I recently built the vertical finger engine from the NAMES plans available on the Internet (see picture below). It worked, but I found it very finicky to keep going. As others have noted, the NAMES design of this engine is far from ideal, so I did a few experiments to see if I could improve performance.
To make a long story short, I found that simply increasing the crank radius from 0.250" to 0.350" made a big difference. I made some other improvements as well, primarily putting a significant counterweight in the crank design. I experimented with other changes, like changing the connecting rod length, but such changes also require redesign of the lever, etc. Simply changing the crank design, however, can be done without changing anything else.
For those interested, I have posted a build log and revised plans which include other minor improvements at the link below (alternatively, if you are building from the NAMES plans, do yourself a favor and change the crank radius!).
https://sites.google.com/site/lagadoacademy/machining---lathes-mills-etc/build---finger-engine
To make a long story short, I found that simply increasing the crank radius from 0.250" to 0.350" made a big difference. I made some other improvements as well, primarily putting a significant counterweight in the crank design. I experimented with other changes, like changing the connecting rod length, but such changes also require redesign of the lever, etc. Simply changing the crank design, however, can be done without changing anything else.
For those interested, I have posted a build log and revised plans which include other minor improvements at the link below (alternatively, if you are building from the NAMES plans, do yourself a favor and change the crank radius!).
https://sites.google.com/site/lagadoacademy/machining---lathes-mills-etc/build---finger-engine