A cable operated "rack and pinion".

The steering-wheel shaft rotates a bobbin (in centre at top of picture). its rotary motion is translated via a cable into a lateral displacement of the "rack". The tie-rods are centrally attached to the rack.

Whole libraries have been written about steering geometry, I will be brief.
Bumpsteer is eliminated by having the outer tie-rod ends move in an arc that closely corresponds to their movement along the pillars.
The steering arms correctly observe the Ackerman principles of steering ensuring that all 3 wheels describe a circle about a common point when cornering.
The centre-line of the kingpins intersects the tyre contact patch for braking stability.
Camber angle is zero as is Toe-in, minimising tyre scrub and rolling resistance.
Castor angle is close to zero, just enough to ensure camber of the outside wheel remains close to zero on turns, further castor action is provided by mounting the stubaxle to the pillar behind its centreline.
In practice the steering is very light, responsive, neutral and not affected by bumps.
It has been in use for a number of years now and appears to be bulletproof.
 

The steering "box" (pictured at right) originally fitted was cunningly adapted from a hand cranked grinding wheel.

It was fine for smooth surface Electrathon racing but not robust enough for uneven surfaces.

The cantilevered steering arm transmitted large twisting loads to the chassis tubes and the pinion's rather small teeth stripped quickly once the steering was occasionally subjected to shock loads.

Various other steering methods were tried before the current system was implemented.
I tried a simple gokart style lever on the end of the steering shaft, again the loads were eccentric and it required setting the steering column at a steep angle in order to maintain the angles between the tie-rods and the sliding pillars.

I tried bobbin & cable and a single unjointed tie-rod, but as the length of cable varies with wheel movements, some very inelegant spring tensioners were needed.
With the steering axis inclination being in the order of 10 degrees, using an unarticulated tie-rod led to severe toe-out on bumps.