Welding Cage - cut holes in floor, or cut roof off vehicle?

[SteveM]

I'm very close to the point where I will be welding the cage into my trucklet (Dodge Rampage).  I had been of the mind that I would cut 4 holes in the floor to allow the primary attachment points to "drop through" the floor for welding the upper portion of the cage, and then do the balance of the work inside the passenger compartment. 

However, someone on the board suggested that I might be better served by cutting the roof off the vehicle, doing all the cage fabrication, then welding the roof back on.  This approach seems to be making more and more sense.  The obvious locations to make the cuts would be low on the A and B pillars, allowing the greatest access to the interior of the vehicle for welding.

My biggest concern with this approach is getting the top welded back on and still allowing the factory windshield to be installed and sealed.  The back window and side windows will have to be custom made from Lexan, so I don't need to worry about getting the dimensions 100% perfectly back to factory specs.  However, the stock windshield needs to go back in place.

I'm thinking that I should scribe some lines on the pillars, a fixed distance apart (maybe 6"), one above the cut line, and one below the cut line.  That way, when I weld it back together, I can re-establish the 6" dimension.

Any suggestions for doing this job as cleanly as possible would be appreciated.

Steve.

[RichFox]

The windshield could be Lexan

[Peter Jack]

In the old days when I was working with steel bodied stock cars and road race cars I'd use a hacksaw. The width of the cuts was negligible and the front and rear windows would go back in with no problem. Those were also the good old days when I was oxy / acetylene welding the roofs back on. 

Pete

[Tman]

We use a portaband and thin cutoff wheel. Never an issue going back together. It is also a good idea to sleeve the joints. You can bend up some sheetmetal sleeves to go inside and rosette weld them in the A pillars before sliding the top in place.

[JimL]

Holes in floor is safer.  Those roof pillars rely on multiple layers, built up by spot welding, to bend but stay intact in a big crash.  Anything designed after FED rollover standards is made this way.  If you cut and reweld, thats where they will break and might become spears.

Hypodermic needles are just sheared off, brittle tubing.  Thats why my MC fairing mounts are soft, solid rod.

JimL

[SPARKY]

Cutting the holes in the floor and lifting and tilting the body to get to one side then the other would be the way I would go ---IF--- you are getting rid of the body mount pads as a lot do.---square holes slightly smaller than the rects. you have to mount the cage to.  YMMV

[SteveM]

Good points on both sides of the issue.  The floorpans in this vehicle were quite rusty before I started working on it.  Right now, the front sections have been completely rebuilt and reinforced with square tubing, and 1/8" thick sheet at the locations where the front down legs will attach.  I am prepared to cut holes through the 1/8" steel if that's the direction I take.  In the rear, there are rectangular holes, just slightly smaller than the 1/8" steel sections that will occupy those locations.  1/4" thick pads will go on top of the 1/8" sheet before the cage will be complete.

The body of the vehicle is currently mounted on a rotisserie.  I plan to take it off the rotisserie and put it on jackstands for the cage fabricaition.

Originally, I was in the mindset of cutting holes in the floor to allow the cage to drop down/move around.  I keep running this around in my mind, trying to figure out how to get ALL of the needed welds done by dropping the cage through the floor holes.  Since this is my first cage build, I am worried about "welding myself into a corner", where I get to a point where I need to weld in another bar, but don't have access to the top side (like after welding in some floor or lower door bars).  At that point, I'd probably have to cut the roof off anyway.

Someone here suggested that it might be easier to cut the roof off.  I certainly agree that having full access to the top side of the cage would be much easier with the roof removed.  However, it's also a good point about the safety of the factory-built A pillars, in particular.  Making an inner sleeve for the A pillar, and rosette welding is a good idea.  I could also weld some gussets between the cage and the A and B pillars to further reinforce the cut-apart and re-welded joint.

Anyway, I'm talking in circles right now, but appreciate the input on both sides of this issue.

Steve.

[Tman]

If the cage is built to SCTA spec the skin is merely a wrapper anyway. By cutting the roof and sleeving it you will not run the risk of having a weld on the cage compromised due to it being hard to get at. After you did such nice work on the floor I would not cut it back apart.

[Tman]

I remembered one other method. We did a cage in a car, I forget what it was, where it was easier to pull the roof skin loose but leave the structure. That let us get to the top joints and gussets easily. NOT an option with all cars.

[Peter Jack]

I guess one more option might be to cut out patches in the roof where the welds have to go. Once they're completed the patches could be welded back in. A little grinding and Bondo and the body would be just like new! 

Pete

[Dean Los Angeles]

If you tack weld a two piece steel bar that is bolted together and bridges over the area of the cut, it will hold position while you are cutting, and allow you to put it back in the same place later. More work now to eliminate alignment issues later. Weld in a patch and cut the tack welds on the bridge.

[SteveM]

Good thinking, Dean.  I was trying to figure out a good way to hold the alignment while cutting.  I was thinking of using a steel bar with 4 holes drilled in it (1/8" diameter), drilling all the way through the bar and into the pillar, so that I could use 1/8" pins, put back in the same bar/fixture to keep the alignment. 

Lots of good ideas, here.  I've pretty much made the mental leap to cutting the roof off.  Now I need to figure out the details, just like what's being described here.

Steve.

[SteveM]

The bolt-together idea seems better than the drill & pin idea.

[manta22]

That is what Clecos are made for.

Regards, Neil  Tucson, AZ

[Tman]

That is what Clecos are made for.

Regards, Neil  Tucson, AZ

I heart Clecos!