About the Keybed
by Steve Woodyard
About the Keybedby Steve Woodyard 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 the red felt to cushion the key return and it has holes to correctly mount the action rail.
The balance rail is the center rail and it is positioned, raised and angled to properly balance or pivot the keys. It has round pins inserted or molded, in two rows. One row is for the natural notes and one row is for the sharp/flat notes. The total pin general spacing is just slightly over _ inch, pin to adjacent pin or note to note. The balance rail has one round felt washer on each pin and a combination of cardboard and paper washers or balance rail punchings added to each pin. They are manually placed, after the action rail with hammers are installed, 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 and it 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 could be broken. The washers are not in play during normal down stroke only come into play at an excessive down stroke. Note: 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 cut to shape to represent the appropriate note, are positioned on each set of balance and guide rail pins and when sufficiently depressed throw the hammer up into the tine setting it into vibration and creating a sound. The keys consist of the pedestal section, the balance section the guide section and the key cap.
The pedestal section is raised and is the 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 then the distance from the balance pin hole to the guide pin hole. This provides leverage to help lift the hammer. The pedestal has had a curved surface, a flat surface and a surface with a small raised area or bump on the front section of the pedestal. It has been lined with red woven felt, white pressed felt or 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 1/8th inch. The top sides of the oblong hole are lined with two small rectangles of woven felt called bushings (not needed on the plastic version). They provide for a close fit to the balance pin without restricting the key 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 to tight, they can be spread by inserting a #1 Phillips screwdriver down through the bushings and into the pin hole and the 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 then the balance bushings but, otherwise are treated the same as the balance bushings (not needed on the plastic version). Because they take slightly more wear and usually spread first, using a key bushing tightner has more of an improvement effect on making the key action feel less sloppy. Also, moisture absorption of the wood can cause the key to swell and become tight around the guide pin causing the keys to stick. Inserting a flat blade screwdriver into the bushing and wiggling it side to side to slightly compress the wood behind the bushing and open up the bushing will alleviate 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 end of the key to offer a comfortable playable surface to the player. There are two types, the black sharp/flat caps and the white natural caps that are cut to the appropriate key shape. The caps can be damaged but they also can be replaced by a qualified technician. There are 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 was cut and shaped as the key was made.