Torsional Rigidity Measurement...warning pseudoscience involved

[JohnJL]

I Darth Vadar'ed my longhood...
















or is that Stormtrooper'ed?




As I was fitting in the signal boxes and an original set of horn grills I went on this tangent. The grills are pretty heavy so I started shopping for lightweight versions, which I see our Host carries. THen I stood back and looked at the car and realized the "sleek" look might fit better with the other mods like cutting the gutters, single central wiper, flush windows, etc.

The grills are also superfluous for this car too, so my though process was to just fill them in with foam and a skim of fiberglass. If I dont like it I can still put the grills back in there.

I am sure others have done this, but I couldnt find any pictures. Its an experiment, I like it so far but will reverse it if it doesnt look right to me.

Also almost finished the dash...lots of sanding, primer, sanding in there. Waiting for the paint to fully cure to wet sand and clearcoat it...


The car is going to be a charcoal/slate color and a few red highlights in side like the dash, shifter tunnel and those gusset plates.

[JohnJL]

A good bit of progress on the bodywork. The backsides and bottom of all panels are done, the front bumper, hood and fenders are all skimmmed, blocked and sanded. I am halfway through the roof and rear quarters. The tail is half done with repairs, there were some spider cracks and I am using a different license plate light so I filled in the old ones.

[JohnJL]

more

[JohnJL]

Bodywork is coming along. Front bumper, hood and fenders are all blocked and ready for final sanding and primer. I spread out the skimcoat last night and will spend a few more hours blocking the A pillars and roof today. I am going for a "sleek" look and there are a lot of little touches to it...the horn grills skimmed over, single, central wiper, extra-tight body gaps, deleted sunroof, flush-mounted rear quarter windows and flush-mounted rear window. It created a lot of extra work but I am digging it...

[JohnJL]

A few more hours of sanding done....

[JohnJL]

Progress has progressed.




https://youtu.be/Q6AbTkNteDQ

[JohnJL]

I laid down and sanded back 2 coats of spraymax 2-part rapid primer-filler, using guidecoat to get things flat and smooth. I sanded to 500 then laid down primer, followed by spraymax 1k solvent-based color and 2 coats of spraymax 2-part glamour gloss clearcoat. I wasnt really happy with the coverage, so I wet sanded that back with 600 then 800 and shot it again with the same base and clear again. Much better. There are a few flaws: a drop of moisture dripped from my respirator onto the car while I was painting and created a discoloration. there is also a stripe of darker color on the hood. Both will be fixed later when the whole thing is buffed out.

Some pics of that process...

[JohnJL]

...then it was game-time. After wetsanding back to 800, washing it with alcohol and dstilled water and finally with spraymax's final paint prep, I shot the final color and clear coats...I wasnt that thrilled with it until I pulled off all the masking and revealed the red interior highlights. I am enthused, the neighbors and wife think it looks great. Of course the kids think it is the coolest thing ever.

Not bad for ~$700 in materials. And a metric ****-ton of hours sanding and prepping!!!

[JohnJL]

Walkaround after paint....

[Neffets]

What happened to the threads topic? it started as a interesting torsional rigidity thread and now ended up as a building thread???

[JohnJL]

Originally Posted by Neffets

What happened to the threads topic? it started as a interesting torsional rigidity thread and now ended up as a building thread???

I got too lazy to have 2 threads going on the build, so since this one was already alive I just kept building on it instead of re-loading pics.

I still need to put the front strut braces together too...

I will still put the beam on the front and check if I see any difference in the measurements, I am sure the debate on validity and accuracy will kick up again...

[JohnJL]

I replicated the initial measuring situations...53kgs on the front tripod point, 41kgs on the lever arm, rears strapped tight to the rear lift arms and took new measurements.

I got 6.1 cm of deflection in the arm before, and 4.9 cm after.

Oh and that is without the front triangulated strut braces in place.

Thoughts?

[JohnJL]

That's 19.6% less by my calcs:

=(6.1-4.9)/6.1

Here is what was structurally done to the car:

Seam welded
driprails shaved and welded
A and B pillars gusseted
Harness bar welded in and gusseted
Torsion bar gusseted to body
Rusty door jambs replaced

[JohnJL]

What, no takers on a little debate-o-rama?

[Flieger]

I forget now, what was the debate? What side was I on?

[JohnJL]

Installed the driver's side window frames, makrolan vent windows and stock side windows for now. It needs to pass street inspection first and my reading of the inspections checklist seems to mandate DOT-marked stock glass as a requirement. Maybe (hopefully) I am wrong, I have a sheet of makrolan AD waiting the be cut into windows. That worked really well on another car of mine. The glass vents with seals weighed 750grams (I know the pic above is w2hen I forgot to add the old seal.) The makrolan with seals weighed 455grams. Thats about 600 grams of 1 +- pound with both sides.

I stripped the frames back and gave them a couple of coats SEM trim gloss black, and new seals all around.

I plan to do a strap pull for the windows, again this worked well on another car and ditches all the steel window mechanisms.















I also started mounting the rear window. I have a GT Racing rear window flush mount piece that is bonded and riveted to the body. I am using a GT Racing rear window, which is cut just about perfect to fit the frams (I had to sand back one side and 2 corners a little bit.)

I started by finding the center of the body and the center of the window. I wanted to be sure the bolts on the rear grill lined up perfectly straight with the window hardware so I used those as part of the centering reference.



I then carefully marked out the points where I wanted to place the countersunk bolts and drilled a pilot 1.5mm bit to mark the window and the corresponding placement for the rivnuts. I started by taping down the window perfectly into place and drilling/installing the top and bottom center bolts. I then worked in a criss-cross pattern mounting the rivnuts into the frames and reinstalling between each bolt or 2 to be sure placement didnt drift at all.



Finally, I decided to use a spare rennline smugglers hatch cover as the mounting point
for my fuse panel and relay mount. I also made up a ABS baseplate for the cut-off switch and wired that up into the stock hole. I forget what part of the vent system uses that hole in the stock car, but it is perfect for cutoff switch mounting. The battery will mount down in the smuggler's box.

[safe]

Originally Posted by JohnJL

Installed the driver's side window frames, makrolan vent windows and stock side windows for now. It needs to pass street inspection first and my reading of the inspections checklist seems to mandate DOT-marked stock glass as a requirement.

Do you need windows to clear inspection?
If not, leave them out or down with no (obvious) way to pull them up.

[JohnJL]

The regs I was pointed to stipulate DOT glass on everything parallel or forward of the drivers head when seated. They are very specific about grades and markings of glass and glass/polycarbonate behind the head.

[1990C4S]

Nice work.

[Walt Fricke]

What are those reddish steering column rods?

Are you going to repeat the torsional deflection test when you add the strut tower bracing? The leverage of the strut top on the tub doesn't seem, geometrically, like it is favorable to moving the tower tops (hence suspicion strut braces don't directly avoid camber changes from the tops moving), but there may be different considerations when talking about the whole front clip twisting.