Hi all, I have been trying to get my SP13 running for a few weeks now without any luck. The issue is that the pendulum loses amplitude after 5-10 minutes and then the escapement stops. What is confusing is the escapement has lots of energy as it rapidly rotates between clicks and once the clock stops, if I slightly move the pendulum manually the escapement rapidly rotates so there is plenty of energy but the pendulum wont let it out!
Here is what I have already checked and tried...
All gears run smoothly on their arbors.
All arbors have free motion forward and backwards in the frame, they are not pinched, the frame is not sagging.
Pendulum free run test = OK. I am using the kit supplied bearings. The pendulum swings for >15 minutes without the escapement.
Changed bob weight from 100 to 300 g, no change.
Drive weight. I have tried from 1.5 to 4.5 kg in 250g increments and this makes no difference.
Free run test = OK. Without the pallet the clock runs smoothly and continuously with only 1 kg weight. I have run it to the ground three times now and i has not stopped once.
As you can see I'm very confused as there appears to be plenty of energy and low friction but the pendulum drops from 5 degrees wing to less than 1 degree in just a few minutes and I cannot understand why.
Thanks for your help,
Al
Hi Steve, appreciate the detailed and quick answer. Before I source some lubricant I am going to re-run the pendulum free swing test as that definitely seems to be the source of the issue.
One thing I'd like to add as I was messing about with it last night, the clock runs fine with only the pallet and first 1/3 of the pendulum attached and no bob. Obviously it ticks very quickly but it doesn't lose energy, in fact it ran in this state all night! Not really sure what that means but seems to confirm that there is plenty of energy in the clock but the pendulum as is cannot let it out.
Once again appreciate the information I will report further on the pendulum free test and the lubrication. I'd really love to get it running.
Cheers, Al
Hi Al,
Thank you for providing lots of information with your post, especially a description of the escapement characteristics and the pendulum free swing test. It is surprising how many people expect debug help by asking "My clock keeps stopping, what should I do?".
If the escapement is energetic, then the entire gear train is likely in good shape. This usually narrows it down to the pendulum support bearings, but the free swing test runs for >15 minutes. The bearings in the kit have a dry lube added for rust protection. Sometimes they work slightly better if you remove it using alcohol.
Sometimes, a pendulum that slowly degrades over time is an indication of not enough drive weight. 4.5kg should be more than enough to keep SP13 running. One caution is to make sure that the frame adjustments are made to keep it from sagging with the extra weight.
All of the things you have done should produce a working clock.
My suspicion is that the involute gear tooth profiles could be the issue. I was always under the impression that involute and cycloidal gears have similar efficiency. Both styles have a mostly rolling action with very little friction. There is always some sliding friction as the teeth start to engage and as they disengage. Friction is higher if the engaging occurs before the line of centers because the teeth push into each other. Friction is lower after the line of centers where the teeth are pushing away.
Involute gears have much more engagement before the line of centers compared to cycloidal gears. Adding extra drive weight sometimes makes the teeth jam together harder. Some filament brands have higher friction than others and I do not know any good way to test them other than to build a clock. A simple fix is to add a very thin coat of lithium grease to the pinion teeth. You can wipe most of it away, so it is nearly invisible. Only the pinions need to be greased.
I have started converting many of my oldest clocks to cycloidal style "Perfect Print Gears". So far, SP2, SP3, SP4, and SP5 have all been upgraded. These were major upgrades because I ended up redrawing the entire frame. The newer clocks should go a bit faster. I am currently converting the SP14 moon phase clock and will start on some of the others next. The biggest difference is that the clocks are more reliable. For example, the 32 day clock used to just barely stay running in 32 day mode with an 11lb weight, and it might randomly stop every few weeks. The new gear profile is extremely stable with a 9lb weight.
Sorry for the long winded description of telling you to try lubricating the pinions.
Steve