Mechanical sheep restoration
This sculpture was originally built by Andy Plant in 1999, installed above the imposing entrance to Wolverhampton Art Gallery. For many years the sheep would rise up over the balcony on the hour, legs waving in the air, before opening up to reveal the wolf hidden within.
The much-loved sculpture had been partially restored back in 2015, but had once again ceased functioning by the time I was contacted by the gallery in 2025.
The gallery were keen to repair the sheep, and an important part of the brief was to replace the control system with something that would be easier to adjust and repair in future.
It was initially expected that the work would be carried out with a separate electrician and a hydraulics company, but of course Nervous Squirrel Ltd. was happy to do everything.
After some investigation it became apparent that the sculpture had ran continuously even after various mechanical features had started to fail over time. Pretty much everything that moved was broken to some extent: sheared brackets, slipping shaft collars, snapped steel rope, split hydraulic hose, blown power supplies, damaged wiring.
The good news was that the sculpture had been designed and built brilliantly in the first place, with industrial parts used throughout, and most of the steel had been galvanised to protect against the elements.
A frequent thought during the project was: "Ah! That's clever, I see why he's done it like that!"
During the first site visit it seemed like the first thing to check out should be the hydraulic system, just to see if anything could be made to move. The wolf within the sheep would be fairly inaccessible anyway unless the hydraulics could be made to lift up and open the sheep.
The pump seemed to be working, but nothing happened after powering each valve individually. The breakthrough came with the realisation that the first valve fed the manifold that allowed fluid to pass to the other valves, so two valves had to be connected before anything moved.
After some precarious rearranging of crocodile clip leads there was a click and a whirring sound, and a very special moment as the gantry began to lift the sheep up into the Wolverhamptonian afternoon.
Site visit no. 2 was a disaster - there was an almightly thunderstorm and monsoon rain out on the balcony. Progress was slow.
During visit no. 3 I worked out that although the gallery's preference was to avoid using a crane to remove the entire sculpture, it might be possible to remove the sheep and wolf from the gantry. I'd recently bought a hearse, which of course is perfect for spontaneously deciding to transport big metal sheep across the country.
I realised I could take the control box too, and so after some careful labelling I took the plunge and cut all the wiring.
With everything back on the workshop bench, work on the project became a lot more efficient.
It was wonderful to discover the brand of flexible drives used to provide movement to the claws: Wolfcraft.
The wolf was coated with a toxic mixture of hydraulic fluid and bird poo, and some small creature (or gallery staff member?) had stashed a cache of nuts inside. All of the wiring shown here was removed...
...and replaced with a freshly made wiring loom.
The photo below shows a delightful example of Andy's skill and ingenuity, possibly one of my favourite bits of the project. It's an improvised shaft collar. There was an arm connected to this, which I later welded back on, but this is the component that grips a reciprocating shaft.
You can see that there's a hole for the shaft to pass through, a slot to allow some flex, and then a bolt with washers to tighten the grip of the collar. All no doubt made in a few minutes by hammering steel strip around a piece of bar.
I really like this quick and confident bit of engineering, bashed out in a few minutes but then going on to work for decades afterwards.
The sheep's legs had been damaged.
Here they are looking like something from a David Lynch film...
Repaired with Isonpon P40 and filler.
Cleaning the sheep's aluminum body. The inside was really grubby.
The trick with the polishing was to use a plastic abrasive cup brush in the angle grinder, but also keep a constant stream of running water from a hose to keep the surface cool.
I replaced around 20 missing rivets, but I can't understand why they were missing. How did they work their way out?
Here is a photo of a 75mm nylon filament abrasive cup brush.
The original wiring had to be figured out in detail before replacing anything.
The control box. Here's another before and after, starting with the original box.
That toroidal transformer had a blown internal fuse, and the 24V PSU next to it was making a worryingly loud humming sound.
The PLC had apparently been changed once before, but it was now time for an arduino replacement, so that any repairs in future will be easier. I realise that PLCs have their place, but they're relatively hard to replace like for like, and not everyone knows how to program them.
The sheep will stand a much better chance of long term survival if it has an easily replaceable arduino board. With apologies to PLC fans.
Here's the completely renovated control box. The enclosure within the main box contains an arduino nano, 5V power supply and a pair of relay boards. I gave the gallery an exact duplicate, so that if ever anything goes wrong with it they can just swap it out to keep the sculpture working while they troubleshoot.
Deutsch connectors were used to allow the boxes to be swapped over.
As well as sorting out the control box, an accurate wiring diagram was created (download here).
Here are some of the old bits that were removed.
Here is a fantastic thing I found inside the control box - a busbar that had been hacksawed right through the "do not hacksaw" logo...
This is the original super oldschool audio playback system, which did still work.
The new audio file is now played by an Adafruit 16MB audio FX board. These things are great.
If the anemometer detects gusts of wind over 25mph the automated sequence is cancelled.
The old manual control box.
The new manual control box.
Starting to pack, ready for the big day re-installing everything back onto the balcony.
It took a day to re-attach all the mechanical parts, and a day to finish the wiring and adjust the code.
This could totally be an album cover by Hipgnosis...
Massive thanks to Al, Naomi and David for their help with the project, and for being splendid human beings.
Thanks also to Andy for making such a great sculpture in the first place.
The wiring diagram, code and other resources for the sheep can be found on this page.
If you have a complex, bespoke, precious kinetic sculpture that needs sympathetic restoration, please stay away.
Only joking! Get in touch and I'll help out:
