1 question about round verves rectangler tubing
 

Silverback 51 From all the reading of the old days with cobras, the issue was about frame flex. I think the issue was that round tubing could bend and TWIST easier than rectangle tubing of say 2" by 4". This is my understanding of the issue. Is there a formula about this? IMO this is why Nascar builds there cars with round tubing for the roll cages. It's easier to work with cheaper to buy, lighter the rectangle, and it bends to absorb an accident easier than rectangle and still hold its strength. I believe that the main frame on nascar is still rectangler tubing. I also think that alot of the round tubing built cars have gone to a thicker wall tubing to cut down on the issue we are talking about. Twist and flex. :) Rick L.

You can't compare a 2 rail chassis to a bird cage style like Kikham,CSX,and D&D.
Don,

Just so you don't think I'm ignoring you, I will answer your questions when I get home after work.

Let's face it, the best (most authentic) replica out there right now is made by Shelby :LOL:

Best Aluminum car award goes to Kirkham hands down (for a company that does more than 6 a year)........

This is almost as much dysfunctional fun as the Big Block vs. Small Block debate.

I'm glad Evan didn't see that one. **)

OK, so.....
 

OK, so what I want is a round framed square reinforced cross-membered do-hickey with a super reinforced skid pad and an aluminum body, so the dents are hard to bang out. And it'l only cost me $300,00.00 ...:confused::confused::confused:

But seriously, I have found this very useful. I just don't know how.

It appears to me that if I buy a:
Shelby
Kirkham
ERA
SPF
FFR
Backdraft
Unique
or a number of smaller manufacturers who have been very kind in contacting me...

That I won't go wrong.

The photo page showing the different manufacturers from the side was very useful to show me that they do, in fact, look different. And I do like the ERA, Kirkham,SPF look the best. The FFR and the Backdraft seam to have a "Bigger Butt" for total lack of a better description. Although I am sure that it is subtle and won't matter once I own one. I think that my pricing will fall somewhere in the FFR/Backdraft to ERA range. I do like the idea of buying a totally American made product (sorry if that offends anyone).

The thread has been informative in that it has provided me with many different opinions and directions in which to focus my own research. So thanks to all for that.

I will make every effort to get to Hope Well this Saturday and I think that will help me a lot. I just hope I can make it.

Keep it going. I would assume at this rate that I'll pick a car before you guys agree. :p

-Matt

Matt, of that you can be sure as it's a given we will NEVER agree. :D

The strong point of a round tube in torsion is that the stress value is the same along it's outer most surface. That is why we have round drivelines, axles, half shafts, etc.. With a square, rectangular, or other shape of structural material the stresses will be concentrated at the outermost fibers where the shape is changing.

Most of the strength of a round shaft is at it's most outer surface. That is why drivelines are always hollow. The closer you get the center, the less strengh is gained by the material in the center. Why are axles solid? Generally because there is less packaging room for a large diameter hollow shaft.

Here is a link to the formula for a round shaft. The formula changes for different structural shapes.

http://www.instron.us/wa/resourcecen...rm.aspx?ID=173

Needless to say, the design of a frame is very complex. And the most efficient design will be a combination of different structural shapes that are choosen to satisfy the stress loads that it's being subjected to.

Take a look at the NASCAR frames. As you pointed out they consist of rectangular main rails and the rest of the frame is mostly different sizes of round tubes.

Now take a look at a top fuel dragster. It's all small diameter round tubing. Different requirements dictate different material shapes and designs. The dragster is a truss design that also allows a great deal of flex in one direction to allow maximum weight transfer for straight line traction. The NASCAR frame is designed with different requirements, so that design is completely different.

Hope that answers your questions.

Matt, I'll go out on a limb here and say that of the three manufacturers you mentioned above, I think you would get an unanimous endorsement of the ERA as the best (of those three).

What is the timing of your desired purchase?

ERA lead times can be a long...so the used market might be an option.

ERA would get my vote too.

ERA is made in New Britain, CT. USA. FFR is made in MA. (also USA). Backdraft and SPF are made in South Africa. I understand the aluminum bodies for the Kirkham and Shelbys are made in Poland. The rest of the Shelbys are made in Mexico, South Africa, and wherever else they have cheap labor. Do your homework. Buy the best you can afford and you won't go wrong.

Ooops! The SPF would be the range you mentioned. I missed that one. So, there goes the unanimity. Oh well.

This is still up for debate.

Unique may not be THE absolute best, but it's certainly one of the best and is a darn good product. The Weavers are second to none! It's definitely worth paying a visit to their facility.

Matt, the ERA is a very nice car too and should definitely be considered. I should have mentioned that. I built an FFR and have had a lot of fun. If I were in your price range again and considering the FFR, BDR, or ERA I'd likely look real hard at the ERA because I also like the look. The good thing is that there are a lot of good cars out there. If you start narrowing cars down by look, frame, and price that probably will focus you on what you want. Just make sure you think about how you will use the car. If you plan to track the car then you need to consider consumables like pads, rotors, etc.

Cobra Revolution VI at Washington Crossing...
 

Went to Cobra Revolution VI in PA today...

Before mentioning the cars, it's necessary to complement the people behind the cars. I met a ton of really good people and asked a lot of (probably very stupid) questions. Got some great answers and really helped to narrow down my choices...

Down to 3:
BDR
SPF
ERA

I would probably prefer an SPF or ERA but if I find that I can get into a BDR with everything I will want when it's purchase time for $10K less, then I'd seriously consider it - the BDR's are gorgeous. Not quite as soft lined and refined, and not as finished; BDR is clearly a more aggressive look. But I would unquestionably be happy with any of the three.

I feel it necessary to qualify that the FFR's where really nice as well and BDR and FFR went into my same category from a looks standpoint. But it looked to me like almost every FFR was home built and I want a turn-key that I know was built by a professional...

So I have finally gotten somewhere. I'm going to keep my eyes on the "For Sale" sites. And I'm also going to call dealers for all three to start learning more about engines. Purchase is still probably some time off. :CRY: But I will have some other toys to play with until that day comes...

-Matt

best Cobra replica
 

Who cares which one is best??
I just want one...
Any Cobra will do :)

Matt,

Glad you could lay your hands on some actual cars.....Might want to add Unique to your list, as there were several top quality cars from that manufacturer there as well. Plan your budget, then go from there, if a brand new turn key is in it, great, if not, there are plenty of nice lightly used ones out there as well. Can't find one in the color you want, you can always repaint it :D ..........


Bill S.

PS: For the record, I had the FFR with the "custom paint" made to replicate an unfinished body :JEKYLHYDE