bending the tabs

The tabs on the tunnel from the last post couldn't be bent in the brake because the near 90° bend causes the adjacent side to not let the work piece under the fingers.  I couldn't put them in my vice because the vice wasn't deep enough.

My neighbor mentioned that you can grind a crease on the fold line then easily bend.  I have to admit that I wasn't wild about that at first. Carol Smith says you should never even scribe on a bend line, let along grind half the thickness away.

I thought about it a little more and remembered the high quality welds I got on .060 before by just pulling straight at a steady travel speed with .024 wire and decided to try it.  It seems reasonable to increase the cross section of some crumby 30ksi material with some 70 ksi material.

Grind about half thickness and bend easily with a BFH:

Weld.  Not awesome welds, but whatevs:

good penetration.  Just starting to sink.

Just to be sure I put this in the press and flattened it.  Looked the same only dead flat.  Then I put it in the vice and pounded it to 90° the other direction.  No cracking or necking:

Looks like a totally acceptable approach.

fold, trim, grind, trim, grind

I looked around on the internet at how other people make tunnels and concluded 2 things

1) This is an unbelievably common thing to have to do.

2) They all look terrible.

This sort of freed me of worrying about how bad this will look when I am done.  My neighbor had a metal brake that will do 16 ga so I stopped over with my tunnel this evening and we folded it up.  I put it in the car and it was pretty close.

I spent about 2 hours trimming and grinding to improve fit at the firewall. I will do more grinding cutting and folding, and will likely have to patch in some spots.

Tunnel blank

I cut out the steel today for bending.  I turned the plasma down to about half power and the pressure back to 40psi.  Left a good edge and went through like butter:

tunnel paper dolls

I wanted to be sure that I have some clearance from the transmission so I attached some wood to the posterboard as a shim.  Just like putting Bernie's toupee back on.  Cachunk:

A couple cuts and bends.  I expect this to look like crud.  Since this is very thin material ~.050 inch I will have to weld with .024 wire on very low heat.  I can forget about gap filling.  But at the same time it will be impossible to not have gaps.  You can see with the paper that I had to splice in a bunch of pieces.  I hope to keep that to a minimum with the steel, but it is probably going to go that way.  

tunnel reconstruction 1

I was making plans to remove the engine now that it is totally positioned and start adding more structure to everything.  I decided to go ahead and put the trans tunnel back now while the trans was still in place so I could be sure of clearance.  First I put the hvac unit back in so I could see if it is possible to clear that too:

Looks possible.  You will notice two electrical connections on the transmission.  The lower one is the reverse switch  which makes the reverse lights go on when you shift into reverse.  I will need to remove the connector from the mustang and be sure that my tunnel allows clearance for this switch.

The top switch is the neutral gear switch (NGS).  This is different from a neutral safety switch which prevents automatics from starting while in gear (that job is done by the clutch safety switch on manual transmission cars).  This NGS is used on cars with factory EFI to communicate with the computer.  Since I will have aftermarket EFI or a carb, I expect to not need it.

My plan is to make a few bends in some 18 ga steel to cover most of it then cut a bunch of little pieces to connect it around the perimeter.  Should look awful, but no one will ever see it again under the carpet.  I started bending up some poster board to lay it out.

This think will have no stiffness which means I still have a 2 1/2 foot long hole down the center of the body.  Looks like my transmission mount is going to do more than just hold the transmission.  I am glad I made it stiff.

Completed trans mount

  Not sure why I named the last post like I did.  I finished the aligning and welding today:

 By splitting this PS plate in the middle, I could gained access to grind a little and avoided having to hit the hole placements perfect:

Weld through primer;  Right when you start to weld you stub out, get a couple burn backs and giant spatter balls, then it settles down and welds fine for the rest of the bead.  That may be due to some other non ideal conditions here, but I suspect the primer as the cause.  That said, it's a relatively minor issue in exchange for rust protection on these inaccessible areas:

Threaded bosses sticking through the rail:

Cap for the end:

I didn't grind these welds down because 1: I didn't bevel the edge prior to welding and the penetration may not be that great, 2: nobody will see them (except all of you!).  Blue and in the corner:

Finally on to something new...

DS trans mount complete

Stuff from Eastwood got here a day early:

Least sexy $80 ever spent on my car, but needed for a quality job.  I finished up burning the insulation off the floor with the flap disk.  Turns out once you are burnt into that coating a razor scraps it off pretty clean:

 Primed:

These are ugly welds.  It was really hard to get my head where I could see.  Really hard to get any reasonable gun angle.  Really hard not to burn through, really hard to weld through the primer.  I found I had to set for the 18ga for the edges to have a chance.  Probably should have used the .024 wire.

Turned out nice from below.

We'll see how far the PS goes tomorrow

waiting...

I was thinking about water from the road getting sloshed onto all the bare steel I created in the floor and frame rails.  Before I weld everything up I ordered some weld through primer, some zinc primer, and some seam sealer from Eastwood.  Those are due in Wednesday which is annoying because I could have just driven over to Eastwood and picked them up.

I did some reading about whether I should remove the mill scale before priming.  I have been repeatedly amazed how tenacious mill scale is.  I have always painted over it in the past, and the internet seems to agree that you are better off leaving it on there if you don't care about the appearance of the end product.

Since welding is the next step, I am doing a little cleaning, and also fixing the busted carriage drive on the lathe.  I got to use my new boring bars to make the coupler.  Of course the coupler would have turned out better if I had a functioning carriage drive.

transmission mount 2...

Bolted the bosses to the cross member and everything lines up

Inside the car.  Have a few pieces to spread the load out and give something thick to weld the metal to.  .135 mild steel.

Have to ground the schmutz off the floor.  Flap disk does take it off, but sort of burnishes / burns it off.  Seems safer then grinding it off or lighting it on fire.  Less messy than acetone.  Looks like the flap disk is the unfortunate win.

transmission mount...

I put a heavy bevel on the bushes to make sure they press through the other side of the tube.  I also countersunk the tube to make sure that the weld gets below the surface and seals things up nice.

Since my McMaster order came I could finally tap the mounting bosses.  These were a real pain to tap!  I also lathed the ends down a little.  I want everything to fit easily so nothing is hard over waiting to not go together later.  Welding will ultimately hold everything, so a little room to move now won't hurt anything.  Also, losing the mill scale on the end will make a much better weld.

Squeezy McSqueeze:

 Zap, grind, job done.  Next is to mount the bosses in the floor.

transmission bracket progress

I decided not to use the bending technique from the other day.  I started laying it out, and just didn't believe that I would be able to lay it out well enough with 4 bends to fit well.  And for something under the middle of the car I choose good fit and ease of fabrication over good looks.

Even so, Figuring out the order to do these many steps to ensure everything goes together took some reasoning.  Here are a couple pieces held in place:

 Here is the result of weld up (fit ended up perfect):

I had decided on 3/8 for the bolts to the floor, but reconsidered and went 7/16-14.  Unfortunately 7/16 is the only bottoming tap in my whole set (odd?) and I can't start the hole.  I don't have the courage to power tap on the lathe yet.  Here are the two holes in the DS floor and the two studs.  I will make a doubler plate out of 1/8 or 3/16 plate and weld it all in once my taps and other bits get here from McMaster:

 Here is the transmission bracket with the center three bushings welded in and ground down and one of the frame rail bushings shown not installed:

trans mount prep

I got my new lathe tooling and got my metal for the transmission mount mount.  I read about a metal tube folding technique to make more natural looking bends in tubing.  I wasn't sure how accurate it would be for what I am trying to do, so I gave it a try:

 

On the whole I was happy with how it looked, and the angle ended up right on what I was trying to do.  I was worried about doing 4 of these and expecting everything to work out.  One option may be to make all the cuts, bend it close, bolt it into the car, then tack it together there.

 

I also made the first bush for the trans mount today: