by Roland Wilhelmy, Bob Hoover, and Ken Hooper
Ken Hooper writes:
There are a lot of people contemplating nose replacement lately. These are in response to my query about replacing the nose in a splitty but once I got to looking at it, much of this may apply to a bay as well, but the flanges are turned 180 degrees the other way in a bay. Modern coachwork.
These are very dense but they start to make a helluva lot of sense once you've read them 10 or 12 times.
Also Rob King noted that "new" replacement noses are not designed wide enough to do flanging/wraparound tricks, you have to get the wide noses from a donor bus rather than a retail source.
Let us commence.
Mr. Roland Wilhelmy writes:
Here are my thoughts. I think it is best to make your cuts on the lines along the areas with tightest radius. Of course you have to make the cuts really carefully and allow extra metal so you can fit pretty precisely, but it is easier to grind the welds to look well on more curved surfaces than running through the flats. You can do sorta fake flanging by fitting for a butt weld and then first welding in backing strips to support the inset panel. These can range from complete backing to just enough pieces to make it easy (huh!) to hold the panel in place while you tack things together -- whatever suits you. And the welding of the strips can range from big tack welds to full length beads, as you choose. I am uneasy about trying to flange, say, ten feet of edge. If you do flange, you will be flanging the bus metal, not the patch. If you don't have the flange depth just right, then you have to do a lot of filling of one side or the other of the patch line, which is about as hard as butt welding it in the first place. And flanging is a lot easier on flat panels than on the middle of a tightly bent line.
One point in deciding where to put your seams is that you will be really thankful if you can reach the back side of the seam lines from inside the bus. This is darn near impossible to arrange, at least fully, but do think about this and do what you can.
If you can rent a plasma cutting torch to trim out your bus' nose, I say spend the money. Cutting with a plasma torch is almost like drawing a line with a magic marker, only there is a narrow little cut where you "draw" instead of a black line. Like with a marker, you use a ruler or straight edge to make straight lines, and cut out patterns in metal and wood to guide you on curved ones (or just cut inside the line, freehand, and clean it up with grinders and files and shears). I have a small 110 volt plasma torch and think it is the handiest tools there is, next to a MIG welder. Plasma torches need very modest amounts of 50 psi compressed air, along with the 110 volt ac. You can cut painted metal with no problem, just be sure that what is behind the panel you are cutting isn't going to catch fire. It isn't nearly as much flame and sparks as a gas cutting torch, but there is some, more like with a grinder.
If you decide to try flanging of some sort, I have a different sort of flanger that I haven't gotten up the courage to use yet: From Eastwood, it makes just a small bend along the edge of the metal, deep enough to let a MIG weld bead sink to almost flat in the V made where the two edges come together. This flanger is of the modified Vicd-Grip plier type. If you guys want to try it, I will lend you mine with the understanding that you will return it to me when you are finished with welding the nose. (If it works well enough, you can get your own).
Most important, if you "don't know what" you're "doing" with a MIG welder, plan to spend at least ten hours practicing on scrap VW sheet metal, making the sort of welds you are going to be doing on the nose. And have a good hand held grinder to finish off your work. "Flap wheels" do a nice looking job, but they aren't cheap. Start on your bus after you are happy or at least satisfied with the look and solidity of your work. MIG welding isn't brain surgery, but a few hours of practice where you can make some of the inevitable mistakes all weldors make is a lot easier to take than having to repair messes that didn't need to happen on your bus. Besides, as you will find, it is a lot easier to weld on horizontal surfaces than on the vertical ones your bus will be offering you. Learn on hunks of horizontal sheet clamped together on a table. Then practice a couple of welds running across and up and down vertical sheets. Then you will be ready.
And Mr. Bob Hoover writes:
The best cut-off tool is an air-driven die-grinder mounting 1/16" thick cut- off disks. Second-best is the standard 4" electrically powered hand-grinder (about $20 at Harbor Freight -- disks are about half a buck each [ie carton of 10 is about five bucks, locally] ). I've got four or five such grinders. Keeps me from having to change disks/flappers as the work progresses.
You can get 1/32" thick disks for a die-grinder -- makes a truely elegant slit in a steel panel... for about a foot. Then you need a new disk. Sixteenth- inch thick, mebbe three feet per disk, depending on the thickness/hardness of the stuff you're cutting. (Oddly enough, harder stuff cuts faster.)
The disks used on 4" angle-grinders are about 3/16" thick, last for as long as you can keep them in contact with the metal (the head of the grinder gets in the way) and are much less expensive than the diamond-hard Resinoid cut-off wheels used with die-grinders.
Saws are normally only used in areas you can't reach with a grinder, such as slicing thru a 2x4 'C' section from the top --- grinder can only cut about 1" deep. Blades are expensive. Disks are cheap.
If you've got the whole front-clip to play with, remove the entire nose skin at the folded seams along each door pillar and the folded seam along the bottom. IF the wipers/windscreen are not rotted out, cut BELOW the level of the wiper indentations, leaving at least half an inch for a flange. (More is better. You can trim it later.)
To cut the seam, you simply grind off the outer edge of the fold then GENTLY go after the spot-welds with a sharp chisel. This will result in local deformation but in almost every case it will be OUTBOARD of the crease between the seam and the body-panel itself. You then dress this flange back to truth, ragged or not.
On the bus to receive the skin, you follow the same general procedure except you cut away the skin INBOARD of the folded seam and go after the spots with the EDGE of your grinder, LEAVING THE OUTER PART OF THE FOLD UNTOUCHED.
What you'll end up with a lip on the edge of the fold. If you will now grind that flat you will see that have a flange to which you can spot-weld PLUS a surviving 'factory' edge on the fold... with a gap between the donor panel and the edge of the fold that will have to be filled, ideally with the migger but schlock shops use Bondo, etc.
The big advantage here is that you end up with flanged surfaces on which to adjust the position/placement of the donor panel yet the visible, significant flanges have retained their factory fold & shape. If you try to build this flange back up by welding/grinding, you'll find yourself spending as much time on that task alone as you spend on the rest of the job. By retaining the edge of the fold -- AND LEAVING IT ALONE -- you need only fill the gap.
Positioning the skin is also much easier when you have 'factory' flanges on three edges. The joint under the nose will require trimming, then forming of the flange, then trial fitting and perhaps more fitting -- flanging can stretch the skin.
The usual flange tool is pneumatic but manual and electric types are available. I use one of those attachments that chucks into a rivet gun. It forms a flange half an inch long and .030 deep. In use, you gotta lean into the thing. The flanger is just a high-speed hammer & dies. The flange won't form itself -- the metal will just vibrate back & forth. It takes the strength of your arm to make the flange 'appear'. Once you get it started, you simply walk the tool along the end. It will guide on the cut-edge, so you want that ground straight and cleaned up real nice. Once you have a good flange, you fit the new panel to the flange by gently grinding it down until the new panel fits neatly into the flange with a gap of about a sixteenth. That is the space into which you will weld or apply filler if the flange is to be spot-welded. The edge of the fitted panel must also be clean and well dressed. If spot-welding, the resulting flange is often painted with weldable primer. After the repair is done, if the lower edge of the flange is accessable, it's a good idea to seal it. In hard-assed repairs, you weld it. (Grendel's new driver-side full-length rocker-panel is welded both sides at the top.)
To secure a new nose skin you start at the middle, top & bottom, then work toward the side seams. You'll need about a zillion round-nose finger-type vise-grips.
Once you get things tacked, focus on NEVER letting the panel get overheated. This is a bitch with gas -- you can't weld more than 3/4" at a time then have to move to another area. With a migger, you can do about 2" before you have to let that section cool. That means, doing about four weldments then waiting until you can put your hand on the LAST one you did before going on.
Spot-welding is the best way to secure the lower & side flanges. With clean surfaces you can tack every 4" or so, alternating, side to side, go back and tack in between (ie, 2" pitch) for about four tacks on one side before alternating. When it's tacked at 2" pitch, take a break, let it cool, go back with dolly & hammer and dress-out any local distortion. Then go back and put a real 'keeper' between each of the previous spot-welds. That gives you a 1" pitch and should result in a symmetrical, drum-tight installation. Then comes the gap-filling (or edge-welding), followed by a lot of flapper-wheel work.
Don't try to polish-out all evidence of the spot-welds -- there are valid applications for body-filler and this is one of them. If you can afford to do so, use the epoxy-based, metal-filled fillers (Eastwood, etc) rather than the polyester-based, silica-filled fillers such as Bondo. You'll need to use more work to get the metal/epoxy filler smooth but you'll end up with a more permanent surface.
If you don't have a spot-welder, look into renting one or borrowing one. They run about $250 for a good one but you can often find them used for about half that. You should even consider buying one for the job, selling it after.
The only secret to good spot-welding is clean surfaces, easy enough to achieve with flapper wheels. And clamps. A lot of guys mistake their spot-welder as a clamping fixture :-), fail to provide enough clamps to hold things together while the welding is done. Pay attention to the shape/condition of the copper electrodes. Polish them (gently!) as the job progresses. If the seam is well-clamped to either side of the target-spot, you won't need all that much clamping pressure to get a perfect 'nugget'. Although infinitely easier than conventional welding, there is a learning curve involved with using a spot-welder, as well as a bit of practice needed if you've not used one for a while. Making up some coupons from the old nose-metal will allow you to practice. Be sure to tear your test-welds apart. The welded-together 'nugget' should not come apart -- the parent metal should tear first.
The top seam, where you'll want to form a flange, will be mostly concealed behind the dash. Before doing a nose job it's a good idea to remove ALL wiring from behind the dash. The package tray, wipers and heater ducts should also come away.
Working with an entire skin you can put clamps on the edges. This is often all you need to bring your flanged-seam into alignment. But you also have the option of using wooden poles or other means of exerting pressure against the back of the seam. This is usually only needed in the center. You may also use clecos or sheet metal screws but if you're not familiar with the technique -- or if you don't have enough clecos -- you can build in some ugly, ugly bulges in an otherwise perfect seam. Holes for clecos or screws are filled later, either with gas or by backing-up the hole with a copper block and hitting it with the migger. The migger does best here. Chamfer the hole -- make it bigger, with a decided taper -- so the heat gets to BOTH panels at the same time. Otherwise, they will heat/cool at different rates and you end up with minor bulges that give the finished seam a slightly 'pillowed' look.
Clamp. Weld. Cool. Move on.
As a general rule, the greater the mass of copper you use to back up a weld, the less will be the heat distortion, risk of burn-thru, blow-out, etc. But the curveture of the panel dictates the size of the contacting surface (unless you specially cast/shape your coppers). For a bus nose the copper block is going to be limited to about an inch square. The usual procedure is to shape/dress raw copper stock then braze it to a steel rod. Grip the rod with vise-grips, etc, press firmly against the hole. Working alone, it goes pretty slow but sometimes that's good.
Welding supply houses offer an assortment of commercially-made coppers.
A lot of guys tackle a nose job without regard to what they're going to find once the skin is off. Often times, once the skin is off they find another weeks-worth of work in the substrcuture. There is a classic water-trap at the foot of the panel (and a hell of a good source for road noise to get into the cockpit). It isn't a very good design.
You'll also see (by the placement of the welds) that the heater-ducting was installed before the nose skin went on. You'll be doing things backwards so plan how you're going to re-install the ducting... if you take them out. (Some shops have the tooling/experience that allows them to leave them in, work around them.)
If you want to build-in a concealed compartment... with the nose skin off, examine the 'well' at the bottom of the panel, between the supports for the bumper. (The trick here is that after removing the front belly pan -- and finding nothing concealed above it, few inspectors extend their search to the frame-rails or body panels that have been concealed by the belly pan. Or, so I've heard.
I suggest you de-rust this area aggressively. This is also the ideal time to deal with those nut-plates for the front belly-pan. Once you've dealt with the rust, flood the space with corroless or other thick-film anti-corrosion paint. Insert steel tubing for the electrical harness to pass through and put globs of RTV over the nut-plates then fill the void with high-density urethane foam, the stuff you mix together and pour (check with a hobby shop. Our local HOme Depot has started carrying it). The anti-corrosion paint should be allowed to dry for two or three days before you foam it.