Strut brace Design
Discussion
My friend is an engineer, and after a lot of cajoling was talked into making three of us strut braces (for our volvo 480's)
Made from schedule 60 1 inch NB tube, with M20 adjusters and 5mm end plates, they are quite possibly somewhat over engineered. They also should be somewhat more use than some that you can buy, seeming to be made out of mickey mouse metal.
These are during construction as you can see, we went for strength rather than lightness....:
Don't have a fitted and painted pic yet, although mines been on for a week...
Now, this is one designed for fitment in an audi of some description:
I would have thought that the cross bolting of the bar to the end plates, rather than welding, would create a pivot point, making it somewhat less effective?
I understand that the length of the bar can't change so the top of the strut towers shouldnt get closer/farther from each other, but doesn't this assume equal loading of the suspension left to right?
Doesn't it still allow up/down movement in relation to each other, and therefore they can get closer to each other - what effect does allowing (or restricting) this movement potentially have on handling?
NB I wasn't expecting any huge change, so I wasn't disappointed when I noticed little to none, but the roads are very greasy, perhaps in the summer I'll know if it was worth the hassle!
Made from schedule 60 1 inch NB tube, with M20 adjusters and 5mm end plates, they are quite possibly somewhat over engineered. They also should be somewhat more use than some that you can buy, seeming to be made out of mickey mouse metal.
These are during construction as you can see, we went for strength rather than lightness....:
Don't have a fitted and painted pic yet, although mines been on for a week...
Now, this is one designed for fitment in an audi of some description:
I would have thought that the cross bolting of the bar to the end plates, rather than welding, would create a pivot point, making it somewhat less effective?
I understand that the length of the bar can't change so the top of the strut towers shouldnt get closer/farther from each other, but doesn't this assume equal loading of the suspension left to right?
Doesn't it still allow up/down movement in relation to each other, and therefore they can get closer to each other - what effect does allowing (or restricting) this movement potentially have on handling?
NB I wasn't expecting any huge change, so I wasn't disappointed when I noticed little to none, but the roads are very greasy, perhaps in the summer I'll know if it was worth the hassle!
It's true the bolted joint on the "proper" one won't be that stiff but neither will yours be just near the two studs where it bolts on to the strut top. If you unbolted one end and lifted it, the Audi one would abviously rotate without contributing any appreciable stiffness but I think if you tried the same exercise with yours, it would probably not be much different. You'd (I guess) be able to lift the un-bolted end by a good half an inch or so by hand before feeling any real resistance - and if the shell moves that much there will be a lot more load on it than you can apply by hand! If you had a third fixing through the suspension turret as close as possible to where the round bar welds on, it would make things a lot better.
That said, this isn't really the plane in which the brace needs to work. They are usually loaded (pretty much) as close as possible to being in pure compression to stop the tops of the struts getting closer together. If the centreline of the bolt on the Audi one lay on an imaginary straight line across the car joining the tops of the two damper rods at the point where they emerged from the steel turret, there would be no tendency for any rotation about its centreline. In fact, it might actually be desirable to have a joint that allowed rotation in this plane to reduce the risk of fatigue failure to either the strut brace or the turret tops!
If you really want to stiffen yours in the vertical plane, another thing you could try would be to add vertical webs from the centreline of the tube on either side of it extending along the 5mm plates and get them as close as possible to the centrelines of the two studs (whilst still being able to get the nuts on)!
That said, this isn't really the plane in which the brace needs to work. They are usually loaded (pretty much) as close as possible to being in pure compression to stop the tops of the struts getting closer together. If the centreline of the bolt on the Audi one lay on an imaginary straight line across the car joining the tops of the two damper rods at the point where they emerged from the steel turret, there would be no tendency for any rotation about its centreline. In fact, it might actually be desirable to have a joint that allowed rotation in this plane to reduce the risk of fatigue failure to either the strut brace or the turret tops!
If you really want to stiffen yours in the vertical plane, another thing you could try would be to add vertical webs from the centreline of the tube on either side of it extending along the 5mm plates and get them as close as possible to the centrelines of the two studs (whilst still being able to get the nuts on)!
Avocet said:
That said, this isn't really the plane in which the brace needs to work. They are usually loaded (pretty much) as close as possible to being in pure compression to stop the tops of the struts getting closer together. If the centreline of the bolt on the Audi one lay on an imaginary straight line across the car joining the tops of the two damper rods at the point where they emerged from the steel turret, there would be no tendency for any rotation about its centreline. In fact, it might actually be desirable to have a joint that allowed rotation in this plane to reduce the risk of fatigue failure to either the strut brace or the turret tops!
Totally agree, I recon those pivots are put there to try to stop cracking. After all, there's no way a strut bar is going to be strong enough to prevent vertical relative movement of the strut tops as its in the wrong plane, so why try?
mave said:
Avocet said:
That said, this isn't really the plane in which the brace needs to work. They are usually loaded (pretty much) as close as possible to being in pure compression to stop the tops of the struts getting closer together. If the centreline of the bolt on the Audi one lay on an imaginary straight line across the car joining the tops of the two damper rods at the point where they emerged from the steel turret, there would be no tendency for any rotation about its centreline. In fact, it might actually be desirable to have a joint that allowed rotation in this plane to reduce the risk of fatigue failure to either the strut brace or the turret tops!
Totally agree, I recon those pivots are put there to try to stop cracking. After all, there's no way a strut bar is going to be strong enough to prevent vertical relative movement of the strut tops as its in the wrong plane, so why try?
Thats universal, thats why it is adjustable (rather than being pivot points!)
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