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KAMM CHOPS AND
Page 53
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PARSNIP
TAILS
They call it the Breadvan7--but that's about its only connection with the hard-headed -.:ornmercial transport world. Under that undulating sea of Italian-Racing-Red aluminium lurks-a rip-roaring five litre engine with fuel injection; dual ignition and two overhead camshafts to each of its twin banks of four cylinders.
'WoeII she do?' We ask the man, in; Lime-honoured curious-bystander, fashion.
'Double-ton . . er, something like 210 m.p.h. to you'. He jerked a grease-stained ihumb towards the bonnet.
`Theie's well over 400 horsepower under y'know'. We didn't know. But we :amid believe it. Even the exhaust outlets, our of them, looked as big as drain-pipes. But why the chopped-off tail ?'. . 'Alb now that's a bit more cornOicated...'
It was. Half an hour and three of our :-xpensive cigarettes Eater we kneW exactly xliy the Breadvan looked the way it did-= ike an everyday suburban delivery vehicle hat got sat on by Ten Ion Tessie the fairground tat-girl and then shunted from )ehind by art AEC Routemaster bus. 3riefly, that particular form of rear-end Jesign is commonly called a Kamm Chop tfter the German professor of aerodynamics, vho first discovered that it doesn't really natter what happens to the airflow round he back of a fast-moving body unless here's MOM to taper it right out like a )oiled parsnip. And since no racing-car lesigner can afford to waste that much veight, the obvious trick is just to slop lesigning,
Chop
'leen Monster
The Kamm theory doesn't just apply to ports-racing GT cars like the Breadvan. tecord-breakers such as American Art tsfons's Green Monster, currently the !lost sudden thing on wheels at well over 00 m.p.h., look startlingly unstreanffiried
it' your thinking stops at the old roundedsnout-and-pointed-tail philosophy. And oddly enough the same idea really does have some highly important down-to-earth applications in the commercial vehicle world.
You see, we didn't start talking about breadvans just for fun, British firms (AEC isn't among. them) which market light weight short-haul delivery vehicles using passenger-car components have known for a long time that the difference in top speed between the parent car and its commercial derivative is seldom anything like as great as you would think. Not long ago a recii breadvan averaged well over 40 m.p.h. for more than 400 miles across France, and nobody did a thing beforehand to its detuned family-car engine.
Maybe there's something in the Kamm idea for British designers of heavy trucks and coaches (AEC is foremost among dim) as well as for little people? AEC may not have as much use as some manufacturers for ultimate top, speed, but the designers at Southall certainlyseare when it conies to such things as economical stressfree cruising and motorway stability. '
Ifs AEC's 106 m.p.h. diesel!
And just in case you're scoffing at all this talk of heavy trucks and ultimate world records, we might as well point out that AEC itself once held a land speed title, The year was 1933. The driver: none other than Captain GeOrge Eyston. The car: a teardrop-shaped BK (Before Kamm) close-coupled saloon with Vanden Plas bodywork and a six-cylinder 135 b.h.p. AEC bus engine. And the record ? Well, it was for diesel-powered four-wheel selfpropelled vehicles and the then current holder was America's George Cummins. Eyston took his AEC LO the old Brooklands track and roared round in teeming rain at nearly 102 in.p,h. to snatch the record back for Britain. His fastest timed kilometre was a startling 106.647 m.p.h.—and he made the run blind, With a broken windscreen wiper Just for the present, though, Art Arfons and the Green Monster can sit .back and relax with their jet-powered title. AEC won't be setting up any challenges for it yet awhile. But you might do well to remember meanwhile that thcise Southall engineers haven't forgotten what they knew in 1933, in fact, !hanks to Professor Kamm and one or two Others, they've managed to learn a whole lot more about high-speed running in the 30-odd, years between.
Why not take a good, long look next time an AEC heavy diesel. roars past on the MI? Pork chops or Kamm chops --there's more there than Meets the eye.