Intro: How to Make a Rope(Elephant) Pump
This pump was made for a Glasgow School of Art Project, "Hydro Do That?". We were divided into groups of 4 and have to design and make a device that can lift 5 litres of water up 60 cm within 5 minutes. The device with the highest efficiency wins.
We were only given a 24V DC motor with 3500RPM to start with.
Groups were named after sea creatures and our group was the "Clown Fish".
After researching, we think that a Rope Pump will be the most efficient water lifting device we can make in the workshop.
Step 1: The Gear Box Platform
A gear box is required to increase to torque of the 24V DC 3500 RPM moter from 0.1nm to 2.5nm. We built a platform for the motor and the gear box.
The gear box consist two 45 teeth driven gear and two 9 teeth pinion gear.
The platform is a 240mm x 320mm x 15mm MDF board. Two triangle support poles were also used.
The motor stand is made of two95mm x 115mm x 18mm MDF board. Cut them by following the instructions on the pictures. The motor given has a diameter of 36mm, change the hole to the required diameter if the motor used is different.
Two set screws for each board will be drilled in. They are very awkward to work with in this case, since it is MDF, drilling from the edges can rip the MDF open very easily, we used MDF only because it matches the platform.
Step 2: The Gear Box
The gear box is mostly laser cut, it is simply two styrene board sandwich the gears. The exact dimensions are shown in the pictures, the two styrene boards are different, one is on the motor side, which has a extra hole for the ball bearing of the pinion drive shaft.
The gears are laser cut, they are produced on computer by a program called the "Gear Generator".
Once the gear box is assembled, mount it on to the platform, and we are ready to move on to the wheel.
Step 3: The Wheel
The wheel is made out of 7 layers of MDF, they were glued together first, then they were turned on a wood lathe when the glued had dried, a V shaped groove will appear when the wood work is done. The wheel acts like a pulley wheel, pulling the rope up by friction. Rubber sheet is recommended to place in the V groove to create more friction
The ball bearing of the main shaft is then fitted in first, the shallow hole should be a little smaller than the ball bearing diameter, making sure it is a tight fit. The ball bearings we used for the main shaft is 24mm diameter and 8mm thick.
The main shaft diameter is 10mm.
Step 4: The Pipe
The pipe is a 850mm long transparent styrene pipe. Its inner diameter is 24mm and outer diameter is 28mm, it has 2mm wall thickness.
The pipe exit is a 110mm long transparent styrene pipe with inner diameter of 50mm and outer 60mm. A 28mm diameter hole is then drilled from the side, 25mm from the bottom. An 80mm section of the pipe is then inserted and glued into the hole, as an water outlet.
Pipe Exit Fillers
They are stacks of 3mm thick black styrene rings laser cut. The ring diameter is 50mm so it fit in the pipe exit and 28mm inner diameter to fit the pipe.
Step 5: Refining
By the time when everything is fully assembled, it should look like this.The first test we had we achieved 9.6% efficiency, however we believe there is still room for improvements.
First from testing, we noticed there is still a lot of water spillage at the pipe exits, so we decided to add a cone on top of the pipe exit to catch the spillage. Spillage is not efficient because all that energy used to bring the water up is wasted as they fall back down again.
Secondly, we also noticed that the wheel was actually rotating on the main shaft not with it, that is caused by oil we used to smooth the bearings soaked into the MDF wheel. The solution was to drill two perpendicular holes to put two grub screws to secure the wheel.
Then we tested the pump again, and we have achieved 12.8% efficiency, winning the competition. We have also beat the record by 1.8%.