Original 4 inch vs. Billet Poll

[alpace@pacificp]

David,

As you know, I am a bit of a novice, notwithstanding considerable research into the deep, dark recesses of the dysfunctional cobra world. Notwithstanding, I have to say that being able to relate to others that the frame is 'tube,old school' goes a long way.

As someone already thinking about a 'second' Kirkham (I have two boys), I would opt for tube, steel. Old School.

But about those magnesium wheels......

al

[David Kirkham]

Originally Posted by alpace@pacificp

David,

As you know, I am a bit of a novice, notwithstanding considerable research into the deep, dark recesses of the dysfunctional cobra world. Notwithstanding, I have to say that being able to relate to others that the frame is 'tube,old school' goes a long way.

As someone already thinking about a 'second' Kirkham (I have two boys), I would opt for tube, steel. Old School.

But about those magnesium wheels......

al

From the poll I can see we aren't going to be throwing the tooling for the original chassis away any time soon

I'm glad to see there are a lot of people who love the billet stuff as well. Funny, when we started, every one wanted everything as original as possible, right down to a date coded dip stick! "Date coded; man I haven't heard that word in a long, long time!

David


David

[decooney]

Originally Posted by David Kirkham

From the poll I can see we aren't going to be throwing the tooling for the original chassis away any time soon

I'm glad to see there are a lot of people who love the billet stuff as well. Funny, when we started, every one wanted everything as original as possible, right down to a date coded dip stick! "Date coded; man I haven't heard that word in a long, long time!

David

Looking at it from a different (maybe stupid) angle... If this situation became a "this or that, but not both options type of decision", I'd be curious what the vote results would be if you asked all of your existing KMP Cobra owners if they (hypothetically) could trade their existing tube chassis cars for billet chassis cars straight across, with no chance to ever obtain or purchase a tube chassis car again, what would they actually vote for?

[goof2]

Originally Posted by David Kirkham

The weight difference between a stainless chassis and a steel chassis is around 20 pounds. The difference between our billet chassis and the original chassis is about 20 pounds as well. The problem is, I can't remember which car (steel or stainless) we compared the billet chassis to!

I will have to go back an look at the numbers...or, just wait until we drive it here in a few days.

David

No need to look back on my account as it is all academic for me at this point anyway. I had assumed the difference in weight would have been on the order of 100 to 200 pounds. For the tuneability and responsiveness that should result from the 300% increase in stiffness I would deal with the extra 40 pounds. If 40 pounds were that big a deal I would loose the weight myself.

[David Kirkham]

Originally Posted by goof2

No need to look back on my account as it is all academic for me at this point anyway. I had assumed the difference in weight would have been on the order of 100 to 200 pounds. For the tuneability and responsiveness that should result from the 300% increase in stiffness I would deal with the extra 40 pounds. If 40 pounds were that big a deal I would loose the weight myself.

I've often thought while working on this billet chassis how much easier it was to remove weight from the car than it was to remove weight from my middle!

David

[COBRANIP]

David,
Won't the billet frame (especially with pushrod suspension) result in a higher center of gravity (relative to the tube frame)? If so any idea how much difference?
Thanks for expanding all our horizons.

John

[Ronbo]

I've often thought while working on this billet chassis how much easier it was to remove weight from the car than it was to remove weight from my middle!

That's a tough one, time on the computer to take more pounds off, however it has the reverse effect on the programmer.

Here's a tip: keep all snacks out of reach of the desk, preferrably on the opposite end of the building.

Personally, I judge how tough a project was by how many pots of coffee and packs of smokes it takes to complete it...

[fostereast]

For David K.

Out of curiosity, do you strain guage any of your designs and stress them in a way that let's you compare actual results to your FEA results. It would be fun to see pictures of copper wire and strain guages all over one of your test-bed cars.

I suspect that as you push the envelope into more and more billet items with weight reduction as a key goal that there are certainly a few parts or connections that would be fun and valuable to test this way.

[David Kirkham]

Originally Posted by fostereast

For David K.

Out of curiosity, do you strain guage any of your designs and stress them in a way that let's you compare actual results to your FEA results. It would be fun to see pictures of copper wire and strain guages all over one of your test-bed cars.

I suspect that as you push the envelope into more and more billet items with weight reduction as a key goal that there are certainly a few parts or connections that would be fun and valuable to test this way.

Now, that would be cool to see all those wires. As for that extensive of testing, no, the testing alone would be hundreds of thousands of dollars. But, we are doing the next best thing. This Thursday (hopefully!) we will be actually testing the car at the track with miles and miles and miles of hard driving. We will then take the car apart and check everything out to make sure FEA does correspond to real life.

As for testing, we do have a wall full of parts that are tested to failure. Some ideas are surprisingly good--others need more time on the drawing board. As for margin of safety, there is a reason we call Thomas "Baja Man."

David

[David Kirkham]

Originally Posted by Ronbo

That's a tough one, time on the computer to take more pounds off, however it has the reverse effect on the programmer.

Here's a tip: keep all snacks out of reach of the desk, preferrably on the opposite end of the building.

Personally, I judge how tough a project was by how many pots of coffee and packs of smokes it takes to complete it...

Good thing I don't smoke or I'd owe stock in Marlboro by now!

David

[David Kirkham]

Originally Posted by COBRANIP

David,
Won't the billet frame (especially with pushrod suspension) result in a higher center of gravity (relative to the tube frame)? If so any idea how much difference?
Thanks for expanding all our horizons.

John

I imagine the CG will move slightly up from a frame stand point. How much??? Not sure--probably not enough to notice any difference.

We also moved the engine back quite a bit so that will certainly help. I guess we could do the calculations as we do have everything in CAD. Also, we can get the front to rear CG when we scale the car.

David

[Dominik]

Hi David,

I prefer the original chassis & suspension for originality reasons, and registration in Europe.
How about a new body, see pm.

Dominik, currently in Gemany

[joey_hv]

How about selling the solidworks files for the CNC chassis, for those do-it yerselffers out there?

[Cobra Lite]

I just found this old poll thread and read through all 9 pages.
Very interesting viewpoints expressed and many questions asked.

Now that the Billet car has been completed, driven, and viewed by many, I wonder if the poll is up to date?

I can see the reasons for each version on the poll. It is just a personal preference of what each of us want in a special car.
I see there is a market for each type.

My preference is for the best handling, best brakes, lightest weight car that looks and sounds like 1964. I would be quite content with a steel spaceframe design with the the billet rocker suspension since most of the billet frame is hidden anyway. The round tube (or square, etc.) ladder frame in any size is my least favorite both in design and appearance. I would really like a modern frame that drops the seats lower. Much lower! And offers modern adjustable suspension.

I think it is similar to hot rods and restored cars. Both have their place and both have die-hard fans.
There is a place for an "as-original-as-possible" as well as the most modern interpretation.

To paraphrase: "Build them, and we will come"
To buy them of course!