Strength of materials in use..

[buZy]

Does anyone know how much static weight the transmission crossmember would have to support with my particular set up?

 

And if to project this idea further, How much weight does it have hold under normal street driving use?

i.e. inertia loads vibs positive to negative g's

 

FWIW... I have a crossmember cnc from 6160 alum that was in use for about 2000 miles and held great no cracks but instincts to me section or two "might" be pushing the limits. At that time it was bolted to the floor pan only. And mean floor pan only! Now the floor is way beefed. (monoque lowered seat pans with interior trans x-member all in alum not showing pics till its assembled) But anyways here is a pic of the piece in question. Unless someone sees something very wrong here I would to use it again because at this rate, in this lame state, I might get to test it once before winter sets in. Temporary, can always make another one of some kind similar fastened. The section in question is the drivers side from the floor up into tunnel. The size is only 1.50 wide front to rear of car X .52 thick. Sorry for the long thread.

Brian

 

[Careless]

can you please post more pics of that underbelly of the car in this pic that you've shown here?

 

it looks as though the frame rail is a u channel with 90 degree angle end-plate strips that are held on both the body and the u channel with rivets.

 

that looks cool, but i just wanna see the rest of it if possible

[buZy]

Here is another pic of the underbelly. I did use 4 angle channels on the full rectangle steel frame rails, that was some time ago. Have not riveted the seat pans in yet it's all being fabbed first before final assembly. Just finshed tiging the inside trans x-members last week. You can better see the section in question on the driver side does have more room for more material. I just took off a bit too much off making it before...opps. When finished there will be 6 fasteners used instead of the 4 shown.

Brian

 

[Careless]

any more pics of the entire underbelly

[boodlefoof]

The crossmember itself looks pretty stout. It is solid aluminum, not boxed correct?

 

The way it is mounted to the floor does look a little shaky though in my opinion. Without seeing how much you've reinforced the floor, I couldn't really comment... but I would personally want the crossmember tied directly into the rocker panels.

 

However, the majority of your rotational forces are going to be controlled by the motor mounts. The tranny mount just needs to keep the tailshaft from moving up or down or trying to go side to side. Best solution would be to have a rear motor plate tied into the frame rails on either side.

[buZy]

The crossmember itself looks pretty stout. It is solid aluminum' date=' not boxed correct?

 

The way it is mounted to the floor does look a little shaky though in my opinion. Without seeing how much you've reinforced the floor, I couldn't really comment... but I would personally want the crossmember tied directly into the rocker panels.[/quote']

 

Correct, it is solid aluminum and not boxed. Actually it is tied to the rocker panels through the interior of the car. The mounting is not the problem its the crossmember itself I worry about.

[Cody 82 ZXT]

That looks pretty stout to me.

[MatMan]

Take a look at this PDF on 6061 T651 aluminum:

http://www.espimetals.com/tech/aluminum6061-t651.pdf#search=%22aluminum%206061%20ultimate%20strength%22

 

the shear strength is 30KSI That's 30000 pounds/sqare inch.

 

If your box cross sectional area is 1.5X 0.5, or .75 square inches, then the shear strength for your member (he he he) is 22500, or it would be able to withstand 22.5KSI. I don't think you will be seeing anywhere near this shear force on the member.

 

Now, the 6 mounting bolts may be a different story, depending how the interior connection goes..

[buZy]

Thanks MatMan! Ok here are pics I wanted to wait but it's almost done.

First pic seat pans. A4's mounted low on top of 1 inch high 1inch hex stock, no sliders. More hex welded to pans between floor for seat mountings through bolts typical. You can't see it but in front of x-members the pan material has a 45 break bend to floor.

2nd shot detail of how the 6 bolts tie into interior crossmembers.

3rd, the block between the seat pans and floor.

4th, rear of pan.

Last, the before shot. The previous owner cut out the non rusted sub bracings to mount 55 pound seats each. Go figure....That's how this whole project started. To replace and improve the structure while keeping seats low back and everything light.

 

Seat pan holes are for great stuff/home depot spray foam for extra strength. Light and maybe some sound loss. When rivited the pans will be captured on all four sides with additional 90 angle on rockers, x-member and bend areas to the rear and tunnel.

 

[Careless]

damn you guys and your milling and cnc'ing.

 

it's just not fair.