24 replies to this topic

[Magoo]

Here's a little story with nice, big, clear photos showing the rules-mandated changes to the NASCAR roll cage for 2013.

MCG exclusive! 2013 NASCAR roll cage | Mac's Motor City Garage

In part the idea is to generate thought and discussion about roll cage design, materials, and fabrication, not necessarily just for NASCAR but for everything using the same sort of tubular construction.

Thanks to Kevin Bryde of Earnhardt Ganassi Racing for providing the photos and other material. Every day I am a little more astounded to learn who is reading MCG. It's a sort of a who's who of the auto world. I will redouble our efforts to deserve it.

Edited by Magoo, 11 September 2012 - 11:07.

[OfficeLinebacker]

That asymmetric diagonal bar from the roof to the passenger side footwell is interesting.

[MatsNorway]

That asymmetric diagonal bar from the roof to the passenger side footwell is interesting.

Why not i say.

I find it a little bit strange that the Earnhard bar is not connected to the lower section going underneath it.

Its like it has been given room to bend.

Perhaps it pushes the engine down and under during a crash?

[bigleagueslider]

In part the idea is to generate thought and discussion about roll cage design, materials, and fabrication, not necessarily just for NASCAR but for everything using the same sort of tubular construction.

Here's a comment on the design of the roll cage shown in the picture. If you look closely at the upper right hand side of the picture, you'll see a small triangular plate gusset welded at the center of two tube walls. Structurally, this is the worst way to locate a gusset when reinforcing an orthogonal tube/tube joint. The purpose of this gusset is to reduce the local weld joint stress due to bending. By locating the gusset on the center of the tube walls, the gusset is transferring loads to the tubes at their weakest point. The gusset should be located at the outer (tangent) edges of the tubes, and welded along their center lines.

With all of the money available to NASCAR you'd think they could have had some engineers check for this sort of thing. It's structural engineering 101.

[Wuzak]

This is the 2013 V8Supercar chassis for comparison.

http://media.speedca...otf-chassis.jpg

[Greg Locock]

Structurally, this is the worst way to locate a gusset when reinforcing an orthogonal tube/tube joint. The purpose of this gusset is to reduce the local weld joint stress due to bending. By locating the gusset on the center of the tube walls, the gusset is transferring loads to the tubes at their weakest point. The gusset should be located at the outer (tangent) edges of the tubes, and welded along their center lines.

Unless it is also there to initiate plastic deformation of the tube.

Long shot!

[Wolf]

Greg, I wouldn't go as far to presume that- as Bigleagueslider points out, it may be inferior way of welding gussets, but I wouldn't say it could be that problematic. One can find this way of welding gussets and various attachment points even in Bruhn's "Analysis and Design of Flight Vehicle Structures", and am *ass*uming that if it was that problematic, the aircraft industry would have picked up on it even back then.

What about this, then? Gussets are as they should be, but what about disturbing lack of triangulation in the area where suspension pick up points are?

[Magoo]

Here's a comment on the design of the roll cage shown in the picture. If you look closely at the upper right hand side of the picture, you'll see a small triangular plate gusset welded at the center of two tube walls. Structurally, this is the worst way to locate a gusset when reinforcing an orthogonal tube/tube joint. The purpose of this gusset is to reduce the local weld joint stress due to bending. By locating the gusset on the center of the tube walls, the gusset is transferring loads to the tubes at their weakest point. The gusset should be located at the outer (tangent) edges of the tubes, and welded along their center lines.

With all of the money available to NASCAR you'd think they could have had some engineers check for this sort of thing. It's structural engineering 101.

They're also too short (barely one tube diameter) to be corner gussets, so I am going to presume they aren't corner gussets.

Note you don't see any corner gussets on the rest of the chassis, which is as I would expect.

[Magoo]

Why not i say.

I find it a little bit strange that the Earnhard bar is not connected to the lower section going underneath it.

Its like it has been given room to bend.

Perhaps it pushes the engine down and under during a crash?

The first photo is a bit of an illusion. Actually, the Eanhardt bar is nearly a foot above the dash bar. The third photo shows their relationship more realistically.




...tubing + photography can produce some interesting illusions, I have found over the years. For example, count the exhaust pipes on this prototype Cadillac V12 engine.

[Fat Boy]

...tubing + photography can produce some interesting illusions, I have found over the years. For example, count the exhaust pipes on this prototype Cadillac V12 engine.

That's the last time we buy an exhaust from Escher Fabrication.

[gruntguru]

This is the 2013 V8Supercar chassis for comparison.

http://media.speedca...otf-chassis.jpg

Note the lack of "bent" tubes compared to the Nascar frame.

[gruntguru]

...tubing + photography can produce some interesting illusions, I have found over the years. For example, count the exhaust pipes on this prototype Cadillac V12 engine.

Yes I remember looking at that when you posted it earlier and thinking WTF thats a V10! Experience prompted me to take a closer look before I picked a fight!

[Kelpiecross]

Note the lack of "bent" tubes compared to the Nascar frame.

Which is what I thought too. Does the Supercar rely at all on its existing unit-constructed body at all? How do they get this spaceframe into the body? Are the body panels just hung on this frame?

[bigleagueslider]

Greg, I wouldn't go as far to presume that- as Bigleagueslider points out, it may be inferior way of welding gussets, but I wouldn't say it could be that problematic. One can find this way of welding gussets and various attachment points even in Bruhn's "Analysis and Design of Flight Vehicle Structures", and am *ass*uming that if it was that problematic, the aircraft industry would have picked up on it even back then.

What about this, then? Gussets are as they should be, but what about disturbing lack of triangulation in the area where suspension pick up points are?

Wolf,

I'm disappointed that you would stoop to taking a classic technical work like Bruhn's out of context simply in an effort to persevere in a technical disagreement! If there is anything that design texts like Bruhn's or MIL-HDBK-5 teach us, it's that weld joints should always be configured such that the stress in the weld joint is equalized. This means that welded tubular space frame structures are triangulated as well as possible. However, since reality usually conflicts with theory, welded tubular space frames usually require some offset at the joint nodal points to facilitate welding. And any offset of attachment points for suspension, etc. from these nodes usually requires some sort of gusset to accommodate bending on the joint.

The only suitable example of a plate gusset being located on the center of a tube joint would be where the plate gusset extends through, and is welded to, both walls of the tubes.

Regards,
slider

[Wolf]

Bigleagueslider- I'm sorry you think I was misusing Bruhn reference, but I'm more surprised that you think we're in technical disagreement of a sort... We agree that that is better way of welding gussets, I was merely pointing out that I do not think it was that bad so that it would be used to further plastic deformation of the joint as Greg speculated. Bruhn was referenced to show it was common practice to use such gussets in the past (hell, my uni textbook in '90ies recommended the same way of attaching gussets), and that if it was that bad, it would've been noticed.

[Greg Locock]

Which is what I thought too. Does the Supercar rely at all on its existing unit-constructed body at all? How do they get this spaceframe into the body? Are the body panels just hung on this frame?

V8 Supercars are a silhouette series, the outer panels are pretty much cosmetic. 20 years ago the bodies were actually based on the production shells. Not now.

[Wuzak]

Which is what I thought too. Does the Supercar rely at all on its existing unit-constructed body at all? How do they get this spaceframe into the body? Are the body panels just hung on this frame?

V8 Supercars are a silhouette series, the outer panels are pretty much cosmetic. 20 years ago the bodies were actually based on the production shells. Not now.

In the current cars I believe the tube chassis is built inside the existing body. The rear floor area is completely cut away to fit the rear suspension arms, etc.

http://www.hostingby...s/3/1294043.jpg

Next year's cars with the standard chassis will just have panels hung on the outside of the frame.

http://resources1.ne...otf-chassis.jpg

The 2013 Falcon
http://cdn-0.motorsp...90/s1_12410.jpg

Note that V8Supercars have been using rules called Project Blueprint for several years, the aim of which is to equalise the marques. As part of this the cars run the same wheelbase, which is based on one of teh earlier model cars. Both the current Holden and Ford have to be shortened to meet this spec.

Also, for 2013 Nissan are joining the sport. They will be using a 5l quad cam 4v V8

http://resources1.ne...-v8-motor-2.jpg

It will be restricted to 7500rpm and 10:1 compression ratio, the same as the Ford and Chevy pushrod OHV engines currently being used.

[Magoo]

In the current cars I believe the tube chassis is built inside the existing body. The rear floor area is completely cut away to fit the rear suspension arms, etc.

That's how they looked to me when I was over there eyeballing them in the 1999-2005 timeframe. Expensive way to build a race car, like a ship in a bottle. Then when you crash it you will probably get to throw it away.

On the other hand, this construction does provide the production car look and sensibility.

[Wuzak]

That's how they looked to me when I was over there eyeballing them in the 1999-2005 timeframe. Expensive way to build a race car, like a ship in a bottle. Then when you crash it you will probably get to throw it away.

Part of the reason for the Car of the Future. The rolling chassis for the 2013 car will cost little more than half that of the current cars. Well, that is the plan!

As Greg says, they probably started out as production chassis with a rol cage and some strengthening, but evolution led them for even more use of the tube frame as part of the chassis.

On the other hand, this construction does provide the production car look and sensibility.

I believe some of the body panels that will be attached to the standard chassis will be based on production. Such as the sides and roof. Others, such as the front guards, will be made of plastic.

Edited by Wuzak, 14 September 2012 - 05:02.

[Magoo]

Here's a little story with nice, big, clear photos showing the rules-mandated changes to the NASCAR roll cage for 2013.

MCG exclusive! 2013 NASCAR roll cage | Mac's Motor City Garage

In part the idea is to generate thought and discussion about roll cage design, materials, and fabrication, not necessarily just for NASCAR but for everything using the same sort of tubular construction.

Thanks to Kevin Bryde of Earnhardt Ganassi Racing for providing the photos and other material. Every day I am a little more astounded to learn who is reading MCG. It's a sort of a who's who of the auto world. I will redouble our efforts to deserve it.

This is sort of interesting... for some reason this story has generated considerable traffic on various sim racing forums. That's not my world, so it beats me. Maybe one of the sim racers around here (Ross?) could explain why they would even care about a detail roll cage change. The game's visuals?

[munks]

This is sort of interesting... for some reason this story has generated considerable traffic on various sim racing forums. That's not my world, so it beats me. Maybe one of the sim racers around here (Ross?) could explain why they would even care about a detail roll cage change. The game's visuals?

Most likely. Detailed, accurate cockpits are in high demand.

[bigleagueslider]

Bigleagueslider- I'm sorry you think I was misusing Bruhn reference, but I'm more surprised that you think we're in technical disagreement of a sort... We agree that that is better way of welding gussets, I was merely pointing out that I do not think it was that bad so that it would be used to further plastic deformation of the joint as Greg speculated. Bruhn was referenced to show it was common practice to use such gussets in the past (hell, my uni textbook in '90ies recommended the same way of attaching gussets), and that if it was that bad, it would've been noticed.

Wolf,

I was just having a bit of fun. To be honest, I am impressed that you even referenced Bruhn in a post about NASCAR welded tube roll structures. There's also no real disagreement between us. I understand that this particular example is NASCAR, and not NASA.

I haven't designed many welded tube structures for race cars. But I have designed some welded tube structures for aircraft tooling and GSE. And I guarantee that no aerospace industry stress analyst would sign-off on a structure using a gusset like that, even for non flight critical tooling or GSE applications. My experience just gives me a different perspective on what is acceptable practice for such design situations.

Best regards,
slider

[Lee Nicolle]

V8 Supercars are a silhouette series, the outer panels are pretty much cosmetic. 20 years ago the bodies were actually based on the production shells. Not now.

Not even a silhouette. They shells are cut and sectioned for so called parity. The shells are assembled around the rollcage, have been for many years. Any similarity to a road car is purely coincidental. The tailights and mirrors are standard,, I think!

[Greg Locock]

here's next years http://www.speedcafe...r-taking-shape/

[Magoo]

Here's a little story with nice, big, clear photos showing the rules-mandated changes to the NASCAR roll cage for 2013.

MCG exclusive! 2013 NASCAR roll cage | Mac's Motor City Garage

In part the idea is to generate thought and discussion about roll cage design, materials, and fabrication, not necessarily just for NASCAR but for everything using the same sort of tubular construction.

Thanks to Kevin Bryde of Earnhardt Ganassi Racing for providing the photos and other material. Every day I am a little more astounded to learn who is reading MCG. It's a sort of a who's who of the auto world. I will redouble our efforts to deserve it.

If you haven't been following it, a pretty decent discussion has developed in the reply section... including MIG vs. TIG, mild steel vs. chrome moly, and so on. You know. Always good to get some different perspectives.





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