via https://old.reddit.com/r/typewriters/comments/1hc2olg/royalite_64_replacement_draw_band/

Royal Typewriter KMG Mainspring Drawband Tightened Adjusted Tension by [[Phoenix Typewriter]]

On the left rear corner underneath the carriage when moved to the right, one can easily see the mainspring and drawband assembly. Just behind it is a worm drive operated by a screw. Turning this screw counterclockwise will advance the worm drive to the left and increase the tension on the mainspring.

Smith Corona Manual Vintage Typewriter Main Spring Removal Flush and Re-Lube Draw Band Attached by [[Phoenix Typewriter]]

Duane puts a few drops of red oil on the mainspring of typewriters as a lubricant before blowing it out to thin it down.

Here he demonstrates how to re-tension the mainspring of a Smith-Corona typewriter.

u/Koponewt aka Pelicram's advice for using fishing line to replace drawbands.

Re-inserting the carriage of an Olympia SM3 timestamp 17:32

Not shown in the video is the reinstallation of the square screw and nut at the end of the carriage to hold the carriage into the machine.

Smith Corona Vintage Typewriter 5 Series Draw Band Install Mainspring Connection Wind Tighten by [[Phoenix Typewriter]]

Smith-Corona 5 series drawband and mainstring attachment and tightening.