How to Build Motorcycle Gas Tank Sides with Ron Covell

Ron Covell is a master of stretching, bending and shaping sheet metal. Eastwood has several DVDs for sale in which Ron teaches you how to do the things that he makes look so easy. He also teaches classes all over the country including at our own shop at the Eastwood headquarters in Pennsylvania. For many years now he has attended the annual SEMA show in Las Vegas, but the past two years he’s been in the Eastwood booth to demonstrate the proper way to use various tools Eastwood sells from simple hammer and dollies to the English Wheel.

This year he showed how to make a motorcycle gas tank side with a voluptuous compound curved shape using some of the most basic metal shaping tools. In this demonstration he shows how to make the left side of the tank. After shaping the two sides, Ron would make the tank complete by TIG welding them to the tunnel, a curved top, and the two curved bottom pieces.

Ron prefers when working with Aluminum to use 3003 aluminum alloy that he’s annealed using an Oxy-Acetylene torch to make it as soft and pliable as possible. For this project he is using 1/16 inch thick flat stock. The same techniques will work on mild steel as well; it just takes more energy and effort, because steel is harder to deform.

Some of the tools used include a Panelbeater sandbag, a teardrop mallet, the Eastwood shrinker, body hammers and dollies, and the benchtop English Wheel. Also, to be safe, whenever you’re working with or fabricating sheet metal, always wear gloves, ear protection, and safety glasses.

1) Start with a flat sheet of metal that’s been cut to the appropriate shape for the piece you’re making. This piece is shaped nearly exactly how the cross section of the tank would be if you were to cut it opened along the seams where the side is welded to the top and bottom pieces.

2) Begin shaping the metal by using the Eastwood Shrinker/Stretcher to shrink the perimeter of the panel where it is going to be domed. Shrinking the edge makes the middle bulge exactly the way the dough of a pie crust or ravioli does when the edges are crimped. Ron inserts the metal ½ the depth of the shrinker jaws, and overlaps approximately 50% as he works along the perimeter of the edge.

3) Here you can see how the shrinker in one pass curved the metal ½ inch or more and 30 degrees away from vertical.

4) Work the shrinker all the way around the edge of the big curved end of the panel.

5) Then do the same thing with the smaller radius at the back of the tank.

6) Shrinking the edges of either end of the tank side work together to dome the back of the tank
more with just one pass.

7) Experience and a trained eye tell Ron that the front dome is not shrunk enough yet. The angle of the edge of the panel is still not quite right when compared to the example of the tank he is copying. Alternatively you can use your buck or the original tank you’re copying to check the progress of the shape of your panel.

8) Ron puts the panel through another pass in the shrinker, this time using even less of the jaw’s depth
to produce a more pronounced angle.

9) The angle at the edge is now much closer to what the tank needs.

10) In the shrinking process an unwanted curvature was created. So what can you do?

11) Supporting the metal on the sandbag and using just his hands, Ron straightens it, and in the process changes the curve to one he does want.

12) By straightening and cupping the center part of the panel, Ron shows metal takes on a much closer approximation of the tank shape.

14) The edges are looking good, but the center of the panel needs much more dome to it.

15) The teardrop mallet and Panelbeater sandbag are used to pound the metal in the center of the large domed portion of the tank. The pounding thins and stretches the metal in the center allowing it to bulge out into the shape Ron is trying to get.

16) Once again, bending and stretching in one direction results in curvature in a second unwanted direction.

17) Ron uses just his hands to straighten it out, which results in the dome getting much more pronounced in the desired direction.

18) The dome is getting to be bulged out enough to match the contours of the tank, but it is very lumpy. Ron begins identifying the low spots that need more attention.

19) Working with less force, Ron works to even out the low spots still using just the mallet and sandbag.

20) Ron explains how putting waves in the metal and then trapping the waves by hammering them flat works to shrink the metal.

21) Ron explains that when you hammer the waves flat, the grains of the metal slide into each other like interlocking fingers. The metal gets a little thicker, but at the same time smaller in surface area.

22) Now the finer shaping and smoothing begins. Using a relatively flat dolly and a common body hammer, Ron begins to smooth out the bumps and low spots.

23) It’s time to move to a more curved dolly that more closely matches the shape Ron is trying to form the metal into.

24) More hammering on the rounded dolly works to get the metal smooth and to get the proper dome.

25) A test fit on the tank shows how close the dome is getting to the desired shape. It also reveals how far off the middle and back parts of the tank are to their correct shape.

26) The mallet and bag are again used, though this time with less force and some additional curvature is added to the middle of the panel.

27) Doming the center once again adds an unwanted curvature that need to be corrected by hand.

28) Then, the flat part of the dolly is used with the curved face of the teardrop mallet to smooth out the rough parts of the middle and rear of the tank panel and to give it the proper contour.

29) The panel is now starting to take on the shape is needs to be made into a fuel tank. At this stage it’s about 90% of the shape it needs to be.

30) Ron again swaps out the post dolly in the vise for one closer to the shape he is trying to make and works the panel with the body hammer.

31) With the correct contour and shape (as confirmed on the tank Ron is copying), all that is left is smoothing the metal as much as possible. There are several options for the final smoothing of the new panel. You can spray high build primer on it then sand to reveal the low spots. You can also metal finish it with a file, which helps smooth out the high spots while showing where to pick or bump out the low spots.

32) Ron chooses to use the English wheel for final smoothing. He could have used the wheel for the whole project, but felt it was more interesting to show how you can do the same job with the simplest body tools. He suggests to select the wheel with the least crown or the closest to the shape of what you are smoothing.

33) Using only a slight amount of pressure on the wheel, roll the panel back and forth, working from one end to the other. After each pass or two across the panel with the wheel, stop and check your progress to make sure the panel has been smoothed out in a uniform manner.

34) And there you have it: one panel of a tank ready to be fit up with the other tank parts and then welded together.