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Bentley 4½ Litre Background

Bentley 4-1/2 litre 1928 (AT5) and 1929 (AT4)

The first standard 4 ½ litre cars used the 10 ft 10 ins chassis of the 3 litre with a similar shaped radiator but wider.  The engine was based on the 3 litre but the cylinder block was larger with a heavier crankshaft, 6 ½ litre con rods and sump as used in the later 3 litres.

Experience gained from racing 4 ½ litre cars ensured that modifications were built into almost every series (each series made up 25 cars).

The 4 ½ litre was in production from 1927 to 1931.

Racing successes were numerous.  The first 4 ½ litre manufactured and affectionately known as ‘Old Mother Gun’ took part in the Le Mans race on 18th/19th June 1927 (running as No.1) driven by Clement and Callingham.  A fastest lap of 73.4 mph was recorded before the drama of the ‘White House’ crash in which both ‘Old Mother Gun’ and the 3 litre (No.2) driven by Duller & d’Erlanger were badly damaged and could not continue.  This left only one Bentley running, the 3 litre of Davis & Benjafield (No.3).  Although considerably damaged, it must have taken strong nerves for Benjafield to have driven so fast that nearing the end of the race, he overtook the Aries of Chassagne & Laly to win.

‘Old Mother Gun’ ran in the Grand Prix de Paris at Montlhery (drivers Clement & Duller) on 19th August 1927 winning the race at an average speed of 51.99 mph.  This was not without drama as the car caught fire twice and the prize money & cup were never presented to the winners as the promoters went bankrupt during the race!  Then followed the 6 hour race at Brooklands on 12th May 1928, when ‘Old Mother Gun’ finished 8th at an average speed of 70.35 mph. 

Le Mans in June of 1928 saw three 4 ½ litre Bentleys on the starting line.  The two new ‘bobtail’ cars of Clement & Benjafield (No.2) and Birkin and Chassagne (No.3).  ‘Old Mother Gun’ (No.4) of Barnato and Rubin made up the trio.

A terrific pace was set during the early part of the race with a top lap speed of 76.2 mph being set by Clement.  Car No.3 retired owing to Birkin going too fast & trying to reach the pits with a flat tyre.  He did not make it and had to run to the pits where his co-driver, the 47 year old Jean Chassagne, putting a jack under each arm, commented: “Maintenant, c’est a moi” ran the three miles, jacked up the car, changed  the wheel, jumped in and was back in the race.  Unfortunately, 3 hours had been lost.

Clement later retired with a cracked chassis frame which had disconnected the water hose and drained the radiator.  Metal fatigue had been the cause of the chassis breakdown.  Continual alternating shocks caused by unevenness meant that it was only a question of time before the other two cars went the same way.

The frame of No.4 , ‘Old Mother Gun’, which led the race, broke with only 15 miles of the race remaining.  The car slowed to 70 mph.  On the very last lap of the race the top water hose pulled out, Barnato timing it perfectly to cross the line just after 4pm winning the race just ahead of the 2nd placed Stutz.

Birkin finished in 5th place with the chassis only just holding out as it cracked on the return journey from Le Mans to Dieppe.

The pinnacle of Bentley’s racing glory was at the 1929 Le Mans when a 6 ½ litre came lst, ‘Old Mother Gun’ 2nd and two other 4 ½ litres in 3rd & 4th places.

Bentley 4 1/2 litre Old Mother Gun

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