This is one of those things you just have to fumble with to produce a template. There are some complex formulas you could use to draw the cutting curve but I take the easy way out.
You probably won't be able to use your first attempt.
I set a BT-5 tube along the side of the BT-50H main air frame. When I decided on a good angle, a pencil line was drawn on the side of the BT-5.
A rough cut was made with a single edge razor blade. Try to get it close, matching up both side cuts on the tube.
On the right is the second attempt.
Wrap some 220 grit sandpaper around the BT-50H tube and sand up and down, parallel with the length of the BT-50H.
Here's a good fit against the main body tube.
In the next post we'll make a template from this intake.
Here's the underside.
When you sand against the body tube, check the inside edge often. Try to get both sides even like a mirror image.
Complex formulas? Nah, you could do it using drafting/mechanical drawing techniques -- using purely "analog" means using only paper, pencil, straightedge, compass and dividers -- no "number-crunching" necessary (though it does require a few intermediate steps involving extra drawings). As for difficulty level -- I do recall a chapter in a book aimed at boys (titled something like "Mechanics for Boys" -- I'll have to check my bookshelf for actual title if anybody is interested) that covered the topic of "developments." I believe you'll find the topic also covered in textbooks on metalworking, in section covering how to make shapes out of sheetmetal.
ReplyDeleteOddly enough however, trying to do the same on a computer (using non-CAD software) often *does* require use of scientific calculator (as you need to use trigonometric functions).
Hi Naoto,
DeleteLike anything else, there is more complicated ways to get the job done but I took the easy route. I wanted to present a way the average Joe could make a form fitted intake. Remember, I'm a banjo player. I count to four - and repeat!
Chris, I must admit I wounded how you were going to pull this off. I am very interested how you going to pull this model out of your bag of tip. I do know if anybody can do it, it will be you. Can't wait for the next post, and the next, and the next.......
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