Wind tunnel Jaguar

[eglf]

When I was serving my apprenticeship at the Royal Aircraft Establishment (RAE) Farnborough in the early eighties I remember seeing a photo of a Jaguar taken in the 24ft wind tunnel in the 1950's. I finally got hold of a copy of this photo and wondered if anyone had any information about it. Could it be the prototype Jaguar D-type XKC401.

[Mike-tf3n0]

Looks to me like an early 'short nose with no fin' Jaguar D type. The fin was added almost immediately as the car displayed a tendency to wander in a straight line, the early fins were fabricated but screwed on so were thus called 'tack on fins'. Later cars had the full width Appendix J windscreen rather than the single screen and later still the long nose and tail with a fully faired and non detachable fin. The side exhaust was only fitted to short nose cars.

[lowdrag]

To add to Mike's post that is a "client" car, since the short nose cars with the fin were either factory or Ecurie Ecosse Le Mans cars. For the first time ever there were practice days for Le Mans, and Jaguar found the cars wandered at speed. so, Malcolm Sayer having an aero background, what would seem more appropriate than a fin? As said, the short nose cars had the fin riveted on, but the 1955 and 1956 long nose cars had the fin incorporated in the design. Jaguar were the first to really use wind tunnels, and of course that came from Malcolm Sayer's aircraft background, so your photo could well be a model of the prototype Jaguar or even be a design template that predated any of the real cars. Thanks for posting that. Very interesting.

[eglf]

Thanks for the comments, I would add that if the car was a model it was a full size model, knowing the scale of the building as I do.
Also the 24ft wind tunnel is still there and is looked after by the Farnborough air science trust.

[Peter3442]

I'd guess that it's the photo is from early 1954. Sayer would have been wind tunnel testing the shape well before Le Mans, most likely before any cars were produced. Once a design is relatively final, you can't change much, so you need to do most of the wind tunnel work as soon as you have what you hope is the final design. Later on you are limited to smaller modifications, the sort that Sayer actually made, add a fin, stretch the nose.

[Mike-tf3n0]

It's interesting to note that despite all Malcolm Sayer's undoubted skills as an aerodynamacist the car still developed enough lift at the rear for Duncan Hamilton to comment that on the Mulsanne Straight at a calculated 179 mph he was getting wheelspin in the wet!

[Allan L]

I think you'll find that in those days the vehicle aerodynamics work concentrated on drag and high speed stability, the latter with and without cross-wind. Lift was largely ignored and the early work (later than the D-type) concentrated on its reduction by spoiling the airflow under the cars.
The Mercedes-Benz 300SLR's airbrake was found to have an unexpected stabilising effect as it destroyed the lift of the rear bodywork.

[Peter3442]

Mike, For car like the D-type, without any deliberate features aimed at developing down force, down force (or lift) is a bit unpredictable and very sensitive to differences in ride height between the back and front suspension (trim). There wasn't much experience of cars with a top speed as high as the that of the D-type. Sayer had achieved a lot by getting the car into a regime where Hamilton could have a wheelspin problem. It's too easy for modern arodymicists and racing car designers to criticise Sayers' Jaguars and say they weren't so special, but comparisons of the D-type with contempory Ferrari and Mercedes shows that not the case. Moreover, he did it all without CFD, modern wind tunnels and the results of half a century of other people's work.

[Mike-tf3n0]

Absolutely understood Peter, I commented not in a critical way but more in a spirit of awe that Hamilton kept his foot down in the wet at that speed and still had time to deal with wheelspin! More than half a century ago I was a competitor and later had the good fortune to cover thousands of miles in D Types so I have a fair idea of what he was dealing with, he must have had very big balls!!

[lowdrag]

No one's mentioned the 1952 C-type, also designed by Sayer on the airplane wing plane principle:-



It achieved the desired result, completely, At 120 mph the rear lifted almost off the ground.

[Mike-tf3n0]

Ah yes, and cooked it's engine through lack of airflow through the radiator opening!

[Peter3442]

Mike, That bit wasn't as much in response to you as some of the opinions from modern writers, engineers and drivers who forget when Sayer was working and the tools he had available (and the fact that -for some of the modern drivers- you don't just get in the car assume that it's perfectly set up for exceeding 150m/h).

In the case of the C-type, he wasn't really working with a clean sheet of paper as he was initially constrained to maintain a resemblance to the XK120. For the 'improved' version, it was a case of rapid, patchwork modifications to an existing design. They almost always turn out a disaster. Personally, if I had to give blame it would be more to Moss for over estimating the speed of the competition and Bill Heynes for listening to him and then under estimating the experience required to design a cooling system. Wasn't the young man who modified the cooling system named Kettle?

[a8hex]

Peter3442 said:

In the case of the C-type, he wasn't really working with a clean sheet of paper as he was initially constrained to maintain a resemblance to the XK120. For the 'improved' version, it was a case of rapid, patchwork modifications to an existing design. They almost always turn out a disaster. Personally, if I had to give blame it would be more to Moss for over estimating the speed of the competition and Bill Heynes for listening to him and then under estimating the experience required to design a cooling system. Wasn't the young man who modified the cooling system named Kettle?

yes, he was named Kettle Lowdrag had a fascinating thread here years back as he had a 52 C Type recreated.
See https://www.pistonheads.com/gassing/topic.asp?h=0&... for the first part


As you say, they got scared by the supposed speed of the Mercs, the expected speed of the 52 C types before the modifications were more than capable of having won in 52.

[tapkaJohnD]

eglf said:

Thanks for the comments, I would add that if the car was a model it was a full size model, knowing the scale of the building as I do.
Also the 24ft wind tunnel is still there and is looked after by the Farnborough air science trust.

Full size? There's nothing in the photo to give scale, unless the "24ft" refers to the fan diameter, inwhihc case that can't be full size model, can it?

John

[airsafari87]

eglf said:

Thanks for the comments, I would add that if the car was a model it was a full size model, knowing the scale of the building as I do.
Also the 24ft wind tunnel is still there and is looked after by the Farnborough air science trust.

I've never managed to get to Farnborough to see that wind tunnel.

I've installed a few flow straighteners in to new wind tunnels as well as historic (70's) tunnels and it would be fascinating to see theirs up close.

[eglf]

airsafari87 said:

eglf said:

Thanks for the comments, I would add that if the car was a model it was a full size model, knowing the scale of the building as I do.
Also the 24ft wind tunnel is still there and is looked after by the Farnborough air science trust.

I've never managed to get to Farnborough to see that wind tunnel.

I've installed a few flow straighteners in to new wind tunnels as well as historic (70's) tunnels and it would be fascinating to see theirs up close.

Believe me if you have ever been in the building you would know that's full size.
There are photos of actual aircraft being tested and yes the fan diameter is 24ft.

[airsafari87]

eglf said:

Believe me if you have ever been in the building you would know that's full size.
There are photos of actual aircraft being tested and yes the fan diameter is 24ft.

I can well believe it.

Back in 2015 I removed the original flow straightner (Honeycomb panels and 4 woven wire screens) and designed and installed the new honeycomb and screens in to the tunnel and that particular tunnel had a fan diameter of around 40'-0" if i remember correctly? Its an incredible thing to walk through.

[tapkaJohnD]

airsafari87 said:

I can well believe it.

Back in 2015 I removed the original flow straightner (Honeycomb panels and 4 woven wire screens) and designed and installed the new honeycomb and screens in to the tunnel and that particular tunnel had a fan diameter of around 40'-0" if i remember correctly? Its an incredible thing to walk through.

Hang on! 40 feet? 24 feet? what is it?

[Peter3442]

A wind tunnel is usually decribed by the size of its working section; that's the place where you put the model and measure something. The diameter of the fan that sucks the air through the tunnel isn't the same as the width of the working section. Very often it's bigger. In addition, the working section is often square and connects to the fan via a diffuser.

[Allan L]

Wind tunnels are usually referred to by the size of the working section rather than size of the fan/fans.
Not sure about the one pictured in this thread which seems to have an open working section.