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striking clock fly adjustment

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Andrew Cattell01/12/2021 21:21:12
12 forum posts

I recently brought an 8 day striking mantlepiece clock into use. While stripping and cleaning it I found that the fly in the striking train was loose on its arbour. A witness mark on the face of the fly and a groove in the arbour show where there should be a spring to enable the fly paddles to grip the arbour but there is no sign of it. As a quick fix to get allow the clock to be test run I bent the fly paddles just enough to make them bind on the arbour and set it all running. It ran for 10 days. Unfortunately, when it strikes it takes an age between bongs. I want to speed up the striking but I don't know how to make a suitable spring for the fly paddles, what material to make one from or how to end up with the correct tension when it is fitted.

Anyone? Thanks.


Michael Gilligan01/12/2021 22:13:08
20289 forum posts
1064 photos

This discussion may [or may not] help, Andrew : **LINK**


Andrew Cattell01/12/2021 22:43:31
12 forum posts

Thanks MG, I had seen that thread before and was bewildered by the range of opinions from the fly should not slip, may slip on starting, may slip on stopping, can be used to regulate the strike speed, etc. I still need to make a replacement spring for the fly as, without one fitted, if the fly is free enough to slip when the arbour rotates it can slid along the arbour and foul other parts of the mechanism. The spring lies between two holes in the blades of the fly across a grove in the arbour allowing rotation slippage but not axial movement. As the clock is of limited historical value it might be a simpler job just to use some tin snips to trim the diameter of the fly down a little to reduce the air drag and keep it gripping the arbour.


Michael Gilligan01/12/2021 22:52:50
20289 forum posts
1064 photos

My own limited understanding is that the spring should provide enough friction for the fly to never slip during normal operation, but to slip in the event of anything like a crash.

Difficult to quantify, and possibly more difficult to implement dont know

I look forward to seeing authoritative guidance if anyone can provide it.



Edit: __ This may be more useful:

Edited By Michael Gilligan on 01/12/2021 23:03:48

Adrian Downes01/12/2021 23:55:27
35 forum posts
15 photos

The clock was made & has run successfully for many years with the fly as it is. I would definitely NOT try to speed up the striking by trimming it!

I suspect that either your cleaning/overhauling has not been thorough or, more likely, that the mainspring needs replacing. Did you completely strip the clock to clean it?

The strength of the friction spring is not that critical. It needs to be strong enough to allow the fly to be carried by the arbour but weak enough to allow a little slippage when the train comes to a sudden stop.

Speedy Builder502/12/2021 06:53:57
2653 forum posts
219 photos

My long case clock (1769) has a thin strip of brass riveted to the wings. It doesn't look like it has been replaced in its lifetime.


Michael Gilligan02/12/2021 08:41:48
20289 forum posts
1064 photos

In the link that I posted last night, Dave West writes :

” … on closer examination the fly was found to be soldiered to it's arbour!! ”

I think we can reasonably assume that he intended to write “soldered”


Andrew Cattell04/12/2021 20:49:32
12 forum posts

When I serviced the clock I stripped it down to individual parts except for not taking the two springs out of their barrels. I must invest in a spring winder. All of the pieces went into an ultrasonic bath (white spirit) before carefully drying and cleaning with a cloth. The pivot holes in the plates were pegged through. I wiped the old sticky oil from the accessible parts of the springs and barrels and then partially tensioned the springs and dropped a couple of drops of oil into the coils. I then reassembled the whole thing, oiling the pinions and pivots as I went. On winding the spring tensions were about as expected, I have several similar sized clocks in regular use and think I would have noticed if the winding up had been easier. The clock in question strikes significantly slower than all of the others I run, it sounds as if it is in need of a service! it is possible that it has always struck more slowly but it does sound a bit "walking wounded".

I still need to sort out a proper pendulum, the temporary one is still keeping the clock running, albeit losing a minute a day.


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