Burt strut

Lore & Background

The Burt strut was introduced to replace previous timing mechanisms that used a chock with a sensor placed behind the rear wheel at the start. Because the chock was at the rear and finish-line readings were taken from the front, precision was limited. As most British hillclimb courses are less than 1500 yards long, competitors' times are often separated by only hundredths of a second, making accurate timing essential. The introduction of light beam timing required a consistent surface to break the beam at both start and finish, but variable vehicle shapes and sensor placement made this difficult before the Burt strut.

Reader's Guide

The Burt strut's significance lies in its role as a compulsory component in most national and international timed sprint events, ensuring consistent and repeatable timing. By providing a standardized rectangular plate mounted at the front of the vehicle, it eliminated the inaccuracies of earlier rear-wheel chock systems. The MSA Competitors' Yearbook (Blue Book) defines its dimensions: a single rectangular plate, painted matt black on both sides, no less than 254 mm in height and 51 mm in width, with the lower edge mounted no more than 200 mm from the ground and the upper edge at least 454 mm from the ground. The strut must be the most forward part of the vehicle, with no restrictions on material. Its legacy is a simple, effective solution that improved timing accuracy in events where fractions of a second decide outcomes.

Did You Know?

• The Burt strut was invented in 1967 by Ron Smith, manager and chief mechanic of Patsy Burt.
• It first appeared on Patsy Burt's McLaren-Oldsmobile.
• The strut replaced a chock with a sensor placed behind the rear wheel at the start.
• In the United Kingdom, its size and position are regulated by the MSA Competitors' Yearbook (Blue Book).

Origins: A Mechanic's Solution Named for a Champion

In 1967, Ron Smith—a man who served as both manager and chief mechanic for a racing driver—devised a simple yet transformative piece of equipment for motorsport timing. That driver was Patsy Burt, who would go on to claim the 1970 British sprint championship and later marry Smith himself. The device Smith created was a black rectangular plate designed to be mounted on the nose of a competition car, giving it a uniform surface through which a light beam could be broken at both the start and finish lines of a timed run. When the strut first took its place on the front of Burt's McLaren-Oldsmobile, her surname was adopted as the device's official name, and it has carried that title ever since. Though the terms 'timing strut' or 'beam splitter' have gradually entered common usage in more recent years, the original Burt name remains the most widely recognized designation in the world of sprint and hillclimb racing.

Solving the Precision Problem

Before the Burt strut existed, timing at the start of a sprint or hillclimb run relied on a chock fitted with a sensor, positioned behind the rear wheel of the car. At the finish, however, the reading was taken from the front of the vehicle. This mismatch meant that the precision of recorded times was inherently limited, a significant drawback on British hillclimb courses that typically measure less than 1500 yards in length. On such short runs, the difference between competitors is often a matter of mere hundredths of a second, making any inconsistency in how the beam is broken a critical source of error. As light-beam timing technology grew more accurate, the sport needed every car to present a consistent, standardized surface at both the start and the finish. The variable shapes of different vehicles and the inconsistent placement of beam sensors made this a genuinely difficult requirement to satisfy. Smith's rectangular plate solved the problem elegantly: by mandating a single, uniform object at the very front of the car, it eliminated the geometric variability that had previously undermined timing accuracy.

The Regulatory Blueprint

Within the United Kingdom, the Royal Automobile Club Motor Sports Association (MSA) sets the precise rules governing the strut's dimensions and placement. These specifications appear in the MSA Competitors' Yearbook, commonly referred to as the Blue Book. According to that document, the strut must be a single rectangular plate, painted matt black on both faces, with a minimum height of 254 millimetres and a minimum width of 51 millimetres. Its lower edge may sit no higher than 200 millimetres above the ground, while the upper edge must be at least 454 millimetres off the surface. Crucially, the strut is required to be the most forward-pointing element on the entire vehicle, ensuring it is always the first thing to intersect the timing beam. Notably, the regulations impose no restriction on the material from which the plate is fabricated; as long as the finished strut meets the dimensional and positional criteria, the constructor is free to use whatever substance suits. In practice, some of the designs in use are remarkably simple to build, reflecting the straightforward engineering philosophy behind the original 1967 concept.

From Niche Fix to Universal Standard

What began as a single plate bolted to the nose of one McLaren-Oldsmobile has evolved into a mandatory feature across the global landscape of timed motorsport. Today, the Burt strut is compulsory in most national and international sprint events, where competitors race the clock rather than another car on the track. Its role is to provide a standardized, repeatable method of breaking the timing light beam at both the start and the finish of a run, ensuring that every vehicle is measured under identical geometric conditions. The device's adoption has been so thorough that the generic term 'timing strut' has become widely used in recent years, a testament to how completely the original Burt name has permeated the sport's vocabulary. From the short, steep gradients of British hillclimb courses to international sprint championships, the small black rectangle at the front of a car remains one of the most critical pieces of timing infrastructure in motorsport, a quiet but indispensable legacy of a mechanic's 1967 innovation.