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Under chassis brace


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The Z tunnel is super weak. There is no bracing of the tunnel on my 240 at all. The trans mount doesn't go all the way around the tunnel circumferentially and doesn't attach to the frame rails or anything else. I think a lot could be done to strengthen the underside of the car by attaching the frame rails or better yet subframe connectors with a big X shaped structure under the car. This would lessen the vertical and horizontal flexing of the center of the car. The problem seems to be the exhaust is in the way...

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The Z tunnel is super weak. There is no bracing of the tunnel on my 240 at all. The trans mount doesn't go all the way around the tunnel circumferentially and doesn't attach to the frame rails or anything else. I think a lot could be done to strengthen the underside of the car by attaching the frame rails or better yet subframe connectors with a big X shaped structure under the car. This would lessen the vertical and horizontal flexing of the center of the car. The problem seems to be the exhaust is in the way...

 

That's why I did this for my tranny mount

 

P10100385.JPG

 

Here's an early shot not yet complete but installed

 

P10100441.JPG

 

Cameron

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Not impressed. Maybe I just don't get it. What movement is it trying to prevent?

 

Here's one that looks like it does something (keeps the frame rails parallel):

http://www.flyinmiata.com/index.php?deptid=4538&parentid=0&stocknumber=13-69920%20%2090-97

 

That the first thing I thought when I saw the Subaru pics, "Why didn't they tie both sides together???"

 

That's why I did this for my tranny mount...

Cameron

 

 

 

That's very nice, I like the idea, I guess if it was to be made out of aluminum, it wouldn't weight to much. Do you have an aproximation of how much your's weight???

 

Thanks.

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That's very nice, I like the idea, I guess if it was to be made out of aluminum, it wouldn't weight to much. Do you have an aproximation of how much your's weight???

 

Thanks.

 

It's made out of 14 and 16 gauge plate so it doesn't weigh much. I would say < 5 lbs. Yeah it took a long time to fabricate. Heaviest part is the tubes that tie over to the SFC and that's just because I used what I had (1x2x.083) instead of getting thinner wall since I have to mail order it.

 

Cameron

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I just saw it the other day. Someone is selling a set of frame rails like the bad-dog ones but it has an X-brace that covers the bottom of the car.

The X brace looked pretty flimsy though since it was just flat sheet metal with no bends in it...

There was a link to that at classiczcars.com. I think the guy wanted $1000+ for it too. It was just a not a very good frame rail with some strap steel bolted across. Bad design and bad implementation at the highest price possible.

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Hey Heavy85....If Im understanding this correctly...the cross brace is bolted to the transmission tunnel for quick removal? Nice work!

 

If you have run it yet.... did it make a big difference?

 

The second pic is half finished but if you look at the first one it actually bolts to the tunnel with two bolts per side PLUS it bolts to the tubes that go out to the SFC also with two bolts per side. It's really a bit of a pain to install as you have to angle it up past the tubes, push it over, and kind of wiggle it up in there. You have to do this because the tubes to the SFC are actually narrower than the top of the mount so you can't just raise it into place. Have not run it yet but it will be hard to tell because I added a bunch of other chassis improvements at the same time + the LS1/T56. I'll know more this Spring when it's driving.

 

Thanks for the compliments guys.

Cameron

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Maybe that first set is just trying to be compatible with this rule that JohnC posted...

 

Maybe, but I'd agree with Mr Mortensen, it the builder seems to have taken

a few random points on the chassis and tied them to nothing.

 

It's a bit like if you have a bike wheel with 8 spokes and you wanted to make it stronger, but instead of adding spokes between the existing ones, you'd just weld a piece of flat stock around the inside circumference, the small advantage you'd gain on rigidity, would be largely overcome by the added weight penalty. If that makes any sense, I'm not an expert, but it seems logical to me.

 

Seems like that sort of thing is worth its weight on a convertible.

 

I'd agree with that, that's the kind of thing, quite more elaborate in this case, that you see on OEM's to give the chassis a bit of compression strength after they've cut off the roof to make it into a convertible.

But even that is not enough.

I learned it the hard way once, at ford, where I worked as a tire guy. This is the other guy on the lift next to me, who waited after wheels left the ground to let me know, "You should unlatch the top from the windshield with these Stangs dude". Me, "why is that???". I quickly understood why...

 

Heard a weird ripping sound, lowered the car ... The roof was torn, across the whole width, right behind the windshield,

while the other idiot was laughing, "Ha ha ha, I knew this was going to happen!!! Ha ha ha..." Instead of letting me know before I lifted the car. What an A-hole, I would have swung my 1/2 drive torque wrench at his stupid face.

Luckily, he got the crap for not telling me.

Sorry for the tread jack, you may proceed.

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The Z tunnel is super weak. There is no bracing of the tunnel on my 240 at all. The trans mount doesn't go all the way around the tunnel circumferentially and doesn't attach to the frame rails or anything else. I think a lot could be done to strengthen the underside of the car by attaching the frame rails or better yet subframe connectors with a big X shaped structure under the car. This would lessen the vertical and horizontal flexing of the center of the car. The problem seems to be the exhaust is in the way...

 

That's why I did floor pans with inteiror/exterior trans x memeber.

FOAMed.JPG

 

Picture_0061.jpg

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Wow, it was about time you removed the carpeting, did you see all that mildew?? Look at the size of those mushrooms.

 

It's all aluminum? That's why it's riveted in place instead of welded???

 

I like this idea of cross members a lot, might as well do it at the same time as my bad dog rails.

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Wow, it was about time you removed the carpeting, did you see all that mildew?? Look at the size of those mushrooms.

 

It's all aluminum? That's why it's riveted in place instead of welded???

 

I like this idea of cross members a lot, might as well do it at the same time as my bad dog rails.

 

Yes, All aluminum and stainless steel rivets.

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