On Sat, 19 Sep 1998 14:10:48 -0700 Simon Matthews
<simon_matthews@avanticorp.com> writes:
>Rick,
>
>yes, but at the time the F1 and Indy cars were front-engine, RWD, were
>not
>most cars? So the engineering problems with FWD had not been worked
>out
Don't tell Alec Igginisis(SP?) the engineering problems hadn't been
worked out. He'll spin in his grave.
.
>Before the cars went FWD, a better solution came along: mid-engine,
>RWD.
Then why for heavens sake does NASCAR convert FWD sedans to RWD before
racing them?
>ALso, I suspect that those early F1 and Indy cars had a much better
>weight
>distribution than the average saloon or sports cars, so they would not
>heve
>benefitted as much from FWD.
>
>When we talk about the average saloon (sorry: sedan) or sports car, I
>really doubt that the weight distribution is 50/50 - look at MGAs and
>Bs --
>the engine is basically between the fron wheels -- there is nothing
>with
>equivalent weight at the back of the car. But I have not looked up the
>figures for this, so perhaps I am wrong.
>From page 58 of the MGB owners manual (BL publication part number AKD
7881)
"Kerbside weight (full fuel tank, all optional extras and accessories)
Total weight Tourer GT
2303Lb 2401lb
Front weight 1127 lb 1162lb
Rear weight 1176 lb 1239lb"
This works out to a front/rear distribution percentage of:
Tourer 48.9 / 51.1
GT 48.4 / 51.6
This makes the MG B and GT "better" because there is more weight on the
rear wheels.??! And if more weight is better, then the GT is better than
the Tourer.
(BOY THAT SHOULD GET SOME FLAMES STARTED :>) )
>I won't dispute that mid engine cars have a lower rotational moment of
>inertia. As to which was the reason and which was a side-effect of
>going for mid-engine design, this is a particularly pointless
discussion --
>both (weight on rear tyres and moment of interia) were advantages
gained,
>so both were important. I doubt the engineering team who designed the
>first mid-engine cars really worried about which was a side-effect.
One of the earliest and probably most succesful mid engined cars was the
Auto Union GP cars before WW II. It was generally considered a real beast
to drive and suffered from horrendous over steer to the point that later
versions sometime ran with "duallies" on the rear. (Obligatory
historical content
>> As for more weight on the rear wheels, not neccessarily so. If two
>>cars, one front engined, one mid engined, weigh the same, and have
>>identical weight distributions, then both have the same weight on
>the
>>rear wheels.
>
>True, but just how do you design 2 cars like this?
It's not too hard. When mid engined cars first made their debut in the
late 50's and early 60's, they were running with front engined cars, both
in F1 and later at Indy. The total weights of the two types were within,
literally, fractions of a pound because no one is going to build
(knowingly) a F1 or Indy car any heavier than the absolute minimum. The
weight distribution was nearly identical too, as the front engined cars
had the engine behind the front axle, and the driver/fuel tank almost
over the rear axle, where as the mid engined cars, with the engine in the
rear, moved the driver as far forward as possible (actually having his
feet and lower legs FORWARD of the front axle line.
The very obvious superiority of the mid engined design really was not so
much due to weight placement as to the lower silouette (due to the
reclining driver) reducing induced drag, and the significantly lower
polar moment of inertia, which made for a car that was easier to turn in,
and easier to unwind out of the corner.
The point is that
>mid engine ALLOWS the designer to put more weight on the back wheels.
It allows the designer to put more weight on the back wheels EASIER.
But more weight on the rear wheel is not a handling panacea. A car with
a large rear weight bias will have a great tendency to oversteer (see
Porsch 911) .
Rick Morrison
72 MGBGT
74 Midget
>Simon
>---
>Simon Matthews
>MailTo:simon_matthews@avanticorp.com
>'57 MGA
>
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