My proposal for a Generation III mid-chassis "stiffening brace"center"box beam.

I designed this mid-chassis brace for my Prius "v," but I have since discovered that the Generation III Prius uses the same center brace.

The Cusco mid-chassis stiffening brace, with the two beams that go to the back brackets that hold the two parking brake cables, and selling for about $200 is definitely overpriced, overdesigned and overembellished
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The two arms that go the the back does nothing much to improve stiffness, given to their small sectional strength and long length of the "lever arm." A long thin "lever arm" equals limp and "whippy."

The massive (by compassison) 1.5x3 inch box beam that I use, has nearly the mathmatic "square" of the strength ratio when compared to the Cusco.

I have not seen the Cusco center brace in the "flesh," but it appears to be 1/2 x 1-1/2 of a rounded end oval box beam of what wall thickness, I don't know. But, it can't likely more than 1/8 inch wall.

Basically, my original 1-1/2 x 3 inch sectional box beam with a 1/8 wall will be approxinaltey 24-36 times as stiff as the small section of the Cusco cross beam.

I have decided that the original is vastly overbuilt and will make any future unit oiut of 1x3x1/8 wall 6061 T651 aluminum extruded alloy. This tubing will be at least 12 times as stiff as the Cusco material.
The Cusco has two welds on it. Mine will be one piece. This means that the Cusco must be 6061 alloy, since the higher strength allows such as 2024 or even 7075 are not availble in extruded tubing, and neither 2024 or 7075 are weldable.

The two welds in the Cusco brace also weakens the 6061 tubing, since high temperature welding destroys the the T651 temper and "anneals" the tubing.

Painting of 6061 alloy is not necessary even in marine environments. 6101 is commonly use for marine gas tanks and survives unpainted for 20 years or more in marine environments. You just don't want 6061 to lie submerged over long period of time in water. Basically, painting would be for looks and embellisment purposes only. The box beams of the Prius bumbers under the covers are made of aluminum and not finished,

A 6061 plate is in no way as strong as a box beam. The surface layers of tubing take nearly all of the tension and compression, when a box beam is bent. A 1/2 inch thick plate can in no way be as strong as a 1x3 beam, since a 1x3 beam is theoretically reaches the same strength as a solid 1x3 beam. The "core" is nearly dead weight and mass. It adds very little dynamic strength to the structure.
It's like this.

A sheet, even 1/2 inch thick is not even remotely as strong as that sheet rolled into a tube or formed into a box.

In the second and probably final incarnation of my box beam brace, I have developed a set of transfer screws that screw into the holes of my vehicle. These transfer screws and my "trade secret" technique allows me to make and exact template for drilling the mounting holes for my box beam brace.

 

Check out this Prius "v" thread.

http://priuschat.com/forums/prius-v...sis-stiffening-box-beam-vs-plate-prius-v.html

The new version will be a little more, since the tubing cost me a few dollars more to get, and I have to "special order" it in a larger quantity to keep the price down.

I'm looking at $56 dleivered.

 

Also, the new version will hange just 1/2 inch lower than the original, but a lot higher than the lowest clearance part of the chassis. This would be ideal for the GenIII.

I will be doing these basically to cover my cost. All of that fancy machining on the BT Tech plate and those fancy welds on the CUSCO are nothing more than "make work" enhancements to justify the rdiculous price that they are charging.

Mine will be done only for function, at the least weight and cost possible. There are no embellisments added for "looks."

 

The amount of material in the place where you assert to me a matter of concern would only be a problem if the area was under tension. When the mounting bolts are properly torque, the brace is retained by the friction in the bottom of the bolt's ehad and the friction against the bottom of the body's floor beam. This area would only be damage by vibration only if the plate was not properly retained or torque down bolts. As with the lug holes in a steel or aluminum wheel, the holes are not damaged and may be thin in that area. Damage would only occur, if the log nuts were loose and the looseness causes a "wearing away" effect from banging together of loose parts. I might make this flange a little longer, but, as Toyota did with their steel brace, it adds no strength of the mounted beam. Being .125 incges in thickness, the aluminum will be at least 100% thicker than the OEM Toyota brace.

2024 or 7075 alloy would be more likely to crack under stress, and in aircraft, especially helicopters, known for a high incidence of engine and operational vibration, have a liminted design life. That's why the 7000 series of aluminum alloy, originally designed in 1936 by Sunitomo for Mitusbishi and used in the airframe of the famous A6M2 "Zero Sen" has no flying examples that have survived.

6061-T6 is a very stable alloy, and being .125 inches thick, and much thicker than any airframe bulkhead on an airplane like the original Douglas DC-3 or the Boeing B-52, will outlast the car many many time over. 6061 is much more stable than 2024. Even in a lindfill 6061 will last a few thousand years, much longer than any of us here in Pruischat.


Sorry for the long technical explanation. It is probably more engineering data than anyone here needs, but it is thorough. I hope it addresses your concerns.

 

Mine will be made in my home machine shop out of 6061-T6 "structual" aluminum alloy. Most of the aluminum alloy rectangular tubing sold commercially is "architectual" alloy, which has about 40% less strength than "structual" alloy. I have the 6061 tubing on "special order," and I expect to receive it by the end of next week.

I use a special metal cutoff saw with a aluminum specific "hollow ground" 14 inch circular saw blade.

To precisely reference the close fitting of the mounting holes, I have fabricated specially designed M10x1.25 "transfer" screws, so that I can make a close fitting pattern to mark and drill the aluminum preform with good repeatability.

Mine is not a fully "mitered" to an edge. The miter is "truncated," so that the mounting area will be strengthened with at least a 1/2 inch wall coming up the side of the bolting area.

To accomodate the "strengtening wall" and still allowing the full use of the 17mm socket need to drive the mounting bolt without restriction for the use of a torque wrench, the end of the bottom section will be "milled" away on each end.

While leeb18c's brace will probably work and function just fine, mine will be engineered and implemented for optimum strength.

That's my goal. Maybe "over-engineered," but that's waht I want on my car.