External Flap valves on the bellows...correct setting?
Hi all On my player grand , the bellows are underneath the piano and facing down.Now the flap valves also face down of course , and i was wondering on what the correct measurement is for movement.By that i mean both have the glued wood on the end with just a single metal spring pushing them taunt. Now both have 2 strips of tacked felt about half way , to keep the leather flap close to the bellow so it sucks close quickly.Now with my bellows facing down , the leather flap is hanging down slightly at each end at all times and I'm guessing it has a memory of been in that position. My questions are: A) How do you measure the correct distance of the felt that is tacked across the leather flap? , should it be firmly tight so only each end of the flap can open or close? B)Would a band of elastic (as used in pants) be a better option to hold the flap taunt and only stretch when the air is forced out?. C)Would more then one felt been tacked across the each flap have a better holding suction results? D)If i was to powder (talcum) the underside of the flap , does it make a difference? Just wondering with all the restorers on here , has anyone experimented with something a little different that worked and is worth sharing on here? Daniel :)

The set-up you describe seems quite normal. If you are replacing the flap valves (and only do so if they need to be done) you will see the old nail-tack positions used to pin the felt retaining strip and leather. Are there two or more sets of old tack holes indicating an earlier change perhaps? You'll probably see some outline from where the leather has sat for years. Use these as a guideline in case a previous restorer got all over-experimental and tried to improve upon the original. Bellows / exhauster flap valves are the least contentious part of any pressure operated instrument - they either do the job or they don't. With the exception of the Carola (metal hinged valves and sprung disc exhauster valves) and the Pistonola (piston cyclinders) every other suction operated instrument uses this same basic leather valve type. Essentially they should he free enough to allow the exhauster to exhale under pressure of the return spring without any impedance whatsoever and thus allow the next treadle stroke to take place as quickly as possible. Felt retaining straps should never be in any way tight or snug. If they are they will restrict the return-spring exhale of that exhauster to some degree or another. Their purpose is to stop the leather billowing outwards at that moment so far that on the suction generating push of the treadle the leather doesn't slap back audiably against the exhauster wood. If you are rebuilding a set of exhausters try experimenting with these and you quickly understand how they function and also their optimum setting. regards Adam

Hi Adam and thankyou... My bellows and flaps don't need replacing as yet , i was double checking that all seems to what they should be.I was also curious as to whether having the leathers flaps hanging horizontal rather then the convectional vertical way was any difference on a player. Regards Daniel :)