Steve's Corner - About the Keybed
The keybed consists of the frame and the keys. Over the life of the Rhodes, the keybeds were supplied by two companies: Pratt Reed and Wurlitzer. The earlier models were Pratt Reed and the later models were Wurlitzer. One generation, late 70's to early 80's, was made out of aluminum and plastic and used the cabinet as its base, so it had no frame. Although the materials were different, the basic concepts were the same.
The frame is the side rails, back rail, balance rail and guide rail, made of maple and attached together in a rectangular shape.
The side rails hold the back rail, balance rail and guide rail in position and have holes for mounting the harp support blocks and a cleat for mounting the plastic cheek blocks.
The back rail has red felt to cushion the key return and has holes to correctly mount the action rail.
The balance rail is the center rail, which is positioned, raised and angled to properly balance or pivot the keys. It has two rows of round pins (either inserted or molded): one row for the white keys and one row for the black keys. The general pin spacing is just slightly over 1/2" between adjacent keys. The balance rail has one round felt washer on each pin, as well as a combination of cardboard and paper washers or balance rail punchings added to each pin. These were manually placed after the action rail and hammers were installed, in order to lift the front of each key to a determined level height. The felt and paper washers were standard piano supply parts.
The guide rail is the front rail, which is flat or stepped depending on the model. It also had two rows of pins in the same pattern as the balance rail. The guide rail pins are oval-shaped (except the plastic version). As the wood behind the key guide bushings collapses due to wear, the guide pins can be turned to compensate and help keep the key action from getting sloppy. There is one large felt washer (later, a long felt strip instead of the washers) on every guide bushing. It is there for over-throw protection: if the key can be forcibly pushed too far down, it is in danger of being broken. The washers have no effect during a normal down stroke, only coming into play with an excessive down stroke. Note that the plastic version did not have the wood-collapsing problem and used a felt strip instead of washers.
The keys, usually made of a soft wood such as sugar pine or bass wood (or plastic foam), are positioned on each set of balance and guide rail pins. When sufficiently depressed, the key throws the hammer up to strike the tine, setting it into vibration and creating a sound. The keys consist of the pedestal section, the balance rail section, the guide section and the key cap.
The pedestal section is the raised portion of the key that comes in contact with the hammer. The distance from the end of the pedestal section to the balance pin hole is shorter than the distance from the balance pin hole to the guide pin hole. This provides leverage to help lift the hammer. The pedestal had 3 different designs: a curved surface, a flat surface, and a surface with a small raised area or "bump" on the front section of the pedestal. It was covered with red woven felt or white pressed felt, or it was just bare wood. The plastic keys also had a stop bump at the back of the pedestal.
The balance rail section has a small hole in the bottom of the key that opens up into an oval or oblong hole after about 1/8". The top sides of the oblong hole are lined with two small rectangles of woven felt called bushings (not necessary on the plastic version). They provide for a close fit to the balance pin without restricting the key's rocking motion. If they spread and become loose (usually caused by the crushing of the wood behind them), they can be tightened by the use of a piano tech's tool called a key bushing tightner. If they become too tight, they can be spread by inserting a #1 Phillips-head screwdriver down through the bushings and into the pin hole, then wiggling the screwdriver front-to-back and slightly side-to-side to open up the bushing. Shaving the bushing is not recommended. Lubricating them with silicone is a good idea.
The guide bushings are slightly larger than the balance rail bushings, but otherwise they are treated the same (again, not necessary on the plastic version). Because they take slightly more wear and usually spread first, using a key bushing tightner has more of an effect in making the key action feel less sloppy. Also, moisture absorbed by the wood can cause the key to swell and become tight around the guide pin, causing the keys to stick. Inserting a flat-head screwdriver into the bushing and wiggling it side-to-side will slightly compress the wood behind the bushing and open it up, alleviating the sticking. It is also a good idea to lubricate them with an acceptable silicone spray.
The key cap is a plastic material glued to the top of the key, creating a comfortable playing surface. These caps can be damaged, but they also can be replaced by a qualified technician. There were some variations over the years in the actual white color, so correct cap selection is important. The earlier Pratt Reed keys had fully-molded caps that were glued to standard key shapes (this was later duplicated with the plastic keys). Otherwise, the caps only covered the top of the key and were cut and shaped as the key was made.