A New Swinger in Town? Pro Modified cars have allways used the four-link rear suspension design.......... Until now that is! There is a growing
trend in the USA towards the swing-arm designed originally by Australian chassis designer Murray Anderson. The main thing that a swing-arm is attemting to do is distribute the power to both rear tyres evenly. By doing
this a car should in theory, launch straight and even much like an alcohol funny car does on a good launch. By being able to absorb all the energy and transferring it to the rear wheels evenly no energy should be lost.
When a four-link car launches it loses some energy trying to twist the car. If this energy is then harnessed as in a swing-arm you use more of the power that the engine produces for forward movement as opposed to
twisting. Now all is well and good at the start but how about when shifting gears? Since the swing arm is a single unit and not four individual bars there is no flex when shifting, which takes care of the inherrent
problem of unloading the rear at shift points. According to chassis builder Murray ANderson, who originally designed the swing arm, Once the arm is built - it is set and this takes away a variable which usually
catches races out when the track conditions change. By having no adjustment, the repeatabilty of a swing-arm is 95% as opposed to the four-link's 60%. It seems that a swing arm takes care of all of the problems
inherrent with a four-link. Not so, since this design is relatively new, not many people know how to run with it and even less people know how to build on correctly. Herein lies the problem: the four-linkvhas 25 years
of development behind it , the swing-arm is so that new that there are only a few people world-wide who understand it. The four link on the other hand is far from being dead. Especially in this country where the
technology takes a while to catch up and budgets are much smaller so teams cannot afford to experiment. There are still areas of the four link that haven't been investigated yet, for example hole locations not just
where you put it from one run to another but in the desigh, location holes in front ofor above the rear axle housing or experiments with axle to chassis heights. In the mid nineties American drivers ran
penomenal times with four-link, much faster that the current Europen records so therelife in the old dog yet. Technical help is much more available for the four link with many chassis buildes in Europe having a wealth
of experience with them. During the first part of the 1999 season most of the drivers using the swing-arm setup in the States had a pesky shock problem, which took them much longer to trace than it would with the much
better known four-link. With more testing and a better understanding of it by racers and chassis builders, the swing-arm may someday overtake the four-link as for the design of chice, but for now the four-link is
still the reigning champion. How long will it be till we see the first swing arm car in Europe, only time will tell ? |
