In an age when there was no electricity or steam yet for driving machines, boat builders mainly used machines in shipyards that were fitted with a large lever with a heavy weight attached to the end. This created a pendulum which allowed a great deal of force to be exerted.
Materials and tools
At the Koningspoort Slipway there are three machines which have a pendulum; a pendulum punch (Image below) and two pendulum shears (Images below). Holes were punched in steel plate using the pendulum punch, through which the rivets were inserted. Steel plates could be cut by using the pendulum shears. The three machines are currently not in use.
Pendulum shears (which are also known as ball shears) and a pendulum punch are operated by two people: one operates the pendulum (Image 2) and the other (or others for larger work pieces) positions the work piece under the machine. Proceed as follows:
- The position of the holes to be punched or the line to be cut is marked on the steel plate using a crayon. You can handle a small piece of plate on your own. A larger plate is either handled by more people or both ends are suspended from hoists so that you can move it back and forth without having to lift it.
- The person operating the pendulum, who is called the 'messenger boy’, holds the pendulum in highest position. The punch or the jaws of the shears is/are then in the up position, so that the steel plate can be slid freely onto the bed.
- Once the steel plate is in the correct position, in other words when the punch (Image 5) or the jaws of the shears (Image 4) is/are precisely above the mark on the steel plate, then the punch man or cutting man gives the messenger boy a signal.
- The messenger boy then pulls the pendulum level down, as a result of which the punch or the shearing jaws are pushed down under great force and a hole is punched through the plate or a cut is made in the steel plate. The pendulum is raised again due to the weight on the end of the lever. For the pendulum punch the messenger boy catches the pendulum and once again holds it in the highest position. For the pendulum shears the messenger boy can allow the pendulum to keep swinging and the cutting man can slowly advance the steel plate further, so that the plate is cut through.
- The punch or the shears is/are now again in the raised position, so that the punch man or cutting man can advance the steel plate a little further until it is again in the correct position for the next hole to be punched or the next section to be cut.
- Good coordination is required between the punch man or the cutting man and the messenger boy because the messenger boy has to launch the pendulum at precisely the correct moment, that moment being when the punch man or the cutting man has positioned the steel plate exactly in the correct position on the machine bed.
Pendulum shears inclined forward
Pendulum shears with two weights
Shear jaws of the pendulum shears
Punch of the pendulum punch
Heavy-duty pendulum shears