Inline cylinder engine Mark4 has almost the same suppleness of Mark3, but I flattened the top by one brick size. The flattening causes a bit more stress in the rubber bands. Although mk4 is more compact than mk3, the crankshaft of mk4 rotates a little less supple, but definitely not less good. The red rubber band too wide, so I used the white rubber band instead.
Uploaded: May 4, 2016