Which Company makes "best" replica?

[Excaliber]

Well the Kirkham certainly has to be considered when it comes to choosing what replica best suits your needs. There are WAY to many builders to list them all in a reasonably worded first post to a thread.

[speed220mph]

Originally Posted by ZOERA-SC7XX

And I long for the day that my car is in the Shelby World Registry.

Can you get in the SAAC registry if CS signs your glovebox?

[RodKnock]

Originally Posted by speed220mph

Can you get in the SAAC registry if CS signs your glovebox?

Possibly, if Team Shelby takes over the Registry. Stay tuned.

[Got the Bug]

If Shelby takes it over it'll be like those cheesy "who's who" books...pay us $500 and we'll be happy to list your name.

Hey Rodney - Glad you drew the line at the leather steering wheel...the reaction is usually gasps of horror when they see my car.

[RodKnock]

Originally Posted by Got the Bug

Hey Rodney - Glad you drew the line at the leather steering wheel...the reaction is usually gasps of horror when they see my car.

A famous philosopher once said "A man has got to know his own limitations." I knew mine.

[Got the Bug]

One famous philosopher who used that line is Dirty Harry.

OK..we're going to smacked for taking this thread WAY off topic.

[Excaliber]

As far as the steering wheel, some of the original cars were modified by wrapping the wheel with various items. After all, that skinny wooden wheel is a handful when your drifting the corners and your a$$ is on the line.

[jmimac351]

I haven't read any of these replies but you're all wrong.

[Silverback51]

Originally Posted by Anthony

They're really not the same size. A square tube is also about 27% heavier.

Even though a round intake port is the most efficient, your analogy is like saying a square 3" intake port will flow more than a 3" round port, which it will.

Okay, I was lazy.

Let go with some real frame component sizes and see what we get.

Superformance.
2 X 4 X .160 wall rectangular tubing. The "I" value of this is 3.69 Inches to the fourth.

ERA.

3 X 4 X .125 wall rectangular tubing. The "I" value of this is 3.92 Inches to the fourth.

Kirkham.

4.0 diameter X .120 wall round tubing. The "I" value of this is 2.76 Inches to the fourth.


Now this is just basic strength of materials for structural shapes and does not take into account the other structural bracing and such that makes up the frames. The only way to really compare any of these frames to determine which is the strongest would be to build a FEM model and run it through a stress program to determine what is happening when like loads are applied.

Unless one of the above manufactures has actually done this for all three frames, they cannot make any claims that theirs is the strongest.

Yes, the ERA 3 X 4 X .125 tube is the strongest, but that single component does not make it the strongest frame. All it would take would be one series of truss members to make the Kirkham tube assembly 10 times stronger.

Besides, don't beleive everything you read from manufactures (or politicians) as they are all trying to sell you something.

Is that better?

And thank you for challenging my response. I don't get to play with numbers much at work anylonger. Even this simple stuff was kind of fun.

[RodKnock]

Originally Posted by Silverback51

Kirkham.

3.0 diameter X .120 wall round tubing. The "I" value of this is 2.76 Inches to the fourth.

Per the Kirkham website, 4" round, not 3".

http://www.kirkhammotorsports.com/mfg/frame_index.html

[Excaliber]

Well heck I said some posts ago that the strength of a square or round tube is more dependant on the overall design that the type of material being used anyway.

Whats the complicated saying? The sum of the parts is greater than the individual, or something like that...

jmimac351 is on to something, were all wrong!

[Silverback51]

Originally Posted by RodKnock

Per the Kirkham website, 4" round, not 3".

http://www.kirkhammotorsports.com/mfg/frame_index.html

You are correct, it is a 4.0 diameter tube.

When I did my calculations I did it for a 4.0 round tube. I just screwed up when I posted the numbers.

I'm going to blame it on the beer.

Thanks for keeping me honest.

[RodKnock]

Silver, I wasn't really out to prove you wrong, but it didn't sound right. So I had to look it up myself. I'm wrong all the time and there's no way I could ever calculate the "I" value without first looking for the formula somewhere on the Internet.

I hope I did not offend you. Not my intention.

[Silverback51]

Originally Posted by RodKnock

Silver, I wasn't really out to prove you wrong, but it didn't sound right. So I had to look it up myself. I'm wrong all the time and there's no way I could ever calculate the "I" value without first looking for the formula somewhere on the Internet.

I hope I did not offend you. Not my intention.

Not offended at all. I'm glad you pointed out my mistake so I could correct it.

[ItBites]

Silverback (and others):

With frames, we usually care about torsional stiffness, not bending stiffness. Ix or Iy is normally the cross-sectional moment of inertia with respect to the neutral bending axis (what you calculated).

Ip is typically the abbreviation for torsional cross-section moment of inertia. I think if you look at torsional stiffness, you will find the 4" round tube is superior to any other shape with dimensions less than 4 x 4 (given similar wall thicknesses). The .120 wall thick 4" round tube is still likely better than the SPF .160 wall thickness, due to the 2" dim on the SPF frame (and with less mass).

Have a nice day

[Anthony]

Originally Posted by Silverback51

Not offended at all. I'm glad you pointed out my mistake so I could correct it.

There are other significant differences as well, such as the cross members, number of them, and how they are placed which I would think significantly affect frame rigidity.

I think CSX4000/Kirkham's have 4 cross members. I don;t know about ERA's, Superformances, and how they they all compare to one another.

I now see you already posted about this.

Originally Posted by Silverback51

--Now this is just basic strength of materials for structural shapes and does not take into account the other structural bracing and such that makes up the frames. The only way to really compare any of these frames to determine which is the strongest would be to build a FEM model and run it through a stress program to determine what is happening when like loads are applied.

Unless one of the above manufactures has actually done this for all three frames, they cannot make any claims that theirs is the strongest.

Yes, the ERA 3 X 4 X .125 tube is the strongest, but that single component does not make it the strongest frame. All it would take would be one series of truss members to make the Kirkham tube assembly 10 times stronger.

Besides, don't beleive everything you read from manufactures (or politicians) as they are all trying to sell you something.

Is that better?

And thank you for challenging my response. I don't get to play with numbers much at work anylonger. Even this simple stuff was kind of fun.

Yes, perfect response. And I don;t believe everything what is told to me from politicians, doctors, and especially lawyers

[Dinobyte]

To compare, you need to compare apples to apples.

Same motor in all cars...since we are talking the SC, then it has to be the 427 FE.

For the SB guys, we will allow a 427 Windsor with 500 or so HP.
(We don't want to upset the SB guys too much with that size thing again.)

Start off with Weighing the cars...measuring the cars (width, length, ride height).

Have a panel look at the cars for fit, comfort, ease of driving.

Rate the car on authenticity based on an agreed upon criteria.

Measure the 0-60, 0-100, 1/4 mile, time to lap Willow Springs (etc...pick your track), so as to understand the performance characteristics of each car given the same power plant.

Next we need to measure the skid pad rating for each.

Then we need equipment to measure the cars responsiveness to lane changes...how fast through the slalom, etc.

Now the bracking....going 100 MPH, slam on the brakes..how quickly does it stop...120 MPH...brakes...how quickly does it stop....140 MPH...brakes, etc.

Now 0-100-0 time...how fast.

0 to 100 time

0 to 120 time

0 to 140 time

All of these measures should be able to provide not only performance in like prepared cars, but also tell us when equipment starts to break.

Last but not least, cost to purchase each car with the identical equipment.


If the kit companies and an engine builder could prepare the various common engines, then we would have real data to look at and not just some BS opinion of someone who thinks they know which car is better. Put them through the Car and Driver test and see who wins. How dumb is that?

[jmimac351]

Originally Posted by Dinobyte

How dumb is that?

Because performance is a very small part of the cobra "ownership experience". I get considerable enjoyment out of just looking at the damn thing while drinking a beer and smoking a cigar in my garage.

The "best" depends on what you want. For me, and many others, it would be a Kirkham.

For guys that want to track the car and build it - maybe a FFR. Building and working on your own car is a completely different experience.

For someone that wants to build but wants a more "authentic" look - Hurricane or the new FFR body.

For a turnkey minus car that looks like a more exotic cobra / tough - Backdraft.

For a turnkey minus car without the cost of the Kirkham - SPF.

I think running the numbers matters very little in this regard. Certain cars will provide different owners entirely different experiences.

[Silverback51]

Originally Posted by ItBites

Silverback (and others):

With frames, we usually care about torsional stiffness, not bending stiffness. Ix or Iy is normally the cross-sectional moment of inertia with respect to the neutral bending axis (what you calculated).

Ip is typically the abbreviation for torsional cross-section moment of inertia. I think if you look at torsional stiffness, you will find the 4" round tube is superior to any other shape with dimensions less than 4 x 4 (given similar wall thicknesses). The .120 wall thick 4" round tube is still likely better than the SPF .160 wall thickness, due to the 2" dim on the SPF frame (and with less mass).

Have a nice day

And that is why we don't have square axles.

But the majority of the torsional stiffness comes from the rest of the frame design.

[RICK LAKE]

DinoByte Kit Car Mag had talked about trying to do something like this. The Big problem was ringers, getting a prodriver to test the cars and be consistent from car to car. You have to find owners who will let some one abuse them. You would need to get the same springs, shocks, wheels and tires, rearend ratios and motors to really make this an honest test. Who is going to swap motors from car to car? This is why the Run&Gun was started back in 90. It is a test of car and driver to see who had the best car. In the last 90's FFR was doing well and winning alot. SPF then got into the game and was winning alot of classes. Shell Valley and Backdraft are now getting there turn in the sun. Others have shown up and done well. Some Companies will not back a car and driver for fear of lawsuits if hurt, ERA is one. Sure there are others. IMO the Windsor strokers guys will beat the FE guys about 65% of the time on most tracks without long straights. It comes down the wieght/ power. I have a 482 motor now and can't get the car to hook up now. I may redegree the cam to take some of the torque out of the lower rpm range to stop this problem. If you look at alot of the guys here with BBF motors, the 482 strokers are the new kid on the block. ERA cars also weight about 2-300 pounds more that SPF, FFR, Backdraft, Shell Valley. I have seen these cars weight at R&G. IMO this test will never be run, at least not by Kit Car Mag. This Mag is just holding on with the small number of people who buy it. If you look at stories and pictures, the editor does everything alone. Some tech write up are done by owners. Rick L