The Crocodile's Bucket & Chain Water Pump




We are The Crocodiles and this is our ‘bucket & chain’ style water pump. We are a group of Product Design Engineering students and were given the brief to construct a water pump which lifts 5 litres of water up a height of 600mm, in under 5 minutes, using the 24v motor provided. The winning team would be the one which completed this task in the most efficient way possible – voltage and amplitude were measured, as well as the total time taken. We decided that simplicity was the key and started work on a Bucket & Chain system.

Step 1: Concept & Planning

After discussion, research and idea generation we came up with a concept for how we could make a bucket and chain pump that would fit the tank provided (pictured below). Our idea consisted of a simple wooden frame, two belts and five water containers – equidistantly spaced along the belt for maximum stability. One of the main features of our design was an adjustable arm that allowed the system to collect water at various gradient increments, meaning that it could be adapted to suit the water level of the tank. Here is a rendered image of our concept (made in SolidWorks):

Step 2: Materials


Pine (frame)
MDF (swing arm)
Screws: M5x40mm
Bearings: 26x10x8 mm
Aluminium (gear-axle connection, brackets)
Sheet Acrylic (gears)
Grub Screws
Foam (spacers)
Styrene (guide plates)
Rubber Belts
Tin Cans (vessel)
Zip Ties,
10mm Steel Rod (axle)

Plastic Robotics Gearbox (Maplins)
24V Motor & Power Source

Step 3: Constructing the Frame

We decided to construct our frame out of 62x37mm pine beams because they were readily available in our workshop, had a relatively good strength to weight ratio and wouldn’t be affected by the time spent underwater in the tank.

1. Cut the required lengths (as measured from our general arrangement drawing) of pine
2. Drilled holes for the bearings
3. Clamped into desired form to prepare for fastening.
4. Fastened together using wood glue and screws (hand drill), into a form of A-frame (as shown in SolidWorks image)
5. Repeated for other side of frame.

Step 4: Adding the Swing Arm

The swing arm would allow us to adjust the gradient of the system.
This is how we constructed it:

1. Marked the curved shape onto a sheet on mdf
2. Cut using band saw
3. Drilled 10mm holes spaced 100mm apart along the swing arm
4. Drilled one 26mm hole at one end of the arm for the bearings
5. Repeated for second swing arm

Step 5: Attaching the Cups to the Belt

1. We sourced two belts that met our spec from the website [] and next had to attach five cups to the belts.
2. To do this we made five brackets by cutting and bending 3mm thick sheet aluminium.
3. Drilled two holes in each bracket for attaching to belt
4. Drilled two more to use with zip ties
5. Fastened to belt using small bolts countersunk into spaces between the teeth, equidistantly around the belt.
6. Attached the cups to the holes in the brackets with the zip ties

Step 6: Making the Gears

We sourced some 10mm steel rod to use as the axles and next had to make gears to fit the belt.

1. Measured the spacing between the teeth on the belt with digital callipers.
2. Used SolidWorks to draw out a stencil for the gears
3. Laser cut this shape out of 4mm sheet acrylic (x8)
4. Cut a rough spacer plate out of foam to place between two of the gears (x4)
5. Cut two guide plates out of 2mm thick styrene, for either side of the gear sets. This was to insure that the belts wouldn’t slip, causing the system to fail.

Once we had made these gear ‘sets’ we had to find a way to connect them to the axle without slipping. To do this we had four aluminium lathed parts that would effectively allow us to grub screw the gear sets to the axle. These are also shown in pictures below.

Step 7: Assembly of System

It was then a case of assembling all the aforementioned components into one system that would fit  the tank.

1. The bearings were push fitted into the holes on the frame
2. Gear sets fastened onto axles
3. Belt configuration placed onto gear sets
4. Axles slid into bearings, into frame
5. Swing arm locked into place with aluminium rod

We then placed the system into the tank to check that everything was ready for testing.

Step 8: Motor and Gearbox

We decided it would be more time effective to buy a gear box, rather than make one ourselves.

1. We sourced a plastic robotics gear box (from a Maplin store) to allow the motor to turn the axle.
2. The gear ratio we were looking for in order to turn our axle was 260:1, which this gear box provided.
3. We then connected the motor to the gear box and mounted this to a piece of MDF.
4. This was then lined up and the motor shaft was grub screwed to the axle.
5. The whole system was then mounted to the frame.

Step 9: Finale

Unfortunately the robotics gearbox failed us as the little plastic gears couldnt handle the amount of torque we required and started to shear. By the time of the event we were still unable to fix the gearbox, however we did manage to run the pump by connecting a hand drill directly to the axle. Here is a brief video of the pump in action.



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    21 Discussions


    4 years ago on Step 9

    i cant see any calculations, where are they, or is it that you employed a try and error method?


    4 years ago on Step 9

    i cant see any calculations, where are they, or is it that you employed a try and error method?


    7 years ago on Introduction

    Why not use an Archimedes screw? Fewer moving parts, much simpler mechanism and much larger volume of liquid moved.'screw

    2 replies

    Reply 7 years ago on Introduction

    That's all fine to suggest, the Archemedes screw is an excellent device, but how would you suggest they build such a thing with simple materials in a short time with simple tools?

    The screw is a great device, but is not as simple to build as you might believe. I think the author's KISS approach was great.


    Reply 7 years ago on Introduction

    They built the screw in the time of Archimedes. I'd say that it can be built with simple materials and tools in a short time. The Chinese have made a similar devices using bamboo as the material and simple tools.


    7 years ago on Introduction

    re-inventing the persian wheel, how amusing. when i was a kid these were in use all over north-west india. an endless bucket chain turned by a camel, bullock, or buffalo. most were galvanized sheet metal but i saw a few that were still using clay pots.


    7 years ago on Step 6

    What brand of laser cutter did you use?


    7 years ago on Introduction

    I wonder if the materials you could use were restricted?!

    In my opinion it would have been way more efficient to get some garden hose and simply build some kind of rotary pump... In particular since you obviously had the opportunity to use a lasercutter.

    Like this:

    But nice work, nevertheless.


    7 years ago on Introduction

    Nice little chain pump there. Concept is around 1000 years old(Chinese). Other possibilities are an Archimedes screw, an air lift or a noria. Or even Ctesiphon's force pump.


    7 years ago on Introduction

    Although it is simple, I believe this could be the basis for harnessing energy from sea waves.
    A series of bucket chains run from the sea up a cliff to a reservoir at the top and a turbine generates electricity in the usual hydroelectric way.
    The sprocket at the bottom of each chain has a ratchet, and an arm connected to a large float.
    The displacement of the float is slightly greater than the total weight of the water in all the full buckets going up.
    The weight of the chain and buckets going up is balanced by those coming down, its just the water we have to lift.
    If the waves are small, the chain moves slowly, but still pumps.
    The turbines are switched off when the reservoir water reaches a lower set level on wind free days.
    A spin-off is the seaside resort / seafood fish farm with no sharks at the top !
    The reservoir could be a dam wall across the mouth of a dry arid valley, ( with no wetlands or vegetation to disrupt ) at the top of a cliff.

    1 reply

    Reply 7 years ago on Introduction

    this might be off topic, but your comment made me think of these things...

    Green Silver

    7 years ago on Introduction

    Big it up, and use buckets as the cups, and you've got a great pond water feature!


    7 years ago on Introduction

    Such a shame about the little gear box - I'd love to know if the design would have won if it wasn't for that!


    Sounds like a perfect application for a spiral pump, only friction from a single bearing.


    7 years ago on Introduction

    Nice job! It had all the ingredients for success: simplicity of design and great execution. Again, good work!

    1 reply