Omaha Vette Graveyard wrote:
The amount of actual movement in the parts moving against each other, e.g. the cowl moving one way, the floor the other is less when the cowl and floor are nearer to one another. Sevens are very narrow and very short, compared to just about any car except maybe classic two-seat MG-like cars. This is not relevant for performance, but it would make a difference for the amount of cowl shake and other undesirable rattles and such.
Ah, ok. I understand now. Probably a moot point, since you can design the scuttle so that it's bonded and riveted directly to scuttle hoops welded to the main frame, in any case, so it's not so prone to shake. As mentioned above, the problem with mainstream production cars is that they have opening doors and large, heavy dashboard assemblies that are relatively loosely attached to the main monocoque.
Omaha Vette Graveyard wrote:
I do agree that a monocoque structure can be made 2x as stiff as a normal 'Seven', but so could the space frame. The monocoque would be lighter in that case, certainly, if it was constructed of aluminum or composite. However, the actual 'frame' of the chassis is what, 10% of the overall weight? How many actual pounds would one actually expect to lose by going to a monocoque?
The actual frame (paneled, which is how they are torsionally tested) can be closer to 15-17% of the overall weight.
To use the example of the FW400 as a benchmark (I daren't mention that designs offering even better stiffness:weight are possible, because someone will get upset
), the weight saving versus a fully paneled steel and aluminium spaceframe of
half the stiffness was around 100lbs. Double the stiffness of the spaceframe to match, and oh, I dunno... maybe you're looking at another 50lbs weight penalty; I'm not sure I've ever seen an uncaged Seven spaceframe that stiff, so it's difficult to benchmark?
The difference is basically similar to that of carrying a passenger, therefore, which has a pretty noticeable effect on both performance and handling on this sort of car.
Certainly, the additional expense of the FW400 was substantial (again, I won't mention that it's possible to do it in a
much cheaper way... possibly even cheaper than a spaceframe, when you factor in the man-hours for a skilled welder.
). Whether it's worth is it is a matter of personal judgement (and affluence). Can you ever truly say that an impractical 'toy' like a Seven offers value for money, so it's surely a matter of individual judgement where the line is drawn?