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United Kingdom
275 Posts |
 Posted - 24/10/2011 : 23:13:50
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Hi all,
I too have just received the most recent Bulletin, and wish to add my thanks to every body involved in its production and distribution.
However, since there are pictures of two P type Airline coupes in this copy I wondered how the closed body affected the performance. I would think that the top speed might be improved over the standard car if compared with a two seater with its screen up. (Even if the overall shape is not particularly aerodynamic the roof and windows at least ought to prevent the terrific vortex that forms behind the windscreen on an open car.) The body would probably weigh a bit more than an open car so that acceleration might be slower, but these are both guesses.
I have never found any independent performance figures for this body, and indeed the only one for a standard PB was affected by the test conditions, so have any of the braver ones of my readers ever tried their Airlines against a stopwatch? Lew?
As a starter my PB was timed in the Seventies by the RAC at the Brighton Speed Trials (which at that time were run over a standing half mile) at 76 mph over the line. This was on carburettors with just one aeroscreen up and a full tonneau cover over most of the passenger space but including its full swept wing set. At the line I believe that we were still accelerating (slowly) against the rapidly rising drag forces. Currently, with the screen up I believe it will still get to the far side of 70 mph, but exactly how far beyond I am not sure.
So my question is does any one have any comparative figures for an Airline and a standard body for PA vs PA, PB vs PB or even N types?
Thanks for any interesting information,
More rambling from,
Andrew Smith - MMM571 |
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LewPalmer
USA
3243 Posts |
Posted - 24/10/2011 : 23:57:35
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Andrew,
I certainly can't comment. My Airline has less than 50 miles since a complete 10 year restoration. I think the fastest I've had it up to is maybe 40 MPH. However, I like the PB gearbox and the slightly larger 939CC engine. It has no apparent problem pulling away from a stop sign smartly, but clearly the hundred or so extra pounds of weight doesn't help anything - especially with two overgrown adults on board.
Lew Palmer
Registrar, NAMMMR |
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David Allison
United Kingdom
665 Posts |
Posted - 25/10/2011 : 09:23:21
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Andrew
I was lucky enough to be involved in building an engine for Gert Jensens Airline coupe when working for Dad.
The car was so pretty and it was a pity that its performance was so bad.
Dad decided that we should keep the car as original as possible but exploit the fact that the engine was already past its best.
We fitted a steel crank and rods - lightened the flywheel and fitted 60 mm pistons (the block was already at 58 mm and bored to 60 with ease).
We breathed lightly on the head and inlet manifold but on the outside the car looked pretty much un-changed.
The car ran much better and Gert used the car a great deal expressing always his suprise at the extra performance we had discovered from the car.
Lew's PB is therefore in pretty much the same state of tune as Gert's lightly modified PA version and will have tolerable performance for a car of it age weight and engine size.
However as a comparison to a standard PB - forget it!
The cars body shape is no help in cleaving the air - as its frontal area is around the same as the standard car - plus it weighs around 200 lbs extra.
A standard PB should be able to manage around 80 mph terminal speed if you can find a long enough stretch of straight road - fold the screen flat and you may achieve a little better but not much.
You could remove the front wings and perhaps manage 85 + but you are starting to push the engine a bit I think because of weight and power.
The Lester lightweights were probably good for about 85 and Don Moores car manged around 90 ish I think but these were ultra low, light and had no screen so had little of the windage.
We are talking of huge outlays for little improvement though - which is why MG went to blowers of course.
A good blown PB will manage around 90 mph with little trouble - but the driver needs to be brave.
The late Mike Hibberd had a very quick blown PB which could keep up with our NA easily and when I drove the car I was convinced it was actually quicker up to 50 mph - but you did need to be brave with it beyond 80 as you do in any MMM car.
Regards David |
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