come and gone. There’s a tendency to dismiss old ideas as being outdated – and of course, many of them are. But others are not, and in fact seem very worthy of a comeback.

So what are five older ideas worth revisiting?

Water Injection

This is the idea with perhaps the most going for it – water injection can give you more power, better fuel economy and reduced emissions. That list of claims may sound a bit like snake oil, but they’ve been well proven over a very long time.

By adding a very fine mist of water droplets to the intake air, the combustion process is altered. In effect, the engine acts like it is running on a higher octane fuel, so the ignition timing can be advanced, or turbo boost pressure can be raised, or a higher compression ratio can be used. 

The reasons that the combustion process alters are (at least) three-fold:

  • The water droplets evaporate on their way to the engine, so reducing the intake air temperature

  • The water remaining as liquid turns to steam in the combustion chamber, so slowing the rate of combustion

  • The combustion chamber, valves and plugs stay much cleaner, so reducing the build-up of carbon hot spots

    In the past people tended to sneer at water injection as a band-aid for bad design, but that is simply wrong. There is absolutely no technical reason why a high quality, electronically-controlled, multi-point or single-point water injection system could not be designed into current engines. 

    It’s especially attractive as some (but not all) testing of water injection has shown decreased outputs of oxides of nitrogen (NOx). 

    With electronic control of the water injection as part of the overall management system, ‘limp home’ strategies could be easily enacted in case the water tank runs dry. It would also be relatively simple to incorporate an atmospheric relative humidity measurement into the system, so that water injection varied not only with load, revs, etc, but also with humidity. That way, on a cold, foggy morning (where water injection naturally occurs!) water use could be curtailed. 

    Water injection has been used on just a handful of production turbo cars, but was widely used in World War II on very high performance piston engine aircraft. 

    With a smart, modern control system, water consumption could be quite small – in fact, potentially so small that the water could be extracted from the exhaust gases...

    See also The H2O Way Part 1

    Interconnected Suspension

    The interconnection of suspension systems has been tried on a number of very successful cars. But fore-aft connection (most suspensions are already laterally connected by the anti-roll bars) is still a rarity, rather than the norm. 

    Individually interconnecting the front and rear wheels on each side of the car allows the suspension system to strongly resist body roll (because the front and rear suspensions on the one side are both in compression, and so are pushing against each other), and reduce pitch (because when a front or rear wheel runs over an object, the wheel at the other end tends to get lifted as well). 

    While the front and rear wheels can be connected in all suspension systems (even those using steel coil springs - the pictured Citroen 2CV suspension did this), most interconnected systems have used either fluid or gas to achieve the link. 

    A gas/fluid system (eg nitrogen gas over oil – many Citroens), or rubber springs used in conjunction with water (eg Austin) allows damping control to be integrated into the springing system itself, rather than requiring separate hydraulic dampers. This has packaging advantages. 

    Self-levelling (eg fast enough to reduce squat and dive) and active height adjust are also easily integrated. 

    Such systems need not be expensive – the aforementioned Austin system was used on quite cheap cars. 

    The ride quality of most current cars is pretty awful – with cheap electronic control, interconnected fluid-based systems could make huge gains in ride quality without sacrificing handling. 

    See also Another Human Powered Vehicle! Part 3 - Interconnected Suspensions

    Body Design

    Go back 50 years and many high performance cars for both the road and track used tubular spaceframe designs. The tubular constructions were very strong yet weighed little. Most usually, the tube frames were covered in hand-beaten aluminium panels. 

    Today, with the major emphasis on crash safety and the desire for lightness, it would seem reasonable to suggest that such structures could well make a comeback. But they wouldn’t look like the spaceframes of half a century ago. 

    Hydroforming (where compound curved tubes can be made via the use of massive internal water pressures) would allow tube diameter and wall thickness to be varied at will, putting the strongest parts only where they are needed. The passenger compartment, suspension pick-up points and engine mounts could all be tied together in a strong and stiff structure. 

    The body panels would then be used only for aerodynamics and aesthetics, and could be made of ultra lightweight plastic. The panels would not be designed to last the life of the car; instead they’d be replaceable in the way in which we currently replace windscreen wiper rubbers. 

    The panels for a complete car – especially a car that will never travel at over 110 km/h – could be thin, light and colour-impregnated. How much would a complete set of panels weigh? 50kg? 100kg – surely no more. 

    The opportunity for one spaceframe structure to support a number of models wearing different panels is obvious.

    See also Hydroforming - Part 2

    Actively Changing Aero

    Back in the 1930s a lot of experimentation occurred with vehicle aerodynamics, especially in Germany. At that time, the drag penalty of poorly shaped vehicles was well recognised, and the German engineers started to wind tunnel test a variety of shapes. 

    One target was the aero drag of long distance vehicles, like buses. These vehicles had a higher average speed than most other traffic, so any drag reduction would immediately pay dividends in terms of fuel costs. (Buses not quite like the pictured vehicle, but you get the idea!)

    One approach that was experimented with was the use of inflatable sections that could change the shape of the vehicle. With most vehicles, it is the low pressure area being dragged along behind the vehicle that causes most of the aero drag. But what if an inflatable tail was used to fill that space, shaped such that the air layers smoothly came back together? In theory there is no reason why it would not work, and as far as I know, when it was trialled it did work!

    Think about it – an interstate bus that once clear of city limits, extends its tail by a few metres. It wouldn’t be hard to achieve an outcome with potential safety benefits (an ever-present low pressure rear airbag!), automatic operation and much reduced aerodynamic drag.

    Three Wheels

    Think ‘car’ and you immediately picture a vehicle with four wheels. But why? The minimum wheel number needed for stability is three, and dropping your wheel count by 25 per cent has immediate benefits in terms of rolling drag, tyre replacement costs, weight and vehicle cost. 

    If the wheels are arranged in a ‘tadpole’ configuration (two at the front and one at the back), it also makes achieving a low aerodynamic drag body much easier, as the vehicle can be ‘boat-tailed’ to a large degree. (The slipperiest shape is a teardrop – the rounded end leading and the long trailing tail allowing the air to come back together, as I described above with inflatable bus tails.)  

    The idea that three wheelers will fall over at the sight of a corner is pretty well as silly as the idea that four wheel cars will roll over – yes, in both cases it can occur, but it comes down to weight distribution, centre of gravity height, track and wheelbase dimensions. And in the same way as four wheel cars can achieve very high cornering forces without toppling, so can well designed three wheelers. Taking into account varying loads (two occupants, one occupant, no luggage, lots of luggage), it’s likely that a practical three-wheel car with not be able to achieve the same absolute cornering limits as a four wheel car – but so what.... very few cars ever need to do that anyway! 

    (But if you want very high cornering limits, just make the three-wheel vehicle lean into the corner...)

    Conclusion

    There’s no point in blaming car companies for not being innovative – they are. But they can only make what customers will buy. So when you say that you want your new car to have an inflatable tail, run on water as well as fuel, use interconnected suspension, have only three wheels and feature body panels you replace every few years... well, unfortunately, there won’t be many other potential buyers who share your views!

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