The Scottish Industrial Railway Centre is run by the ARPG, and it's entirely staffed by volunteers. The group has existed for over 40 years, originally at Minnivey and now at Dunaskin, just outside of Patna (confusingly, Dunaskin is also called Waterside, and there are two Waterside's in East Ayrshire). But come out of Patna heading for Dalmellington and you really can't miss it - there are also regular buses from Ayr which stop right outside.
The site contains many preserved industrial railway artefacts - locos, wagons and bits and pieces both outdoors and in a small museum. The volunteer run shop has everything the Thomas-obsessed child (and grown up) could hope for, and there's a cafe for a cup of tea and a biscuit after a trip on the star attraction - the NCB no 10 steam train. A rare fireless loco also runs on some Sundays - check ahead if you're keen to see this. There's only a third of a mile of track - negotiations are ongoing to get access to more - but each trip goes up and down twice, and you can go as many times as you like.
Look kids - a sunny day in the Doon Valley...
It's a great day out for all of the family - I've been with small children and with elderly relatives - and it's a fascinating insight into the industrial history of the area. The centre is based at the site of the Dalmellington Iron Works company, and while the iron works buildings are sadly unsafe, you can imagine the site at its industrial peak. What's particularly poignant is the number of children who come to see the footplate and have never seen coal - 'why are you putting stones in the fire'? is a common question - in an area which existed for coal less than 30 years ago.
There are some nice walks in the area too, around Dunaskin, further down the valley at Loch Doon, and up to Lethanhill from neighbouring Patna.
Steam Sundays until the end of August and on Sunday 25 September - the centre is closed to the public at other times, but new volunteers are welcome.
PS. For a different view of the site (and some amazing footage of the iron works), check out Danny Macaskill's cycling genius: https://www.youtube.com/watch?v=ShbC5yVqOdI