Welding in reinforcement plates for a roll bar
 

Hey Guys,

I've been prepping my 89' FC for installing a Kirk Racing bolt in roll bar over the past few days and I just had a quick question about metal to metal contact.

Where the plate is going to bolt to the floor behind the seats I made some 1/8" sheet metal reinforcement plates to weld onto the floor inside before bolting the bar in. I removed the rubber plugs, metal plugs, sound deadening tar, and cleaned the floorpan down to the metal with a wire brush and flap wheel.
After that I wiped it all down with kerosene, cleaned it with brake cleaner and then brushed on some of that stuff that eats and prevents rust. I did the same to the underside where I will be welding the old plug holes to the new reinforcement plates.
I treated the plates with the same rust preventative.

Is it okay just to weld the plates on now and leave the bare metal in between making contact since both surfaces are treated?

After welding I am going to paint the floor wiht rustoleum, drill the holes, bolt the bar in and spray new undercoating on the bottom of the car over the bolts and lower(under the car) plates.

Let me know if you need pictures, I can take some if necessary.

Thanks!

it is better to have bare metal when welding. after you weld clean it up real good and paint it. You should be fine with bare metal between if your welds are good.

What I do is clean the area of undercoating etc, down to paint. I then place the plate in its spot and trace around the perimeter with a sharpy. I only take the area near the sharpy line down to clean metal, maybe an inch wide or so.

Now, for you plate design. Skip the under plate if you are welding the upper plate in, it isn't needed. What you should do is make sure your mounting plate extends onto a vertical surface like the rocker or rear 'kick up' from the floor. If you have the metal Kirk sent you for the lower plate, use that and just add it onto the plate already there. Most car's floors aren't that thick(Honda's are the worst)and the rockers are where the car gets it's strength.

Another detail I do is to round off the corners of the plates so you don't have sharp corners that can punch through the floor by giving the metal a place to start to tear.

Thanks for the input guys. I went ahead and took pictures, I think I'll be okay going with what I have, It's not perfect, but I think it will suffice judging by what you've said. I don't have a whole lot of metal working tools, a few files, a medium size vice, and a grinder is it.
One more question I have is how should I form these to the contour of the floor? I was just going to jack up on the floor with a wood block and hammer the plate down from the inside until everything is snug.

Here are pics;
Passenger's Side
https://www.rx7club.com/attachment.p...1&d=1300646642
https://www.rx7club.com/attachment.p...1&d=1300646642
https://www.rx7club.com/attachment.p...1&d=1300646642


Driver's Side(The extra hole was a small rust hole I filed out)
https://www.rx7club.com/attachment.p...1&d=1300646642
https://www.rx7club.com/attachment.p...1&d=1300646642

That should work fine.

Put the plate in place, tack it in and hammer it down as you weld. Once its tacked in it won't spring back as much. I little pressure as you weld will help too, I usually have a hammer in my hand anyway and I just push down with that.

If you are concerned about corrosion between the plate and the floorpan you can use the weld-through primer sold at most welding supply stores. I have not really used (or thought about really) thats stuff in years but it does work and I know guys who use it religously.

Thanks guys! I'm going to pick up some Weld Through primer tomorrow. I'll take some after pics when I'm done.

Everything you are doing is fine. I would not worry about the metal to metal areas as it would take a very long time for corrosion to take effect. I've done alllot of cage work and I have never seen an issue with this. Just primer/paint when you are done.

One thing I would strongly recommend is that you DO NOT us brake clean on surfaces you are going to weld. Heating and buring brake clean generates some really bad stuff. Google this....it is is nasty stuff.

I use Martin Senour Kleanz Easy paint prep solvent. A gallon of it from NAPA lasts a long time. It cuts grease quickly and won't kill you when it burns.

Thanks man!

My progress is delayed, I'm hoping to get the plates welded in on Wednesday. Unfortunately I have no garage, so the weather here and my friend with the welder make the schedule. I picked up some weld through primer and my friend did get a couple coats down for me today.

The brake cleaner should be evaporated just fine since we last used it on Sunday, and I've taken note to never use it again. I've read that BrewDude story a few times and that is rough.

Putting in the plates under the bolt in roll bar is the way to go.

I am looking at the first picture you posted. I would suggest that you weld a plate to the side of the rocker panel (inside the car) to the plate you are adding to the floor. Reinforcing the floor in two planes will better integrate the cage to the car. If you do that you can skip the plate on the bottom of the car.

Also check with your sanctioning body rules (if this car is going to be competitive at any point) to ensure your mounting plates are the correct size. Mine had to be a minimum of 20 inches square. My plates at the front drops have one inch of vertical on one edge and I ran it snug to the door sill edge (as also mentioned in the message right above) to increase rigidity and meet my own rules of plate surface area.