Hot Rods Flex City: Can your car do this?

Photos and video are awesome tools these days. I always enjoyed looking at video of what my OT rockcrawler was doing during comps, and not because I am THAT self centered.
What you think is happening in the seat, and what is REALLY going on are sometimes entirely different. This is not any different than the kids watching football films. learn from and correct problems.

 

In the same boat now with my '31 Brookville that made it's maiden voyage about 3 weeks ago, but thankfully I found it before I had a total failure.
Car was an uncompleted project when I bought it,Brookville '31 on '32 chassis from Pete & Jake. I thought the rear wish bones looked kinda long and spindly, but thought: "What the hell, P&J know their stuff".
Throttle linkage wasn't quite right, only getting a little over half throttle, and the 8.20X15 Coker BFGs don't give much traction. This saved me from big problems.
Turned out that the rear wishbones were specified by the previous owner in preference to P&J items. They are the 36" "Kurtiss" type from Speedway, no center brace or web, just 2 long 7/8" tubes with a tie rod end at front and clevis' at rear brackets to 9" rear. The bottom tube bowed down and is bent down by over an inch. Rear axle rotated pinion up into floorboards and made a helluva racket! Just lucky that's all it did! More throttle and better traction woulda torn up some shit!
Ordered a new set from Speedy Bill, and a local fab shop is using their CNC plasma cutter to cut out some nice webs to go almost full length outta 1/8" stock with lightening holes that I'll weld in before installation.

 

You speak for a large percentage of us. I know I don't drive worth a flip and I'm not afraid to admit it.

Not a problem, we are actually working on a new design for the roll bar. That bar came with the body and is part of the steel cage built into it. A lot of changes before the next competition. The car is edging up on will need it and with a little luck will get into has to have it this year.

I think you multiply by the length of the arm, it is like a long bar on a fulcrum.

The trans is a 200R and they have a pretty deep first gear, actually the shots of the car it is most likely in second already, stock converter unlocked. He is shifting @ 6500.

The ring gear is 4.11:1.

The tire diamter is along the lines of 30" if I recall.

Someone should know what first and second in a 200R is.

 

Agreed, just keep me outa those early swing-axle 'Vairs.
Hmm. might just make a title for a book...er...
a Kindle fer the younger ones!

As to post #33 and Vicky's calc's,
Depending upon which forces you can estimate,
I would take the force at the front wishbone mt. (F1) X length of arm (R1) = T1 Torque
then divide by R2 (radial dist, from axle ctr, out to rear housing wishbone mount bolts.
This would give a shearing force (F3) applied to the mt. bolts, clevises, etc, or easily give a value (adjust the R2 value) for bending force at a chosen point in the wishbone joint somewhat near the bolt mounts...exactly where you'd suspect it might break.
IE: F1 X R1 = F2 X R2 which is a 'sum' or balance of moments/torque problem. T1=T2
There are many additional elements to consider in making a safe long-lived design. Fatigue being one of the toughter to figure ones.

 

2.74 1st and 1.57 second.

Probably doesn't happen like this , but it could
4800 rpm launch, with a converter to match.


I get 9910 ft lbs at the axle shaft flange at launch moment but drops to 1/2 of that quickly quickly.

9910 initial and 4950 at axle shaft flange.

1.25' radius wheel based on 30" tire so divide by 1.25

7928 initial and 3690 to the axle housing.

Tire traction ? ?
"Like driving on oil" to me thats 50-75% maybe but less than 100.
Completely up in smoke with no forward movement would be zero.

 

Probably closer to 50%, on his last pass he was still spinning the tires in the lights.

I would just about imagine that if he was able to hook up the little car would have gone home on a stretcher.


Now think about it the little car probably weighs in the 1500 to 2000 lb range, take a heavier steel coupe and add another 60-70 pound feet of torque and run those same bones, not re-enforced as most are not, add another 5" of tread and softer more modern rubber compound.

 

When I built my roadster, I used 36 bones in front. I cut them as close as possible to the factory weld. The tube wall was .156 I used 39 bones in back, shortened. The wall was .136 Henry used the torque tube for the power transfer, and the bones to keep it straight. I always thought if I wanted that look for more than flathead power, I would drill 3/8 holes every eight inches or so, and rosette weld one inch tube inside before I welded the bung in. I heated and bent the axle end, then boxed the forged part.

 

None taken. When I built the car, it was a 'tip-of-the-hat' to the early dry lakes racers, but I'm a drag racer guy, born into it.
I posted this as a heads up to everyone building their car to look out for these kinds of things that we may not think about.
I was surprised at how much those bones bent ahead of the bracing I welded on the top. That came from breaking the bone mounts at the rear end twice before. I never intended for the car to evolve the way it has, but I am enjoying every minute of it and plan on making the proper adjustments to continue this direction.

 

Well right now it is like riding a loosley saddled razor blade. But it does stand up and cut a straight line. Its going to be real fun once it gets sorted out.

Although I do think that you should have chosen your friends more wisely.

 

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That came from breaking the bone mounts at the rear end twice before.


Think its time for a different train of thought on this ?

 

Ladder bars, it broke the bones with the wimpy engine and the bones got beefed because of it.