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MG Midget and Sprite Technical - MG midget hardtop + aerodynamics question !

Hi i was just wondering if anyone knows the aerodynamic values of the midgets ? so far i have got coefficient of drag @ 0.49, however i cant confirm this is correct , or for which year ? Not sure on the frontal are either ?

Now the hardtop questions,
Basically i was wondering what is the most aerodynamic hardtop i can get for my mkii ?
are there any decent bonnets or bodykits that would help ??
any wind tunnel data or figures?
any help would be so appreciated!
regards
Fred
f rawlings

typo on first paragraph above sorry ^ frontal area .
ta
f rawlings

Undoubtedly the most aerodynamic bonnet ever fitted to Spridgets was the early Speedwell Monza bonnet, at the top on this page:

http://www.sebringsprite.com/price_list.htm

Designed by aerodynamicist Frank Costin, it had the smallest practicable air intake for the least drag. The Sprinzel Sebring bonnet is also better than a standard square Spridget for this reason.

As for hardtops - I don't think the choice for the Mk II Midget tends to that great, because of its unique rear deck fitting. The shape of the works hardtop must be reasonably efficient, as it has been used by so many racers over the years, though it could be lower and therefore present less frontal area.

The Ashley fastback hardtop is always popular - and fetching sizable prices on eBay at the moment, though it must produce a fair amount of lift at the back.

If Williams & Pritchard's did make its GT hardtop for the Mk II Midget, then that would be a prime candidate, the slight ducktail spoiler killing the lift at the expense of a little exctra drag:

http://www.williamsandpritchardregister.co.uk/

I know the Speedwell GT coupe top was highly efficient aerodynaically, and the Sprinzel Sebring copue tested very well in the MIRA windtunnel.

'Road & Track' gives a frontal area for the Mk II Sprite of 14.8 sq ft and a 'total drag at 60 mph: 80lb', though the 1098 notches up 14.3 sq ft for frontal area and 75lb total drag at 60 mph without any bodywork changes - but perhaps the 948 was 'hood up' and the 1098 tested with tonneau in place.

Tom
Tom Coulthard

Last weekend at RAF Marham my (satellite registered)top speed at the end of the 1 mile straight was 95mph with the hood up and early plastic type sidescreens.
This is 8mph faster than the same straight taken with the roof down and no sidescreens.
Not definitive but all the same it's quite a gain.
G Lazarus

In a Frogeye.
G Lazarus

I have always felt that a Spridget with either a soft top or hard top in place is faster that with NO top, however the thrill of being 'topless' is greater. Like Tom, I would suspect the Ashley or W&P top with their 'Fastback' styling would be the best options.

Fred, are you aware that there is a thriving Midget and Sprite community in Yorkshire?

Mark.
Mark Boldry

Gentlemen, I believe it is a truth universally acknowledged that a single sportscar not in possession of a hard or soft top will be in want of one in order to go faster.

What the position is with tonneaus I don't kneau (even I am not pernickety enough to write 'tonneaux', though 'criterias' makes my teeth grind). I suspect a tonneau can make a considerable difference - especially of course the infamous 'metal tonneaus' of 50s sports-racing cars.

However, my point was to give Fred a figure for frontal area as he asked for one. I only included the figures for 'total drag' out of interest and have no idea how they were arrived at. I agree you might expect them to be the other way round, if the 948 was 'hood up': very slightly greater frontal area, but less drag.

One of the bigger bugaboos (? bugabooes) with the Spridget is how upright the screen is - hence the modern propensity of racers to do without them - without pride in history or prejudice against getting wet!

Tom
Tom Coulthard

Interesting point about the tonneau Tom

Last year at Marham I had the tonneau on when running solo and got around 103/4 mph (speeds were different with passengers of course)
This year I had the hood up instead and recorded around 108 so although the tonneau was better than open the hood itself was significantly better for slipperynessness.

I had the tonneau off after I started doing ferry round rides, naturally.

But total fun both ways, both years

(speeds were bike computer provided, rather than the Smiths measurement devices)
Bill

Tom, without pride in history? Au contraire, very much pride in history, see pic !


David Smith(davidDOTsmithATstonesDOTcom

No, OK, I admit I was just trying to work 'Pride and Prejudice' in to make the "truth universally acknowledged" joke. Apologies and present company excepted etc.

I've got a pic of a frogeye racing at Goodwood in 59 with just an oblong of Perspex jammed between the rear of the bonnet and the scuttle.

But I do find screenless square Spridgets racing with wheelarch extensions or flares and the 'flying bedstead' look of a modern cage pretty unlovely - even though I know that if I were risking my neck on the circuits, a full cage is exactly what I'd want.

Those guys who race Lola T70s and the like without roll bars or even seat belts (as I have seen at a Coys meeting) because their cars are too historic to have them fitted are plain crazy.

But that wonderful pic is a reminder that there is another really aerodynamic Spridget bonnet shape, designed by Syd Enever with wind tunnel assistance (?MIRA), if only someone would reproduce it. Just don't anyone replicate the 'half-inch gas pipe' roll bar!

Tom

Tom Coulthard

Looks like a "Jacobs-midget" frontend to me.
Never knew there were more then 3(jacob midgets?) frontends like that produced.
After the Monza-frontend i think this is the most beautifull one.
Some body call Brian Archer to get these molds sorted! :)
Arie de Best

Tom, David & I have more than a pasing interest in this given the Championship we both race in is having a bust-up about this very subject!

We both run full cages without screens and whilst I "take your comments onboard", having hung upside down by my belts supported by a full roll cage I'd go no other way. As you correctly surmised.

The pic David posted is one that Roger E himself sent me while I was researching this subject at the start of last season. It just goes to show that racing in the 60s was aesthetically pleasing but bl**dy dangerous. It was the best of times, it was the worst of times.
Max T

I don't think anyone mentioned fuel consumption or did I miss it?

When I was just married with one child, how many years ago was that? I worked all over the UK trying to earn enough to buy a house. Anyway the point is that to get enough money for the deposit for our first home I could not afford to have the hood down on my MGB, the fuel consumption was too high. I had to use it mostly with the hood up until finances improved a little that allowed me to be able to buy the extra fuel necessary when running with the hood down!!!
Bob (robert) Midget Turbo

Fuel consumption is the reverse of speed if you like.

Improved aerodynamics either increases maximum speed or if driven at less than maximum speedimproves fuel consumption.

A journey of about 55 miles involving mostly motorway cruising at 85-95mph, even in 5th is a lot thirstier hood down than hood up. In fact it's fairly obvious that will be the case because you have your foot down that much harder doing those speeds with the roof down (or so I'm told .....).

Ten people, £100 each, a couple of cars and it's half a day in the MIRA wind tunnell. If I can afford it I'll do it myself one day.
Daniel Thirteen-Twelve

Fred, the Williams & Pritchard Sebring GT hardtop fits perfectly on a Mk II Midget and at 4,500 rpm in 4th appears to give around an extra 5 mph (well, on our speedo, appreciate this is not going to be hugely accurate before anyone jumps on me!) - so the aerodynamics must be having some positive and noticeable effect - with plenty of grip which enhances cornering at speed.

It's just finding one that's the problem, as they are very very rare.

Here it is fitted to our Mk II Midget:

http://www.williamsandpritchardregister.co.uk/EOW651D.htm
Mothy

You are always going to have better areo with the top up or hard top on.....

there is a rolling ball of air right behind the seat backs may be 15-24 inches back, that creates alot of drag....I found this out some time back with a ream of paper by mistake....you might be able to see this if you take a large cooking pan and build a smoky fire in it and drive down the road with a buddy holding the pan in that area....I have always meant to try it, but my friends are to smart to talk them into it...so not sure if it will work...but Im asumming it will being that the 500 sheet ream of paper did.

thats with the top down....not sure what happens with the top up.

prop
Prop

For my sins I work in a wind tunnel, not while its running(40 meters per second!). I have been tempted but never tried the idea of sticking wool tufts on the car. Someone should tape 50mm lengths of wool all over the car with the roof up and down and then get someone to video it from another car at maybe 60 mph. Put it on you tube and we could all look at it and try and work out what is going on with the aerodynamics.

Its just an idea! Carl
C Bintcliffe

http://www.spritespot.com/gallery/view_photo.php?set_albumName=toomanyspridgets&id=a863_3

Very quick and the wind didn't ruffle the hair more than a standard screen. Bit of a bugger at traffic lights in the rain, hence the lack of carpets plus the GRP seats!
rob multi-sheds thomas

This thread was discussed between 16/04/2008 and 21/04/2008

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