I am fabricating a custom motorcycle tank emblem that needs to end up being about 3" x 5" in area and just over 1/2" thick and follows the complex and rather deep contour of the side of the tank. Does anyone have a suggestion about how I might go about duplicating the inverse of this tank contour on the back of the completed emblem? The contour will be up to 5/8" deep in the area where the emblem needs to be mounted.
How are you fabricating the emblem, Terry? Are you casting it?
If so, that's a plaster job, taking a splash mold off of the tank (a five-minute job) and then transfer-molding a core (it could be made from one of several materials) to get the contour on the back side of your casting. Zinc or aluminum castings are suited for this.
If you're going to fabricate the piece in some other way, let us know, and someone may have a solution suited for your fabrication method.
I'll be cutting, grinding, filing and polishing it by hand from a chunk of billet aluminum. There will only be two made and they will be mounted to the tank with 3-M double-sided trim tape. And so because of the method of mounting and for esthetics I need to keep the contour accurate to +/- 1/16" or so.
Well, the traditional method is to mark the workpiece with some kind of indicator and remove small amounts and re-indicate. A traditional indicator is candle smoke: you smoke the side of the tank, rub the emblem against it, and carve/sand the area where the smoke has rubbed off on the back of the emblem. If you can find any carbon paper, that would be less messy.
Done carefully, this method is wonderfully accurate. If you want a good looking job, and a good bond, you will want **MUCH** better than +/- 1/16". I think +/- .005 would be more like it. This and better can easily (not quickly, but easily) be done by the indicating method. With care you could get into the +/- .001" range.
-- --Pete "Peter W. Meek"
Terry, Since this will be hand work then a contour gauge would work great. Lay some of that blue masking tape on the tank so that it surrounds and covers the area to be copied. Mark the tape with lines forming a grid to be used for reference. Then, use the contour gauge to transfer the shape to your part. The contour gauge is a tool which is made up of many wires, either metal or plastic, held so they are lined up in a row. When the tool is pressed onto the surface to be copied the wires follow the countour. So one side of the tool has the contour and the other side has the negative of the contour. These gauges are available at any good hardware store. Make your part in such a way that when you compare it to the gauge it is always in the same spot. This way the grid on the tank and the grid on your part will line up. ERS
||>> > I am fabricating a custom motorcycle tank emblem that needs to end up ||>> being ||>> > about 3" x 5" in area and just over 1/2" thick and follows the complex ||>and ||>> > rather deep contour of the side of the tank.
||Terry, ||Since this will be hand work then a contour gauge would work great. ||Lay some of that blue masking tape on the tank so that it surrounds ||and covers the area to be copied. Mark the tape with lines forming a ||grid to be used for reference. Then, use the contour gauge to transfer ||the shape to your part. The contour gauge is a tool which is made up ||of many wires, either metal or plastic, held so they are lined up in a ||row. When the tool is pressed onto the surface to be copied the wires ||follow the countour. So one side of the tool has the contour and the ||other side has the negative of the contour. These gauges are available ||at any good hardware store. Make your part in such a way that when you ||compare it to the gauge it is always in the same spot. This way the ||grid on the tank and the grid on your part will line up. ||ERS
Well yeah, but then what do you do with it? I can see using the cordinates in a CNC or at least some sort of pantograph. Perhaps use the coordinates x-y-z in a mill-drill with an endmill to rough out the countour, then finish by hand? Texas Parts Guy
Does the whole thing need to match the tank or just the edges? It strikes me that it'd be easier if you just needed to get the edges to match the tank contours and then hog out the rest of the back. You could attach it with silicone seal or something appropriate...
Peter
Given that, I see you've already been given some good tips on spotting it to custom-fit each emblem. It's tedious, but you can get very close that way.
I didn't ask how you're attaching the emblem. Keep in mind that, if you're thinking about using an epoxy adhesive, you get the strongest joints with close to 0.005" of joint clearance. Don't go any closer than that or you'll lose peel strength. And you don't lose much strength as the epoxy layer gets thicker, up to around 0.020" or so.
Good luck!
Mount tank on CNC machine. Mount probe on CNC. Run program which probes an area, thus providing map of contour. Takes a while if you try to be precise, especially if you have a slow CNC. Then cut...it's not the movies, but it works right now, not in some never never land that never never arrives.
For a metalworker you forgot the most obvious vice - the Record
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