I get asked to replace a lot of platform escapements – or at least this becomes part of the job as the movement is cleaned and it has been discovered that the platform is worn out. The first thing is to get the old one off and count the amount of teeth on the escapement pinion gear. Look at the angle the pinion gear has been set at as well. With a carriage clock it will normally be facing a 90″ tangent to the clock escapement drive wheel (the one that looks like a crown). On a french barrel movement it really could be anywhere however. This is because unlike the carriage clock, they do not have a crown cog that is inverts force by 90″ and the ideal direction for the pinion wheel facing teeth could be anywhere. I mention this because if you buy the wrong platform escapement type you are not going to get anywhere – they cannot be modified easily and are fragile.
Once you have sourced the correct platform escapement then you are going to need to fit it. This is difficult unless you know the trick……which is blu-tak.
You blu-tak the escapement to the back plate with the clock unwound. You can then side it into position so the protruding platform escapement pinion gear is touching its drive cog and give the key one wind (you want to check it will work at low power). If its in position it will start to run. If it doesn’t then just slide it a very small amount to re-engage the drive cog and you will find the sweet spot.
Once you have positioned it then leave the clock to check if its running in time for an hour or so. You will pick up any serious deviation in this timescale if there is one.
Heres one I’m doing today.
The next step is to mark up the new screw points using the platforms holes as a guide. Then its a matter of measuring your screw diameters and drilling / tapping holes to mount the platform – you will need a standing drill for this job; never drill clock holes “by hand” – all sorts of things can go wrong but mostly its about keeping the hole at 90 degrees to the face.