So I have had the past 3 days off and I have been working on a pet project of mine... designing a radial engine.
Yup. not a model one either. 7 cylinder probably about 500 cubic inch displacement.
So anyway... it has a REALLY nasty geometry problem I cant seem to figure out. I'm no wizard at math... but I do run a program called solidworks and am pretty good at figuring out the "graphical solution" to problems... which solidworks calculates out to .00000001 inch which is more than enough seeing as how my machines cant hold much better than .0002in manufacturing tolerance. but this one I cant seem to figure out...
7 cylinder radial engine. each piston/cylinder is evenly spaced around the engine. 360°/7~ 51.428° so lets just call it (360°/7).
The design calls for a "master link" this link is the one that all the other link rods attach to. Google search "radial engine master rod" if you're not familiar.
Assume the #1 cylinder is vertical at the top. #2 is the next one clockwise and so on... so #1=#7.
See the attached picture: It is showing the master link "green" at maximum top dead center for cylinder 6.
Line CE and line CG have to be the same length... thus the top dead center circle has to be the same... otherwise the engines compression is erratic and I will never get the thing balanced.
In the picture a crank CA is constrained to rotate around the point C. Link AB is the master rod and B is the slider that slides along CE. Link AF and AB are constrained in angle to 360°/7.
I cant figure out... how to get point G on line FG to be on top dead center circle... thus what the length of AF needs to be...that is where the adjustment needs to occur (Line FG needs to be the same length for all the other cylinder positions).
I initially figured that top dead center would be when point F was on line AG... but it isn't working out that way and the solution isn't apparent to me.
Thanks for looking!