SGT/SC#0471 Posted April 9, 2009 Report Share Posted April 9, 2009 I don't have a supercharger and I was looking to buy the Shelby aluminum strut brace just for looks, but I needed to know for sure that the 6061 aluminum weldment was post-weld heat treated. 6061-T6 aluminum will lose it temper around the heat affected zone when welded and therefore needs to go thru the heat treat process to regain its strength. So I asked SPP and I got this response from Scott Drake: "Yes after welding the part does go through a final precipitation heat treatment to regain the strength of the T6 temper of the material after welding. Not really necessary on this part, but we did it anyways for consistency. The engine bays on these cars have been tested and there is little to no deflection on the strut towers to warrant the need for this part even in extreme driving. This info was given to us By Ford Racing SVT from testing they have done on body safety structure. " They say they regain the T6 temper after heat treatment but they would only know that if they took a sample around the weld area and did pull-tests on it. My guess is they got at least T4 which is good enough for this part. However, the key thing is they really don't believe a strut brace is actually of any use! Very interesting! Of course, I checked and the FR500S has strut tower brace so go figure?? interesting... Link to comment Share on other sites More sharing options...
SGT/SC#0471 Posted April 9, 2009 Report Share Posted April 9, 2009 McCoy, Perhaps I am misunderstanding what you are trying to say here. So please clarify for me. We'll use a 3 foot long, one-inch diameter, solid 4130 steel rod as an example. Imagine I were to lay the two ends of that solid steel rod upon supports and then place a 200 pound load in the center of that rod after which I would measure its total deflection (bend). After taking that measurement I then removed the rod and drilled a 3/4 inch hole through it lengthwise, leaving me with a hollow tube that had a wall thickness of 1/8" all the way around. Are you contending that if I laid that hollow steel rod upon the same supports and then placed the same 200 pound load in its center that the hollow rod would deflect less than the solid rod? Such an experiment is quite easy to conduct, given the right equipment. While the hollow tube will probably have a better strength to weight ratio, it is nowhere near as resistant to bending as the solid rod which is much heavier. A real world example would be the steel tubes protruding from the ground of many parking lots that function as crash barriers to keep expensive items like gasoline pumps and propane tanks from being hit by cars. After these hollow steel tubes are sunk into the ground, they are easily bent and damaged UNTIL they are filled with cement. Once filled they are a ton stronger and far more resistant to bending. Now that I'm out of the car business I build service stations for a living and utilize a lot of these crash barriers. In the aircraft building business we are concerned primarily with strength to weight ratios. Here, a triangulated hollow structure provides the best strength/weight ratio. But where outright resistance to deflection is required in a constrained space such as in the center section of an aircraft wing or in our project here, sandwiched between the tight spacing of the mustang hood and our supercharger components, a solid structure will provide us with the best rigidly though it will be heavier than a hollow structure. Chip Chip I read that on the internet too, I guess I am wrong. However, I had always been told that tube was stronger than solid from fabricators that I learned from, do not know why. It seems stronger when you are working with it too...no idea. I do know that aluminum work hardens and cracks. But am by no means an engineer, in fact I hate math unless it involves counting money...haha! I would perfer a collapsed steel tube to a 1/4 inch thick aluminum bar but maybe the aluminum would be beter? I am getting 2 large steel sculptures out of my shop today and so I may be able to get my car into my shop to take a little look at the idea.... Maybe the old guys always said that beacause in practice making something solid did not warrant the marginal gain in bending strength over the weight of the tube. Weight for weight the tube is stronger than solid. In testing the soild stock may be stronger, but I have yet to see any solid bar motorcycle or car frames. Anyway seems like you are right about that and man I guess I learn something every day. Link to comment Share on other sites More sharing options...
blueshawk Posted April 9, 2009 Report Share Posted April 9, 2009 Chip I read that on the internet too, I guess I am wrong. However, I had always been told that tube was stronger than solid from fabricators that I learned from, do not know why. It seems stronger when you are working with it too...no idea. I do know that aluminum work hardens and cracks. But am by no means an engineer, in fact I hate math unless it involves counting money...haha! I would perfer a collapsed steel tube to a 1/4 inch thick aluminum bar but maybe the aluminum would be beter? I am getting 2 large steel sculptures out of my shop today and so I may be able to get my car into my shop to take a little look at the idea.... Maybe the old guys always said that beacause in practice making something solid did not warrant the marginal gain in bending strength over the weight of the tube. Weight for weight the tube is stronger than solid. In testing the soild stock may be stronger, but I have yet to see any solid bar motorcycle or car frames. Anyway seems like you are right about that and man I guess I learn something every day. The pros of using aluminum vs. steel depends on the application. The yeild strength of tempered aluminum can be the same as mild steel. Also, the weight of aluminum is about 1/3 of steel. However, the stiffness of aluminum is also 1/3 of steel. So if you are looking to replace the steel strut with an aluminum strut, you need to account for more aluminum to make-up for the reduced stiffness. The strength is not as much of a consideration since it is unlikely that you'll break a strut brace because you want the strut so stiff that the towers won't flex. Such stiffness has inherent strength. When you look at the Shelby strut brace it is a hunk of aluminum compared to the steel tubes. I just think it looks more impressive. I plan to buy one this weekend and swap out the SGT brace. I'll let you know if it "feels" like there is any difference in weight. Link to comment Share on other sites More sharing options...
HORSBYT Posted April 9, 2009 Report Share Posted April 9, 2009 I saw this design at a recent car show and found it to be pretty interesting... Link to comment Share on other sites More sharing options...
blueshawk Posted April 9, 2009 Report Share Posted April 9, 2009 I saw this design at a recent car show and found it to be pretty interesting... You know, the stock SGT strut brace is only supported by the two inner bolts on each strut tower. The brace in the pic above has a hinge joint at each end. Therefore neither brace can support a moment at either end. Therefore, they behave more like a rod connection than a beam connection. The Shelby brace actually has a substantial connection to the strut towers using all four bolts opn each end and behaves more like a beam which resists tension/compression and "bending". So the connections to the strut towers are also important in how the brace actually stiffens the body. Keep in mind the pushing/pulling and twisting exerted on the brace will be imparted by the motion of the strut towers. Link to comment Share on other sites More sharing options...
HORSBYT Posted May 7, 2009 Report Share Posted May 7, 2009 prototype 1 Link to comment Share on other sites More sharing options...
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