Gus the crank guy wrote:
That makes no sense, if 50% of the area is 10mm how would you get 100% at 20mm, 100% is all of it. 50% of a 70mm bore is 35 divided by 2 which is 17.5mm. the wider the band width the more clearance it needs.
eeuhm ... a circle with a 10mm radius has a surface of Pi*R^2, or Pi*100. a circle with a radius of 20mm has a surface of Pi*400 -> double the bore but 4 times bigger, because in a circle-surface, the radius is squared !
Gus the crank guy wrote:
I understand what your saying on volume or area, the way to do squish is a percentage of the bore not the area, you would also need to remove the area of the Piston from the area of the head, I'm not a politician to try and do a smoke and mirrors on things, I would not say 50% it just confuses people give them a number they can relate too not percentages
percentage of bore or percentage of area is just a way of name-calling, it gives different numbers, but the result should be the same.
If I (and everyone else I know of, that talks about squish-area's on fora worldwide I read) talk about area,
we do not talk about the actual surface of the combustion-chamber or the piston if it is domed, we talk about the area of the bore-surface, so the area of a flat circle. Why should you talk about percentages and not about numbers ? because percentages are universal, numbers are not. so a 50% squish area is a value that is true for anyone that wants good performance from any 2-stroke, from a 50cc to a 500cc cylindre : it is true for all of them. If you talk about a number, it is only true if you know what bore it is for.
free for all that want to use it, an excell I made :
http://users.telenet.be/jannemie/JanBro ... c%20B.xlsmsquish velocity gives exact same result as Prof Blair in his books. password protected to avoid messing it up. password is x (just the letter x) in case you would want to change/add something. the password is also embedded in the macro of the "autograph" button, as that needs the password temporarily removed. so if you want to change it, you also have to change it in there.