Having seen people throw their money away cutting vees out of expensive copper pipe, I thought I would offer a lo-tech tutorial for making a frustum pattern.
1. You know how long your fustrum needs to be, how wide you want it at the base and how wide you want it at the shnozzle end. Draw the base of your frustum. A frustum is a portion of a cone, or a cone with the tip chopped off. I have marked the base here "A".
2. At 90 degrees to the middle of your base "A", draw a line the length you want you frustum. At the top of this, and parallel with "A", draw the schnozzle end of your fustrum, "B".
3. The photo for this step is missing, but you are able to see the results in the picture below; Draw straight lines from each end of "A", to the corresponding end of "B", but carry the lines through until they meet. What you are doing is drawing the cone/triangle from which the frustum is derived.
4. Put the pointy end of your compass at the tip of the cone, and draw an arc outwards from one end of "A". Be aware that your compass needs to be as big as the frustum you are making. For our applications, this equates to a pretty big compass. However, the compass can be substituted by a piece of string, or a piece of more solid material with 2 holes drilled in it, 1 where the pointy bit needs to be and 1 where the pencil goes. These substitutes will not be as accurate.
6. Now, multiply the length of "A" by "pi". "Pi" is an endless number that relates the radius/diameter of a circle to its circumference. For our purposes, "pi" can be understood to be around 3.142.
E.G. If the base of my frustum is 200mm in diameter (i.e. the length of "A" is 200mm), then the circumference of the base of my frustum, multiplied by 3.142, is going to be 628mm.
Okay, so now you have your circumference. Let's say it's 628mm. Divide that number by an arbitrary number, let's say 20. That gives us 31.4mm.
Now set your compass at that distance, e.g. 31.4mm. Now starting where the arc begins, "walk" your compass along the arc 20 times. That will give you frustum's base circumference measured out on your arc.
N.B. The greater the arbitrary number you divide circumference by, the greater your accuracy (and the greater the pain in your arse).
I hope this is of use to someone. I know there are computer programs out there that do this, but it's is really not at all difficult to do yourself. You can also do it straight onto the copper.
-Dan
Dan P. wrote:I hope this is of use to someone. I know there are computer programs out there that do this, but it's is really not at all difficult to do yourself. You can also do it straight onto the copper.
-Dan
It would take me longer to wait for my prehistoric laptop to fire up than it would to lay one out on the job.
Its also a waste of paper and time cutting a printed pettern out.
You design it, I make it. Copper and Stainless. Down under. PM me.
Great Frustum calculator. Gives you the option to play with the dimensions and maximize the amount on a sheet. http://www.i-logic.com/conecalc.htm" onclick="window.open(this.href);return false;" rel="nofollow
Man, wish I would have had this when I built my parrot. Ended up just cutting a circle and then cutting out a narrow slice to get it where I wanted it.
Thanks for posting
scoutdoors1000 wrote:Great Frustum calculator. Gives you the option to play with the dimensions and maximize the amount on a sheet. http://www.i-logic.com/conecalc.htm" onclick="window.open(this.href);return false;" rel="nofollow
Thats a good link. Thanks. I do it like Dan when Bushman is not around with his cad program. I use thumb tacks and a sewing tape than calculate to compass degrees to match radius. It usually matches real close to walking a small divider. I have two beautiful sheets of copper in stock that will be a sweet boiler when I get time.
