02GF74 Posted September 3, 2006 Share Posted September 3, 2006 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. Quote Link to comment Share on other sites More sharing options...
najw Posted September 3, 2006 Share Posted September 3, 2006 maim, name, make What exactly is it you're after ? Quote Link to comment Share on other sites More sharing options...
02GF74 Posted September 3, 2006 Author Share Posted September 3, 2006 maim, name, makeWhat exactly is it you're after ? it's a bit of a longer story but...... my kit car is due for SVA on tuesday and the word is that the exhaust can will not pass due to sharp edge. (the way it is made is a sheet of steel rolled inot a cylinder then a round inserte welded in leaving an ege - see piccy) What I am thinking of doing, and I have one day to do it in - is to make a cone that fits over the exhaust pipe with an extra bit held on using a jubilee clip and flares out to fit inside the can; hence the truncated cone. been thinking about it and I think I know how do to it - it is all about diameters, now where's me scissors and paper.... Quote Link to comment Share on other sites More sharing options...
pugwash Posted September 3, 2006 Share Posted September 3, 2006 i think this is quite a simple one as you are using side of 45degrees. basically draw a very large circle of radius 62mm, mark a sector out on this circle of 114.5 degrees- am going to refer to the sector marks as A and B. Cut this large circle out. from the same centre point in the large circle marke out a circle of radius 24mm. draw a line from a to centre of circles. draw a line from B to centre of circles. cut smaller circle out of large. then cut along your two sector lines. you should then have the perfect cone shape but in flat. you willl need someone clever like SimonR to check my calculations, but i think they are right. Quote Link to comment Share on other sites More sharing options...
02GF74 Posted September 3, 2006 Author Share Posted September 3, 2006 i think this is quite a simple one as you are using side of 45degrees.basically draw a very large circle of radius 62mm, mark a sector out on this circle of 114.5 degrees- am going to refer to the sector marks as A and B. Cut this large circle out. from the same centre point in the large circle marke out a circle of radius 24mm. draw a line from a to centre of circles. draw a line from B to centre of circles. cut smaller circle out of large. then cut along your two sector lines. you should then have the perfect cone shape but in flat. you willl need someone clever like SimonR to check my calculations, but i think they are right. I see where you are heading (45 degress was chosen arbitrarily to keep the sums right) but your numbers have got to be wrong surely? The big circle, radius 62; dia 128 is the diameter of the can already so cutting a segment out of that will mean the cone base will be less than 128 dia; I think I just need to scale those numbers up (damn, I hate having to think so late on a sunday night, in fact any night .... or day for that matter ....). Quote Link to comment Share on other sites More sharing options...
bishbosh Posted September 3, 2006 Share Posted September 3, 2006 Draw a vertical section through the middle of the truncated cone and extend it up to form a triangle. A bit of trig will give you a total hypotenuse of 87.68mm made up of 53.7 & 33.98. Draw one circle of radius 87.68 with a second of radius 33.98 inside it (same centre). The angle you need comes from the circumference of one of your truncated cone ends. Take the larger one, circumference = pi * d = 390mm. Circumference of your big circle = 551mm. Angle = 390 / 551 * 360 = 255 degrees. Et voila! If that makes no sense try HERE Quote Link to comment Share on other sites More sharing options...
02GF74 Posted September 3, 2006 Author Share Posted September 3, 2006 thanks - school boy maths, how very embarrassing Quote Link to comment Share on other sites More sharing options...
Guest diesel_jim Posted September 4, 2006 Share Posted September 4, 2006 it's a bit of a longer story but......my kit car is due for SVA on tuesday and the word is that the exhaust can will not pass due to sharp edge. (the way it is made is a sheet of steel rolled inot a cylinder then a round inserte welded in leaving an ege - see piccy) No mention of someone actually burning themselves on the hot exhaust then? just the sharp edge? why not make a cover to go over it? (like lorries have on their upright stacks) and throw it away after the SVA! Quote Link to comment Share on other sites More sharing options...
dollythelw Posted September 4, 2006 Share Posted September 4, 2006 for the truly lazy (me) try Cone Software Quote Link to comment Share on other sites More sharing options...
02GF74 Posted September 5, 2006 Author Share Posted September 5, 2006 No mention of someone actually burning themselves on the hot exhaust then? just the sharp edge?why not make a cover to go over it? (like lorries have on their upright stacks) and throw it away after the SVA! yep - exhausrtr gaurd is one of the idosynchronacies (sp?) of the sva. well the cones worked but the SVA man did nnot l ike the rubber edging I used as it was deemed not durable even though it had been drive 30 mkiles wiothout melting, oh well.... Quote Link to comment Share on other sites More sharing options...
dollythelw Posted September 6, 2006 Share Posted September 6, 2006 bit of round bar, heat and roll to form a ring, weld on and flush off - nice rad then if you cant be bothered get a slip on end piece from a zorst shop? Quote Link to comment Share on other sites More sharing options...
02GF74 Posted September 6, 2006 Author Share Posted September 6, 2006 bit of round bar, heat and roll to form a ring, weld on and flush off - nice rad then I lime the way you're thinking (I am looking for non permanent solution BTW) think a small diameter copper tupe or pipe, slit and opened up so it grips the edge may be one way...... Quote Link to comment Share on other sites More sharing options...
Les Brock Posted September 6, 2006 Share Posted September 6, 2006 But........................ Is that all it failed on Quote Link to comment Share on other sites More sharing options...
02GF74 Posted September 6, 2006 Author Share Posted September 6, 2006 But........................ Is that all it failed on unfortunately not - 2 pages worth of stuff, nothing serious. speedo was out by a factor of 2! seat belt mounts too low tyres projecting outside of body plan rear suspension fouling on body work nyloc nuts not fully filled (nowt to do with me) radiussing - gear knob, hand brake lever, wishbones, steering arm, exhaust some wiring deemed loose here it is on the SVA ramp. I went for an angle of 60 o to keep the maths simple; here it is cut from 1 mm ali and this is how the can looked; I used exhaust paste to smooth the hose clamp edeges but the rubber trim was not deemed durable enough. I Quote Link to comment Share on other sites More sharing options...
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