So after completing the project, we have since made two minor changes.

(1) The Raspberry Pi we used has been replaced with a Raspberry Pi Zero (much smaller than the standard Pi), and the speakers have been replaced by a fitted 'Speaker pHat' that sits on top of the Pi Zero. This has saved lots of room. The strange white cable is a USB connector that allows the Pi to access the school wifi - although anyone about to start a similar project might want to use the recently released Raspberry Pi Zero W (with built in Wifi).

(2) The analogue clock face now has the same background 3D printed shapes as the other faces.

On Monday of this week the children planned out and added the code to make a Raspberry Pi chime and bong so that it sounds like the real clock in London.

And today the small speaker we were waiting for arrived, meaning we could finish off the project.

The Raspberry Pi, the USB powered speaker and the3D printed base were all placed inside the tower.

It was plugged in and the children eagerly awaited the working clock to show half past.

As half past twelve arrived, we heard the unmistakeable chimes of Big Ben, and at one o'clock we again heard the chimes followed by a single bong.

Project completed!

The Raspberry Pi and speaker that will be needed to make the clock chime every hour will need to have a way of staying inside the tower - even if the tower is lifted, and so I've used the Morphi 3D design app to create these two files.

The base of the tower will sit inside the cut out groove to add stability and also give an internal solid base. The cut out on the right hand side will allow the power cable for the Raspberry Pi to reach inside. The small speaker could sit on this base if the pupils choose.

This wil sit on top of the base piece (above). The groove will allow the Raspberry Pi to be fitted and stand at a slight angle. As with the other piece, the power lead will pass through the cut groove. The small speaker could also sit on this level if pupils decide they prefer it higher.

The clock is almost finished, but already there are requests to do more with it. The DHT has asked whether it could go in the hall, and chime like the real clock does.

I've not spoken to the children yet about this as I want to make sure it's possible - but I'm thinking a Raspberry Pi Zero, a speaker, the computer clock and some audio files might help it to chime.

Watch this space!

Update: after testing with an older Raspberry Pi Model (version2) and a set of headphones, I'm pleased to say that the idea works. A short program in the terminal window of the Raspberry Pi, a change to the cron settings to run the program automatically and that's it!

Today we finally added the working clock to the 3D printed tower. I had drilled a hole in preparation for this session (as I couldn't let the children near a drill!) so that the children were able to get on with the fitting of the working clock parts.

The back of the clock was placed inside the tower section, but then a problem was noticed - the sections on the outside of the clock that create the clock face were too wide for the retaining nut to be fitted to the clock mechanism and so they had to be removed before they could continue.

However, once the washer was in place the hands were fitted easily, and then cut to size to fit within the rectangular clock face.

A battery was fitted to the mechanism, the time on it adjusted and then...

there was a working clock installed into the model.

The final job to be completed will be a little bit of tidying up, painting over areas that have peeled, and adding an effect behind the working clock face.

After weeks of painting, the tower is beginning to take shape;

A little more painting, and then the pupils get to add the working clock parts to one side of the tower so that they have a working clock face.

More painting of the pieces in todays session. When the pupils looked at last weeks work they realised that they had missed several areas within each piece of the tower, and that they needed to go back and carefully add a second coat to

(1) ensure none of the original white plastic was showing through, and

(2) ensure that a consistent colour was applied across each piece.

So after much printing out of all the parts of Elizabeth Tower (see here for files) today we began the project. With one child off ill, we were down to just three children (and two after half an hour when another fell ill and left early), so initial painting did not get as far as we'd hoped for.

However, by the end of this session we had managed to put a first black coat on two of the roof sections and one clock face, and get several of the tower pieces painted with their first coat of cream.

We also briefly looked at the clock kit that will be used to fit working hands onto one of the sides of the tower turning this construction into a fully functioning clock, and began thinking about how it would be fitted (and more importantly how the battery would be reached in the future when it needed to be changed). The end result of this looks like a little bit of careful drilling work will be required to ensure that the clock shaft will fit through several layers of PLA. I wonder who will be put in control of that job...

All the parts needed for the new project are now printed and ready. Painting begins on Monday.

So whilst the pupils are busy working through their first project, they've already decided what their second project is going to be, and so the 3D printer is busy preparing the pieces they'll need for when we start.

This is just the fist of six of these tower sections, followed by a whole range of additional parts for the roof and rails.