Welded or removable engine braces
Discussion
I have the "opportunity" to rework the frame braces that go from the top of the firewall roll bar diagonally back down to the engine bay as I start on my build. I went to a shop to have the work done, and when discussing options they said that I really need to weld that bar in, and that it is 'unsafe' to have it removable. I have tried to tell them that the standard spec is for a removable bar, and that is how most of these cars are built. They have gone so far as to call me an idiot for suggesting to go this route. I have decided not to use them, as we appear to have a personality conflict, and am looking for someone else to do the work, but it has got me to thinking, what are the pros & cons of welded vs. removable?
Anyone with removable bars that wishes they had gone welded?
Anyone with welded bars that wishes they had gone removable?
How much do welded bars get in the way during the build?
How important is it be able to install/remove the engine without removing the headers (I can imagine that the engine may be going in/out a number of times to check clearances, etc. during the build)?
How much additional frame stiffness is gained with welded bars? (Qualitative assessment is adequate i.e. not perceptible/modest/lots)
My use will be mostly for the street, and I am pretty sure that a removable brace will suite me just fine from a stiffness/performance perspective, but I wouldn't mind going welded as it is easier to install & probably is better structurally. I just want to know what I'd be committing myself to by going this route. Will I be cursing it constantly as I struggle to work around it? Should I use a slightly bent bar that clears the headers to make engine installation easier? If going welded, my instinct is to take the attach point back to the frame just in front of the A-Arm attach (where the removable brace attaches), but it looks like the factory does their welded bars forward of that, near back of the fuel tank. Is there a good reason to go there instead of further back?
Thanks for any advise or insight you can offer,
-Sky
Anyone with removable bars that wishes they had gone welded?
Anyone with welded bars that wishes they had gone removable?
How much do welded bars get in the way during the build?
How important is it be able to install/remove the engine without removing the headers (I can imagine that the engine may be going in/out a number of times to check clearances, etc. during the build)?
How much additional frame stiffness is gained with welded bars? (Qualitative assessment is adequate i.e. not perceptible/modest/lots)
My use will be mostly for the street, and I am pretty sure that a removable brace will suite me just fine from a stiffness/performance perspective, but I wouldn't mind going welded as it is easier to install & probably is better structurally. I just want to know what I'd be committing myself to by going this route. Will I be cursing it constantly as I struggle to work around it? Should I use a slightly bent bar that clears the headers to make engine installation easier? If going welded, my instinct is to take the attach point back to the frame just in front of the A-Arm attach (where the removable brace attaches), but it looks like the factory does their welded bars forward of that, near back of the fuel tank. Is there a good reason to go there instead of further back?
Thanks for any advise or insight you can offer,
-Sky
The FIA chassis does have this bar welded in but also uses a different spec for the tubing.
The bolt in bar has been extremely helpful on many occasions while constructing the car and servicing it thereafter.
The chassis is a great foundation for a road and track car and it has plenty of torsional rigidity. Use it as is. Let that shop build their own car.
It's funny you should say that Ken. Those were pretty much the last words that I said to them when I picked the car up.
One of the compelling reasons to weld them in now, is that it would be easier than making the removable bar setup. This used to be an FIA cage, so used to have the welded bars, but those have been removed, so I am starting from scratch. If I am going to be fighting with them throughout the build though, then I'll gladly go the extra effort of making up the removable style.
As to the strength of a bar with a bend in it - I think I understand, and agree that for a given tube, a bend will reduce its strength along a given axis, but the factory FIA cage brace has a pretty dramatic bend - about 45° in fact (Take a look at FIA7.JPG in the build manual)- but is still probably better than nothing(?) That is one of the reasons I was going to pull my bar back to the A-Arm, so that I could keep it much straighter, but may still need a little bend to clear the headers. (Probably need a little bend even in removable bar in fact because of header clearance.) I understand that all of car design is about balancing compromises though.
One of the compelling reasons to weld them in now, is that it would be easier than making the removable bar setup. This used to be an FIA cage, so used to have the welded bars, but those have been removed, so I am starting from scratch. If I am going to be fighting with them throughout the build though, then I'll gladly go the extra effort of making up the removable style.
As to the strength of a bar with a bend in it - I think I understand, and agree that for a given tube, a bend will reduce its strength along a given axis, but the factory FIA cage brace has a pretty dramatic bend - about 45° in fact (Take a look at FIA7.JPG in the build manual)- but is still probably better than nothing(?) That is one of the reasons I was going to pull my bar back to the A-Arm, so that I could keep it much straighter, but may still need a little bend to clear the headers. (Probably need a little bend even in removable bar in fact because of header clearance.) I understand that all of car design is about balancing compromises though.
it can get complicated very quickly, i have sat in the chassis that Neil R is developing in this thread and speek to him on a regular basis so have an idea of what some of his issues are.
http://forums.autosport.com/index.php?showtopic=15...
there is a good hand book to some joint design info here (thanks to Neil for pointing me to this one)
http://www.tatasteeleurope.com/file_source/StaticF...
Ryan
http://forums.autosport.com/index.php?showtopic=15...
there is a good hand book to some joint design info here (thanks to Neil for pointing me to this one)
http://www.tatasteeleurope.com/file_source/StaticF...
Ryan
As long as the top bolted mount is not in single sheer then I see no reason why it would be bad . The normal top mount has a spigot and mating lug so that the sheer stress is removed from the bolt and that's fine, the bottom mount is normaly in double sheer as its though 2 plates. Just best to stay away from single sheer on any chassis or suspension loaded bolts .
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