Archive for WOT Blog

Update gearbox design

Sunday, June 27th, 2021 1 Comment

Since the last post about the new windpump gearbox a lot of progress has been made. In this blog, we will discuss some of the findings during the process. Also, some important changes are made to the design which will be discussed. Starting from the last blog post about the gearbox the test installation is finalized from the first design.

Bearings

One of the first major changes to the design is the type of bearing used. At first normal bearings are used for which a housing is made and welded to the gearbox casing. As could be expected the alignment of the bearings was rather difficult. When the bearings were installed it was not possible anymore to change the distance between the two gears.

Both problems are solved by making use of flanged bearings which have a couple of advantages:

  • Easy to replace.
  • Axle can be fixed in place, so no additional parts are required.
  • The ability to compensate for some misalignment.

First run

In the video below the first rotations of the gearbox are shown including the counting of the strokes. The transparant window is only for inspection purposes during the test phase of the gearbox.

Now all the main components are working the gearbox is painted and the last details are worked out such as preventing the weight from rotating during yawing.

Steel cable

At first a steel cable is used to transfer the rotating motion of the rotor into a translating motion. A 6mm thick steel cable is used, however this cable snapped after 59.535 strokes due to the small pully (60mm diameter) used to guide the cable. According to the steel cable manufacturer, a pully of a steel cable should have a minimum diameter of 20x the cable diameter. This would result in a pulley with a minimum diameter of 120mm, within the gearbox there is no space for such a pulley.

A smaller steel cable of 4mm in diameter is used in combination with a slightly larger pulley (85mm). This cable snapped after only 19.334 strokes, a final test is done with the 6mm cable in combination with the larger pulley. This helped a bit, however the cable still snapped after 69.591 strokes.

Another problem with the steel cable is that if the tension by the weight is released it will immediately ‘jump’ of the guide pulley. Whenever the gearbox is started after that the cable is damaged, which is not preferred if the gearbox is up a windpump.

Solution: Instead of the cable, a chain is used in the newest improvement of the gearbox. This new configuration has done over 120.000 strokes without problems.

Test results

Based on the previous blog post about the gearbox several things where tested and monitored during the manufacturing and working of the test setup:

  • Effect of yawing on the cable: The weight is fixed and cannot rotate as we expect that the cable/chain will fail before the pump starts rotating in the borehole. Therefore a coupling is made which will account for the yawing motion of the windpump head. This connection can also be used as a safety feature if the pump will get stuck in the borehole for instance. –> this coupling is working well and will be discussed in a later blog.
  • Ease of manufacturing: As discussed before, alignment of the bearings appeared to be difficult. With the new flanged bearings, the tolerances on the different shafts can be less precise.
  • Oil consumption: Oil will leak through almost every hole present in the gearbox, so the correct type of seals have to be used where the axle goes through the gearbox housing and where the gearbox is bolted to the tower head. Most of the oil will leak via the cable/chain through the tower pipe if the cable/chain is touching the main gear. This can be easily prevented by making the gearbox housing a bit bigger.
  • Failure modes: The main failure mode appeared to be the snapping of the cable, this is solved by using a chain instead of the cable. To find more failure modes the gearbox has to be tested with contamination like sand and water from outside the gearbox.
  • Maximum load: The maximum load and the weight of the weight is not determined yet. It is assumed that the maximum load is currently limited by the motor simulating the rotor.



Instructional video Breurram

Sunday, April 18th, 2021 4 Comments

The Breurram is a type of waterram pump that was developed by a WOT volunteer in the 90s. There already is an elaborate manual on how it works and how to build one. In addition to this we decided to make an instructional video about this great pump.

The video shows the pump in action, it explains how it works exactly and a timelapse of the assembly process is made. Also the yield of the pump at different heights is shown.

For more information about the Breurram please go to this page. The manual you can find here in multiple languages.




WOT, Epic challenges

Monday, March 8th, 2021 No Comments

As WOT members we love making things playing around with all kinds of different tools and materials, since we are not able to collectively do that at our terrain we decided to do it separately.

For this reason we organised the Epic challenges every week we work on a different small project.

-Challenge #3
For this week’s challenge members were asked to create an instructional video to explain how to build a marble pump. The video of the winning team would be placed on the youtube channel of the WOT.

Only two submissions were entered and since they both elaborated on a different type of design, it was decided that both videos would be put on the Youtube channel. You can check out the video’s at our youtube channel: https://www.youtube.com/channel/UCD9iM7XU_iuZWsFQ9A_F2kg


-Challenge #2
We are making bird houses, but not just any bird house contestants are encouraged to make their birdhouse as comfortable and luxurious as possible, and of course creativity and originality are very welcome in this mini project.

On Wednesday 10-3-2021 we voted and birdhouse #3 won, of course hugely due to the Bob Ross television, now we just have to wait and see if the birds like our creations.


-Challenge #1
Contestants would fabricate their own unique coffee mug to be used in the kiwanda, for this members used all kinds of techniques, from electroplating and welding to turning and 3d printing.
These are some of the resulting mugs that where produced:

On Wednesday 3-03-21 we voted to determine the winner, and although it was a close call mug #4 won! A mug shaped out of wood using a lathe, a chisel and probably quite some time.




Plastic pump system under Kijito.

Wednesday, February 17th, 2021 No Comments

As a duration test the plastic pump system which is currently tested at the WOT is placed under the Kjito windpump in the second half of 2020. During the last couple of weeks the pump was struggling with pumping water, only delivering during high wind speeds. This made the foot valve the suspect of the problems. However, during the period of low temperatures of the last couple of weeks all the windpumps where shut down to prevent damage due to freezing of the pipes. This gave a opportunity to remove the pump from the Kijito and investigate the pump in more detail to find the actual cause of the problems.

Kijito well

The well under the Kijito windpump consists of a well which is dug out. The sides are reinforced with concrete and there is no bottom in the well which makes it dependent on the level of the ground water. The well is around 4.5 meters deep with at the moment (February) water at 2.5 meters. During summer and high winds the well be pumped empty which is not good for the longevity of the piston.

Cause of the problem

As mentioned above the pump showed signs of a bad foot valve, however the foot valve was in great condition! the part that failed was the outer pipe of the pump, the piston had so much friction that the wear on the pipe was so big that the wall thickness decreased resulting in:

It is remarkable that this problem occurs only after a couple of months. This pump design is already used for multiple years without maintenance in South-Africa. However, the main difference is the well or borehole used. The boreholes in South-Africa are mainly 10″ holes of tens of meters deep, sometimes even over 80 meters deep. These deep and narrow holes force the plastic tubes of the pump to be straight and therefore easy operation.

The well of the Kijito is very shallow and wide compared to these boreholes. This results in the tube not being straightened properly and therefore creating two point of high pressure on the outer pipe (at the point of the piston and where the inner tube changes to the solid plastic rod). When the pump was removed from under the windpump the tubes where still not straight:

Solution

Since the cause of the problem is not found in the design of the pump but the way the materials are used, the most important lesson to be learnt is: Make sure the pipes are straight. In case of the Kijito well, which is shallow and wide this is not a straightforward job. For now there will be ordered a new outer tube and a way to straighten out the the pipes will be found.




Students TU Delft follow rope pump course

Sunday, January 17th, 2021 No Comments

At the end of 2020 a group of students from the TU Delft contacted the WOT because of a project they were working on for their minor. They were to work out and implement a system to provide water for a company and a community in Sierra Leone. When researching they found out about the rope pump and decided they wanted to build one of these. The WOT has provided a course in the making of such a pump.

During the workshop parts of a rope pump were made. The students wanted to take these along to Sierra Leone. They would however, built more pumps with the local people. This is important to insure a greater degree of autonomy and sustainability.

The workshop

Because of the corona measures and limited capacity of our workshop only two members of the group could attend the course. Making a whole pump in one day was too ambitious and since the students had very limited welding skills, we decided to only create the parts that could be made without welding. Some welding was done by WOTters beforehand and in Sierra Leona as there also was a skilled welder available.

Metal forming as well as PVC forming were discussed. Also a part of the rope was made and the campus rope pump was removed and installed again.

The implementation

The students decided they wanted to go to Sierra Leone to install the pump. They did so successfully. Two more pumps were made over there, together with the locals, which will be installed soon.

The first pump works!



Comparing irrigation systems in our garden

Sunday, December 6th, 2020 No Comments

At the beginning of this year several irrigation systems have been tested in the vegetable garden at the WOT. The aim of this project was to find a low cost but efficient method to irrigate crops. Three systems were tested: a bought transpiring hose, a system made from terracotta pots, and a system made from plastic bottles or jugs. To read more about the setup please read the previous blog on this project.

The garden has a relatively small area (approximately 4m x 4m) and multiple crops were grown in it. Therefore a quantitative analysis cannot be justified. Instead of looking at the crop size, the practical considerations are tested. Below is a table that summarises the findings.

Effectiveness   Cost  Complexity
Irrigation hose + +/- ++
Ceramic pots ++ +/-
Plastic jugs ++ +

Irrigation hose

The irrigation hose was off the self and installation was simple. With a conventional garden hose the tube was connected to the water tank. The hose was buried at 20 cm so it would hydrate the ground below the surface. Often, however, the ground at the surface was dry. In general this is an advantage because moisture on the surface may evaporate. Also, weed growth is less. However, when seeds have just been sowed or the crops are still small, they cannot reach the water and thus spraying the surface with water was still necessary.


It should be noted that the pressure in our system was low (0.1-0.2 bar) because it was connected directly to a water tank. If the irrigation hose is connected to the tap (2-3 bar) maybe the water will reach the surface of the ground.

Ceramic pots

The installation of the ceramic pots required much more work. Pots needed to be sealed together, unwanted holes had to be sealed and a system had to be made to connect a hose to the pot. Then the pots were buried and connected with T-joints to the water supply. The price of such a system is comparable or higher than the price of an off-the-self irrigation hose.

The pots did however perform best with irrigation. Because they have a large height they distribute water deep in the ground as well as near the surface. This irrigation setup is therefore also suitable for seeds or young plants.

Plastic Jugs

The plastic jugs are the cheapest solution since waste materials can be used for it. The performance is however not consistent. The working principle behind this system is that because the holes in the jugs are small and the lid is on the jug, air can’t enter the jugs easily. Because of this water also can’t flow out easily. We noticed however that air quickly entered the jugs and thus water quickly flowed out. This is probably because the ground in our garden is loose sand through which air can move fairly easily. In dense clay water will likely disperse much slower. Of course, the holes could have been made smaller to decrease the flow, but the holes were already small and making them smaller would be technically challenging.

Furthermore opening and closing the jugs everytime you water is a tedious task.

Air quickly entering a jug

Conclusion

If you want to irrigate a small patch, irrigations with ceramic pots may be interesting. Especially if you can get a hold of specially designed irrigation pots. Connecting such a system to a water storage for continuous supply is rather complex and expensive. If you prefer a more cheap and low tech solution the plastic jugs could be a good option. It is a good idea to first do some tests to see if the holes are the right size and if your ground is suitable.

If you want to irrigate a larger area, the self irrigation hose is a good option. Be aware that if you connect it to a water storage the pressure is generally low and the hose might function less well.

In the future, the WOT might research irrigation methods that are low tech and cheap but also easy to manufacture locally.




New Windpump gearbox design

Monday, October 12th, 2020 No Comments

During the last working weekend at three and four october progress has been made with the new gearbox design test setup.
This new gearbox design has a couple of unique features for windpumps which have a gearbox between the rotor and pumping rod (to slow it down and increase the pumping force). These type of wind pumps are widely used in South Africa. The following text is from my internship report on the design of a new wind pump which was mainly focused on the rotor but also adresses the gearbox shortly:

Gearbox of a Climax windpump

To ensure starting at low wind speeds and deep boreholes a gearbox is needed in these wind pump. Together with the new rotor design a new gearbox was designed which is simple in design and can be maintained easily.
Current gearbox design’s like the Climax and Southern Cross windmills consist of cast iron housings which cannot be welded when broken. Furthermore, there are two sets of gears which have to be synchronised to work properly. The use of solid pumping rods leads to ’knock’s’ in the gearbox which are described in the instruction manual for southern cross.

The new gearbox design

These knock’s are caused by the speed of the pumping rods during the upward stroke. The rod pushes the gears up which results in knocking over of
the gears. To prevent this a gearbox with cable is designed since a wind pump doesn’t have to push the pump down in normal operation. To make sure the pump rods will go down springs are added to pull the rods down. Furthermore, only two gears are used with a ratio of 3.2 : 1 which requires 3.2 rotations of the rotor to perform one pumping stroke. The casing consists of welded sheet metal instead of cast iron to make it possible for people with a welding machine to repair it themselfs.

Experimental setup

Since this type of gearbox has never been used before a test-setup is designed to be able to see if the gearbox is working without building a complete windpump. This setup will simulate the rotation of the rotor using an electric motor. The same will be done to simulate the yawing of the windpump. This is expected to be one of the major challenges with this design since the pump will not rotate, but the head of the windpump will. using a stiff pumping rod is not a big deal, but the cable that will be used in this design is not able to resist against torsion. It can be assumed that the windpump will yaw an even amount of times clockwise and anti clockwise, but it is still usefull to know how much rotations the cable will resist without problems.

The bracket around the gearbox is used to make sure that the power cable going to the motor which simulates the rotor rotation doesn’t get strangled up. Furthermore, ball bearings are used as yawing bearings which happened to be quite a challenge to install. So in the final design friction bearings will probably be used since they are much easier to install, allow for less tight tolerances and are more resistant against dust and moisture. But for this proof of concept it won’t affect the results.

Besides this there will be a couple of other things be tested during manufacturing and testing:

  • Effect of yawing on the cable
  • Easy manufacturing without expensive precision tools
  • Oil consumption of the gearbox (how oil tight can it be?)
  • Failure modes
  • Maximum load

Currently the frame of the setup is tagged together, the gearbox itself is tagged together and the different bearing housings are finished. The big gear is machined, only the teeth have yet to be touched with an angle grinder to make it ready to use. The next step is to manufacture a new ‘rotor’ axle since the current one turned out to be bent. Furthermore, manufacturing of the axle for the big gear which has some tight tolerances.




Visit Happy Green Islands

Tuesday, September 1st, 2020 No Comments

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

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.