AusS2000

The X brace mounts to 4 points under the front of the car.

Can I assume that the two points on either side are on the same member? Sorta like |X| .

In that case, is there any reason an X brace can't be hinged in the middle?

If you imagine the installed X brace to be approximately two isosceles triangles (two equal sides, two equal angles) whose points meet in the centre (|> <|) and the purpose of these braces is to stop any movement between these four points along the line of the braces, then a hinged brace is as secure as a rigid brace. This is because each triangle forms a rigid shape.

Why do I mention this? Well if this is the case I'm sure I can manufacture and ship collapsable X braces for about $US120.

Does anyone have pictures of the four mounting points they can post?

dbarnes

I doubt a hinged x-brace would work, especially if it is a modified version of the Spoon x-brace. The x-brace most likely carries load axially and in bending. By adding a "pinned" joint at the center of the brace, you will remove the bending moment continuity between the two legs of the "X" as well as reduce the overall buckling load of the brace. Some type of a mechanically fastened joint would need to exist at the vertex (one capable of transferring load in all six degrees of freedom - 3 translations, and 3 rotations) such as a lug-clevis joint with sufficient bending rigidity.

-Donnie

AusS2000

I think I see what you are saying, but one the members (Reverend I think) has a behemoth friend who demonstrated how easily the bars of the X-brace could be bent. Ths is one of the things that leads me to believe that the X-brace has little torsional rigidity and is only relying on the strength along it's axis's (is that correct English?) to maintain the distances of the 4 points on the plane parallel to the ground.

When you think about what the STB does, it resists the tendency of the chassis rails (and hence strut towers) to twist in towards each other when excessive force is applied to the suspension. The X-brace does the same, but rather than by applying an outward force to the top of the suspension....

|<-->| (< > represent vector of force)
|___|

it applies an inwards force to the lower part of the suspension (or chassis as the case might be)

|------| (< > represent vector of force)
|>--<|

Am I making any sense ?

[Edited by AusS2000 on 03-05-2001 at 06:04 AM]

dbarnes

Adding a hinge at the center will eliminate the bending moment about the hinge axis at the vertex. Although, it appears that the moment in the other plane (perpendicular to the brace) is more important based on the orientation of the cross section, there is probably a secondary moment in the plane of the brace that would require some moment continuity at the "hinged" location (load lines do not intersect and thus will produce bending, torsion and axial load). Also, by adding a hinge at the vertex, instead of the double gusset arrangement found on the Spoon x-brace, there would be a significant reduction in local torsional rigidity. Finally, by adding a hinge at the central location, there would be a huge reduction in the ability of the brace to carry load inplane (axial compression) due to the brace wanting to buckle out of plane.

I still recommend not adding a hinge at the vertex of the x-brace.

cmnsnse

A hinge to make it fold in half would not be perpendicular to the stress. It would wear out wery quickly.

BUT you could make two beams that overlap like lincon logs with a bushing and large bolt in the center . . .

AusS2000

[QUOTE]Originally posted by cmnsnse
[B]you could make two beams that overlap like lincon logs with a bushing and large bolt in the center . . .

Giampiero

AusS2000;when you buy an x brace (or any other parts) and it works good ,I think in my opinion that saving $5.00 in shipping will not be a priority.
I agree with you, by the way that it will be possible to copy the x brace from Spoon and sell it for less;it will be
much easier.
Giampiero
MG RACING

cmnsnse

[QUOTE]Originally posted by AusS2000

Quote:

That is the idea, and with a fairly large coupling block in the centre. The idea is not for a hinge, but for a disassemblable (now is that a word?) brace that can be shipped easily. Might even be possible to weld once assembled.

Expect a prototype soon.

OK I thought you meant they would actually fold . . .


One benifit is the two beams could be identical, and one is just overturned for assembly. That would mean VERY simple design and initial manufacturing.

AusS2000

Cool G, please accept this post as confirmation of my order for 1 Spoon X-brace for MRSP plus $5 shipping to Sydney Australia

I guess you haven't shipped much round these parts recently

Giampiero

AusS2000;my English is not so good;I meant that with a different design you might "shave"$5.00 from the shipping cost ,not that the cost of shipping is $5.00.

Yes we sold some X braces also in OZ;we sent them directly from Japan at $32.00 with EMS.

Giampiero