Recent developments in hand-operated drilling rig design in Zimbabwe.

Transcription

1 Recent developments in hand-operated drilling rig design in Zimbabwe. Peter Morgan A publication by Aquamor-Zimbabwe. March 2014

2 Introduction The Vonder Rig is the best known hand operated drilling rig in Zimbabwe. This robust machine was designed by the late Erwin von Elling of V&W Engineering in Harare. It uses an earth auger system and a work table and when used with a hole saw, is able to drill through decomposing granite. This machine is capable of drilling tube wells down to a depth of 25m. The Vonder Rig has been used in several countries around the world. More recently a lighter duty hand operated drilling rig has been designed for use in softer soil formations and is currently under trial. Apart from the auger itself, which is the same as that used on the Vonder Rig, all other components are off the shelf and can be made in any local workshop. To save on cost the tripod legs, drilling stems and cross-bar have been made of box steel tube rather than steel pipe. Welding was undertaken by street welders. The central components are a strongly made upper tripod to which the tripod legs are connected and a strong cross bar adaptor which fits around the square drilling stem. The machine is designed to work specifically in shallow, sandy soil formations which are not uncommon in some areas of Zimbabwe. Currently the drilling stems drill to a maximum of 12m. This depth is suitable for the use of simple water lifting devices like the Bucket Pump and light duty pumps, like the Blair Pump. Peter Morgan Harare March Acknowledgement Many thanks are due to Mr Oswald Chakauya, who has assisted me in the construction and testing of this equipment. 2

3 Drilling rig description and how it s made Like its hardy predecessor, the Vonder Rig, this lighter duty machine uses an auger to drill holes into the ground. The same auger is used in fact, in combination with a lighter duty tripod, drilling stems and cross bar. The Vonder Rig is still available commercially and can penetrate decomposing granite and can drill down to over 20m depth. This lighter duty machine has been designed for construction in the small back yard machine shop and is built to drill holes to shallow depth (max 12m) and through softer soils. To cut down on costs square box tubing has been used for the tripod, drilling stems and cross bar. These are considerably less in cost compared to steel piping. Three of the stouter parts are welded together strongly. These are the auger itself to steel pipe and the upper tripod on to which the 3m long tripod legs are fitted. The third strong weld is the cross bar adaptor which slots around the squared drilling stems and accepts a cross bar made of square box tube. Box tubing is sold in 6m lengths and 40mm and 50mm tubing have been used to make the rig. The gas welding has been performed by street welders. The joints in the 40mm drilling stem, connecting one drilling stem to the next have been made with connectors made from 50mm box tube. The gap between the 40mm and 50mm box tubes has been reduced by inserting and bonding cut sections of box tube inside the 50mm tube. The photos show this more clearly. Most parts are cut with a hacksaw and bolted together. The aim of this experimental design is to re-introduce the concept of hand drilling to Zimbabwe. 3

4 Parts of the drilling rig Assembled rig and auger, attached to steel pipe and then box tube. The upper tripod - a sturdy steel disc and 3 X 200mm long legs made from 32mm steel pipe. Three 400mm extensions of 50mm box tube are placed over the steel pipe legs and bolted in position. The 3m long 40mm box tube legs are bolted within these extensions. The base of each tripod leg is embedded in a concrete anchor into which a short length of 50mm box tube has been set. The 40mm tripod leg slides into the 50mm box tube and is held there with a nut and bolt. These stabilise the tripod. 4

5 The Cross Bar adaptor The cross bar adaptor is made from steel plate. Like the upper tripod, it is assembled from strong materials and welded by gas. The cross bar adaptor slots around the 40mm drilling stem and is welded to a 50mm steel pipe, through which 40mm box tube cross bars can fit. Both longer and shorter cross bars can be used. A bolt pushed through holes made in the adaptor holds it in place on the drilling stem. The drilling stems have holes drilled in them at about 30cm intervals. The adaptor is held up by a 15cm nail pushed through holes in the stem. Thus the position of the adaptor on the stem can be changed as the drilling proceeds. 5

6 The auger bit This is a part currently made by V&W Engineering. An original modification of this stout auger was to drill holes for trees in an earlier ecological sanitation program. It has been adapted again to suit this rig. The upper part of the auger is welded to strong 25mm box tube and then through a weld to 40mm steel pipe. A 90 cm length of 32mm steel pipe is welded through strong 25mm box tube to the auger. A 350mm length of 50mm box tube fits over the pipe and is bolted in three places. A further length of 40mm box tube is inserted within the larger tube, with the cut sections of plate placed inside to reduce the gap. The protruding 40mm box tube is then connected to the drilling stems, through adaptors. The connectors are held in place by bolts as shown. 6

7 The drilling stems A series of stems cut at different lengths (1m and 2m long) are made from 40mm box tube with 50mm box tube adaptors fitted at each lower end. Drilling stem joints. The drilling stems and tripod legs are made of 40mm steel box tube. The stem joints of 50mm box tube with cut inserts to reduce the space between 40mm and 50mm box tubes. Each stem is labelled and tested before taken to the drilling site to ensure that all the bolts fit properly when the drilling is being performed. On this prototype there are sufficient stems to drill a hole to 12m deep. Connecting the stems. 7

8 One of the drilling stems is permanently positioned on top, passing through the hole in the circular plate of the upper tripod. This connects on to the lower drilling stems. As the drilling gets deeper additional lower drilling stems are added. As additional stems are added to the lower series the upper stem is parked on a hook mounted on one tripod leg. The pulley system As the string of stems gets longer it gets heavier to lift. Thus a pulley system which assists the driller to pull up the stems has been fitted. The pulley system attached to upper tripod plate. The rope moves over 2 pulleys, the upper one attached to the top plate through a D shackle and the lower one also to a D shackle. A rope threaded through the D shackle is attached to either the cross bar adaptor or to the stem itself around a nail introduced through holes in the stem. Tool box Spare nails and bolts are required. They can be stored in the tubular tool box. 8

9 Stem support plate This plate is used to hold up the drill stems whilst they are being removed or added. At first a wooden plate was used. Later a steel plate was made to perform this task. A long nail is passed through holes made in the stem, the nail is supported by the plate. Conclusions This home-made unit was fabricated in the back yard, but used an existing and well-tried auger from the successful Vonder Rig. It is hoped that copies of the rig can be made and tested in certain parts of Zimbabwe, where the ground soil is soft and the water table relatively high. Perhaps it can join the well-established techniques of upgrading family owned wells and drilling boreholes fitted with Bush Pumps in Zimbabwe. Each situation requires a method designed for the purpose. The overall aim is to make available to the citizens of Zimbabwe, fresh potable water by using methods which are easily maintained and easily understood. The method of using the rig and how the drilling is cased and fitted with a simple water lifting device is described in another manual. Peter Morgan Harare March