412 virtues

[Kevin H]

Originally Posted by lansdownplace

Hi Kevin, I started with my own experience on the relative difference, but as 'why' was asked I thought I should go off and check for myself.

I have now managed to lay my hands on some facts and figures on this
handling issue, which do explain my thesis.

The 412 S1 has 32% more torsional rigidity than the 411 although the beam rigidity is the same, The 412 S2 has the bars at the top of the windows connecting the A and B pillars and other chassis modifications so the torsional rigidity rises to 45% more than the 411 with 25% stiffening in beam rigidity.

Paul, it's always interesting to get more information about our cars, but I'm sure you won't be surprised if I ask where these facts and figures come from?

It's worth pointing out that differences expressed only in percentages are all relational, and the 411 was reckoned to handle very well indeed, and not just by Setright.

There is probably an optimal point for chassis rigidity, and increasing it past that point doesn't necessarily translate into better handling because it also depends upon the suspension (spring rates, damping), roll axis. C of G, wheels and tyres, tyre pressure, anti roll bar, weight distribution and probably one or two other things we haven't thought of!

The other data to hand now is that the center of gravity is 8 mm lower in the 412 than the 411, which I thought sounded small, but the effect is magnified because the center of gravity on a 411 is 80mm above the roll axis, whereas it is 72mm on the 412 ( and lower again on the Beaufighter).That represents a 10% improvement in the roll couple ratio which does make a difference to the balance of the car. In a perfect world the center of gravity would sit on the roll axis, but there you are.

Surely it depends where the roll axis is? This would also induce jacking effect would it not?

I would be keen to know just how the C of G has been lowered, and if the weight distribution differs between the cars.

Some other interesting technical stuff I picked up is that the
Blenheim is three times stiffer than the 411 and the Blenheim had the
highest torsional rigidity of any passenger car up until '98. It is
stiffer than the McLaren F1.

This is quite amazing, if it's true. And if it is true, it clearly demonstrates that chassis stiffness or torsional rigidity does not dictate handling (because a Blenheim does not handle as well as a McLaren F1).

There is another point to consider here. Any figures that come out of BCL refer to original specification cars as they left the factory. There aren't many like that any more, especially when we are talking about 412 or earlier.

For example the 412 S2 had wider, lower profile tyres than the 411, but I now have the same wheels and tyres on my 411, as do many other 411 owners. This in itself lowers the 411 slightly, lowers the roll centres, roll axis and C of G, although it doesn't reduce the roll couple value. But it does makes a very noticeable improvement to how the car handles over the standard steel wheels and tyres. Stick an uprated anti roll bar on it and it improves it further.

Having completely dismantled the front end on my 411 it became clear that what appeared to be a reasonably good and standard condition suspension, was nothing of the sort. And I suspect this is the case with many of the cars that haven't been restored, in which case this all becomes theoretical!

[TLF799R]

I give up!

Has anyone else ever noticed how Kevin only ever likes facts and figures that support his theories!!!

Philippa

[lansdownplace]

Kevin, I have presented the facts,to back my argument, I disagree
with many of your points, but politeness has prevented me from
pointing out some inconsistencies in your argument. For example you
simultaneously argue that lowering the center of gravity by moving
mass downwards in the car and lightening it have no effect whatever,
whilst acknowledging in the next breath that putting weight on the
roof(in a roof box) or by adding passengers will obviously affect
handling. You can't have both sides of the argument.

I scoured all the available sources for this data and when I
couldn't find the information I wanted I rang the factory and asked
then very nicely. Rather than answer my question I was invited out
to examine the information myself, which I did yesterday, I live
five miles away. I suppose it is one of the benefits of buying/
rebuilding and maintaining your car with BCL and being politely if
enthusiastically interested in what they do out there. Also having
the same people (individuals that is) work on the car as built it
the first time around helps. The figures I quoted are figures I have
seen personally from original documentation before anyone asks.

Phillipa mentioned Jeff saying that his view is that the 412 was the
best handling of their cars, and he has said the same to me. However
unlike Philippa or I, Jeff isn't a die hard 412 fan, he loves the 411s
which is what he was building when he started with the company.

Yes they do refer to original spec, but fortunately for me, my own 412
which was pretty unmolested, was recently rebuilt from the ground up
by the factory to the original spec so apart from 7 inch Blenheim
Alloys, my car rides as built. I drove lot of V8s before buying my
first Bristol, the most memorably awful was a 410 that someone in the
car business had rebuilt themselves, he was proudly telling me how he
had used bushes from a ford and done the front suspension himself as I
plowed straight on at a roundabout at about 10 miles and hour with the
most astonishing understeer ever. I didn't conclude that 410s were
bad, merely that you have to be very careful where you get them from.
You can get a good version or a bad version of any car, the best bet
is to get one from BCL that they have rebuilt or converted to a Series
6, or better still a brand new car. I can't imagine any aftermarket
version of the cars being better, or at least I haven't seen one. You
get what you pay for in life I guess.

I choose a 412 over a 411 although the latter has been reckoned to be
more of a safe bet financially in the past because I like the styling
more, it handles better (IMHO) and I can drive with the wind in (what
very little is left) of my hair. It is personal choice and enjoying
the car is all that matters. If it was just a financial decision I
would have bought a smart car.

One final point, I haven't checked the McLaren F1 figures yet. but it
has completely different suspension set up, for racing and not
cruising so they are not apples and apples. I am at McLaren in a
couple of weeks so I will ask them for the figures. Also lack of
torsional stiffness is one of the major problems in handling that no
amount of suspension tweaking will overcome. A good example is the
Aston Martin DB7 coupe got rave reviews for handling, whilst the rag
top with exactly the same suspension gets panned. It has to be set
soft because the torsional rigidity so so impaired it won't ride
properly.

Anyway, If the facts are with you, you can argue the facts, if
principle is with you, you can argue the principle, or you can just
argue.

I am off to the races.

Regards

Paul

[UK6]

Hello Paul, Kevin and other Technophiles,
A relatively easy way to compare one car's cornering ability with respect to another's is to compare their respective maximum lateral accelerations around a fixed radius bend.

Acceleration values can be obtained by attaching a relatively inexpensive accelerometer to the cockpit of each car in turn and drive each test car in turn at max speed (point of breaking traction) around a, say, 100m diameter "track" defined by witches hats on a safe, deserted car park or airfield. The higher lateral 'g'reading gives an indication of superior road holding.

One could swap wheel/tyres from one test vehicle to the other (if they fit!) to determine the effect of tyre selection.

"G Tech" offer a 3 axis accelerometer for ~ $110 US at...
http://www.gtechprostore.com/cgi-bin...on&key=0400452

As a point of comparison, a 1998 Lexus SC 400 attains ~ 0.8g on a 300ft skid pan.

The more advanced accelerometers can also give one a fair estimate of linear acceleration and horsepower output values - useful for other arguements!!

Regards,

Brett

[Ashley James]

I think you'll find that iPhone offer an application that can do the
same thing. However in Britain the traffic moves so slowly that it
wouldn't test the cornering potential of a 1903 De Dion!
Ash

[TBC]

I have to say that the usual expectation of a car manufacturer is that the new product should build upon the qualities of its predecessor. As such I fail to see why the 412 wouldn't handle better than the 411.

Comparing the 412 with a new Blenheim, would, i feel, be an unfair comparison based on two factors: more than 30 years divides the two so such items as suspension units, shock absorbers, etc have improved immeasurably in that time (if we are comparing original specification). The set up on the Blenheim is considerably different to the 412 and not just in the technology used but also areas such as the track where this has been eased out over the last few years on Blenheims. These two alone would be enough to make a marked difference to the way a car handles.

As both have adjustable suspension it should be possible to adjust to suit virtually any owner. But then that was always the Bristol way.

Keith

[lansdownplace]

Good point Keith, My 412 is a product of 70s engineering, pre-
computers (lets ignore lean burn, I have). That they can compete
with modern cars at all is something of a miracle in it's self.


The Bleheim 3 is a very different to the 1 & 2 they made a lot of
changes after Toby Silverton came on board. When I was making my
mind up on what car to go for I had started out with the idea of
upgrading to a secondhand Blenheim. I drove a 1, a 2S and a 3 back
to back. It was hard to believe that the same company had built the
the 1 and the 3, the difference in quality, performance and
refinement was that great. As an aside the 2S was a special car
built to a very high spec and heavily personalised which I really
really liked. Indeed comparing the panel quality and very tight
shut lines on the new B4 it seems they have stepped up further. On
reflection at the time I wanted the quality of the 3 but applied to
an older car hence my choice. The S is a great engine. Mind you the
Brigand/Beaufighter Turbo is awesome fun. I like the smell you get
with the carburetor engines, especially when mixed with the whiff of
leather which I would miss with a fuel injected car.

On the adjustability point, I have been looking into this as I am
building a specification for my' wish list' car so that I have
something to aim for. Aside from having a Bleheim you can pick any
V8 model and then start specifying. There are so many tunable
options on the cars it beggars belief. Beyond the shocks, you can
have different spring rates and sizes, the ride height is
adjustable, you can have a 5.9 engine in three basic states of tune,
a 6.3, a 6.7, a 7.7 engine are also available with choices of
manifolds , heads, camshaft profile, exhausts in standard or sports
(I believe someone has a straight through exhaust) or anything else
you want, I asked about the 6.1 Hemi but apparently it's low end
performance is not considered good enough to add to the line up and
the bigger engines throw out more power and torque. For those who
really know their onions the engines can be custom mapped for you.
You can even specify the foam in the seats, or have different
density foam on different panels on the seat to fit your frame.
there isn't an option list, dream it and you can have it (for a
price of course). And if you don't like t it can all be readjusted
anytime you like. Once you have done that you can start on colours,
finishes and trim. You could always go the whole hog and have a
completely one off car built like the Bleinheim 4, or perhaps as we
were discussing before this part of the thread morphed, commission
your own designer to run up design.

The bottom line is there is so much choice that you really do end up
with a one off car, which makes comparison difficult however as you
point out the trend is always improvement. It is the uniqueness of
every car that appeals to me. There really are no two alike.

At a more mundane level, I think tyres make a big big difference to
handling and ride, as do tyre pressures. Also I have to say I was
both amused and astonished that Bristol still test every shock
absorber individually on the same machine they have been using for
60 years. It is powered by a small car engine with a gearbox! it
produces a small card with graph drawn on it that shows the
performance of the part. They reject many more than they accept and
they pair them to get the best match. I knew they used to do this in
the early years but I really didn't think they would still have to
do it, or bother. It is an amazing level of attention to engineering
detail. If I hadn't seen it I wouldn't have believed it.

Paul

[Kevin H]

Originally Posted by TBC

I have to say that the usual expectation of a car manufacturer is that the new product should build upon the qualities of its predecessor. As such I fail to see why the 412 wouldn't handle better than the 411.

The point is Keith, beneath the skin the 412 is NOT different to the later 411's. The 411 S5 is not a predecessor to the 412. They were made at the same time and have the same, engine, transmission, suspension, wheels, tyres, diff and chassis, save for perhaps a couple of plates or box sections welded onto the chassis (to make up for the missing roof).

Only with the 412 S2 did things start to change.

I have yet to hear any rational argument as to why the 412 would handle better than the contemporary series 5 of the 411.

I concede that the 412 S2 may handle better than a *standard* 411 S5. Setright would only say "it is said to handle better", even though he himself had tested the 412 S2 for an article in an American car magazine.

I can see why the Beaufighter should handle better than a 411, because it is quite different to the original 412 (different engine, transmission, wheels, tyres and considerable chassis reinforcement). No doubt that's why Bristol gave it different name, because it was a different car.