Pump part III: Pedals of Metal

The major functional components of the pump were discussed last time, but we still need to talk hardware. There are small bits of hardware (metal arm and springs) that get reattached to the exhausters, after the hardware has been cleaned.

There is an assembly of metal pieces that form the treadles and linkage arms which allow the considerable force of the player’s legs and feet to be transferred smoothly and efficiently into kinetic energy which drives the exhausters.

This assembly is naturally very well secured to the pump and so there will be many screws to remove before it can be detached. As always make a map of where things go and take photos.

pump disassembly with first two screw maps
treadle linkage screw map

Once that is all apart evaluate the condition. Hopefully the fact that the assembly is made from sturdy metal (steel or iron) will mean that it is in serviceable condition with no breaks or deformities.
In my case there was a crack in one of the treadle plates so I had to take it to a local machinist for welding. It was a relatively minor repair.

cracked left treadle

Cosmetics on the other hand is a different matter.
There is a very high chance that there are decades of grime covering the metal and possibly corrosion as well.
Clean all the surfaces with solvent or your cleaning agent of choice; you may need to take a firm bristle or soft wire brush, or very fine steel wool to get it to clean up.
If the plating is heavily damaged or corroded you will have to decide if it is desirable or possible to have the pieces replated. In my case I am not so concerned about that aspect, I like the patina as I have previously stated.

Here is a photo of before and after cleaning; the angle of light is not optimized but it’s a real difference that you can both see and feel.

Before and after simple cleaning

One issue I ran into is that the old bearings for the link pins were worn through. These were originally made from vulcanized fibre, like the valve backing discs in secondary valves.

bearings/bushings worn out completely

It’s not so easy to get exact replacements of these, but the good news is you can make your own from brass hobby tubing (much easier to source) and it will do the same job.
The pins are 1/4″ O.D. so with 9/32″ and 5/16″ tubing, you can make several sets of nested-pair bearings that will fit fairly snugly but with enough play to move freely.
I used a small pipe cutter to cut the pieces cleanly.

cutting new nested bearings for center pins

Other miscellaneous things that need doing are replacing the treadle mats. Take out the backing boards, rip off the old rubber (if needed), clean the old adhesive, cut new mats to fit, and glue them back on the boards. It will make a noticeable difference in the look.

new mats for the treadles

After that just give the bearings a little lubrication (e.g. 3 in 1 oil) and reattach the treadle assembly to the pump. Put any self-contained tubing in place, and it’s ready to go back in the bottom of the piano!

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