THE MINI MAG. Volume 2 No.4
  April 2000

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From The Production Line.
With Nairn Hindaugh.
Nairn worked for BMC in the 60’s. Here is another article from his memorabilia.


Want headlamps that steer around corners, hold the beams on the centre white line or cats’s-eyes on a tight bend, don’t glare across the road at approaching drivers on turns, and can be aimed up and down with a finger tip lever in the cockpit to place the light just where you want it?

Well this is the answer, peek-a-boo lights called “Rotadippers”. The basic idea is simple yet ingenious. A BMC Mini was used as the test guinea pig. The normal 7inch lamps were replaced with bolt-on plastic shells housing 5 inch units. These were clamped in stainless steel rings with swivel pins at top and bottom with the assembly enclosed in a plastic dome. Control lever on the dash dips the lights 10 degrees.

Sideways aiming of each light is controlled by a lever linked to the appropriate steering track rod through a swinging lever and slender rotating shaft. The lights not only swing from side to side with the steering wheel, they anticipate the turn. They do this by swivelling faster than the road wheels when you begin turning into a bend. They shine around the corner before you get there so you can see where you’re going, then slacken their angular movement as the car follows.

But there’s more. As the units swivel to one side they also tilt down progressively, automatically lowering the beams as the steering angle increases for close in illumination of the curbs and shoulders in the inside. In effect, they swing through an arc in both horizontal and vertical planes.

These geometric antics come from a clever arrangement of levers and cams on the underside of each plastic housing. The first of two levers, positioned by the rotating shaft, has a fixed pivot. A peg on its outer end slides in a slot in the second lever, which is bolted to the lower swivel pin on the light’s clamping ring.

As the first lever moves with the steered wheels, it imparts a differential cam action against the second. The slotted swings rapidly at the start of a turn, because the peg is then at the inner end of the slot and therefore close to the fulcrum.

Downward tilting is crafty too. The lower swivel pin locates in a longitudinal slot in the plastic housing. Its operating lever is T-shaped. When this swung to either side, one of the outer corners of the “T” wipes against the housing flange, levering the bottom of the light back against a spring. If that isn’t enough, you can also tilt the units by hand through a 10 degree angle, varying the beam between horizontal and a pool of brilliance right under your nose. This lets you depress the beams before crossing a hump-back bridge, illuminate a tricky driveway, avoid mirror dazzle in the car ahead, or correct tail loading.

Capping it all is that it is “fail safe”. If anything breaks in the linkage, the lights are spring loaded to self-centre straight ahead.

The kits sold for 25 U.K. pound back then, about \$75 Aus. I don’t know if they were a big seller though!