For the local Island Bay School Fair I made a water-powered duck race. As with all creations it didn't come out as expected, and unfortunatly one of the pumps died at the fair after 2 hours (diaphragm seal perished), but there were lots of happy kids and a few excited adults from a few hundred litres of water spewing down some guttering with 2 abused ducks going down.
I'd seen some examples of duck race games online, but they all looked a bit lame, using squirter bottles to propel the object down the race.
However one design that used old water pumps started me thinking. I couldn't source any pumps like that, so I found youtube instructions on making manual draw(?) pumps with old PVC downpipes, some plywood and some old broom handles (funnily enough a Kiwi!)
note: I used a hole saw to cut seals and plunger end, his approach is pretty laborious , but full credit for hand-tooling).
These ones I made using ~500x60mm downpipe sucked up heaps of water each draw (3-4 litres) and made a torrent of water that required the buckets under them to be continuously filled, I thought about some ballcocks or toilet cisterns but it was going to get more complicated so I went back to the drawing board. They also could have broken fairly easily if mistreated by heavy-handed kids. :(
The local kindy had 2 self-contained water play contraptions that I borrowed, these had bilge pumps installed with ~70litre rubbish bins inside them as water storage for the pump's intake. You can see the contraption in the video, they are wooden drums with the pump handle and spout exposed.
These apparently could pump out 95lpm, had 1 and 1/2 inch (?) in and out pipes on them so clearly a fair amount of pumping ability.
These lever-action pumps were easy to use for the kids, and smooth pumping motion was easily taught in 10 seconds test before each race started.
Originally I had plans of cross-overs in the guttering (like slot cars), teetering see-saws, swinging logs etc. In the end a few zig-zags, a drop into a old plastic lampshade acting as a funnel, and some tunnels added some excitement. Depending on how much water was pumped, each of these obstacles would pose a problem.
Lots of water = no problems
Only the un-energetic or erratic pumpers would encounter duck stuckage.
I made a Y-adapter for the garden hose so that I could trickle-fill the intake drums, as you need to prime the pumps if they got dry...
This is for one of the runs, as there were 2 side-by-side.
Length of run: ~6 meters
Guttering: PVC
Water drums: 68Litre rubbish bins
Ducks: Tommee Tippee Dippi Duck (these are smallish ones)