Archive for 2021

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!