Here's the finished fender,...
Here's the finished fender, after a little work on an English wheel, sanding, and polishing.
Paul Propst, from Holland, Michigan, is building a car and he needed some cycle-style fenders made. He made a female form for the fender from wood. You'll see in the photos how he made a series of blocks from oak about 2 inches thick, with the concave cross-section of the fender cut into each one. The blocks are screwed to plywood side pieces, which hold them in the proper arrangement. While Paul's form is more elaborate, it is something that anyone with some basic woodworking tools can make, and a very low cost.
Paul used a hydraulic H-frame press to push the sheetmetal into the form. The press shown is a 20-ton version, which has much more force than needed, but it had enough vertical reach to clear his somewhat bulky form. The ram of the press is fitted with a shaped hardwood block that matches the inside contour of the finished fender.
Paul, too, found that the force and location of the pushes is a major factor in the efficiency of the process. The procedure he developed is to start at one end, and push the metal about half-way down into the concave wooden block, then release the pressure, and slide the form down about an inch, so he is pressing on a fresh area. After he works an area about 6 inches long, he goes back to the beginning position, and pushes the metal down tightly against the concave blocks, releases the pressure, slides the form another inch down, and so forth. Working with a helper, Paul can shape one fender in about an hour. After the fender is rough-shaped in the form, Paul smoothes it in an English wheel, and then polishes it. These fenders are made from 1/8-inch thick aluminum, which would have been nearly impossible to shape with a mallet and sandbag!
Dave Propst, from Walla Walla, Washington, (no relation to Paul) has experimented with his own version of this process. In a dramatic demonstration of how a fairly large and deep panel can be roughed-out with a press, Dave made the sample panel, shown in the photos, similar to the front half of a fender like a '36 Ford. Dave made his own H-frame press, which is unusually large, and has many adjustments that most presses don't have. He uses an air-over hydraulic pump to cycle the press ram quickly and effortlessly.
While Paul and Bob allow the edge ruffles to form naturally, Dave uses a tucking fork to start the folds initially, so that when he press-forms the center of the panel, the tucks develop automatically in the areas where the edges are disturbed. Dave used ordinary cold-rolled 18-gauge steel for this demonstration, which would have been quite difficult to shape with a mallet and sandbag. The rough forming shown here was done in about 10 minutes on his press, working into a urethane pad.
In the photos, you'll see a beautiful example of a '40 Willys lower grille panel that Dave rough-shaped with his hydraulic press. Never one to rest on his laurels, Dave has recently developed an unconventional way to use an English wheel to quickly do the initial stretching for panels like this. Look for a future article on Dave's techniques for rapidly making deeply-domed parts on the English wheel.
Construction details of a shop-built, extremely versatile H-frame press, and detail photos of press-formed sheetmetal parts:www.davepropst.com
Starter kit of dies and a special sandbag for the press-forming process, using an inexpensive arbor press:Bob Haverstock (217) 752-6873
After about an hour, the fender...
After about an hour, the fender is formed to a point where only a tiny bit of finish work is needed.
Taking a slightly different...
Taking a slightly different approach, Paul Propst has made a wooden form that matches the shape of the fender to be made.
Another shaped oak block is...
Another shaped oak block is positioned against the hydraulic press ram to push against the sheetmetal. The dowels keep the metal blank from creeping away from the form.
This close-up shot gives a...
This close-up shot gives a better view of the surface finish developed at the different stages of forming.
The sidepieces of the form...
The sidepieces of the form are made from plywood, and segments of solid oak with the fender cross-section cutout are screwed into place to create the form. A metal test piece is shown on the contoured oak blocks.
Here you can see a fender...
Here you can see a fender with no press forming, with the first series of pushes, and nearing completion.
Dave Propst uses a slightly...
Dave Propst uses a slightly different version of the press forming process. These are differently-shaped nose-pieces for the ram of his hydraulic press.
For deep shapes, Dave first...
For deep shapes, Dave first puts tucks, or folds in the edge of the panel, using the tucking fork shown in the foreground.
Here, Dave is pressing 18-gauge...
Here, Dave is pressing 18-gauge sheet steel into a urethane pad.
With the tucks started on...
With the tucks started on the edge, the press forming creates the depth of the part quickly, and increases the size of the folds on the edge of the panel. These folds are worked down by hammering and wheeling, which shrinks the edge of the panel.
This is the panel that fits...
This is the panel that fits under the grille of a '40 Willys, rough-shaped by the press forming process.
This is a close-up view of...
This is a close-up view of the Willys panel-note how smooth it is after the finish work is done. All of the flanging on the edges of the panel was done with hand tools.