[BillyGman]

I know very little about body and sheet metal work. I know two guys that I can ask about this, but I want as many opinions, viewpoints, and advice as possible, so here it goes:

If I wanted to attempt to have a safety shield to contain a possible automatic trans front drum, flex plate, or torque converter explosion during drag strip racing from going through the trans floor tunnel and severing one or both of my feet, what would be the thickest piece of steel that a body fab guy can contour into the shape of the transmission floor tunnel, with an english wheel or whatever else is used for bending and shaping body parts? Would 1/8" thick mild steel be way too thick to do this with? If so, what about aluminum?

Like I said, I know very little about body work, or sheet metal work in general. I'm wondering if I can have two pieces of mild steel fabbed and contoured into the same shape as the trans tunnel on my 70 Chevelle. One to fit snug on the outside, underneath the floor tunnel, and one to fit over the tunnel inside of the car. I would then drill matching holes around the circumference of both the pieces, and then bolt them together once I have them placed under and over the floor trans tunnel to sandwich the tunnel in. It would be a double wall sandwich of mild steel,(or aluminum if need be). Would this be possible to fabricate? Or am I dreaming? If this is out in left field, don't shoot me. I'm just trying to think outside of the box here.

Just brainstorming right now. The two fabbed pieces would have to fit snug to the the floor tunnel, and follow it's contours closely. Especially the outter/bottom piece which would have to fit between the top of my TH400 transmission, and the bottom of the floorboard trans tunnel. If there are any shops or interenet sites that sell something like this already fabbed specifically for GM A-body cars, then please make mention of that. I haven't found anything like that.

 

[pcguy]

Sounds like you're going to put down some serious HP??? What is the factor that requires the English wheel?

Nick

 

[BillyGman]

Sounds like you're going to put down some serious HP??? What is the factor that requires the English wheel?

Nick

I'm not even sure if your question is sarcastic jesting or not Nick. I'll repeat myself by saying that I know very little about sheet metal fabrication, so IDK if an english wheel would even be used for such a task. I might be way off on that. I saw one in my buddy's fab shop a couple years ago, along with a brake also. I know that both are used for sheet metal fab work, but that's all I know. I'm building a very heavy, (3900 LB) street/strip Chevelle with a TH400 equipped with a trans brake, behind 850 HP and in front of 30" tall bias-ply 12" wide slicks. I'm just trying to investigate alternative options. The bolt-on trans sheild I tried won't fit without me cutting the floor tunnel, and the SFI approved thick transmission cases cost $1,300. It would be nice if I could have something fabbed up for 1/2 or even 1/3 of that cost.

 

[pcguy]

No sarcasm here; just trying to understand the project. Sounds like you're looking in the right direction. Did you look into a built 400 that has the case already? What rear end?

Also, what class and what ET expectation?

Here's a link to a discussion about ET.
Trans shield rule?? - CLASS RACER FORUM

Might be good to post this question on a DR forum as well...

Nick

 

[69SS454]

If you are going drag racing, a thick floor will not replace the mandatory SFI shields.

 

[BillyGman]

No sarcasm here; just trying to understand the project. Sounds like you're looking in the right direction. Did you look into a built 400 that has the case already? What rear end?

Also, what class and what ET expectation?

Here's a link to a discussion about ET.
Trans shield rule?? - CLASS RACER FORUM

Might be good to post this question on a DR forum as well...

Nick

Thanks Nick. I'll check out that link in a minute. I bought the transmission years ago, and installed it in the car with the intention of using an aluminum bolt-on shield like a number of guys use. However, after dropping $2,300 on the trans and another $1,300 on the torque converter, I was unpleasantly surprised when I went to install the trans with the bolt-on shield in place, it didn't even come close. In fact, I had to tweak and flex the trans tunnel just to get the TH400 installed without the case.

So the transmission I have hasn't even been used yet, and I'm not in the position to go out and purchase a whole new transmission just to have it included with an SFI case. And I'm trying to avoid having to pull my present transmission apart, in an attempt to re-install all the internals into a new $1,300 SFI case, (which BTW would likely turn into a giant learning curve for me if I was to do it myself, and at least half the cost of a whole new transmission if I were to have someone else do it).

And to answer your questions: I have a Strange Engineering S-60/Dana 60 rear with 35 spline axles, and I'm expecting low 10;s until I get the suspension dialed in, and then perhaps high 9's.

If you are going drag racing, a thick floor will not replace the mandatory SFI shields.

Ihear ya. Your point is well taken and I know that you're correct on that, but I'm just a test and tune racer, and I believe it depends on what track and what tech inspector. I don't think all of them are going to crawl underneath the car to check for a shield. I'm mostly concerned about my own safety. Isn't it true that a shield is only required when turning ET's of 9.99 sec and quicker? Well I'm not going to declare a sub 10 second ET to the tech inspector, nor 850 HP under the hood before I run it. And just because a home made shield isn't SFI approved doesn't mean that it cannot be safe.

I just want to get this car together and get some seat time with it. When it's time for a new transmission, then I will welcome the thought of an expensive SFI case with my next transmission. Not meaning to argue with your logic here. I just cannot see going out and buying a whole new trans, nor ripping my current one apart just to obtain an SFI case. I think I would cut the floor up myself just to fit a bolt-on shield before I would do that right now(which I might have to do if this idea I've mentioned above is a no-go). I'm hoping that there are some experienced fabricators on here who will be kind enough to chime in to address my question.

 

[TechNova]

an english wheel is only going to do about half that thickness. You would want a slip rolls for 1/8".
You could build the tunnel a little bigger with regular sheet metal which would give room for the bolt on SFI shield underneath. 18 or 20 ga would be easier to work with.

 

[BillyGman]

an english wheel is only going to do about half that thickness. You would want a slip rolls for 1/8".
You could build the tunnel a little bigger with regular sheet metal which would give room for the bolt on SFI shield underneath. 18 or 20 ga would be easier to work with.

I like your idea. I'll talk it over with my two co-workers tomorrow, (one of whom does fab and body work on the side in his own private shop). And now that you mention it, I guess I could either use my sawzall or 4.5" angle grinder with a metal cutting diamond wheel to cut the floor tunnel out, and bring it to the guy in one piece for him to make a slightly taller copy of, instead of having to bring the whole car to him as I might have to do if I was going to do it this the way I mentioned in my first post.

Furthermore, I'd also be able to use an SFI approved aluminum shield, so I wouldn't need to be concerned with getting by the pre-race track tech inspections in the future. So I guess that would cover all the bases. Thanks very much for your input on this.

 

[cheveslakr]

You'd have a tough time with a slip role. I'd just use a press break, hitting every 1/2" and hanging the end out 1/3 off the dies. A power role won't even taper 1/8" very much.

 

[BillyGman]

You'd have a tough time with a slip role. I'd just use a press break, hitting every 1/2" and hanging the end out 1/3 off the dies. A power role won't even taper 1/8" very much.

I just watched a youtube vid where the guy used a break like you said. he first used a piece of cardboard as a template to form the shape and size that he wanted over the existing tunnel from inside of the car. He even used an angle finder to bend the sections precisely. I guess this is something else I'll have to ask my co-worker about, because this stuff is way past my skill level....

Fabricating T56 Tunnel part 1 - YouTube

 

[cheveslakr]

The angle finder will just confuse matters. Get a sample piece and bump it every 1/2" and adjust the ram depth till your happy with the radius. You have to adjust for the length, a 30" long section will need a good deal more force than a 12" but it's a good gauge. You can go back and bump it a little more to fine tune. Also, your best buddy is a mallet on the concrete floor to get it perfect. If he's never bumped a taper, you need a great deal of taper on your ram (upper die) and possibly even shimming the lower die with broken sections of a metal tape measure.

 

[BillyGman]

The angle finder will just confuse matters. Get a sample piece and bump it every 1/2" and adjust the ram depth till your happy with the radius. You have to adjust for the length, a 30" long section will need a good deal more force than a 12" but it's a good gauge. You can go back and bump it a little more to fine tune. Also, your best buddy is a mallet on the concrete floor to get it perfect. If he's never bumped a taper, you need a great deal of taper on your ram (upper die) and possibly even shimming the lower die with broken sections of a metal tape measure.

Obviously you have done lotsa fab work of this type before. Thanks

 

[Bob Tiley]

Use a blanket, that should fit.

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[TechNova]

You'd have a tough time with a slip role. I'd just use a press break, hitting every 1/2" and hanging the end out 1/3 off the dies. A power role won't even taper 1/8" very much.

we made one way plows this way, much larger and the bends about 2" apart.

 

[cheveslakr]

I agree it can be done, just much simpler in a press.