I’m a late learner, have recently replaced a broken pedal spring and renewed felts for the first time. I’ve read that the rag visible inside is really a diaper and serves a purpose – but what ? Is it just padding to stop knocking or what and why couldn’t the harp function without it ?
As the rods exit the column at the lower end and connect up to the pedal bars, they all bend outward in order to reach the connection point on the pedal bar. The ‘diaper’ is there to support the rods through that bend so that they don’t flex every time you move a pedal. It does that by pushing the curved area of the rod against the outside wall of the hole in the column. The felt diaper also helps to prevent noise or vibration of the rods when the instrument is being played.
Carl is right. The diaper is there to support the rods so they move up and down properly. On occasion it can slide downward toward the pedals and cause some problems in pedaling. One harpist wrote me a few months ago because two of her pedals suddenly stopped turning the discs all the open when pedaling into flat. Why? Because the diaper had come out of position. The diaper needs to be “stuffed” in a proper way to support the rods without hindering them. I actually position diapers differently depending on the how the rod approaches the tube and what kind of material the tube is (the old harps have brass tubes, newer ones are plastic). But then again lots of people have just stuffed the diaper in any old way.