trying to use my brain on a sunday and failing

im trying to work out how much to skim off a head to get a desired compression ratio. now ive worked out its 2cc's i need to loose. assuming the combustion chamber is circle ive worked it out as 0.05mm but that sounds not enough. my workings

77.8mm bore

77.8 / 2 = 38.9
38.9 * 38.9 = 1513.21
1513.21 * 3.141 = 4752.9926 / 10 = 47.52cc.

47.52 / 20 = 2.376cc ..... close enough

of course this is assuming the are of a circle calculation assume the circle is 1cm/100mm deep does it not?

it'll probably all make sence after sleep

Go to sleep. lol

2cc's is naff all per pot, but even so.

http://www.calculatorfreeonline.com/...s/cylinder.php

That 'confirms' the half mm removal :) Although you have to bear in mind the chamber isnt a cylinder ;)

Quote:

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Originally Posted by burgo

im trying to work out how much to skim off a head to get a desired compression ratio. now ive worked out its 2cc's i need to loose. assuming the combustion chamber is circle ive worked it out as 0.05mm but that sounds not enough. my workings

77.8mm bore

77.8 / 2 = 38.9
38.9 * 38.9 = 1513.21
1513.21 * 3.141 = 4752.9926 / 10 = 47.52cc.

47.52 / 20 = 2.376cc ..... close enough

of course this is assuming the are of a circle calculation assume the circle is 1cm/100mm deep does it not?

it'll probably all make sence after sleep

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I lose you at the /20 point, but...

47.52 cm^2 is your area of chamber (not sure why you have cc at this point?) 47.52* x = 2, so

x=2/47.52=0.0421cm or 0.421mm

Area of a circle calculation doesn't assume anything by the way, if it assumed a depth it'd be a volume not an area? If the depth of the circle was 1 in whatever units you were using then the volume (in m^3) would be the same numerical value as the area (in m^2) but this is just coincidence. There's 10mm to a cm also, not 100. 100 mm^2 to a cm^2 though.

i dunno how but it made sence in my head on the way to work and i came up with half a mm which you have both confirmed, but also as said the chamber isnt a cylinder so i'll just add a bit more lmfao, i recon 0.7mm should do :p

lol yea thats it if in doubt, guess :)

it'll be close enough lol

There is a way to calculate the area of a chord of a circle if you wanted to be more accurate lol

just whip 0.75mm off and if its too much then grind some of the chamber out ;)

Quote:

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Originally Posted by Stuart

just whip 0.75mm off and if its too much then grind some of the chamber out ;)

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Been there and done that before so sounds good to me. call it a nice round mm off then lol