Designing the Satchell Link

[Norm Peterson]

I found out the hard way that the crossmember needs to be braced. I broke it in two and tore up my floor.

I think the crossmember needs at minimum some fore/aft bracing at each of those LCA chassis side pickups, and the other ends need to be tied off to something more substantial than just being bolted to the middle of some sheetmetal. Not having this bracing means that the longitudinal components of the LCA forces are being resisted by the crossmember in torsion.

The inside "corners" of the existing crossmember at the top of the tunnel should probably be filled in with a plate formed to a radius, as sharp corners = fatigue "hot spots".

I'd also consider adding some lateral bracing from the LCA brackets if you can fit it underneath. Or some sort of transverse structure above the floor and solidly welded to it from the tunnel to the sills if you can't (given the roll bar, I don't see the back seat area ever being occupied). Any bending loads that you can get off the crossmember where it goes up and over the tunnel can only help things.


Norm

[911industries]

Sorry for the delay guys. My car kinda took dump and life stepped in to say my time needs to be spent on other projects. The car problem is burning coolant which took out the O2 sensor which the computer didnt like. Basically I need to tear out the engine to see if its the heads or head gaskets.

Anyways back to the subject.

-Heims and bushings. I cant remember where I got the bushings but if you like certain size tube and call up energy suspension with some numbers Im pretty sure they can find a bushing that will work. I put the heims on the body side so they will see less road debris and last longer. I dont think that putting them on the axle would make them work any better. The axle and links roll the same no matter where they are restricted from. The roll restriction is the bushings.

-crossmember destruction. I've talked to some guru's about that and basically it was do to the POWER. Ha, ha, ha. After looking at all the aspects of the failure the desire for the axle to roll under hard launches makes the most sense. When you launch the lower arms which are those want to push forward and thats exactly what they did.

I had room to put a 45 degree tube above my exhaust from the LCA to a roll cage crossmember. That seems to have done the trick but I havent had much rough testing lately.

-Roll steer. Because I dont have a rear swaybar and a bad front swaybar its hard to tell. The thing I can say is that this car is scary at 140! Why you ask? It has more to go and it feels like Im going 60. Another fun fact. Bad hood hinges and high speeds will actually make your hood lift up and really make pucker.

Even though I roll like a boat the car still takes the line I choose. I was playing with an Audi R8(I think) and he never pulled me even in 30 mile curves with 80 on my speedo.

-Crossmember construction. I also added some diamond shaped plates over my weld points. Those ar supposed to help distribute the load away from the weak point just outside of the main weld. Thats the thing with a weld is; it is strong and so is the tube but the weak point is th hot spot created in between the two.

[911industries]

Here are some pics of my problem and the solution. I've done a couple of drags since I installed the diagonal braces and everything is looking good.

The first shot you can see my crossmember with the break on the left side of center. If you look real hard you can also see how it buckled the floor pan on the left hand side. My idea was that the floor pan would help with the structure. Turns out it helped until the crossmember broke.

Second shot is inside where the rear seat normally is. You can see my diamond gausetts. Also behind the crossmember is a crack in the floor that was also caused from the broken crossmember.

Third shot you can see the diagonal braces. Outside where they connect to the frame rail are connectors to the rocker and roll cage. One thing that isnt pictured is another diamond gausett I put spanning the two center welds. I actually broke it a second time after I installed just the braces.

[sik68]

Sorry, I have nothing to contribute...but everytime I see this thread I think of this: