Springs information

[Bill Goldie]

I'm currently working on a Brunsviga 13RK, and had to dismantle the rotor with its W-shaped detent springs. Due to the obsessive desire for these springs to launch themselves into obscure corners, I had to make some replacements. I found that the wire is 0.3mm diameter, corresponding to No.3 piano wire, which I obtained from a nearby harpsichord maker ( a top E steel guitar string might also do). It isn't hard to form a new spring to the correct shape but you have to allow for the tendency for the wire to rotate when sprung, to make sure that the bent arms are pointing the right way when they are fully in place. If you don't allow for this, the springs are even more likely to disappear without warning when trying to assemble the pin-wheel discs. I found that the best way was to get the spring in position last, then hold it flat with a thin strip of something whilst the next disc is lowered into place. Pull out the strip at the last moment and don't try to lift the disc again! I needed to make three springs for every one initially lost, due to the launch rate. Also note that the detent pawl which is being held by these springs has chamfers on one edge; this side has to be upwards so that the next rotating ring doesn't catch it. Ask me how I know...

It's helpful to set up an enclosure when dismantling stuff, to catch anything which unexpectedly flies out.