Archive for 2020

Visit Happy Green Islands

Tuesday, September 1st, 2020 No Comments

Past weekend several members of the organisation Happy Green Islands visited the WOT terrain to look at all the demonstration models and to discuss about a possible colaberatoin.

Happy Green Islands is an organisation that focuses on the waste problem on small islands in the moluccas. On these islands there is no well organised system to deal with waste and most of it ends up in the ocean.

Although waste management is not something the WOT has much experience on, we think it would be interesting to see if our practical knowledge could be of use to help HGI. Furthermore already existing technologies on water and energy supply could prove useful on the islands in the moluccas as well. We hope to start one or more projects based on this collaboration.

Introduction activities

Friday, August 14th, 2020 No Comments

Click here to sign up for activities.

  • Open day

Wednesday 2 September

Tour on our terrain and introduction to projects.

  • Open day

Wednesday 9 September

Well drilling workshop and marble pump workshop, optional tour.

  • Project evening

Wednesday 16 September

Learn more about the projects the WOT has to offer.

  • Pubquiz

Thursday 17 September

The one and only WOT-pubquiz!

  • Workshop course

Wednesday 23 September

Learn to use machinery from our workshop.

  • Lecture wind energy

Wednesday 30 September

For beginners, no worries 😉 Also possible to work on projects.

NOTE: the activities listed at the end of the video are no longer up to date

Kijito pump maintenance

Wednesday, May 27th, 2020 No Comments

During the last few months there were problems with the safety system of the Kijito windmill. The breakpin snapped much more frequently than usual. Last year the Diever had the same problem, then because of rising sand level in the well. Sand clogged the pump and caused frequent snapping of the breakpin, which was solved by dredging out the well. We assumed that for the Kijito the problem would now be the same and that dredging would solve our issues. This turned out not to be the case.

After removing the pump we noticed that the piston could get stuck in the higher range of its movement. This was a bit hard to spot, it is normal for the cups to sit quite tightly. In this case it was the support rings that got stuck; we noticed it because of some wear on the brass.

In 2017 the pump under the Kijito windmill had been removed for replacement of the cup leathers. Back the cylinder was quite stuck and we used a lot of force. This caused the cylinder to become very slightly oval shaped on the top. It is likely that this is what caused the piston to become stuck. Over time the brass of the cylinder was damaged and a small rim was formed.

Sanding down the rim proved quite difficult, but some efforts were made (professionally cylinders can be “honed” to make them perfectly round again). To be sure that the piston would not get stuck again, we used the lathe to shave a few millimeters off the cup support rings.

Our advice: when the safety on a windmill fails repeatedly, you will find yourself tempted to use a heavier breakpin. Always first inspect your pump. The safety is there for a reason. Should you see damage to the piston, expect damage to the cylinder as well.

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.

Update airlift drilling: Motorised drilling

Monday, April 6th, 2020 No 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 of the pipes was more time consuming since the motor was attached to them. Also, starting of the petrol engine was hard, as the engine was at an unpractical location for starting and unwilling. 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 Haje 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 is, 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 certain extends. The drilling can namely 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).
  • De 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 ready 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 during 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.