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Restoration of the ex-Irvin's Marenghi

16 Keyframe and tubing

I was now ready to install the keyframe. Work had started on this a full 12 months earlier, dismantling and cleaning the parts - all 822 of them (excluding screws). A Marenghi keyframe is a nightmare piece of engineering; I can't understand why Charles Marenghi, who had been Gavioli's foreman, developed this design. It's easily the most complicated of the keyed keyframe layouts. The two "touch-boxes" are mounted on their sides, with a common wind chamber. This is the simple part, as there is only one wind entry point, and all internal pallets and springs are held within, reached from one panel accessible from below.

However, all the external "exhaust" pallets are actuated by levers which swing the action from vertical below the keys to horizontal, culminating in adjustable wires and buttons. Beneath these levers are two cam rods, one on each side, which serve to hold the keys in the down position when required, by actuating a handle on the front of the keyframe. This "muting" system needs to be accurately set-up to be out of the way during normal operation, but prevent the internal pallets opening when actuated. This, in conjunction with the other adjustments is very time-consuming. Not wanting to do it twice I decided to fit a new set of keys, so ordered some from Andrew Pilmer, and began to restore the touch-boxes. Re-leathering the pallets, I glued them furry side down, so the smooth side acts as the valve surface. This prevents dust getting caught up in the leather, and provides a more air-tight seal over the very small "land" when closed. Theoretically "wrong", but more reliable. The tiny springs were in very good condition, so I decided to re-use them after re-setting their shape.

The intermediate levers, mentioned above, had become somewhat rusty, so needed to be cleaned up. Ideally, they should have been cadmium plated, but as they were fitted with mahogany blocks for the adjusting wires, this would have been impractical. They were instead treated to a thin coat of Hammerite. The brass guides were cleaned and polished, and the levers re-fitted. The original springs were thoroughly de-greased and cleaned. They were re-used, as they were in good condition. To make new ones would have taken up much time re-forming their complicated shape.

Upon re-assembly in the outer frame, all parts were then adjusted to work correctly and the levers tweaked to ensure them running in their guides without tightness, and to make sure the keys sat on top - they are prone to slipping down the sides and jamming. The little pins serving as guides for the springs had begun to split the mounting blocks, so they were re-positioned; slightly staggered to help prevent the same thing happening again.

Afer five months I had given up on Andrew Pilmer supplying the keys, so ordered a set from Kevin Meayers at the beginning of March 2005. He had assured me that I would have them in three weeks. They never did materialise, so I had to re-use the old set. They were not completely worn out, and had some life left in them.

While adjusting the wires and buttons on the end of the levers to set the keys at the correct height, I found several were beginning to slip their threads. This meant, to be safe, renewing them all with a new set made from slightly thicker phosphor bronze wire with their rolled threads set on the deep side.

This exercise involved setting up the thread-rolling machine for wires not much longer than one inch, then forming loops on the wires' ends, for use as adjusting handles, without letting them bend too near the thread, as they would have been seriously weakened - rolling a thread on PB wire causes it to work-harden. New leather buttons were fitted to the wires once they had been threaded onto the levers. Then the setting-up process had to begin again. This was achieved on the dining-room table, being completed at the end of June 2005, and stored in the organ lorry until required.

Installing the keyframe on the end of the organ's main case involved setting up its wind supply, which is routed through a membrane muting box, in turn activated by a tiny valve block mounted on the keyframe. This is activted mechanically by the appropriate key. This valve block is connected to the wind supply through the normal tubing run, from a hole in the face-board of the main chest.

Now getting round the organ would be more of an obstacle course. I had decided to re-utilize the original short tubing run from the bottom of the keyframe's touch-box to the manifold block mounted just inside the case at the end of the relay. Inspection found it to be sound, and a very neat and tidy piece of tubing. The tube's bore was on the small side, but as it was such a short run this would pose no problem, unlike the rest of the run inside the case, which had all been of the same small size.

Now I had to work out which tube outlet went to which relay action. I turned to my chart of the order of channels, and the note layout of VB music. I then worked systematically through with the scale book in the keyframe, writing down on the chart from which hole the wind blew. It was during this exercise that the problems began. Several of the keys failed to work, or failed to stop working. These keys had insisted on dropping down the sides of their actuating levers instead of sitting on top of them. I had meticulously tested this before, as described above. Something had moved while the keyframe was stored, but for the moment I was stuck with it, so I persevered. When the charting was complete, I set to work with my coil of plastic tube, snips and heat gun. Eight hours later it was done.

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