MAKING A CUSTOM SEAT

Transcription

1 MAKING A CUSTOM SEAT Making a custom seat is a reality all boober or café racer builders will have to face. The original HONDA CB550 seats are durable, good looking and very comfortable. But, a dual seat is against the bobber principle and so it must go. In addition, a new seat utilizing an aluminum seat pan, light ½ foam and marine-quality vinyl will help shed 6-8 lbs. of weight off the bike. That alone is an excellent reason for going the custom-seat route. There is a huge variety of solo seats out there in all imaginable shapes and choice of materials. From the simplest to the most ornate. It should not be that difficult to find one that would suit your style and that could be fitted with only minor modifications. This approach is very tempting as it offers an easy way to put the seat issue to bed especially when pondering the alternative of making a seat from scratch: the materials that need to be procured, the special tools needed, the special skills required, etc. If you insist on a perfect harmony between the tank and seat in both their shapes and looks, then a custom seat becomes a necessity. Before setting out to find somebody who could make you one, consider the possibility of making your own. It s not that difficult. And it is very rewarding. I hope the following will help. I started by stripping the original seat down to the steel pan and then cutting and trimming the pan until I got a rough shape of what I needed. I then placed it on the frame. It looked like this: The yellow line shows the rough contours of the seat I thought would look right. The blue line shows where I intended to cut the frame. I took all the necessary measurements and made a few very rough drawings. See below:

2 Drawing #1 Drawing #2

3 Next, I drew the outlines of the seat including the skirt (in blue below) on a piece of aluminum 1.6 mm or 1/16 thick (Gauge 14; note that aluminum thickness gauges are different from that of other metals like steel for example.) Using a jigsaw, I cut the shape along the outer lines:

4 Next, I bent the piece into the cradle-like shape shown in the drawings above: While it is relatively easy to bend, even at this thickness aluminum is pretty strong and very difficult to work into shape. It has to be heated in order make it softer (the process is called annealing ) and much more malleable. I used a blow torch and first tried on a couple of small pieces to make sure I understood what needed to be done. I noticed that, when sufficiently heated, the aluminum surface changes appearance and becomes duller. It is at this point that it becomes annealed. It would remain soft for some time so there is no need to work it immediately while it is super-hot. I placed the seat pan on a 10-lbs canvas bag of rice (professionals use a leather bag filled with buckshot) and using the narrow end of a wooden mallet I had made myself, I started to hammer the seat into shape; first forming the skirt by banging at the inner (black) line.

5 As the metal cools, it becomes harder again and needs to be re-heated. It makes all the difference in the world working with a soft sheet of metal! It is possible to split the aluminum sheet when hammering too hard, so you need to be careful. But overall, it is fairly easy to do and if you made a mistake, you can always start with a new sheet. Once you have shaped the seat pan to a point where you are happy with its look and fit, reheat it completely again and then plunge it into a sink filled with cold water. This will cool the metal instantly and will harden it to its original hardness. Here is what the seat pan looked like when finished: I had assumed, incorrectly, that the skirt would look alright at about 1.25 height. But, when I mounted the seat pan on the frame I realized that a much shorter skirt would look and feel much better. It was an easy fix; I just trimmed the skirt to the appropriate height (about ¾ ). Next, I glued a ½ thick foam pad to the seat pan covering mostly just the flat platform and after the glue had set I trimmed and tapered the foam as needed. I drilled 1/8-inch diameter holes about 1.5 inches apart all along the perimeter so the vinyl cover could be properly riveted to the seat and was then ready to finish it.

6 I used marine-quality vinyl, which is known for its durability under all conditions. (Initially, I insisted steadfastly on leather and actually bought and tried a few different ones. But neither the look nor the feel appealed to me in the end. I also found leather to be more difficult to work with. I did, however, use a small piece of black suede sewn to the vinyl and positioned on the underside of the curved front section, which faces the tank. This created a kind of pocket that the curved lip fits into for a near-perfect fit so there is no need to fold the material on the underside as it is secured to the seat pan. The suede is also extremely soft and will not scratch the tank if there is an occasional contact during removal or installation.) The photo above shows all the tools needed. The clamps will help you when stretching the vinyl cover to ensure a wrinkle-free fit. The hole puncher is used to punch holes in the vinyl prior to pitting a rivet through. You just stretch the vinyl until you get the perfect fit, mark where it meets the pre-drilled hole on the seat pan, punch a hole at that mark and then insert the rivet through. Putting the vinyl cover on and securing it with aluminum rivets and washers is fairly easy. It is important to use the washers as they provide a much larger surface area for keeping the vinyl against the surface of the aluminum seat pan than just the rivet itself otherwise would. It takes a little practice to get it right, but it is not all that difficult. Here is the final result:

7 And mounted on the bike:

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