Archive for WOT Blog

Working weekend March 14-15

Saturday, May 16th, 2020 No Comments

Several weeks ago, just before the wot had to close due to the effects of the coronavirus, a working weekend was held. A lot of people were present, a lot of work has been done and the atmosphere was great.  A new method of airlift drilling was tested, the cubicle of the outside shower was replaced, maintenance was done for the bicycle rope pump, the lustrum tiles were put on the wall of the indoor solar shower and work has been done for an experimental irrigation system.

You can read more about the airlift drilling here.

Solar shower cubicle

Now that the solar collector of the outdoor solar shower has been renewed, the rickety shower cubicle could not be left behind. This was made clear on a stormy day when half of the stall was blown apart. The working weekend was therefore a good time to pick up this project thoroughly.

The concrete foundation, in which a drain pipe was poured, was still perfectly usable. The plan was to make the walls of recycled fence boards. The underside of the walls would be made from bricks to prevent the wood from being in constant contact with water. Besides, the expectation was that this would give a good looking result.

Wooden posts were placed on each corner of the booth, which was attached to the foundation using a U-profile. With the base frame in place, two teams could work simultaneously on the masonry work (Allard and Kasper) and on the planks and crossbeams of the walls (Joost, Victor, Michelle and Willem). This was no easy task for a cubicle measuring just under a square meter!

At the end of the weekend, the stall stood proudly in front of us. The water tubes and the shower tap were also reinstalled by Willem. The masonry still needed mortar joints, but for this the masonry had to harden for two weeks. Also, the door was not yet completed and the shower lacked a roof. Joost finished the door a day later and Kasper later added the mortar joints. The roof is still missing, but the old door can possibly be reused for this.

Bicycle rope pump

Also the bicycle-powered rope pump was provided maintenance. With a new bracket to hold the pump and the return tube. After this the old paint was sanded off and a new layer was applied to help this pump stay rust-free.

5 WOTters watching, 1 WOTter works

Tiling of the indoor solar shower

Previous year, as a lustrum activity, tiles were decorated by the WOT-members so that they could add some flair to the walls of the indoor shower. It did take some time however before they were also actually placed on the wall. This weekend the task was finally started with. At the end of the day this resulted in a beautiful wall, to which a lot of members contributed. Only some finalising still has to be done.

Of course no working weekend would be complete without a campfire

Experimental irrigation systems

Thursday, May 7th, 2020 No Comments

Besides all the handpumps, windmills and solar collectors, the WOT-terrain also maintains a garden bed for growing vegetables.

For irrigation 3 different systems are tested in the garden. A bought irrigation hose, a flower pot based system and a system made from plastic milk bottles. The systems are applied in rows perpendicular to the rows of different vegetables. The conditions on the field are relatively constant but it is only a few square meters so drawing conclusions on the yield of the plants is not really justified. The main goal of the experiment is to discover advantages and disadvantages of the systems and not to perform a scientifically justified comparison. First all three systems will be described, later updates will be placed to comment on the systems.

Irrigation hose

First of all there is the irrigation hose. This is a readily bought polymer hose produced by REHAU. The material of the hose possesses the property to ‘sweat’ so that when water is inside this slowly enters the soil. To ensure a constant water supply, we’ve connected this pipe to our water tank. The pipe is buried at a depth of approximately 20 cm.

Because the water directly flows into the soil less water evaporates.The company claims that by using this system correctly, up to 70% of water can be saved compared to conventional watering. A 15 meter pipe was bought for approximately 20 euros.

Close-up of the ‘sweating’ hose

Ceramic Plant pots

The second system is based on flower pots. Unglazed ceramic pots possess a similar property to that of the irrigation hose. The material is porous and when there is dry soil around the pot water is ‘pulled’ through the material. When the ground is wet however, less water will flow through the ceramic material. This method is a proven system for irrigation and so called ‘ollas’, pots with a large body and a smaller neck, have been used for a long time. The pots are buried and plants are placed in the vicinity of the pot, the roots grow towards the olla and the plants always get the right amount of water.

Pottery with a shape similar to the ollas, relatively expensive in the Netherlands and the skills to make them ourselves we do not possess. Therefore we decided to make our system out of unglazed ceramic flower pots. These are both cheap and readily available. The large opening of the pots were closed off with other pots and sealed with sealant. The hole in the bottom of the pot was fitted with a cable gland so that a garden hose could be attached to it. Several of these pots were connected and attached to the water supply. Two different designs have been made.

Plastic jugs

Finally a system made of plastic jugs is tested. Small holes are poked in an empty plastic milk jug. These jugs are buried, filled and the cap is fermly put on. The principle behind this method is that because the cap is on and because there are such small holes, air can’t easily enter the jug and thus water doesn’t flow out easily. Because of this water is dispersed over a large amount of time. Also if the ground is wet, possibly, this causes the water flow to decrease even more since less air is present in the soil. Because we did not know the effectiveness of this method and we didn’t exclude the possibility that water would flow out at a to large rate, we didn’t connect this system to the water storage for a continious water supply. The jugs were to be filled manually.

A small hole in the milk jug

Below are some pictures of the setup of the complete system. Updates of the operation of the systems will be given in the future.

Flow controll

In order to be able to control the flow going to each system, a clamping system was made. It is shown below. One tube goes to the irrigation hose while the other goes to ceramic pots.

Update airlift drilling: Motorised drilling

Monday, April 6th, 2020 7 Comments

A new experiment with airlift drilling is performed at the WOT. A motor of a petrol auger was used to drive the drill stem of the airlift drilling method. This produced a continuous rotational movement, so two couplings were required. One for the outlet of the drilling fluid and air mixture. Another one to couple the pressurized air hose to the drill shaft.

The main advantage of the system compared to the previous manual setup was the increased drilling speed. The maximal speed was measured to be 12 meter per hour. The record with manual shaft rotation was 7.5 meter per hour. However, the average speed of the whole borehole was only 5.4 meter
per hour. This is not a very large increase, compared to the 4.5 meter per hour during manually rotating in an earlier test.

This is mainly because changing the pipes was more time consuming since the motor was attached to them. Also, starting the petrol engine was hard, as the engine was unwilling and at an unpractical location for starting. The couplings for air and water, which were finished a day before the test, performed perfectly. The air coupling was not leaking up to a pressure of 8 bar. Thanks to Hedzer and Haye who helped to turn them to specifications.

Problems with starting the engine

There is the option to make a new test setup with a proper rig to guide the motor assembly. Also, an updated version of the air and water coupling can be made, where the length of the coupling assembly will be decreased (currently ~45cm long). A pipe clamp can be mounted on the rig, to hold the pipes during adding and removing. Changing pipes is then preferably done with three-meter pieces at the time, to minimize the time spend on it. The average speed of drilling can come very close to the 12 meter per hour (in Dutch soil) with these upgrades.

Product development at the WOT: Drilling with compressed air

Saturday, February 22nd, 2020 Comments Off on Product development at the WOT: Drilling with compressed air

(An update on this system using a motorised drill can be found here)

The WOT has years of experience with manual well drilling with the Baptist- and EMAS method. Both methods require tools that can easily be manufactured in a workshop with readily available materials. De drilling sets can be made in a simple workshop with an angle grinder and a stick welder. Because of this, the methods can be used in remote areas. The baptist method, developed by Terry Waller, uses the principle of an inertia pump. The drilling set essentially consists of a drilling pipe with a one-directional valve which is moved up and down in the well. If the downward acceleration is higher than the gravitational acceleration, the drilling fluid (which contains the sediment) will be accelerated up the drilling pipe. Because of this, water with sediment can be transported to the surface where it enters a basin. The sediment will settle and clean water flows back into the well via a small duct.

The EMAS method is developed by Wolfgang Buchner. Here the water flows in the other direction; via the drilling pipe water is pumped down with a manual pump. Then the water flows upwards through the annulus taking sediment with it. The dirty water enters a basin and the sediment sinks. The clean water can be pumped into the well again.

The higher the speed of the drilling fluid, the more particles can be taken along. An advantage of the Baptist method is the fact that the drilling fluid is brought up through the drilling pipe. Because the drilling pipe has a relatively small cross-section compared to the annulus, high fluid speeds can be achieved with a small amount of volume displacement. The EMAS method uses the annulus to transport the sediment up. This means that if the diameter of the well increases more volume should be moved to achieve the desired velocity, or the diameter of the pipe should be increased, but this increases the weight which is undesirable. Therefore, the diameter of wells made with the EMAS method is limited.

There are many ways to automate the drilling methods to a certain extend. Manual drilling can be a labour intensive job which requires increasingly more effort at increasing depths. Jetting drilling sets are for example available or another option is to replace the manual pump for EMAS drilling with an automated pump. Also, attempts have been made at automating the up and down movement of the drilling rod.


Since 2019 the WOT has been working on another method, which uses compressed air to pump around the drilling fluid. The method uses an airconditioning compressor (Power: 400 W, V ≈ 40 Lpm Atm, Pmax > 20 bar). The hose from the compressor enters the drilling pipe 40 cm above the drill. The air that is injected decreases the average density of the mixture in the drilling pipe. Because of this, it will ‘float’ on the liquid in the well. As a result, the fluid with sediment exits the drilling pipe at the top. It enters a basin where the particles sink and clean water flows back into the well.

Setup for airlift-drilling (at the background behind the PVC-tube a bucket with the compressor is visible)
The compressor, cooled in water

This method has a few great advantages:

  • The water flows back through the drilling pipe. Because of this, a bigger well diameter can be realised with a relatively small drilling pipe diameter because the flow will stay high (light material).
  • The flow down through the annulus is low, reducing the erosion on the walls of the well
  • A relatively small flow is required to meet the required speed for particle transport. Little work for pumping and thus low electricity costs.
  • No mechanical components (valves, pumps) get into contact with the drilling fluid. So there is no time loss or maintenance needed.
  • Used refrigerator/arco pumps are readily available.
  • Small fuel generators are readily available.

The method is tested 6 times at different places in the Netherlands. Drilling times are measured. The well diameter is about 150 mm in all cases. Factors governing the speed of drilling are mostly the person drilling and the ground type. The average drilling speed (excluding brakes) was 3.8 meters per hour.

Furthermore, the speed is dependent on the used drill. It was developed further during the drilling attempts. The most successful design, which worked on multiple locations, is shaped like shown in the picture below. The latest version is made of wear-resistant steel (RAEX 400), because of which resharpening is needed less often. Plans have aroused to try the drilling method in harder ground types. Soon the technical drawings of the most recent design will be shared with relevant organisations and will be placed on this website. Also is being looked into further automation of the drilling process. This way we hope to contribute to increasing the accessibility of clean drinking- and irrigation water.

Flower Rope pump

Friday, February 21st, 2020 No Comments

At the beginning of 2019, a request came in from Maarten Rijgersberg, IN KNOWLEDGE / ExpositionRent, a company that rents interactive exhibitions in the field of environment and nature. They were interested in a model made in the past by WOTters in which a rope pump pumped water to another container so that fake flowers slowly floated upwards. They also wanted a normal demonstration model of a rope pump. A model in a mortar tub has been refurbished and repainted. The flower rope pump no longer existed and it was decided to rebuild it. The flower rope pump demonstrates two things: 1. The operation of the rope pump, a very cost-effective pump used a lot in developing areas. At the WOT we have a lot of experience with this type of pump. Read more about it here. 2. The call for more biodiversity through planting more plants is increasing worldwide. Decreasing the amount of pavement in gardens and public spaces is a must, considering the dramatic decline of insect life around the world. According to this study by Radboud University in 2017, there has been a two thirds decrease in the insect life in the past 27 years. Partly with the flower pump rope pump, ExpositionRent, together with other demonstration objects and exhibition materials, wants to direct people to greening gardens and thus stimulating life. The Flower Box Rope Pump can be rented for Festivals & Events, Municipalities, Environmental Education Centers, Visitor Centers and Museums. via the website of ExpositionRent.

Standard rope pump model

First, a plan was drawn and the design was carefully considered. The model would have the same principle as the previous version, but would be more robust. Due to regulations, it was important that the pump would be child-friendly and that no one could lose their fingers. The entire box would be closed with a number of parts made of transparent plastic so that people could look inside. When the plan seemed comprehensive (that was of course not the case), construction started.

A large sheet of plywood was bought along with a sheet of plastic and a pot of rubber seal. The plate was cut into the correct pieces based on the drawings. This has resulted in a lot of puzzle work and despite the fact that (as usual) something has been cut wrong, everything ended up quite well at this point. Work was also carried out on the PVC parts and steelwork. Furthermore, the flowers had to be made. The plastic rubish from the store turned out to be too fragile. That is why the flowers are made of sheet steel with styrofoam floats.

The box slowly but surely took shape. The wood was covered with a large number of layers of yacht varnish and the metalwork was painted. The outside of the box was also painted and the plastic cut to size. At some point it was time to do the first test with water. The workshop was temporarily transformed into a swimming pool. There were leaks at seams between the wooden plates and at the connection between wood and plastic. More sealant and rubber seal seemed to partially solve the problem. However, accessibility for maintenance proved to be a difficult problem. In order to be able to enter the tank, the top had to be able to come off, so it was not possible to seal everything shut. After the workshop floor already had to endure a lot of moisture, the majority of the leaks have been fixed. When pumping, however, water still splashes around in the top part of the container and some water will leak.

During the work, most of the plastic has been replaced, it has been discovered that silicone sealant that has expired does not harden, that children have to pump very hard to get flowers up and much more. But in the end the model was finished. The container was delivered about ten months after the request. A project that took longer than expected and was more complicated than initially planned, but very educational. And it is of course very nice that a WOT production is now part of an exhibition. Perhaps more models will follow in the future.

Renewed solar shower

Wednesday, November 13th, 2019 No Comments

It was no longer operational and started to deteriorate further: the solar collector made of beer bottles, garden hose, and PVC. During tours, it was quickly passed by, so we had to do something about it. Nothing was reusable from the old collector, so it was decided to use the renovation as an excuse to increase the capacity. Two glass plates of the same width (85 cm) were found in storage, which together had a length of 210 cm. So that had to be the new format. At the hardware store, it turned out that luck was with us because 210 cm turned out to be a standard length for planks.

The box was built from wooden plates, planks, and battens connected to angle brackets. A double bottom is made with insulation plates in between. The entire box is primed and finished with two layers of blackboard paint. The black, matte colour gives the best result for heat absorption.

The next obstacle was the storage system. We opted for a complete PVC system with as big and many pipes as possible, which were connected to standard couplings. The box turned out to be able to host 8 tubes of 80 mm using 40 mm connectors resulting in a total capacity of approximately 65 liters. This is almost twice the capacity of the old system!

In the meantime, the idea had arisen to completely close the box, with the option at the bottom to remove a plank and to slide out the entire storage system. As a result, the glass plates never need to be removed, which reduces the risk of breakage. Ironically, one of the glass plates was broken when cutting to size (a piece had broken off in the past and this had to be cut straight again). Attaching the 40 mm pipe to the shower’s 16 mm garden hose required a series of flared pipes to achieve the correct diameter. At the same time, this should not protrude too far, which would eliminate the possibility to slide the system out of the box. As a result, the hose could not be secured with a hose clamp due to lack of space. Cutting thread on a piece of PVC pipe seemed to be the solution, but the connection could not be made waterproof. In the end, a PP hose nozzle was used which is not really compatible with gluing to PVC.

All in all, the renewed solar shower was prepared just before the T-week, where it was frequently used by the enthusiastic participants and volunteers. It quickly became clear that the connection of the hose nozzle was leaking a little and when the water is warm, the garden hose softens a little bit and can come loose. So this is another point for improvement for the future.

During the T-week, a thermometer was installed in the tank, which indicated temperatures from 40 to 50 °C in the sunny weather we were in. Adding a little cold water is all it needs to have a comfortable shower!

Now that the solar collector has been replaced, the renovation of the corresponding cubicle is next on the agenda.

Introduction evening

Monday, August 26th, 2019 No Comments

On wednesday September 11 the WOT organizes an introduction evening. We will start off at 17:00 with a tour around the terrain to show everything we have at the WOT. After that, we will have dinner and you are welcome to join our projects. If you plan on coming please send a mail to and mention whether you will join dinner. We will end the evening with a drink around the campfire.

If you cannot be there this Wednesday, that’s not a problem. You are welcome to join the next week. We meet up every Wednesday afternoon/evening to have dinner and work on projects.

The weeks after the introduction evening we will organize several activities such as a welding workshop and a scrapheap challenge. But we will tell you all about this when we have a chance to meet you!

Publication of Technical Report 2018 Diever 450

Sunday, November 11th, 2018 No Comments

In light of the recent construction of a Diever windmill in South Africa, we have decided to publish a new Technical Report to describe recent developments and provide suggestions for further improvements. The TR2018 serves at once as a construction guide and as a comprehensive source of technical information on the Diever 450 windmill, supplementing the construction drawings.

The report can be obtained here.

The Technical Report 2018 was written by Chris Vos for the Working Group on Development Techniques (WOT), located in Enschede, The Netherlands. It replaces the Technical Report 1990 by Frans Brughuis which deals with an older version of the Diever 450.

Recent work done on the Diever prototype located on the WOT test terrain is described in the TR2018; this especially concerns the transmission and bearings. Many further improvements are suggested, including an improved rotor design, addition of counterweights to improve starting behaviour as well as more easily constructed foundation blocks. A completely new Diever design is also presented which completely consists of galvanised steel components.

Whoever wishes to start construction on their own Diever windmill is invited to contact the WOT to obtain construction drawings. The volunteers at WOT are more than willing to provide further advice where needed.

The Diever 450 is a water pumping windmill for use with deep wells in developing countries. The design has an Intermediate Technology character and use of advanced machinery is avoided. Main axle height is 10,5 meter and the mill is easily erected using a winch or tractor; when disassembled it can be transported on a Land Rover. Dievers have been built in a number of different countries, from Boliva to Nepal, and remain a reliable way of water supply all over the globe.

Maintenance Wooden Handpump

Thursday, September 6th, 2018 No Comments

For some time now the wooden pump frame has been in a bad condition. Due to this pumping was not possible anymore. After a long time of lying around, this summer the components of the pump were dusted off and the renovation was a fact. Most of the wood was rotten and had to be replaced, although some components could be re-used. Nevertheless the renovated pump wasn’t to be as colourful as the old version, so the components that had not rotten still had to be cleared from their old coating. Instead of paint, the wood would now be stained. The steel piping and base plate also required some work, and were repainted in a colour best described as british racing green, or simply darkish green. With the use of the construction manual and old pictures the frame was assembled.

But before all this, the pump itself had to be checked and mounted. It turned out that the top of the pumping rod was missing. Therefore a piece of rod was cut at the right length and mounted to the existing rod. At this moment the pump seemed to be complete, and assembly of the pump was the logical next step.

Nevertheless it was evident quickly that the pumping did not go well. The water that was collected seemed to be flowing back into the well, so that all the pumping effort was in vain. The pomp was drawn from the well, and opened up for inspection. In order to open the pump, it had to be dissected, a system that proved inconvenient. When the pump was opened the piston valve turned out to be jammed. As it was loosened it was free to move again. Another interesting observation was the large amount of sand and debris in the system, this explained the jamming of the valve. Besides this the components appeared to be alright. After the pump was cleaned of dirt the gauze at the bottom of the pump was replaced with a finer grid gauze so that less debris would be able to enter. After this the pomp was assembled in a more convenient way than previous, using steel plumbing parts so that the pumping tube could be easily mounted to the pump. Now, finally, the pump could be installed.

And it worked! The water was slightly dirty at the beginning, but this problem solved itself quickly. One drawback of the system however is the fact that the well empties quickly. Whether this is because the pump is to high in the well or whether the sublime renovation made the pump to good for the well, is still subject of discussion.

Introduction activities

Tuesday, August 28th, 2018 No Comments

  • Introduction evening
    1. Wednesday 12-9-2018

    Tour and dinner on our terrain at 18:00 with afterwards a drink.
    To join dinner please e-mail before 16:00.

  • Project evening
    1. Wednesday 19-9-2018

    Presentation about the current projects at the WOT.

  • Presentation WOT-member
    1. Wednesday 26-9-2018

    WOT-member Hilbert-Jan will be speaking about his experiences in Ethiopia.

  • Workweekend
    1. 29 and 30-9-2018

    A whole weekend of WOT-fun!

  • Course on workshop skills
    1. Wednesday 3-10-2018
  • Scrapheap Challenge
    1. Sunday 7-10-2018
  • Fix your own bike
    1. Wednesday 10-10-2018