Tech: Amateur firewall fabrication

Here is how I went about building a firewall for my sedan project:
http://www.jalopyjournal.com/forum/showthread.php?t=147848
With the stock firewall removed, I began by making a cardboard pattern to capture the shape of my new firewall. I covered the opening in the cowl and traced the cowl perimeter from inside the car. I took some measurements of the bell housing and laid out what needed to be removed to clear it. Here is the pattern I ended up with:

The next step in my fabrication was to form up the flange that would attach the firewall to the cowl. Here I used some .125" x 1" flat bar. I made a mark at the center of the bar’s length. From the center mark I laid out where corners of the cowl were. I then began hand forming the bar into the "u" shape of the cowl. As I got close to the rough shape I positioned the flat bar in the cowl and clamped it in place working out from the center. With the flat bar well clamped and tightly matching the shape of the cowl I got out the torch and heated the flat bar to stress relieve the piece so it didn’t want to spring out when removed from the cowl.

Once I was happy with the shape of the flat bar I welded some .187 round bar to brace the flat bar and preventing it from springing when removed. I welded this with the flat bar clamped in place in the cowl. Here is the previous picture doctored up to show the bracing scheme:

I was now ready to cut out the main firewall sheetmetal. I transferred the shape from my pattern onto a sheet of 18 ga. sheet steel. I cut it out using some power shears:

For the interior cutout I was planning on forming a 1" flange where the trans tunnel meets the firewall around the bell housing. I offset a line 1" from the line I transferred from the cardboard pattern. At the "L" shaped cutouts, one on each side, I planned on having a wired edge to give the cutout a finished look. I offset a line .375" here to leave enough material for a .12" dia wired edge. Here is a pic of the layout:

To finish the prep of the flat sheet intended for the firewall I layed out a pattern for some beads to be rolled in the upper portion. This was mainly done to make the flat 18 ga. more interesting. The picture above shows the beads rolled in the upper portion of the firewall.
The final two things to finish the 18 ga. sheet for the firewall were to hammerform the flange and add the wired edges. I started with the wire edges. I tipped up the metal with a homemade tool I found at metalmeet.com. Here is a link to the post I used to learn how to do the wire edge: http://metalmeet.com/forum/showthread.php?t=4065&highlight=wire+edge
And a sketch of what the flange tipping tool looks like:

I made my tool from some .5x.5 s**** steel bar stock. I used a cutoff wheel to cut the slot in the end and rounded the sharp edges on the belt sander. Here is a bad picture of the tool:

To begin the wire edge I used the tool to gradually tip the edge up. I move from one end of the edge to the other making small tipping movements as I go. After I get the entire edge tipped up to 90 degrees I take a homemade dolly and hammer and begin gradually hammering the edge over past 90 degrees. As the edge gets close to having an .12" gap I slide the wire in place and continue hammering it over to tightly fit around the wire. Here are the pic's:




To form the 1" flange for the trans tunnel I built a simple hammer form. I used two s**** pieces of .75" plywood I had laying around. I transfered the shape of the flange from the cardboard pattern and cutout the semi-circle with a jig saw. I clamped the two halves together and used a belt sander to get a nice uniform semicircular cutout. I used the router to route reliefs in the one half of the hammerform to allow reliefs for the beads & wired edges in place in the firewall sheet. On one of the hammerform halves I used the router to bullnose a radius on the semi-circular edge cut out with the jig saw I drilled several holes for 1/4-20 bolts to clamp the two pieces of plywood together, outside of where the metal was. I also positioned two holes that went through the plywood and metal. I drilled two .125" holes for #4-40 bolts. These bolts don't add a tremendous amount of clamping force but they do position the metal to the hammerform. I positined the metal in the form and began hammering the flange down with a plastic hammer. I worked gradually along the hole edge, working the flange further down with every p***. Here is what it looked like in the hammer form:

More hammering:

When everything is hammered evenly and tightly against the hammerform, I removed the firewall from the hammerform:

The only thing that remained was to attach the formed flange to the sheetmetal. I layed the braced flange onto the sheetmetal and traced the shape onto the sheetmetal. I used hand shears to trim the outsided edge of the sheetmetal to perfectly match the outer edge of the flat bar flange. I then tacked the pieces together and test fit hole ***embly into the cowl. Here is a pic:

After finish welding I fit the new firewall ***embly into the cowl:

 

That is freakin' beautiful!! I wish i had the talent you have in your pinky!!

 

Great job man!! Skills!!

Ian

 

Nice Job! Looks great.

 

Very nice, looks great.

 

I am really just a beginner. The hardest part was having big enough balls to go for it and try some of these things I have been reading about here on the HAMB. I too was suprised at the results!

 

Looks good similar to how I did mine...

 

That came out awesome man!!!! MUCH better than a flat sheet, thanks for taking the time to post.

 

nice job

 

impressive work , and mostly by hand

Thanks for posting , show us more of what you did on other parts !

Beaulieu

 

damn dude ! very nice work ! awesome job !

 

wow that is super nice and you didn't have any fancy high dollar equipment either..VERY WELL DONE!!!

 

Awesome fab work at a low tech level....I love it.

 

I am afraid that the term Amateur in the ***le is not correct. This is a very well thought out project. KEEP UP THE GREAT WORK

 

very nice !!!!!!

 

very cool fab but that foot well looks tiny

 

nice!!!!thats usin your dipstick jimmy!!!

 

^^^^^ Royalshifter captured my thoughts. Very nice!

 

Very good results given the simple tools used to make it.

 

I like that cant wait till you get what you would call good .

 

Amateur? I think you've missed your calling...you have some metal fab talent for sure! Looks great...

 

My hats off to you, looks good. Mine is still a MESS!

 

Real nice work. Some great ideas you found to turn an amateurs work into looking like you paid a pro to do it.

 

i think is a great job,,compliments

 

amateur,ha,ha......you`re not an amateur!!!! thats beautiful,great...

 

Nice job... keep it up.

 

The factory couldn't have done any better. Really impressed with your work.

 

Freaking beautiful! Thanks for the detailed pics.

 

Thanks, I learned some things I'm going to need to know. This is the beauty of the HAMB!

 

Looking good!