A moving waterwheel

outward facing corners made with plasticardMy exhibition layout will feature a mill with turning waterwheel. This article explains the simple electrics behind this.

The mill house and waterwheel I’m building are from Wills Kit CK22 with added plastic card sheets for the wooden flooring, internal walls and secondary building on the side. The waterwheel was also modified, using parts from a second wheel to increase the number of paddles although this isn’t shown here.

For power to the waterwheel, I initially considered an Arduino-controlled motor that could vary the timing and speed but in the end went for something much simpler, a basic DC motor controlled by a simple on/off switch at the rear of the layout.

The problem was that most DC motors – 9v or 12v – have rotation speeds that are far too fast. Water wheels turn slowly and certainly not at the thousands of RPM that typical DC motors spin at.

>This post is part of a series on the construction of a lifelike model railway for exhibitions. To read other posts in the series covering its development, track work, scenery and model building making, see building an exhibition model railway.

I tried various DIY gearing assembles but couldn’t get these to fit in the OO /  1:76.2 scale building that will house it. Especially as I want it to have two floors and I couldn’t get the motor unit and my clunky collection of assorted gears to fit in the available space available under the plasti-card first floor ceiling.

Instead, I went with this geared motor.. It’s got the DC motor and gearbox built into a small form factor box that just fitted between the base of the model and the first floor.

Running this at 3v – using a switchable power supply – gave roughly the speed I wanted. As seen below.

geared down DC motor for model railway animation

A hole with the diameter of the waterwheel axel was carefully drilled through the mill house wall and the motor was glued to the base of the model so the shaft from the motor aligned with the hole. Given the vibration that comes off the motor, the usual Poly cement wasn’t strong enough to hold the motor in place so I used a two-part epoxy glue.

[The axel was positioned at a height so that the wheel reaches below the base of the model as it will sit “in the river” and therefore will need to be lower than the building].

The water wheel axel was then pushed through the hole and twisted into the hollow end of the motor shaft. The other end of the axle will rest on a wall in the river so it needs to protrude out further than expected. Once I had this distance measured, I then glued the axel into the shaft again using two-part epoxy glue.

After a bit of further sanding of the axel, the wheel itself was pushed on, some further work was done to the building and it was all tested. Here’s it as it stands, still a lot to do on the mill itself but the water wheel works.

model railway animation water wheel

The two leads from the motor are a bit short by default so these need extending to reach to under the baseboard for connection to the DC accessory bus wiring and control switch but this is straightforward enough with a bit of soldering.

Next up add some furniture and other mill house objects to the first floor that will be visible through the windows and at some point I’ll add the fake water for the river.

> A final, personal, note: I spend a huge amount of time testing, photographing, writing and researching techniques for these articles and pay for all the running costs of MRE out of my own pocket. If you found this article useful you can support me by making a donation on my fund-raising page. Thanks and happy modelling, Andy.  


Founder of ModelRailwayEngineer, Andy Leaning

Andy is a lifelong modeler, writer, and founder of modelrailwayengineer.com. He has been building model railways, dioramas, and miniatures for over 20 years. His passion for model making and railways began when he was a child, building his first layout at the age of seven.
Andy’s particular passion is making scenery and structures in 4mm scale, which he sells commercially. He is particularly interested in modelling the railways of South West England during the late Victorian/early Edwardian era, although he also enjoys making sci-fi and fantasy figures and dioramas. His website has won several awards, and he is a member of MERG (Model Railway Electronics Group) and the 009 Society.
When not making models, Andy lives in Surrey with his wife and teenage son. Other interests include history, science fiction, photography, and programming. Read more about Andy.

Afflliate disclosure:The links on this page may take you to carefully selected businesses, such as Hornby, Amazon, eBay and Scale Model Scenery, where you can purchase the product under affiliate programmes. This means I receive a small commission on any orders placed although the price you pay does not change. You can read my full affiliate policy here. I also sell my my own ready to use, pre-made and painted buildings and terrain features. browse the range.

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