Hi Stu,
to your question about frame.
The Thrust SSC, the NAE or the Soa, all three got a frame structure.
The Thrust was designed so heavy (this car is really the heaviest record racer ever built, 10,7 tons (the original calculation was 7 tons) by purpose - the most weight was on the front axle to keep the car down, with a controlled air cushion - like a hovercraft - under the main floor (left/right engine and cockpit) the car was stabelized permant in the same level to the ground - all support by a computer controlled suspension.
Ayers/Bowsher tried to keep the car by weight on the ground, especially in the moment when the car went thru the sound barrier and than, when he slows down, back out off the "sound barrier".
Which sounds in the first moment strange, but to go back from a speed over the mach marker to under mach speed is so critical as to go thru the sound barrier.
The Trust from was so solid, that the car could run high speed without any panels on (limited to the drag which the only frame racer creates), they was there only to cover the frame and to create streamline - by the way, aerodynamicely this car was a brick....a damn fast brick.
This concept with this covering panels was necessary, especially in the rear end. Due to this that the engines outlet was not the end of the body, the extremely heat, create from the engines "exhaust" the panels on the rear end deformed extremely, at last so much that the rivets collapsed and broke.
If this panels would be a part of the stiff structure of the car, the reaction in the panels would create a effect to the whole construction and to the suspension - in other words - twist and bending (talking about some mm).
To the NAE, this car is not a real monocoque - this is a sheetmatel spaceframe design. Instead of tubes the frame is create by sheetmetal profiles - typical plane design from the fifties and sixties - the NSU Baumm was build the same way. Using open profiles as a space frame with screwed/riveted panels on you get a very stiff construction.
But to build a single racer this way is a long and hard work. Without press tools, so as used for the F104, it will need a lot of work to get each spaceframe rip and longitudinal together. A other problems are the joints.
Different to a tube frame, which you can weld together with soft and hard knots (joint points) this open profil frame needs to be spot welded.
Also this frame will be never strong enough to stay stiff by his own. It needs the panels to get the necessary strength. But the result is a very stiff design with a low weight.
By this design it is necessary that the shockwave reaction, especially with a ground bound vehicle like a record racer, had to be controlled only by aerodynamic.
Now to the Spirit of America (96/97 version). This racer used the best of both worlds. It was a very light spaceframe done with round tubes. It was designed with a upper and lower half "tube" frame. This two halfs was screwed together, the jet engine was used as a part (of strength) to stiff this spaceframe. A so tube frame is very easy to build and could be done with standard work shop equipment. Also the joints are very easy to modify - from a soft to a hard knot or back it needs only a cutter and a welder.
Alone (frame + engine) this design was not stiff enough. In this build status it was necessary to have a support under the frame, otherwise the frame bend through (by inches). Only the 1/5 inches thick aluminium (stressed) panels, fixed with hundreds of screws on the spaceframe, done the whole construction stiff and strong enough to run fast. In 96 the 700 mph u-turn on two wheels showed how strong a so design could be.
The result of this design was a very light construction, about 10 % heavier than the F104 way, but with a very easy to build construction.
The SoA weight at last 4 tons with his single engine - against the 10,7 of the twin engine SSC. The weight of the engines are very similar.
This shows how heavy the SSC frame design was.
If you like to go for a tube frame design, don't forget CREMONA. This mathematic frame rule helps a lot to keep the weight of the frame down.
Used CREMONA the right way, you can reach very easy a 30 % stiffer frame by the same weight to a standard frame, or a weight reduction from 30 % by the same stiffness.
Cremona comes from a Italian mathematics, you find this mathematic rule especially in crane design, but it works also by a car frame design.
Hope this helps.
Think fast....always
