Thoughts on a fast platform escapement

[oli]

Hi all

I am working on clock with a small ABEC/ SMITHS platform escapement.

It had a broken balance staff, which I have now replaced. I also fully stripped the movement, cleaned it, reassembled and lubricated it.

Now the movement seems to run reasonably well in terms of amplitude and beat error, but it is very fast, even with the regulator finger in the beginning of its range (several minutes a day.)

I spent a lot of time observing the escapement, and can confirm that: 

- the escapement is not magnetised.

- the hairspring is true is and not fouling with anything

- the hairspring coils looks to be in good shape, with no contact between the coil. It is clean and the coils are not sticking together.

 

So I am at a loss to see what the issue is!

I noticed that if I open the regulator boot, so that neither the pin nor the boot touch the hairspring at all, then the clock runs about right (still about 10/15 sec fast).

All I can think of is that the balance is fitted with an incorrect hairspring? Is there anything else I should be looking at?

Thank you very much in advance

 

 

[clockboy]

I have not worked on one of these movements but it seems to be that the regulator boot is not altering the effective hairspring length or maybe the hairspring needs to be further out of the end stud to make it a bit longer.

[oldhippy]

The hairspring should bounce between the regulator pins in whatever position the regulator is in. clockboy is right, let the hairspring out a little from the end but remember you will need to adjust to make sure it’s in beat. Make sure you use a thin oil on the entire escapement but do not over oil as this can cause problems. The platforms fitted in these movements are not the top end when it comes to quality but I have never had any trouble with them. Looking at the photo of the hairspring and balance the hairspring looks small for the balance.

[oli]

Thank you gents

I am going to move the pinning point of the stud on the spring, to extent the effective length of the hairspring a little, but I get the feeling it won't be sufficient, if this does not work I really don't know what else to do, and would strongly suspect an incorrect hairspring.

@ Oldhippy, the hairspring does "bounce" as you say and makes contact as it should,  throughout the regulator range when the boot is closed. It is only when I open the boot fully that I get no contact on either side (At the beginning of the range of the regulator) - And the fact that the movement still runs fast despite no contact of the hairspring whatsoever with the regulator pin / boot is puzzling me: it is effectively running with the full length of the hairspring (and should be very slow)

Thank you very much for your advice! I shall report back!

Edited March 14, 2017 by oli

[oli]

Well that didn't go well! i removed the stud, but as I straightened the spring it broke near where it was secured by the pin (it was very bent/ damaged). So I am back to square one, as i have pretty much the same length of hairspring as before I started.

i have just bought another identical clock on ebay, so it will be interesting to see what the hairspring is like on this one!