Landracing Forum
Tech Information => Technical Discussion => Topic started by: SteveM on October 02, 2012, 09:38:02 AM
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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.
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The windshield could be Lexan
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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. :roll: :roll: :roll:
Pete
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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.
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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
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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
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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.
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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.
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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.
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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! :roll: :roll: :roll:
Pete
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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.
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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.
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The bolt-together idea seems better than the drill & pin idea.
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That is what Clecos are made for.
Regards, Neil Tucson, AZ
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That is what Clecos are made for.
Regards, Neil Tucson, AZ
I heart Clecos!
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Ahhh, yes. I've been meaning to invest in some Clecos anyway. This is the perfect reason.
Steve.
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Ordered a kit of 25 Clecos and a pair of Cleco pliers. Port-A-Band saw is on standby. Cut locations have been "scoped" out on the pillars. Mental leap has been made. I'm hoping to make the cuts this weekend.
Pics to follow.
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When I was a kid and had more time than tools. I cut out glass templates from very thin plywood. When it was time to put the roof back on I laid the front and rear ply wood template in with six sheet metal screws. Leaving the propper air gap on the edge for the glass expansion. Tacked my roof and then welded most of it up. removed the wood to weld the inside channel. Not very high tech but it worked.
Bill
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If you "Z" cut the pillars you will have strong weld and wont need to plug it ...
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Z-cut. Another good idea. I can picture how to make the two horizontal cuts of the "Z", but I'm open to suggestions about how to make the middle (angled portion of the Z) cut through the entire pillar.
Steve.
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Thin cutoff wheel Steve. I prefer Metabos that Fastenal sells.
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I agree on the thin cutoff wheels. I think I can get my hands on some that are 0.040" thick. The B-pillar is just 2 layers, and is a fairly flat shape. Those cuts should be straightforward.
The A-pillar might be a little tricky, still. It's got a funny cross section, and is pretty thick. I'm hoping that the center of the channel will have a usable shape, where I can fit some kind of tubular or sheet metal sleeve.
I hope to have the cuts made and pics taken by Sunday evening. I'm planning to leave the truck's body on the rotisserie, but level it out and lower it down onto 4 jackstands, placed to minimize the bending stress on the whole vehicle. I'm also going to lay out some lines on the pillars, and measure carefully between the lines (A to B pillars), in order to document the initial distance between the lines. When it goes back together, all the dimensions had better be close to the initial ones, or I screwed up somewhere along the way.
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Don't forget to brace it up before taking the roof off, it will have a tendency to twist otherwise. Tony
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The door openings are X braced, but based on what you are saying, I can probably find a couple of other spots to brace (passenger's side floorboar/kick panel junction to driver's side B pillar, just below the cut location, and vice-versa the other direction). Is that what you had in mind?
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Yes, that will work steve.
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Z-cut. Another good idea. I can picture how to make the two horizontal cuts of the "Z", but I'm open to suggestions about how to make the middle (angled portion of the Z) cut through the entire pillar.
Steve.
I think he means that you should cut it at a steep angle, rather than straight across, to give you more contact area for welding.
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Rich:
That's certainly possible, but I have also seen sheet metal work where a zig-zag, or Z shaped cut was used when removing a section. I'm learning some new stuff - that's good.
Steve.
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Cut horizontally half way thru from the front. Drop down a couple of inchs and make another horizontal cut half way thru from the back. Then make a vertical cut connecting the first 2 cuts. Sort of a Z .... Gives a lot of welding surface.
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Cut horizontally half way thru from the front. Drop down a couple of inchs and make another horizontal cut half way thru from the back. Then make a vertical cut connecting the first 2 cuts. Sort of a Z .... Gives a lot of welding surface.
thats what I had in my head
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Cleco set was just delivered :-D :-D I'm planning to make a patch/template piece , held in place with the clecos before making the cuts. Then, when it's time to go back together, I can re-establish the correct alignment and spacing with the same patch/template panels.
The B pillars will be pretty easy to cut with the "Z" type cut. I don't think it's too practical to do the same thing on the A pillars, however. Unless someone proposes a better idea (which they probably will), I'm thinking of doing a "V" shaped cut in the A pillars, which sill still provide additional weld surface,and should help with the alignment somewhat.
I still need to study the anti-twist bracing some more. I realize that the bracing can't interfere with the location of any of the tubes for the actual roll cage, since the bracing will need to remain in place until the cage is at least tacked all the way around.
Thanks for the good ideas.
Steve.
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I still need to study the anti-twist bracing some more. I realize that the bracing can't interfere with the location of any of the tubes for the actual roll cage, since the bracing will need to remain in place until the cage is at least tacked all the way around.
Bracing for the roof does not necessarily need to be on the inside of the roof piece.
Larry
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I was thinking in terms of bracing the body from twisting, but maybe I need to be thinks about bracing the roof/pillar section as well. I'm planning to make the cuts pretty low on the pillars.
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Roof should be fine w/o bracing.
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Thanks for all the good advice, guys. The roof has been removed. Extra diagonal bracing was welded in place before the cuts were made, template pieces were Cleco'ed into place, and the B pillars were done with a Z type cut. The A pillars were done with a V shaped cut.
Pics are in the "Build Diary" section.
Thanks again.
Steve.