marcmeng59
Member
I am considering building a Hit and Miss engine of my own design. A few starting questions: What is a good Bore to Stroke Ratio? What is a good Connecting rod to Stroke Ratio? I would be using 5.5" Flywheel diameter.
Hit and Miss Design Ratios
- Thread starter marcmeng59
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Help Support Home Model Engine Machinist Forum:
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For me a 1.4-1.5 stroke to 1 piston dia. ratio is about right for a slow runner. I have seen some engines from 1.25 : 1 Usually the smaller the ratio the faster the engine will run.
Con rod length can vary dramatically but the minimum is that which will allow the conrod to clear the bore when at its highest or lowest point. On a horizontal with clockwise rotation this is around 20-25 degrees before vertical on the crank. The longest can be anything more than that. I go for 3.5 to 4 x the bore.
Purely based on engines I know. Although there may be some basic rules written down somewhere.
Con rod length can vary dramatically but the minimum is that which will allow the conrod to clear the bore when at its highest or lowest point. On a horizontal with clockwise rotation this is around 20-25 degrees before vertical on the crank. The longest can be anything more than that. I go for 3.5 to 4 x the bore.
Purely based on engines I know. Although there may be some basic rules written down somewhere.
