A story about an engineering assignment I did in about 2003.

4th year mechanical engineering students were given a task of making a pump and generator from scratch, to demonstrate on a two resorvoir system at uni. Two tanks, one 3m up. Pump water up, make electricity down.
Uni provided a little electric motor with shaft which could work as a generator as well. The winning team would be the "best round trip efficiency", best ratio of energy spent and energy returned as electricity
Teams ran off into different strategies. The ones in proper engineering jobs used work equipment *extensively*.

One group machined their pump components out of solid aluminium. Consumer $8k worth of machine time. There were 6 teams with various strategies.
Every team except ours used a combined pump/generator. Same their pumps would run backwards to generate power on the way back down. We went the other way, with a dedicated pump and a separate pelton wheel for generating power.
I made our pump in Dad's shed, using a CD spindle case, hot glue and PVC pipe. I sectioned the PVC to make vanes for the pump, then glued them between two CDs. Water came in through the centre, the pressed out to a rising volume manifold to pump the water out. It looked terrible
BUT! The bastard worked. We were one of only three groups that managed to lift water to the top resorvoir. The $8k machined guys made it too, thankfully. For everyone else their internal friction was too high!
To make ours work I had to hold it together with my hands, there were water jets coming out everywhere, but that's because the pump pressure was so high. We easily filled the tank and I got soaking wet.
On the way back down, we WERE THE ONLY TEAM TO GENERATE POWER. We made a pelton wheel using spoons from the cafeteria, jammed into a polystyrene hub, on a metal shaft. We spun the shaft, no one else did.
Now, why am I telling this story?
It was a pivotal moment for me looking at Good and Dodgy ways of doing things. The Good approach used $8k in resources and barely worked.
Our shit box worked first go and could have been converted into a workable design with a little bit more effort.
The $8k one didn't work and is very hard to change.

So do the dodgiest prototypes you can get away with. First lesson.
The second lesson was about scale. Things work differently at different scales, and pumps are the best example. Internal friction scales with surface area:volume ratio. Big pumps have a better ratio and are inherently more efficient as a result. Small pumps are terrible
This is interesting for pumped hydro projects and pumps in general. Go big or go home! No point mucking around with little systems.
I have photos of the rig somewhere but can't recall where. On a CD somewhere no doubt.
hahahahah shit I was thinking of going looking for the CD the photos are on but I don't have an optical drive any more!
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