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today's homework - template to mame a cone
02GF74 - 3/9/06 at 07:30 PM

it's been yonks since I did TD and I am sure I knew how to do it but my brain ain't what it useda be.

I need to make a truncated cone, 48 mm dia at top and 124 mm dia at base; angle of side is 45 degree - what is the shape I need to cut?

would be most grateful is someone could either post the shape or explain how to derive the template (I know it needs to be curved).

Ta.

JoelP - 3/9/06 at 07:46 PM

you need to draw a circle with a radius of 87.7mms. Draw a smaller one inside this with a radius of 34mms. You then need to take a segment of this (70.7% (1/root2)?) i think and turn it into a cone.

edit to confirm, its 70.7% you need, or 254.5 degrees.

[Edited on 3/9/06 by JoelP]

907 - 3/9/06 at 08:10 PM

quote:
Originally posted by JoelP
you need to draw a circle with a radius of 87.7mms. Draw a smaller one inside this with a radius of 34mms. You then need to take a segment of this (70.7% (1/root2)?) i think and turn it into a cone.

edit to confirm, its 70.7% you need, or 254.5 degrees.


[Edited on 3/9/06 by JoelP]




I've been making cones for years and I couldn't follow that Joel.

Paul G

02GF74 - 3/9/06 at 09:01 PM

thanks - just did that on paper and looks pretty good - it is to fit in the front/back of the exhaust can to get round the sharp edge problem.

now what if the cone had base angle of 60 degrees? (like previous one but would be taller)

02GF74 - 3/9/06 at 09:26 PM

how embarrassing - school boy maths

it is explained in here:

http://jwilson.coe.uga.edu/EMT725/CarlCone/Solution.html

MikeRJ - 4/9/06 at 06:05 PM

quote:
Originally posted by 907
I've been making cones for years and I couldn't follow that Joel.

Paul G


Do you stick a flake in the top of yours though ?

JoelP - 4/9/06 at 06:46 PM

60 degrees should equate to 50% of the circle, buit obviously different sizes. That link seems to make it sound a lot harder than it is!

907 - 4/9/06 at 08:42 PM

I would work out the circumference of the finished cone using pi

124 X 3.142 = 389.6

and measure this round the edge of the disc I'd cut out.

Paul G

02GF74 - 5/9/06 at 08:30 PM

quote:
Originally posted by JoelP
60 degrees should equate to 50% of the circle, buit obviously different sizes. That link seems to make it sound a lot harder than it is!

yep - that is what I used in the end; kept the match simpler for working out the angle; 180 degreess of 1/2 the circle.

40inches - 8/9/06 at 08:19 AM

You can get a trial version of a cone layout software here http://www.pulserate.com/ Havn,t used it yet, you have to buy it to use it after 16 days (I think)

[Edited on 8-9-06 by 40inches]