Chassis rigidity

[Tim7139]

While I've seen a lot of information on the subject, has there been any hard test data on the rigidity/flex of the more popular platforms such as SPF, ERA, Contemporary, FF, BD ?
Anybody care to grid them less to more, etc. etc.

[PSB]

Do a search

[Tim7139]

Originally Posted by PSB

Do a search

I did a search, in fact several. I get snippets here and there but not anything comprehensive. What am I missing ?

[PSB]

This subject is almost as controversial as the "Real" subject, and brings just as many unsubstantiated "expert" opinions. The only difference is the FFR guys usually lead the delusional charge

The truth is there is no real data out there to make a comparison.

[xlr8tr]

what about the aussie guys where I think they have to show chassis rigidity data before they can register the vehicle?

[DanEC]

Car manufacturers are reporting torsional and bending rigidity for their frames/bodies all the time but I suspect most of it is derived from mega-buck super computers, finite element analysis and all that stuff. Small, custom, fabricators are not going to have access to that for the most part. Some assumptions and even rough calculations can be made looking at the structural properties of the main frame rails, number of crossmembers, etc. The structural properties for 4 inch round tube, 4 x 3 inch tube and 2 x 4 inch tube of specified thickness and steel grade are easy enough to come up with and I think if someone had the time they could make a ranking from that - but it would have some limitations.

[Dimis]

Originally Posted by Tim7139

While I've seen a lot of information on the subject, has there been any hard test data on the rigidity/flex of the more popular platforms such as SPF, ERA, Contemporary, FF, BD ?
Anybody care to grid them less to more, etc. etc.

Originally Posted by xlr8tr

what about the aussie guys where I think they have to show chassis rigidity data before they can register the vehicle?

True... Our compliance process requires this, its mandated into the hoops of fire that need to be jumped through.

However, despite this, I doubt the information is held in one place.

Further I doubt the kits requested above are circulating in Aus without modification. I'm not aware of any ERAs or BDRs (for example) in standard guise that are getting around...

It would be interesting though... and I'd hazard a guess and say I wouldn't expect any of the US made kits to come close to the Aussie kits on this level.

[john chesnut]

What are the Aussie requirements and how do they test the car/frame?

[Tommy]

John,
I'm not sure their chassis standards would work up here -

[john chesnut]

Thanks Tommy.

[letsboogie351]

Here is a guide from Australia. If you are that way inclined and have the skillset to build a jig you can do your own test

reading commences on page 6

http://www.google.com.au/url?sa=t&rc...JJ8z6NOkbWZnIg

[AL427SBF]

Originally Posted by Dimis

... and I'd hazard a guess and say I wouldn't expect any of the US made kits to come close to the Aussie kits on this level.

I expect JBL would cruise through aussie regs in flying colors, in excess of 4800 lbs per degree torsional stiffness done on a chassis weighing 418 lbs
.

[strictlypersonl]

Chassis design logic

[Dimis]

Originally Posted by AL427SBF

I expect JBL would cruise through aussie regs in flying colors, in excess of 4800 lbs per degree torsional stiffness done on a chassis weighing 418 lbs
.

True. JBL is impressive, but when you consider our minimum is 4000nm per degree, the JBL really ain't the bench mark now... Wouldn't you agree?

Particularly when you consider some ICV kits here are quoted in at reaching over 30,000nm per degree. Though I can't claim to know their weight for the sake of comparison.

[vector1]

Originally Posted by Dimis

True. JBL is impressive, but when you consider our minimum is 4000nm per degree, the JBL really ain't the bench mark now... Wouldn't you agree?

Particularly when you consider some ICV kits here are quoted in at reaching over 30,000nm per degree. Though I can't claim to know their weight for the sake of comparison.

I think you have to consider the frequency also. Don't understand it all but the JBL was measured at 24 Hz minimum, I've seen different frequencies listed for whatever the test produce considerable difference in numbers. Maybe Richard will chime in.

[vector1]

Originally Posted by strictlypersonl

Chassis design logic

That is an interesting article. One of the diagrams is very similar to the JBL.

[DanEC]

Originally Posted by strictlypersonl

Chassis design logic

I will vouch that the ERA chassis seems very rigid, especially for an open car.

[strictlypersonl]

Originally Posted by Dimis

True. JBL is impressive, but when you consider our minimum is 4000nm per degree, the JBL really ain't the bench mark now... Wouldn't you agree?

Particularly when you consider some ICV kits here are quoted in at reaching over 30,000nm per degree. Though I can't claim to know their weight for the sake of comparison.

The problem with a Cobra replica that is a close visual copy of the original is that it it totally restricted by what will fit "under the skin". We are very limited by the space necessary for the driver and engine, in what is really a pretty tiny package. The JBL skirts this a little by being a little creative with the original dimensions. i.e. wider and longer.
In addition, this is an open car. Cars with roofs have a big structural advantage.

[john chesnut]

My home built frame. I kept the stock body dimensions.

[Tim7139]

Guys, with all due respect, however interesting this may be, it's got little to do with the initial post. I am very familiar with what's possible and theoretically what's desirable. I was more curious about what's out there on a more less relative bassis.
It sounds like nothing in the way of any testing and / or ratings have ever been done, lots of "seat of the pants" type stuff.