We are team el Elefante and this is our submission for Hydro Do That..., a team project in our second year of Product Design Engineering at Glasgow School of Art. The brief was to raise 5 litres of water 600mm in the most efficient way possible. Supplied with a 24V motor, it was up to each team to design and build a pump over a 6 week period. A rope pump (or elephant pump) works by passing a loop of stoppers through a pipe. Each stopper lifts a section of water; once running at a high enough speed, the flow of water is quite smooth.
The Rope Pump is built using a length of 22mm copper pipe with a 28mm section attached to the top as a reservoir to prevent overspill. A funnel is attached to the bottom to help feed the rubber stoppers into the pipe. For the loop of stoppers, we sourced some rubber furniture feet that fit in the pipe with 1mm clearance. For increased efficiency, as small a clearance between the stoppers and the pipe is required - whilst still minimizing friction.
The drive wheel is made of MDF, although we would recommend a more waterproof material. It has a diameter of 120mm and has flared edges to help grip the rubber stoppers. Beneath the water is a small plastic wheel that is free to rotate and is there only to maintain tension in the nylon rope and guide the stoppers.
We sourced a gearbox from RS Components, using several 4:1 gear drops and controlling our input voltage to achieve the desired speed. A small metal base was added to one of the gears as it was slipping when we ran the pump. (This can be seen half way through the video, attached to the green gear.)
The video you see here is not the final event in which we competed against the other teams, it is just one of our final tests.
Out of the six teams that ran this project, our team was the most efficient (11% compared to second place 3% and third place 0.01%) We ran the pump at 18V, achieving the 5 litres of water in just over 33 seconds.