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In the 2009 season, the DT Red Bull, Adrian Newey has shown in Formula 1 a concept of suspension, which was no longer used for several years: the so-called pull-rod suspension.
About 20 years ago, the suspensions were all pull-rod and were introduced by Murray. Evolution of the suspensions were a rocker. With the increase in torsional rigidity of the car, the balance of the suspension becomes too flexible so that the elastic component of the suspension was made by the budget. And this is harmful because it does not control. Murray decided to do, then, a very short barbell. The motion was given by a strut inclined. As a material is subjected to stretch does not cause (within limits), an inclined strut suspension gave much greater stiffness.
But given the limits given by the diameter of the rim fixed by regulation 13 inches, the strut could not be tilted too much. At that point, they decided to reverse the drift, and to raise the frame front of the pilot. In this way, the strut angle became more and more diminished force component that generates flexion. All this was helped by the fact that since the 90's, the F1 had begun to lift the front of the case for aerodynamic reasons. So the new push-rod solution is perfectly in keeping with this need.
Little by little all the stables converted the front suspension and rear push-rod.
At the beginning of the year 2000, the designer Amidji Arrows brought back the pull-rod front suspension. This was done for aerodynamic reasons. In fact, since a strut supports better traction than the compression strut can have a smaller cross-sectional pull a suspension. This was supposed to help the aerodynamics combined with a muzzle lower than usual. But the solution was unsuccessful and returned to the push.
Sketch of pull rod suspension
Sketch suspension push rod
Why has returned to the pull rod suspension?
With the advent of double decker speakers introduced by Williams, Toyota and Brawn at the beginning of the 2009 season, this suspension solution was the most likely to create more space in the back and make sure that the speakers is the most effective possible. Note that the only Red Bull and the "sister" Toro Rosso use this suspension system, in fact, have the rear speaker much more effective than the other teams that use the push rod suspension system. In my opinion, next year, even if the speakers double decker will be banned by regulation, many teams remember well a pull rod suspension system. As described can be understood better by looking at the drawings below, you see the free space above the gearbox that can be used to go to feed the speaker by increasing the downforce in the rear.
What is it and how does a suspension?
First, the term "suspension" means the so-called "unsprung weight", ie the set of bodies interposed between ground and car body (sprung mass). The suspension, in a vertical direction, have the task of absorbing the undulations of the ground accelerations, to transmit to or from the soil weight, aerodynamic measures, the transfer of cargo. In most people the task of transmitting, horizontally, or from the ground to the braking, aerodynamics, engines, centrifuges. Second, suspensions retain and control the trim of the car (for example, the height of the bottom of the track). The suspensions also interact directly with the steering linkage and steering angles (toe, camber, caster spindle is longitudinal and transverse steering, trail, etc..), Which should not vary in roll, pitch, shaking and all driving conditions.
How do the suspension?
The push-rod has a kickstand, working in compression: it transmits the drive and connects the bottom of the upright to the bar (or rocker) which controls the spring-damper and torsion bar / damper. The pull-rod, in contrast, presents a tie, who works in traction and drives the spring-damper or shock absorber of torsion-bar: it transmits the drive and connects the top of the upright to the bar (or rocker) which controls the spring-damper and torsion bar / damper.
All this is available in classic double wishbone pattern. It is now general practice for some years, spring to install two sets \ torsion-bar front and rear shocks (in the past, the shock was also used), connected to a third element, a third shock in charge of monitoring the height and the inclination of the car from the ground. This third element, which is inherited from Indy cars (just to reiterate that it is not the only F1 to export ideas and technology ...), was introduced for the first time in F1 in 1994 by Alan Jenkins on Arrows. To this, add the ever-useful anti-roll bars, the size very small.
The location of the spring groups \ torsion bar / damper is one of the most obvious differences between push-pull-rod and rod. The push-rod, which provides a strut and thus the need to place the groups spring \ torsion bar / damper above the rider's legs (by binding to the body and placing them lengthwise or just apart), goes well with so-called "musical high, "in vogue in F1 since the early 90's, in the wake of the revolutionary Tyrrell 019. The need to free the bottom of the muzzle, so that you face a sheet of air to flow more abundant and less perturbed towards the bottom of the car, is one factor that has contributed, from the 90's, to phase out all the pull-rod ' Anterior to the push-rod.
The push-rod also allows rapid control measures and less complicated, it is sufficient, in fact, remove the upper body of the snout to access the strut \ torsion bar / damper, an operation that, in contrast, requires a lot more work for a pull-rod.
The pull-rod, for its part, has the advantage of very small dimensions, so much for the linkage (which section is much thinner than a push-rod strut) and for the general height of the entire system, thus resulting in benefits the center of gravity. The pull-rod, in fact, draws a very clean, aerodynamic, tapered and tapered.
It is for this reason that Newey, for his Red Bull RB5 and RB6, opted for a pull-rod rear aerodynamic cleaner, less disturbed airflow directly behind the rear wing, lower sides at the rear Coca Cola and more tapered, lower center of gravity. All this, without affecting the efficiency of the car and the bottom of the extractor.
On the current Formula 1 cars, take a pull-rod front operation would now be almost impossible. The musical, in fact, are too high (even uphill!) And dug too inferiorly to accommodate groups spring \ torsion bar / damper. Not by chance, that released later the lower area of the snout to accoglirere also possible aerodynamic and flow direction, has been eliminated as a central keel attachment for the lower triangle of the suspension. The latter, therefore, are bound directly to the body: it is for this reason that the triangles are on the downside. Not only that: the rod, in addition, is practically level (actually, more like a push-rod strut!), Ineffective and therefore subjected to abnormal stress, more than they are already in "normal" pull-push rod with respect to the strut -rod, which due to its marked inclination, is able to withstand higher stresses.
Later, however, as there is more space, you can sbizzarrisrsi: push-rod and pull-rod, but also the positioning of strut \ torsion bar / damper very different and original.
In addition, Red Bull RB6 take extreme geometries in terms of suspension. For example, the strut front push-rod is not anchored to the ends of the lower triangle, but directly to the upright. Solution that, combined with other "found" by Newey (calipers lying horizontally at the bottom, etc..) Means that in this area are concentrated loads and stresses which are relevant.
Ultimately, it is the best push-rod or pull-rod?
There is no right answer and final. Both types are reliable, functional, profitable equivalent. As often happens, the choice of either scheme depends only on the will and eslusivamente and Evaluation of the project. And, as often happens when it comes to car technology, there are no dogmas, but only alternative.
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