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Thanks Richard - best explanation I have seen on this topic. Have tried (and failed) to make useful waterwheel myself for use with scout / school groups Your assessment sounds spot on Would love to visit somewhere with this type of hands-on exhibit. Fingers crossed ! Cara Sent from my iPhone > On 24 Aug 2018, at 16:00, Richard Ellam <[log in to unmask]> wrote: > > Dear Simon, Holly and all > > Small-scale waterwheel models are pretty hopeless because the basic physics of water-power works against them. The reason that little model waterwheels just spin round uselessly is that this is just about all they can manage. Real waterwheels need very large flows of water to obtain modest amounts of power. The real problems you face with small models is that if you just scale big waterwheel down the power output you get scales as the inverse cube (half the size gives 1/8 the power) but the losses probably only go down in proportion to the scale. So you fairly quickly get to a thing that’s using all its efforts just to keep going with nothing over to do anything interesting. And waterwheels also need a lot of water. > > I live not far from the splendid Claverton Mill, a water-powered pumping station built just over 200 years ago to supply the Kennet and Avon Canal. This machine has a waterwheel which is some 24 ft long and 17 ft in diameter. Working flat out 2 tonnes of water, that’s 2 cubic meters, say 20 bathfuls, flow through the water wheel every second and yet this house-sized machine produces a useful output of less than 25 hp measured as water raised to the canal. If, by contrast, you’re trying to make something that works off the flow you can get from an average tap then you can pretty much forget doing anything other than spin round fitfully. > > My experience of making interactive exhibits and working models suggests that a waterwheel model less than about 300 mm, one foot, in diameter and say 150 mm (six inches) wide is going to struggle to produce any sort of useful output at all. A waterwheel this size will require a greater flow through it than can be provide just by running a tap, and I would;t advocate doing this anyway as running the tap is a dreadful waste of high-quality drinking water. A decent working model should have its own water tanks and circulating pump. And the pump probably ought to be worked by hand as it will give your youthful audience something to do with their surplus energy. > > Its also not really practical to have a single model waterwheel that can be converted between undershot and overshot principles as the construction of the wheels is totally different. Its rather like asking for a bicycle that can be converted into a canoe. I don’t say its not possible, but the resulting machine would likely fail as both vehicle and vessel. > > I am quite convinced that it is possible to build a really good waterwheel demonstration exhibit that ‘does something’, and that allows the differences between undershot and overshot wheels to be explored. I think it might end up looking a bit like the rig that John Smeaton built back in the 1760s to investigate the efficiency of waterwheels - His model wheels had to be about 2 ft diameter to get reliable results, but we’ve got better bearings and things than Smeaton could use so the wheels could probably be a bit smaller. > > If there was the demand, from say three or four different museums, and a willingness to pay a reasonable sum for a piece of bespoke equipment then I would be willing to have a go at designing and making a properly useful and engaging waterwheel demonstration exhibit/activity prop. > > If there’s any interest out there in this plan its probably best to contact me off list via [log in to unmask] > > Hope this helps > > Richard. > > Richard Ellam > L M Interactive > Science Shows and Hands-On Stuff > [log in to unmask] > www.lminteractive.co.uk > >> On 23 Aug 2018, at 13:30, Simon Watts <[log in to unmask]> wrote: >> >> Holly, >> >> I’m not aware of one but would be very interested in any reply. I’m looking for similar but potentially looking at getting Key Stage 2 groups to build their own and to modify the design (overshot vs undershot, change wheel size, cups vs paddles, etc.) >> >> Would you mind sharing any responses? >> >> Cheers, >> >> Simon Watts >> DNAire Community Engagement Officer >> >> The Aire Rivers Trust I Kirkgate House, 30 Kirkgate, Shipley, BD183QN >> 07578 708025 I [log in to unmask] >> www.aireriverstrust.org.uk I www.dnaire.org.uk >> >> >> <image002.jpg> >> >> From: List for discussion of issues in museum education in the UK. <[log in to unmask]> On Behalf Of Education (Tiverton Museum) >> Sent: 23 August 2018 12:50 >> To: [log in to unmask] >> Subject: Waterwheel >> >> Hello Gemmers! >> >> Does anyone know of an ‘off the peg’ waterwheel toy that actually drives something else? It is for use with KS1 and all the waterwheel water play toys I can find have pointless wheels that just spin around – it would be great to show that this could drive something else. I have looked at cog and gear sets and can build something, but if anyone knows of anything that is off the peg and ready to go, that would be fantastic. >> >> Thanks, >> >> Holly >> >> Holly Jarrett >> Education and Outreach Officer >> >> Please note my working days are Monday – Thursday 9am – 5pm. >> >> Tiverton Museum of Mid Devon Life >> Beck's Square >> Tiverton >> EX16 6PJ >> 01884 256295 >> Registered charity 239531 >> >> WINNER of the Bronze Award, Small Attraction, Visit Devon Awards 2015 >> WINNER of the Bronze Award, Access & Inclusivity, Visit Devon Awards 2015 >> LONGLISTED for The Telegraph’s Family Friendly Museum of the Year Award 2015 >> WINNER of the GOLD Award Small Visitor Attraction, Visit Devon Awards 2013 >> WINNER of the Bronze Award, Small Visitor Attraction, South West Tourism Excellence Awards 2013/14 >> >> Home of Tiverton's Tourist Information Service - WINNER of the Bronze Award, Information Service of the Year, Visit Devon Awards 2014 www.exploretiverton.co.uk >> >> Visit our website to find out what's on: www.tivertonmuseum.org.uk >> Find us on Facebook: www.facebook.com/TivertonMuseum >> Follow us on Twitter: twitter.com/TivertonMuseum >> >> >> >> + + + + + + + + + + + + + + + + + + + + GEM list: Contact the list owner for assistance at [log in to unmask] Anyone can join for free at any time by sending this message [log in to unmask]: Join GEM Firstname Secondname Include only the text above, without email signature etc. The title of the email doesn’t matter. 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