[R-390] Friction in KC Change Chain

[Drew P.]

Curt Nixon wrote: 

"I am hunting down all sources of friction in the KC change chain and
decided to pull and inspect the PTO.  It is smooth but stiffer than I
would expect with ball bearings.  So it is apart and looks to be in
clean condition..pix on my blog site."

On both Cosmos and non-Cosmos design PTO's, there is a small o-ring in a groove in the bore in the housing through which the lead screw shaft passes.  The function of that o-ring is to provide a seal to prevent the pressurized nitrogen from escaping.  The small o-ring is in addition to the larger one around the outside of the housing between it and the can.

Removal of the shaft o-ring will quite noticeably reduce PTO shaft drag. The o-ring would not be needed by most of us as the nitrogen leaked out long ago.  To remove the o-ring will require disassembly of the PTO and removal of the tank coil, slug, and lead screw.  Once these parts are removed, the o-ring may be removed with a sharp hooked tool such as an appropriate dental pick.  I have also found that the anti-backlash nut on the slug can be set somewhat looser and this will reduce drag further and make tuning smoother as well.  If too loose, there will be annoying backlash.

It has been recommended to remove the dessicant packs inside the can as these have been known to disintegrate, filling the PTO mechanism with an apparently corrosive grit, as mentioned in forum postings past.

Drew