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Track Locater Installation

Added on 2007-12-01

In my opinion, diagonal link track locaters should always be installed front left to rear right. I have however seen many successfull locaters installed the other way around, but they always require larger tube as they bend more easily. If installed left front, right rear, smaller tube can be used because it is under tension in high load situations.

The reason for this is that the rear end housing tries to fire itself out the right hand side of the vehicle when viewed fom behind. This can easily be confirmed, if you stand behind a leaf spring equipped vehicle on the start line. These vehicles use the leaves to control sideways motion, as there is no track locater. The leaves however are rubber bushed in the eyes and do allow an amount of twisting when viewed for the rear. At launch, the body always moves to the left of the housing, and some leaf spring vehicles start swaying side to side after the next gear is selected. This happens because the side load is momentarily relaxed on shifting, and allows the housing to start a side to side oscillation within the tyres due to the low pressures used in drag racing.

Highslide JSA correctly installed track locater. (Nuts have not been tightened in this picture)On four link/ladder bar equpped cars the housing brackets should also be braced back to the centre of the housing, as I have seen many bend side ways due to track locater loads. When the bending happens with a correctly installed locater, the right hand side brackets (Australian drivers side), always bend towards the centre of the housing, further confirming the side load situation.

I am a fan of installing the track locater, either diagonal link or wisbone, on the top of the housing. The reason for this is because it raises the roll centre of the vehicle. When a drag racing vehicle is going dead straight, its primary roll centre is the tailshaft centreline, due to engine torque. However if things get ugly, and the vehicle gets side ways, circuit racing evaluations come in to play. The centreing device (track locater etc.) determines the roll centre of a circuit racing vehicle. It is about this point that all the vehicle mass rolls and can be different front to rear.

If a drag racing vehicle has the track locater on the bottom of the housing, the roll centre is extremely low. This allows the vehicle to transfer nearly all its rear weight over the roll centre if the vehicle gets side ways. With the low tyre pressures and soft wall tyres that drag racing vehicles run, this allows the body mass to get over the tyres, causing them to dig in, and in some cases the vehicle to roll.

With a track locater mounted on top of the housing, the vehicle cannot transfer anywhere near as much weight if it gets sideways. I believe this is the reason that today we see a lot of out of control vehicles slide rather than dig in and roll as used to happen years ago. Another advantage is that the 3rd member can be removed without having to remove the track locater.

And NEVER EVER jack the vehicle up by the track locater. I have seen people do this over the years and it always ends in tears!

Rod Andrews
Andrews Race Cars