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On Sun, 21 Nov 2004 20:08:30 GMT, "Ed Huntress"
wrote:

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.. .
On Sun, 21 Nov 2004 05:54:15 GMT, "Ed Huntress"
wrote:

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.. .


I like the job my buddy does with the tig welder.
Another friend of mine has built a lot of race cars - and is
building
one now with an aluminum chassis (a "clone" of a Lotus 7 - not an
abomination like a Locost, but actually to accurate lotus 7
dimensions, modified to make out of aluminum angle, and running a V
twin bike engine.) It is ALL being rivetted, as he says with welded
6061T6, unless you can re-heat-treat it (which is NOT a
do-it-yourself
job) you have no idea WHAT you have after welding. So, he's building
it according to "aircraft standards" - all joints rivetted and
gussetted.

Does he have anything online about this? I'm curious about how he
modified
the 7 chassis so it could be made out of angle.

Ed Huntress

Nothing online, and it has not been proven yet - but this guy has
repaired, rebuilt, and reproduced more sevens over the years than
likely anyone else in Canada. He's got all the jigs.

The "angle seven" is being built by his son, actually, (with Dad's
help) for one of the "formula grassroots" type races - something like
Formula 2005? where you get to spend up to $2005 US to build a car and
then race it.
He expects to also drive it on the street.

The seven is built mostly of square steel tubing (mild steel at that)
- much of it 1" square.

The "Angle Seven" is made of 6061T6 or 6061T651 1 1/2 inch (I think)
angle and will have the driveshaft tube fully triagulated into the
front bulkhead.

He estimates the material cost for the chassis, with some carefull
scrounging, to be about $200 Canadian plus rivets. Mostly stainless
steel Pop rivets

It sounds interesting. If he puts any photos of it online, let us know.

Ed Huntress

He won't, but I might.

The idea of making a space frame with L-channel raises all sorts of
engineering questions, but the bottom line will be how well it actually
performs -- and what it winds up weighing.

As a matter of interest, the radius of gyration for L-channels sucks in a
major way, compared to tubes, which means that it's unlikely to resist
buckling nearly as well as a tube-based space frame. That's the major rub, I
would think. But there are more issues that this design raises as well.

However, a finished Lotus 7 is actually a hybrid chassis, with shear-panel
design combined with space frame. And the torsional weakness in a 7 (Mk. II
or Mk. III; I don't recall how the Mk. IV stresses out, but almost all
replicas are Mk. IIIs) is in the cockpit bay, anyway, which can generously
be called parallel girders with a shear-panel floor. That's true of many
open space-frame cars.

So a good, tightly riveted cockpit bay, made of L-channels, could make the
car stiffer than the original. I don't know. It would take a complete FEA
analysis, or a model analysis, to tell.

In any case, if the car is raced, they'll find out a lot about it from the
way it performs on the track. And I'd find it very interesting, as I'm sure
many other people who follow chassis design will find it interesting.

Also for the record, a true space frame is the design concept, among all
design concepts for car chassis, which benefits LEAST from use a low-density
material: aluminum over steel. There have been aluminum-tube space frames
(1960s Bobsy sports-racer; Porsche 917; a special made by the Locost folks),
but, in general, the slight weight savings have never been worth pursuing.
In theory, if not in practice, a steel space frame versus an aluminum one
should come out weighing exactly the same, for equal stiffness and strength.

But there are issues other than the pure, simplified engineering theory
involved, and aluminum may provide a fairly large advantage with channel. It
will help the column stiffness and help prevent buckling in compressed
members.

We'll find out when they get it on the track.

Ed Huntress