HRP Manholes

The making of manholes does not present much difficulty.

We will deal with manholes made in copper. First cut out your actual hole in-the boiler barrel; this can be achieved with a hand drill, drilling a series of holes just inside your scribed lines, and then ultimately filing and cleaning to size, producing a nice even hole. This is important as it is necessary for the removal of the cover itself. Cut a piece of copper plate so that it is slightly bigger than the hole you have just made in the barrel. Then anneal this and beat it on the inside of your main boiler barrel (at end). This will produce a curvature which is almost correct, and at this stage, the edges can be trimmed so that the plate will just pass through the oval hole in the barrel. It is best to put the retaining studs into this plate, as it is then easier to handle whilst checking the fit. Take a second piece of copper sheet, big enough for the back plate of the manhole door, anneal it and carefully beat it to exactly lay down flat on the curve of the barrel inside. At this stage the inner plate may be annealed again, and then lightly beaten onto the back plate to correct its curvature. It will be necessary after this to just clear the edges with a file, since you will have very slightly flattened the curve and widened the door.

When you have a good fit, put the two plates together and braze up with a suitable free flowing rod; after which trim the outer edge of the door to the size shown on your drawing, and clean off any flux or brazing from the sealing face before checking the final fit into the inspection hole.

The door will often only enter one way and it may be sometimes necessary to trim a little extra away from the outer edge, thus achieving entry into the boiler. It will help matters considerably, if the rear edges of the door and the outer edges of the inspection hole of the boiler itself, are heavily radiused. Make sure that the door will enter into its' mating hole freely before you are satisfied with this fit.

Next prepare your mud door clamp or clamps, as these will soon be needed.

An ideal way to produce a perfect seal is as follows:- first make sure that the door faces are absolutely clean, and then coat them with Metolux Cold Casting Compound (see front of book). Then take a piece of graphited yarn or asbestos, and starting at the centre of the door, gradually wind this around working to the outside, so that each turn lays closely alongside the previous one, and is held in place by the adhesion of the Metolux. You will generally find you can get 5 or 6 turns on your door, after which, cut off the surplus, and seal the end against the door with a little Metolux. With your finger, oil the inside face of the boiler manhole all over, at the point of contact of the door. Next fit the door carefully so as not to disturb the yam, pull it into place, and fit the clamps, then tighten up to a sensible and reasonable extent. Leave this for hah* an hour, and then on removing the door, you will find that you have a perfect seal to the boiler, and that the sealing yarn is locked in position by the Metolux underneath it (simple, quick and effective). When fitting the studs finally to the doors, the inner should be well brazed over, so as to prevent rusting.

Steel mud doors would be made in the same manner, although those of the larger tractor are very much easier as the mud doors are completely flat