This is a very quick and easy thing to do and doesn't need any special tools or skills. I can't guarantee you won't break the clock you're using, but it's a risk you'll have to take.
You will need:
- A cheap clock (mine came from Ikea for about £1
- Something to prod with. Keys work well
- A suitably evil sense of humour
- A new clock background (optional)
1. Examine
Take a good look at your clock and try and work out which way the second hand is going. If all is well it should be ticking at a steady rate of 1 tick per second. If it's going slower then you're probably looking at the minute hand. If it's going faster I have no idea what's wrong. Also have a little look at the back of the clock. You'll see a nice shiny black box. It's similar to the black box they have on aeroplanes in colour, but not in many other ways. This is the movement. You'll never guess what is does. You may notice the rather attractive design on the clock in the picture. I elected for perpetual Pimm's O'clock or Hammer Time when I was designing. You'll also notice the rather helpful red arrow I added to show you which way it normally goes.
2. Start removing stuff
The first thing you want to remove is the battery. I'll let you work that one out for yourself. The bit to get rid of next is the invisible plastic bit on the front that stops you prodding the hands during normal operation. On my clock this held in place by three little plastic tab things which you get at from the back. Prodding these with keys seems to be a fairly effective way of getting the front bit loose. Once you've got that off remove the hands as well. They should come off with gently pulling. Keep the battery, invisible plastic and hands in a safe place. You'd be amazed at how tricky it is to get a photo of something that isn't meant to be seen.
3. Carry on removing stuff
The next bit to remove is the movement. Remember the little black box we discussed earlier? It's normally held in by a couple of little clips which can easily be overcome by some keys. Prod at it until you're holding the beautiful black box in your hands. There's the little wheel to set the time and the battery compartment on one side and little white sticky out bits on the other that the hands were attached to.
4. Open the box
If your name is Pandora and the clock is yours then you should probably stop now just to be on the safe side. Otherwise carry on. The next thing you have to do is open the box. To do this look for two little clips on the sides. Keeping the box pointy-white-things down pull at one of these until the back comes off to reveal the inner workings of the clock. You should see four little white cogs, a copper wire coil and a sideways U shaped plate going through the coil. There's a photo below of what it should look like. If you're looks much different to this then give up now. My expertise doesn't extend that far.
5. Remove the cogs
The little white cogs have to be removed but before you start pulling away at them take a minute to note where they go, which order they go in and how they mesh together. Be careful about the order you take them out. Refer to the picture for the order I removed mine in. You need to make sure you can put them back in the same order that they started in otherwise the clock won't work. While you're examining the picture take a quick peek at the copper coil and the U shaped plate. That's what we're going to be playing with next.
6. Gently...
At this stage you should have the movement open and looking fairly empty with a little pile of cogs next to it. You should have left a copper coil with a U-shaped plate going through the middle of it. This step is the one which will, with any luck, make the clock run backwards. What you need to do is carefully and gently slide the plate out of the coil. It should come out easily enough with some gentle persuasion. Once you're holding the little piece of metal (on my clock is was actually two piled up) you need to flip it over length ways so you can see the other side of the plate. Now slip it back into the coil so it sits back where it was, just with the opposite side of the plate facing up. Looking at the photo on the right of the plate back inside the movement the curvy corner of the plate (bottom right) started off at the top right and the square corner started at the bottom right.
7. Put it all back together again
Once the plate has been flipped put all the cogs back in in the right order and put the back on the movement. At this point you can put the second hand back on and the battery in to see if a) you're clock still works and b) whether it's going backwards or not. If all is well the take the battery out and the second hand off and put all the pieces of the clock back together. Just before putting the hands back on would be a good time to add a new background to the clock if you so desire. Once it's all back together put the battery back in, set the time (remembering that it'll be the mirror of a normal clock), put it back where you got it from and watch the confusion spread.
I had a clock like this in my room at university halls in my first year. People would come in and it would usually take them quite a while to notice something was amiss. After a day you'll be able to tell the time as well as you can on a normal clock and after about a year a normal clock will, occasionally, catch you off guard and confuse the buggery out of you.
Questions and comments are welcome.
Enjoy!
p.s. Sorry this isn't a video guide. I realise that it would have been far clearer but I lack a suitable camera and the will to faff about with youtube. Hopefully it's all suitably clear anyway.