LocostUSA.com

In their December, 1953, issue Road and Track proclaimed that “Frank Kurtis of Glendale, California, deserves full credit for being the first man in America to attempt to produce an American production sports car.”

In the early 1950’s Kurtis Kraft Indy roadsters dominated the 500 mile race. Billy Vukovich won both the 1953 and 1954 races with Kurtis’ taking the first three positions each year.

Kurtis built the 500S to meet the FIA rules for sports cars. The 500S is the Vukovich KK500 Indy winning roadster, widened for two cozy passengers and fitted with fenders and headlights to produce a race car which can be driven on the street. Drawings by John Bond in October of 1953 show the basic Indianapolis frame with typical Kurtis combination Hat-section flanged side beams and tubular cross-members. Approximately 26 500S models were eventually produced.

http://www.fantasyjunction.com/cars/132 ... 8-Cylinder
http://www.forgottenfiberglass.com/tech ... ober-1953/

My next project?
It's right in line with a Seven, just chunkier....... With a tube front axle.
It would be interesting to see a FEA study on this chassis and see what chassis flex there is..........

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Ahh; gitty up!

I looked at the continuation site, and of course, your photo of the silver one above. It looks pretty cool in the way the old 50's Caddies do - lots of chrome and big, big features. It is pretty unique and I can see why you like it.

So, you're planning to build one from scratch? It would be interesting to see an FEA analysis of the chassis just out of curiosity.

Cheers,

Lonnie

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886

I've seen many variations of the chassis and would probably do one of my own flavor, based loosely on a 5 bar sprint car chassis....... So it would have an integrated roll bar and modern torsion bar geometry, although I like the way the torsion bars cross and ya wonder if it might actually give it torsional rigidity?

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Ahh; gitty up!

I just did a rough Solidworks model of the Kurtis Kraft chassis - 215 lbs!

Now for the FEA model.....

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-Andrew
Build Log
Youtube

Andrew,
Looking forward to to seeing what comes of the FEA action........ The weight surprised me

In the mean time

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Ahh; gitty up!

Just finished the Grape model and ran it.

According to Grape's displacement numbers, it works out to 1,579 ft-lbs/deg.

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-Andrew
Build Log
Youtube

Andrew,
Thanks for taking the time to do a FEA study on the chassis. So, comparing grapes to oranges is that a good thing for us laymen? I'm assuming there's a lot of chassis flex..........

Just found a post that Cheapracer had done on the Kurtis 500s http://www.locostusa.com/forums/viewtop ... 32&t=13715

A lot of variations to the the kurtis 500s just like the lotus 7

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Ahh; gitty up!

I like the sweeping front fenders of the black one.

Cheers,

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886

The black one's front fenders remind me of the manx buggy in the 60s movie, "The Thomas Crown Affair".

I like the red one.

Amoore, it looks like you need to add a few more lines at the crossmember and another node where they cross in grape.

Would you circle what you are referring to on the Grape screen shot I posted?

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-Andrew
Build Log
Youtube

I'm sure you know more about grape than me. Not sure how you put in the equivalent of 1x4 and the upper crossmember ahead of the radiator is missing. The torsion bars load into plates between the upper and lower tubes and those plates are missing. Because it is torsion bar and not coilover, the constraint should be at the plates instead of the upper damper mount. The plates are hard to see in the pics and the blueprint.

I think you said it was a rough approximation though.

Grape just represents all the members with a simple line in the drawing but not in the math. So the X in the frame is there, made from 1x4 but doesn't look like it. It looks like Andrew is trying to "teach" grape how those tube at the front and back connect to the top and bottom of the 1x4.

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Marcus Barrow - Car9 an open design community supported sports car for home builders!
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Aren't these the torsion bars highlighted in red and the lever arms highlighted in green? To be truly accurate the front points should go forward and the rears should go backwards. This is going to lower the torsional stiffness number I posed earlier since the length of the "spring" is getting longer but it isn't getting stiffer.






I'm honestly not sure if it was necessary since they are close enough that they should act like they are going into the same node.

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-Andrew
Build Log
Youtube

You are not checking the roll resistance of the suspension, but the torsional rigidity of the frame. The constraint should be the point on the frame loaded by the suspension. You've left out several structural components that will only improve the strength of the frame. Look at the blue print in the side view to see those plates. The rear plates align with the loading point. The fronts do not appear to but it is hard to tell from the photos.

It gets weird here because the spring and the arm are the same part on this car. The spots circled in yellow are where you should most accurately constrain the chassis and have it match what is going on in the real world. It needs to be where the spring (torsion, coil, etc) attaches to the frame.

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-Andrew
Build Log
Youtube