What is the beauty's name?
GT40 side impact protection
- Thread starter Brisc
- Start date
What is the beauty's name?
Brisc,
Scott was echoing what Andy from Tornado feels about stiffeners on the side sill tube members. They feel that if you put stiffeners between the outer front-rear sill tubes, you will transmit forces to the inner frame rail which could push the inner side rail onto the driver or passenger if there were a side impact. Evidently this has happened.
I chose to do this on my build. See photo number 5 in post #54 in my build log.
http://www.gt40s.com/forum/gt40-build-logs/42186-tornado-gt40-texas-3.html
I see three reasons to do this. First, I wanted support for the side sill panels when you stepped or sat on them to get in and out of the car. Without the tubes, the panels were deflecting too much. Second, I think it will increase the torsional stiffness since you lose most of your stiffness in the cockpit area of a tube frame. This is more significant since there are no tubes across the top of the cockpit in any direction.
The third and most significant reason is the vulnerability of the fuel tanks to side impact. The only protection to the fuel tank for a side impact is the one tube at the top outside of the side sill. I placed two tubes from the outer for-aft tube to the inner tube. This probably more than doubles the lateral stiffness from the middle of the outer tube for deflections inward. Therefore, the outer tube will not deform as much with a side impact and hence will protect the fuel tank better. If the outer tube deflects too much in a side impact, it will burst the fuel tank and be a huge risk of fire. With the added stiffness, I think the fuel tank is better protected. I think that if I didn't add these tubes, then it would be almost certainly damage the tank in a side impact.
In retrospect. I should have triangulated the lateral tubes to transfer lateral loads more to the front and rear nodes of the frame. Then both Andy and I would be happy, or happier.
-Bob Woods
Scott was echoing what Andy from Tornado feels about stiffeners on the side sill tube members. They feel that if you put stiffeners between the outer front-rear sill tubes, you will transmit forces to the inner frame rail which could push the inner side rail onto the driver or passenger if there were a side impact. Evidently this has happened.
I chose to do this on my build. See photo number 5 in post #54 in my build log.
http://www.gt40s.com/forum/gt40-build-logs/42186-tornado-gt40-texas-3.html
I see three reasons to do this. First, I wanted support for the side sill panels when you stepped or sat on them to get in and out of the car. Without the tubes, the panels were deflecting too much. Second, I think it will increase the torsional stiffness since you lose most of your stiffness in the cockpit area of a tube frame. This is more significant since there are no tubes across the top of the cockpit in any direction.
The third and most significant reason is the vulnerability of the fuel tanks to side impact. The only protection to the fuel tank for a side impact is the one tube at the top outside of the side sill. I placed two tubes from the outer for-aft tube to the inner tube. This probably more than doubles the lateral stiffness from the middle of the outer tube for deflections inward. Therefore, the outer tube will not deform as much with a side impact and hence will protect the fuel tank better. If the outer tube deflects too much in a side impact, it will burst the fuel tank and be a huge risk of fire. With the added stiffness, I think the fuel tank is better protected. I think that if I didn't add these tubes, then it would be almost certainly damage the tank in a side impact.
In retrospect. I should have triangulated the lateral tubes to transfer lateral loads more to the front and rear nodes of the frame. Then both Andy and I would be happy, or happier.
-Bob Woods
Hi Bob,
thanks for your reply. I have looked at your build in detail and do not think that the triangulated solution, as I understand it, is any better. I am unsure if I do properly understand the situation, but it looks like you are saying that instead of the two 90 degree cross members you want two longer members to the forward and rearward points of the frame. Well these would be much longer tubes so the solution would be much worse.
Tubular structures with thin-walled members fail due to buckling of the longest compression-loaded members.
In your case, you have divided the structure into almost perfect squares which is the near-perfect solution to the problem. The compression loaded members are only, say 40cm long. If you were to triangulate, the triangulated members would be much longer and therefore without function (triangulation only works if you generate triangles with equal length sides). The triangulated members would be almost twice as long as your short cross members and they would sit at an angle that is very small, say about 20 degrees, rather than the 90 degrees in your solution. That means that the entire structure would buckle much, much earlier. The compression load on the long, triangulated tubes would be 1/sin(20deg) = 3 times higher for the same side impact load. The buckling resistance of the triangulated tubes could be up to 2^2 = 4 times lower because they are twice as long. Overall, the triangulated structure could buckle 4*3=12 times earlier than your solution. The inner tube will then not be pushed into the passenger through the cross tubes that exist in your solution, correct, but by the tree itself. Overall, there is a chance that your solution will be 12 times stronger. Of course, these quick calculations are all for linear approximations and the difference in real life might not be as high.
The best way to design that structure is to reduce the lengths between the nodes and generating squares is sometimes better than generating triangles that are skewed so much that they are no longer equal-length triangles. You could divide your three squares introducing additional members that would sit at angles of about 45 degrees. Then you would end up with only triangles that have roughly equal lengths and even more margin.
Still not sure if I understood the proposed alternative to what you have done properly though. Maybe a sketch would help.
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Brisc,
I agree with what you said. Perhaps I should have said two V's might be better. What I was trying to accomplish is to put some load into the rear bulkhead that goes across the cockpit and hence is very stiff laterally.
In either case, it appears that you agree with the concept of transferring some of the load on the outside tube to the inside tube to stiffen the sill structure to protect the tanks.
-Bob Woods
I agree with what you said. Perhaps I should have said two V's might be better. What I was trying to accomplish is to put some load into the rear bulkhead that goes across the cockpit and hence is very stiff laterally.
In either case, it appears that you agree with the concept of transferring some of the load on the outside tube to the inside tube to stiffen the sill structure to protect the tanks.
-Bob Woods
For the space frame cars another thought would be to fold up a sheet diaphragm along the lines of the white drawing Ive added to Bobs chassis pic. This would spread a side impact force over the whole length of the inner sill tube as well as adding additional support for the alloy sill/tank cover panels.
Safer option is to 'steer' clear of any wayward trees, power poles that appear hell bent on colliding with you!
Safer option is to 'steer' clear of any wayward trees, power poles that appear hell bent on colliding with you!
Attachments
any chance you can post some more details on this car?
Ian Anderson
Lifetime Supporter
The new Ford GT is about 15% larger in all dimensions than the GT40 and is a much better size. I somewhat do not like the shape as much though. I wish there would be a GT40 kit that is simply 15-20% larger, with all proportions kept the same, tires scaled properly, etc.
There is
It was built by DAX in the early 1990's
I have one and a few members on here likewise have them
Rare as hen's teeth as only about 35 were produced
Ian
Mike
Lifetime Supporter
Safer option is to 'steer' clear of any wayward trees, power poles that appear hell bent on colliding with you!
For the life of me I don't understand why the majority of people who have or want a GT40 don't just get a new Corvette. They have the comfort, the cup holders, the backup cameras, the A/C, the visibility, the crash protection, and dozens of other features that people want to fit to a 1960s race car. Now someone wants a GT40 scaled up by 25% so they can get in and out. So much silliness...
Is it probably because people want to build their car from a kit? Is it because people want to create something unique with their own blood, sweat and tears? Ever thought about that? Hey: this is a kit car forum, sure you have understood that after more than 1600 posts! Last time I checked with Chevy I couldn't get the Corvette as a kit car, and even if they would sell it as a kit car, I would not get one because chances are that you have got one as well! So much silliness...
Pat
Supporter
Who did you check with at Chevy that last time you inquired?
They must not be familiar with Art Morrison, Art Morrison Enterprises - 1953-1962 GT Sport Corvette Information, Mongoose Mortosports, www.mongoosems.com or Advanced Automotive, AAT Cars ????
You can find plenty more here: Corvette Kits
I bet one of the forum Superformance dealers would be more than happy to line you up with one of their stunning Grand Sport replicas. Superformance | Corvette Grand Sport
The fact that you've apparently never seen or recognized one is a testament to their rarity.
News flash, they do make Corvette kit cars and you completely missed Mike's excellent point.
They must not be familiar with Art Morrison, Art Morrison Enterprises - 1953-1962 GT Sport Corvette Information, Mongoose Mortosports, www.mongoosems.com or Advanced Automotive, AAT Cars ????
You can find plenty more here: Corvette Kits
I bet one of the forum Superformance dealers would be more than happy to line you up with one of their stunning Grand Sport replicas. Superformance | Corvette Grand Sport
The fact that you've apparently never seen or recognized one is a testament to their rarity.
News flash, they do make Corvette kit cars and you completely missed Mike's excellent point.
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I didn't realize the Bricklin was Ford powered. I do recall people getting really wet in the rain while waiting for the hydraulic doors to lift
Hi there. Great to see that you find a few nice words to support your friend Mike, he will be happy and may buy you an ice cream next time you meet to cuddle together!
With respect to your post: you have missed the point entirely and taken things out of context. Mike has meant and written "new Corvette" instead of kit car. Please scroll up and read again. If you cannot read it, turn around the screen and try again (may help, or may not!). He also wrote "majority of people who have or want a GT40" implying that most folks on this forum must be idiots in his view just because they think about safety or other features to add to these modern kit cars.
For me (and I speak only of me), you have proven that you understand the issue I was discussing in this topic as little as Mike or Scott.
Thank you very much for the link to the C1, C2 and C3 Corvette kit cars. They are great!
Pat
Supporter
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Chevrolet did sell 13 or 15 (I forget the actual number) kits of the C5 Corvette called C5R. The race team I worked for bought 3 of them, built two and sold one. They were sold for Racing use only, had no VINs and were not available to the general public.
Okay that said - let's just call that done..
There are many reasons to work towrd some sort of side impact protection. Mine was not necessarily to stop a Soccer Mom in a Ford Excursion flying through an intersection at 50 MPH to broadside me, but it will at least deflect a lighter vehicle in an incidental highway or street accident. It also provides a much better and more solid mount for the latch mechanism than just bolting it to unsupported fiberglass.
I applaud any efforts to make these cars a bit more safe..
Oh and the Bricklin owned by one of my neighbors many years ago had a 351w engine. It was no GT40, but had a bit more snap than many Corvettes of the time.
Okay that said - let's just call that done..
There are many reasons to work towrd some sort of side impact protection. Mine was not necessarily to stop a Soccer Mom in a Ford Excursion flying through an intersection at 50 MPH to broadside me, but it will at least deflect a lighter vehicle in an incidental highway or street accident. It also provides a much better and more solid mount for the latch mechanism than just bolting it to unsupported fiberglass.
I applaud any efforts to make these cars a bit more safe..
Oh and the Bricklin owned by one of my neighbors many years ago had a 351w engine. It was no GT40, but had a bit more snap than many Corvettes of the time.
