KIRK Posted August 16, 2012 Share Posted August 16, 2012 but how many degrees is 10mm? Quote Link to comment Share on other sites More sharing options...
Testament Posted August 16, 2012 Author Share Posted August 16, 2012 AGMC tohatsu badly timed machine? hit it on the head there! GREG - 10mm is about 20 degrees of crankshaft rotation in this case Quote Link to comment Share on other sites More sharing options...
Steelies Posted August 16, 2012 Share Posted August 16, 2012 do the math http://en.wikipedia.org/wiki/Piston_motion_equations Quote Link to comment Share on other sites More sharing options...
Testament Posted August 16, 2012 Author Share Posted August 16, 2012 you need to know the stroke and rod length to do the math....... Quote Link to comment Share on other sites More sharing options...
Steelies Posted August 16, 2012 Share Posted August 16, 2012 oh yeah it's not apart. as you were Quote Link to comment Share on other sites More sharing options...
Testament Posted August 17, 2012 Author Share Posted August 17, 2012 I don't plan on doing that/the magic might escape! Quote Link to comment Share on other sites More sharing options...
Steelies Posted August 17, 2012 Share Posted August 17, 2012 big blocks, who'd have em Quote Link to comment Share on other sites More sharing options...
Testament Posted August 17, 2012 Author Share Posted August 17, 2012 Chuck Norris Quote Link to comment Share on other sites More sharing options...
Steelies Posted August 19, 2012 Share Posted August 19, 2012 you wish. any improvement? Quote Link to comment Share on other sites More sharing options...
Testament Posted August 20, 2012 Author Share Posted August 20, 2012 no joy, pulle head and jug only to find it looks brand spankers inside. So back to drawing board/carb/timing/building a spanny Quote Link to comment Share on other sites More sharing options...
Steelies Posted August 20, 2012 Share Posted August 20, 2012 nice. guesspanny or full blown measure-up spec? Quote Link to comment Share on other sites More sharing options...
alfalfa Posted August 20, 2012 Share Posted August 20, 2012 We did some calcs and came up with something ridiculous like 2m from head to start of stinger. So probably guesspanny haha Quote Link to comment Share on other sites More sharing options...
Vintage Grumble Posted August 20, 2012 Share Posted August 20, 2012 Cant you make it fatter and shorter and it still works the same? Quote Link to comment Share on other sites More sharing options...
Steelies Posted August 20, 2012 Share Posted August 20, 2012 dont think so. quickly sketched one out for the villiers last night and it's hilariously close to a straight pipe, even though it's being based on fingers-crossed power and rpm values haha Quote Link to comment Share on other sites More sharing options...
KIRK Posted August 20, 2012 Share Posted August 20, 2012 manu what did you use to calculate? cos stephen and dave used some software or something and stephen said domensions also came out like what you said Quote Link to comment Share on other sites More sharing options...
Steelies Posted August 20, 2012 Share Posted August 20, 2012 a bunch of formulae from the web, under 'expansion chamber design according to blair' for a two stage chamber. probly the same shit that's in the software. the constants for diameters dont range very much but tuned length changes heaps with exhaust duration and temperature. it's all divided by RPM so more of those make for a shorter spanny Quote Link to comment Share on other sites More sharing options...
KIRK Posted August 20, 2012 Share Posted August 20, 2012 try using the formule and figures from that jennings book maybe Quote Link to comment Share on other sites More sharing options...
Steelies Posted August 20, 2012 Share Posted August 20, 2012 yeh, almost up to that bit. thought it'd be too dry to hold my attention but actually quite an interesting read! Quote Link to comment Share on other sites More sharing options...
KIRK Posted August 20, 2012 Share Posted August 20, 2012 yeh alot of his expansion chamber figures are guessamations and working backwards from dimensions he saw on early 70's yamaha gp bikes. dunno how his stuff compares to more modern techniques but they must work ok/easier for diy probably Quote Link to comment Share on other sites More sharing options...
Testament Posted August 21, 2012 Author Share Posted August 21, 2012 Yeah, I used jennings formulae really roughly worked to something between 1.5m and 2m for 4000 or 5000rpms. Which makes sense since tuned length for speed of sound in air is around 0.9m which would eqaute to the length from the piston to the expansion chamber. Remember mx motors etc do 3x this rpms! Quote Link to comment Share on other sites More sharing options...
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