Archive for WOT Blog

Introduction evening

Monday, August 26th, 2019 No Comments

On wednesday September 11 the WOT organizes an introduction evening. We will start of 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

    Upcoming activities @ WOT

    Sunday, September 11th, 2016 No Comments

    Feel like learning something beyond your current study program? Want to use your hands and learn something about technology for developing countries? Our activities and courses might be just the thing for you!

    All activities will be free admission for WOT members. If you do not want to become a member just yet, you can also sign up for participation through our contact form. Check the google calendar app on the homepage for up-to-date starting times for activities. It’s no problem if you need to come later than the listed starting time though!

    When? What? What??
    14 september Info night Introduction and a tour of the terrain, as well as free dinner and fun at the campfire!
    22 september Masonry workshop Learn how to stack bricks while we work on our shed!
    24+25 september Survivalweekend We camp out on the WOT field while a professional instructor teaches you how to survive in the bush.
    29 september Bike repair workshop Learn how to fix your bike using spare parts. Make sure to bring your own bike if you’re have any problems with it! Otherwise, we’ll have some busted bikes for you to exercise with.
    6 october Advanced metalworking course This course will be teaching you the basics of milling and turning with our own mill and lathe in the WOT workshop. If you’d like to learn how to weld, you can also sign up for an individual welding course.
    15+16 october Project weekend Various odd jobs and DIY projects will be tackled during this weekend of hard labour and great fun! We need all the help we can get!

    Innovative freewheel clutch for rope pumps

    Wednesday, May 18th, 2011 2 Comments

    A directional brake

    A directional brake

    Since we already installed a number of rope pumps in the Netherlands, we were looking for a safety brake that is reliable and stultify the appearance of the rope pump not too much. As users rope pumps knows, the wheel and handle swings back firmly as they stopped with pumping. In developing countries the user get instructions to use the hook to prevent turning back of the handel. For public places where anyone can use the pump, the blocking hook will not be used and there is a change injuring the user.

    Therefore our search for an automatic device that prevents the reversal movement.

    Already been experimented with a kind of rattle that stucks in the spokes of the wheel. Tests showed that the forces where so enormous that the rattle pin bended. Another solution might be a band brake. This is also tested. Alongside that it is vulnerable to vandalism and this looks not so pretty, the braking power is not sufficient and reliable enough. A third type of a oneway brake with a nail into a wedge-shaped space in the bearing bush gave good results being better than expected. The video shows the pricipele operation, construction and testing of the oneway brake.

    Spring on the WOT-field

    Wednesday, March 23rd, 2011 No Comments

    Daffodils in bloom at the Kijito

    Daffodils in bloom at the Kijito

    The days are starting to lengthen and temperatures rise. And on the WOT-field the nature has actually been in effect. Sometime in the distant past on the back WOT-field by a WOT member with very green fingers has planted daffodil bulbs. And miraculously come each spring the daffodils appear in the open field for us to cheer.

    DIY Power Unit

    Saturday, March 12th, 2011 No Comments

    3kW generator lawnmower engine

    generator in the making

    After a quick experiment with a drill, an asynchronous electric motor, a capacitor and a lamp, we got the idea to build a generator. The aim was to connect the 3 kW electric motor to a 3.5 hp Briggs & Stratton petrol engine from a lawn mower. We fabricated a frame where both engines can be put down in two evenings. We took some pullyes and a v-belt for the transmission. The electric motor is fixed with wire ends, so the v-belt can be always be set tighter.

    After cleaning up the engine the combination works perfectly. Only some vibrations appear caused by the engine. Perhaps the pulley must be fasten tighter or a damping suspension is needed. After that the capacitor must be connected to provide power. More news about the homemade power unit coming soon.

    The lamp, we spoke about in the first sentence, had not a long life: After a high number of revolutions and huge light output the 60 watt bulb broke down.

    ThW donates gas cylinder carts

    Friday, March 11th, 2011 No Comments

    From the Department of Thermal Engineering (ThW) of the University of Twente we got three gas cylinder carts for free! Ideas about what to do with it were found easily. One cart will be modified into a trolley and the other two will probably be combined into a convenient caddy.

    Three cylinder carts in a row

    Three cylinder carts in a row

    Installation of rope pump in New Rotsoord, Utrecht

    Wednesday, February 2nd, 2011 1 Comment

    On Sunday, January 23rd, Freddy and Rene went to Utrecht to install a rope pump at the patting zoo ‘New Rotsoord’. This pump is the very first sample of a new design: the pump has a single support instead of a whole frame. As a result, the material costs drop 20 percent and the design becomes simpler.
    The construction of the pump was done in Enschede. The only thing necessary at Nieuw Rotsoord, was the installation of the pump.

    The pump is placed in a concrete foundation next to a 6-meter deep well. The intention is to let the volunteers of Rotsoord make a drive gear based on a bicycle.

    Once we receive a picture we will definitely post here.