GT40s.com - View Single Post

Manny · 07-26-08, 05:44 PM

It was a different time and place and the expectations were that if you crashed heavily you paid dearly for it.

Today a track car is expected to provide sufficient protection that in most cases you won't get killed if you crash it. It isn't totally about weight, but a track car designed today is going to have a full cage and protection for the drivers feet (as well as some crush structure ahead of that). This is pretty much as it should have been then, but frankly we weren't smart enought to realize it at the time. A good friend of mine designed the Fabcar and he was amazed at how unsafe a 917 was. He got to look one over carefully and in his words it was a "death trap". Like I said, it was a different place and time.....

What is interesting is that if you design a nice cage that provides sufficient protection for the driver and passenger, you have plenty of structural strenght and stiffness and all you need to do at that point is skin it with light sheet and that IS your track car. You need to hang suspension on it and get the frame back to pick up the rear suspension, and that can be much like it was in the past. If you look at what it is going to cost you in weight do it that way as compared to the very light space frame structures of a 917, the impact is probaly on the order of 100-150 pounds. That comes from an estimate of about 90 feet of tubing that is required for the cage (at about twice the weight of the uncaged car), compared to the same tubing that would be required for a 917 space frame (assuming both were closed cars with a steel windshield hoop). So really the weight impact isn't a big deal. And it might be less than that if you realize that you don't need as much triangulation (the skin does that just fine if the edge tubing is as big as it needs to be for the cage) in the caged car.

With the need for a cage in a track car tho, I don't think that a light sheet monoque (like in a T70) makes much sense anymore. Just build a cage, skin it and go to town.

07-26-08, 05:44 PM	#38 (permalink)
Manny Solofast Rookie Join Date: Oct 2007 Location: Indianapolis Posts: 21 Rep Power: 2	Re: Why was the 917 so revolutionary? It was a different time and place and the expectations were that if you crashed heavily you paid dearly for it. Today a track car is expected to provide sufficient protection that in most cases you won't get killed if you crash it. It isn't totally about weight, but a track car designed today is going to have a full cage and protection for the drivers feet (as well as some crush structure ahead of that). This is pretty much as it should have been then, but frankly we weren't smart enought to realize it at the time. A good friend of mine designed the Fabcar and he was amazed at how unsafe a 917 was. He got to look one over carefully and in his words it was a "death trap". Like I said, it was a different place and time..... What is interesting is that if you design a nice cage that provides sufficient protection for the driver and passenger, you have plenty of structural strenght and stiffness and all you need to do at that point is skin it with light sheet and that IS your track car. You need to hang suspension on it and get the frame back to pick up the rear suspension, and that can be much like it was in the past. If you look at what it is going to cost you in weight do it that way as compared to the very light space frame structures of a 917, the impact is probaly on the order of 100-150 pounds. That comes from an estimate of about 90 feet of tubing that is required for the cage (at about twice the weight of the uncaged car), compared to the same tubing that would be required for a 917 space frame (assuming both were closed cars with a steel windshield hoop). So really the weight impact isn't a big deal. And it might be less than that if you realize that you don't need as much triangulation (the skin does that just fine if the edge tubing is as big as it needs to be for the cage) in the caged car. With the need for a cage in a track car tho, I don't think that a light sheet monoque (like in a T70) makes much sense anymore. Just build a cage, skin it and go to town.