Making Motorcycle Gas Tanks
(First Published In Hot Bike Magazine)
©Ron Covell 2005
If you're doing sheet metal work on motorcycles, there are a number of specialized tools to choose from. Some tools (like hammers and welders) are essential, while others (like English Wheels and Plasma cutters) can speed the work, but are not absolutely necessary. In this article you will see
how Ron Covell goes through the process of making a chopper-style gas tank with an unusual embossed design, and you'll see which tools he selects for his style of working.
The bike is a new project from Crime Scene Choppers, who wanted a tank that matched the flavor of their new stainless steel seat. This seat has truly unique styling, featuring a split through the center
of the padded area. This 'bifurcated' design led to the pattern of the embossed area on the tank,
which was made by using the English wheel in an unusual way.
Follow along with the photos, and you'll soon have a good understanding of how custom work like
this is done.
|1. Before you can make anything from metal, you have to envision what you are going to make. Here Ron is using masking tape and heavy paper to make a template, showing the size and shape of the tank as seen from the side. This template will be used to create a wooden 'buck', or form, that the metal pieces will be fitted to as the tank progresses.|
|2. Once the buck is made, patterns are taken from it and used to lay out the metal pieces. Ron is using 16 guage cold-rolled steel here and cutting it with a Beverly Shear.|
|3. Tools come in all forms, and sometimes home-made tools are the best way to go. Here Ron is shaping the curl on the front edge of the tank sides, using a roll of butcher paper as the form.|
|4. As the pieces are shaped, they are constantly tried against the wooden buck to check their contours. Note that the buck has holes that allow the use of spring clamps to hold the metal tightly against it.|
|5. Once the general contour is put into the tank sides, the top edge needs to be curled down. Here Ron is using a hand-operated metal shrinking machine to start the process.|
|6. Once the edge is rough-shaped with the shrinker, it is refined by running it through a beading machine with a special set of 'edge rounding' dies. This makes the edge radius smooth and uniform.|
|7. Here's a close-up shot of the dies. This set has a 1-1/2" radius, and they are also available in smaller sizes.|
|8. Small irregularities are taken out by hammering. Here Ron is using a heavy slap hammer, working against a post dolly. These are some of Ron's favorite tools for hand-shaping sheet metal.|
|9. Once both tank sides are nicely shaped, they are clamped tightly against the buck, and tack-welded together down the center. Ron is using a new, portable Inverter-style TIG welder.|
|10. Next, a pattern is made for the top of the tank. The pattern is transferred to a sheet of steel and cut out. Next, the edges of the panel are pulled down with the shrinking machine.|
|11. The shrinker only affects metal near the edge of a panel, so Ron uses a Polyurethane teardrop mallet, and works into a sandbag to dome the center of the part.|
12. The mallet and bag make fast work of raising the center, although they leave a pretty bumpy surface.
|13. Here Ron is using a benchtop English wheel to smooth out the bumps. This is a very nice way to do metal smoothing, although this work could be done with a hammer and dolly if an English wheel wasn't available.|
|14. The design of this tank was spawned by the unusual seat design from Crime Scene Choppers. Here Ron is using masking tape to lay out a pattern on the tank top, in preparation for making the tooling used for embossing.|
|15. Here you see pieces of 16-gauge steel cut out in the pattern of the 'valleys' in the tank top. Underneath are matching pieces of metal. The upper and lower pieces fit together somewhat like pieces of a jigsaw puzzle. Ron is using Clecos (temporary fasteners) to hold the panels together.|
16. Next, Ron runs the metal sandwich through the English wheel, using the force of the wheels to squeeze the tank top tightly against the upper and lower forming pieces.
17. Here's a close-up of the metal being embossed in the English wheel. The Clecos have been replaced with pop-rivets here, which don't interfere with the wheels as much.
18. And here's our freshly-embossed piece! On the left, you can see the 'male' and 'female' forming pieces. The embossing goes fairly quickly, but making the forming pieces is tricky work for a domed panel like this.
|19. Once the tank top is completely shaped, it is tack welded to the tank sides. The tacks should be no more than 1" apart. Next, the entire seam is worked with a hammer and dolly to ensure that everything is properly aligned, and the seam is finish welded.|
|20. After the tank top is welded to the sides, the weld can be ground smooth. Here, Ron is using a hole saw to make an opening for the Hot Match flush-fitting fuel cap. It is very important to install the cap before the tank bottom is welded into place!|
|21. Here, Ron is using a plasma cutter to make the notch in the front of the tank that fits over the top frame tube. Plasma cutters make fast work of cutting heavy sheet metal, and are especially well-suited to cutting in restricted areas like the front of this tank.|
|22. Last, the tank bottom and tunnel are welded into place, the bung for the petcock is fitted, and the tank mounts are positioned. Here you can appreciate the design continuity between the tank and the Crime Scene Choppers seat.|