Hybrid_From_Hell Posted May 28, 2006 Share Posted May 28, 2006 Right 86mm ID Tube. SO : How many 20mm Holes would I have to have in a 'Snorkel Top' to give the same Area as 1 single 86mm hole ? HELP, I can't remeber how to do this !! Nige Quote Link to comment Share on other sites More sharing options...
BogMonster Posted May 28, 2006 Share Posted May 28, 2006 (edited) area of a circle = pi x radius^2 radius = diameter / 2 so 43mm for big hole and 10mm for little hole pi = 3.141592653589 (if you want to be picky) so 5808.80481mm2 for the big hole (43 x 43 x 3.141.....) 314.15927mm2 for the little hole (10 x 10 x 3.141.....) so approximately 18.48999906 of em to be moderately accurate Gettin' old and forgetting your sums eh old chap? Edited to expand on my calculations/accuracy to prove I am right in the light of later answers Edited May 28, 2006 by BogMonster Quote Link to comment Share on other sites More sharing options...
Buddy Posted May 28, 2006 Share Posted May 28, 2006 Area of a circle = Pie(Radius Squared) There (22/7) x (43x43) = Area of large circle, divide this by (22/7) x (20x20) = Area of little circle OK Quote Link to comment Share on other sites More sharing options...
BogMonster Posted May 28, 2006 Share Posted May 28, 2006 Area of a circle = Pie(Radius Squared)There (22/7) x (43x43) = Area of large circle, divide this by (22/7) x (20x20) = Area of little circle OK Er no last one should be 10x10 not 20x20, 20mm is the diameter not the radius Quote Link to comment Share on other sites More sharing options...
siggy Posted May 28, 2006 Share Posted May 28, 2006 4.6 holes so 5 holes will do I suppose I shouldn't try and do complicated mathematics after being awake for 18+ hours and before sleeping. Please ignoe this post hangs head in shame Quote Link to comment Share on other sites More sharing options...
Hybrid_From_Hell Posted May 28, 2006 Author Share Posted May 28, 2006 HAHAHA So somewhere between 4.6 and 18 holes then !! Make yer minds up please <drum fingers mode on> Nige Quote Link to comment Share on other sites More sharing options...
LandyManLuke Posted May 28, 2006 Share Posted May 28, 2006 18.49 so 19, can't go rounding down tsk tsk 20 in a 4 x 5 grid? Luke Incidently, as Pi is a common factor, it cancels out. 43² / 10² = 18.49 siggy you forgot to square. Quote Link to comment Share on other sites More sharing options...
BogMonster Posted May 28, 2006 Share Posted May 28, 2006 HAHAHASo somewhere between 4.6 and 18 holes then !! Make yer minds up please <drum fingers mode on> Nige Ignore them I got a B in a level maths and I guess the others all failed it Edited my original post above to add some accuracy I should make it 20 holes because the airflow at the edge of the hole is probably less smooth than the blah of the wibble linear turbulent flow coefficient aerodynamic efficiency frictional heating throughout the airflow range leading to less than perfectly laminar flow across the outer 15% of the hole area etc etc Just drill about 20 holes then Quote Link to comment Share on other sites More sharing options...
LandyManLuke Posted May 28, 2006 Share Posted May 28, 2006 I agree with you, but you can't round 18.49 down, cos then Nige hasn't got enough hole for his hole. so to speak. Luke Quote Link to comment Share on other sites More sharing options...
landrover598 Posted May 28, 2006 Share Posted May 28, 2006 I make it 18.5, so you'll need 19 holes Quote Link to comment Share on other sites More sharing options...
bishbosh Posted May 28, 2006 Share Posted May 28, 2006 Nige, The bit that Boggy said: the blah of the wibble linear turbulent flow coefficient aerodynamic efficiency frictional heating throughout the airflow range leading to less than perfectly laminar flow across the outer 15% of the hole area etc etc is the important bit. Flow through lots of small holes will be less efficient than through one large one so I'd go for more rather than less as it were...... Quote Link to comment Share on other sites More sharing options...
Turbocharger Posted May 28, 2006 Share Posted May 28, 2006 ^^ what he said. Your big hole has only got one edge to disrupt the flow, so you need rather more smaller holes. Although I wouldn't normally consider mentioning it, the thickness of the plate will also have an effect on the formation of the boundary layer Quote Link to comment Share on other sites More sharing options...
nas90 Posted May 28, 2006 Share Posted May 28, 2006 HAHAHASo somewhere between 4.6 and 18 holes then !! Make yer minds up please <drum fingers mode on> Nige So now send me some tube for laser cutting the holes. However, to confuse matters you could have slots, slots at an angle, triangular shape, square, shape, 5,6,7,8 sided shapes, text, maybe NIGE in Times New Roman, in fact any old shape you like. Now how about the mathematicians working thet one out! Or should we use some Cad surface generation software?..................................... Quote Link to comment Share on other sites More sharing options...
simonr Posted May 28, 2006 Share Posted May 28, 2006 Agree with 19 holes. Charles & John got in there before me with the turbulance around smaller holes issue. If there is space, I would go for close to 40 holes if you can. Probably overkill - but better than throttling (you need all the power you can get I'm told ) Si Quote Link to comment Share on other sites More sharing options...
roguevogue Posted May 28, 2006 Share Posted May 28, 2006 So now send me some tube for laser cutting the holes. However, to confuse matters you could have slots, slots at an angle, triangular shape, square, shape, 5,6,7,8 sided shapes, text, maybe NIGE in Times New Roman, in fact any old shape you like. Now how about the mathematicians working thet one out! Or should we use some Cad surface generation software?..................................... We can all see who got a new toy for Christmas Dave! No-one likes a show off! Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted May 28, 2006 Share Posted May 28, 2006 Nige is used to rounding things up - he rounds all his material thicknesses up to the nearest 6mm Quote Link to comment Share on other sites More sharing options...
Hybrid_From_Hell Posted May 28, 2006 Author Share Posted May 28, 2006 Anyone now wnat to run this through solid works with a H&S analyisis Ta everso Guess wot I'm up to Monday Nige Quote Link to comment Share on other sites More sharing options...
freeagent Posted May 28, 2006 Share Posted May 28, 2006 Anyone now wnat to run this through solid works with a H&S analyisis Nige what is H&S analysis...? i'd have thought a bit of CFD is more apropriate... Quote Link to comment Share on other sites More sharing options...
BogMonster Posted May 28, 2006 Share Posted May 28, 2006 Or just tie a bit of chicken wire over the front of the drainpipe. Then it is nearly all hole Actually chicken wire would look a bit rough, but some sort of welded mesh might be worth looking at, if all you want to avoid is sucking up small furry animals from nearby trees when you mash the pedal to the floor? That's basically what the Safari has got in the front, a diamond-pattern mesh on the intake, plastic rather than metal but no reason you couldn't do something in metal. Also, rather than using round holes, if NAS90 or whoever has got something that can laser cut a series of holes accurately then taking the bit of metal that is going to form this "filter" and lasering a series of square holes in a grid pattern would fit a lot more "hole" into the same frontal area, than a series of round holes. Quote Link to comment Share on other sites More sharing options...
Hybrid_From_Hell Posted May 28, 2006 Author Share Posted May 28, 2006 Or just tie a bit of chicken wire over the front of the drainpipe. Then it is nearly all hole Actually chicken wire would look a bit rough, but some sort of welded mesh might be worth looking at, if all you want to avoid is sucking up small furry animals from nearby trees when you mash the pedal to the floor? That's basically what the Safari has got in the front, a diamond-pattern mesh on the intake, plastic rather than metal but no reason you couldn't do something in metal. Also, rather than using round holes, if NAS90 or whoever has got something that can laser cut a series of holes accurately then taking the bit of metal that is going to form this "filter" and lasering a series of square holes in a grid pattern would fit a lot more "hole" into the same frontal area, than a series of round holes. Plan 3 is good enough for me.....20mm cutter and a milling machine. Wait and see if it works, getting P*ssed off with this snorkel I can own uo to and admit FFS Nige Quote Link to comment Share on other sites More sharing options...
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