Plate 1419 help needed

[MartinM]

The method prescribed by Kurt is the most efficacious given the variables of sandpaper manufacturer, grit, pressure used and what backing method is employed. Find a spring that's a bit fast with the weights in mid position and work it slowly down in consistent steps.

 

[Barry Armstrong]

I'm about to try thinning the spring. The spring isn't square, so, do you only sand the flat side or do you do both? Is there a thread already explaining the thinning process? I can't find it if there is.

 

[KurtinSA]

You sand the flat sides...it's virtually impossible I think to sand the edges. Two ways...cut a small piece of sandpaper and fold in half over the spring while holding the bottom block between your fingers. Stroke the spring towards the other end of the spring. Another way is to glue pieces of sandpaper to sides of a popsicle stick...tape the ends of the stick together and then fit the spring between the two pieces of sandpaper and again slide from the bottom block off the other end. Check your work as you go, either by measuring the spring in several places or by hanging the pendulum in such a way that you can time the rotations to see if the duration is getting closer to your goal.

Kurt

 

[etmb61]

I just use the finer side of an emery board, cut a couple of short lengths and pinch the spring between them. What you are doing is reducing the cross section area of the spring. Once you've tried it you'll get the idea. Pull the spring straight as possible as any angle will cause it to curl. I hook the bottom block to the top of the pendulum and use it as a handle.

Eric

 

[Barry Armstrong]

Without the fork, 8 revolutions in 58 seconds. Do I continue to sand or use the weights to adjust for the difference?

 

[KurtinSA]

A thicker spring runs faster, so you are 2 seconds too fast. Likely you could use the adjuster on your pendulum to account for that, but it's on the edge of being too much. I think you should sand some...then recheck. After sanding say 10 strokes, recheck the rate...see if it slows a bit...then use that to gage how much further to go.

Kurt

 

[etmb61]

Two seconds should be within the adjustment range for the weights. I'd stop there and see how it runs.

Eric