reply to question about tension control at https://reddit.com/r/typewriters/comments/1orxtvt/strange_lever/

Joe Van Cleave has a great video on this with respect to the Smith-Corona 5 series that will give one an idea on the entirety of adjustment points that are at play in some typewriters. https://www.youtube.com/watch?v=OYOXgqiHBmg

Personally, I've yet to run across a vintage Series 5 machine whose user-facing control lever was adjusted in a way such that it did anything at all because the linkages were so far out of whack. I suspect this may be the case on a lot of vintage machines.

On some machines the adjustment isn't controlling the amount of finger force one must apply, but it's controlling springs relating more to the return of the typebars and the slugs so that touch typers can type much faster without having issues with typebar return jamming things up.

Further, on many machines the dynamic range of forces involved is so narrow that most hobbyist and occasional typists aren't going to really notice a significant difference. This may be different for those who are more experienced and used to typing on a manual machine for several hours a day.

Part 4: COMPLETE Olympia SM3 Service and Repair Series: STICKY RIBBON LIFTER by [[The HotRod Typewriter Co.]]

The universal bar lifts the ribbon vibrator.

Adjustment points to adjust the ribbon lift heights for issues with red/black on bichrome use.

Maximum travel of the universal bar adjustment screws on crossbar that attaches to springs. timestamp 5:29

Screws at the ends of the cross bar which are attached to the key springs can be adjusted slightly to provide for heavier or lighter touch control. Timestamp 6:07

Smith-Corona 5-Series Touch Adjustment by [[Joe Van Cleave]]