Saturday, April 19, 2014

Fixing the con rod ends and pressure testing.

I got some more washers, nut, bolts and other stuff from McMaster-Carr, so I thought I'd finish up and fix the con rod ends before moving on to something else.

During cranking, the con rod ends (where they attach to the bellows) weren't quite smooth enough for my liking - if I tightened the end nut all the way, there wasn't enough play for the bellows arm to slightly swivel/rock between the leather washer, and if I left the nut a little loose, I could feel the clunking as the rod reached its end travel dead spot.

Turning the organ upside-down, I first dropped a 1/4" brass washer onto the rod. The rods are nested inside brass tubing, so the bigger diameter tubing keeps the washer in place. Next I dropped on a short spring, followed by another brass washer, then a leather washer. Next, I put the rod through the bellows arm, put on another leather washer, another brass washer, and finally a nylon locknut which I tightened down so that the spring was just less than fully compressed.

I put a fake brass coating on all of the steel parts.

John Smith Busker Organ Con Rods




Now the con rods are nice and snug, but still have a little bit of spring-loaded flexibility.



Even though I don't have the crank handle made and installed, I still wanted to do a preliminary pressure test on the bellows/reservoir assembly.


I think it's OK, but I find conflicting information about how much pressure I should have and how long the pressurized reservoir should stay up before fully collapsing.

I originally was getting about 8 and a half inches of pressure, but I adjusted the spring back a little to lower it somewhat.

Here's the test, using a manometer set at inches of water: