Firstly, there was the car. The glorious green giants thundering along England’s country lanes; Sir Henry ‘Tim” Birkin was one of the famed “Bentley Boys”, and campaigned a privateer Bentley Four and a half liter monoposto. Over fourteen feet long, and weighing nearly two tons, the car was huge. There is a reason why Bugatti’s reported description of the Bentleys of the day as being “the world’s fastest trucks” has stuck.
Birkin felt his car insufficiently quick in normally aspirated form, and he tried to persuade W.O. Bentley to add a supercharger. Bentley’s preferred route to a faster car was to race a bigger engine; he wouldn’t get behind a supercharging development, so Sir Tim went forward on his own, burning through his family inheritance in the process. Adding the ‘charger nearly doubled the available horsepower, and the car took track results, but ultimately proved too delicate for the war of attrition which which was road racing, where the bigger naturally aspirated cars held sway. Either faction could have claimed their point was made.
1928 4 1/2 Liter “BLOWER” BENTLEY MONOPOSTO
To fit into the cyclecart world, ‘le Camion’ would need to be be big, and lightly built. Stepping away from the frequently used “steel ladder frame”, this car is really a boat.
She has no ‘chassis’ as such – the stressed skin of the car was built in lightweight plywood with the “stitch and glue” technique over minimal bulkheads. All the cross-frame bulkheads form significant parts of the finished cart – the front mounts the cowl, the dummy ‘charger, the steering shaft bearing and the latch for the bonnet. The zig-zag behind the driver carries the seatback, the drive-chain adjuster mechanism, functional and aesthetic aspects of the rear cowl mountings and lends triangulating rigidity to the front end of the horizontal engine bearing shelf.
Almost no metal is used – the car could readily be built without any welding. Those hefty looking frame girders down the outside are lightly constructed plywood torsion boxes.
Curved sections such as the front cowl and headrest streamlining are empty plywood boxes clad with just enough household insulation to allow the required shape to be sanded in place and covered with glass cloth and epoxy resin.
A very conventional go-kart style steering system is used, with off-the shelf parts. Here, as throughout the car, low speed bearings are simple bushings made in plastic from old kitchen chopping boards.
Similar material forms a set of slides on the horizontal plate behind the driver, and these are matched to the underside of a stoutly laminated plywood engine mounting board. This board has the engine and transmission firmly bolted to it. Drive chain tension and alignment can be done in seconds with a single pair of wrenches.
The same modular engine mount system made it simple to build a drop-in electric drive conversion unit for comparison testing.
Throughout the build great joy has been taken when thrift store finds could be incorporated; the red leather ‘tuck and roll’ upholstery used to be women’s pants, the steering wheel is a re-purposed pan lid, brake and accelerator pedals used to be kitchen spatulas, and so on. Louvres in the panels are faked up from Popsicle sticks and tongue depressors.
Before and during the build, perhaps more mental energy was expended worrying about suitable sources for leaf springs than on anything else (only the front has any suspension) and in the end it was decided to try single leaves from the lightest locally available trailer springs. These have given perfectly adequate service through a number of campaigns over a range of terrain.
Le Camion remains a ‘middle of the pack’ performer, even geared for acceleration over top speed. Occasional class wins are generally achieved by waiting for the leaders to self-destruct. None of this should be thought to detract from the fun to be had employing a flamboyant cornering style, breaking rear end traction with a quick dab of the pedals, before swinging the tail out in a wide drift and waiting for that long hood to point down the next straight.
LE CAMION BUILD
Chassis No. 1304
Front track: 39″
Overall length: 120″
Weight: 250 lbs
Ground Clearance: 7″
Rear track: 34″
Body width: 24.5″
Height at scuttle: 31″
Radiator width: 19″
Engine: Rato 212 (similar to Predator) – Stage 1 modifications
Transmission: Comet TAV-2, #40 chain, 7.2:1 ratio, one wheel or two wheel drive (option)
Brake: Foot pedal operated 6″ mechanical disk
Wheels: 17″ x 140 Honda CT110
Tires: 2.75 trials type front and rear
Front suspension: Single leaf semi-elliptical slipper, side ground from utility trailer springs
Rear suspension: none
Frame: Softwood longerons with plywood facing and steel plate hardpoints
Bodywork: 1/4″ Meranti marine plywood tub with mixed bulkhead and panel work in wood and ply ranging from doorskin bodywork, to 1/2″ firewall bulkhead behind driver; curved panel edges in glass cloth over insulation foam board
LE CAMION GALLERY
BENTLEY BOYS AT TIETON
by Reginald Molehusband