Sessions Mantel Clock- Help Needed

Discussion in 'Clock Repair' started by Ravens_Time, Jun 20, 2019.

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  1. Ravens_Time

    Ravens_Time Registered User
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    Greetings one and all,

    I have a typical Sessions Bim Bam mantel clock that I have overhauled. When I received the clock it did not run. I replaced a number of bushings, burnished the pivots, cleaned everything up and lubricated everything as well. The mainsprings were cleaned and inspected and looked to be in very good condition except they may have been "Set". They just didn't seem to expand very much when relaxed. No rust but lots of old gummy lube all of which was cleaned using kerosene and 0000 steel wool. Wiped down and lubed with Keystone mainspring lube. Put everything back together and the movement was running right away. Had some trouble at first regulating and had to adjust the crutch loop and that seemed to have fixed the issue. Put the movement back in the case and started 'test runs" before giving it back to the owner. For some reason I just cannot get this clock to regulate. The slightest adjustment to the pendulum has huge effects on timing. I don't have a timing machine but I really need one now. When I had the movement apart I checked for bent pivots, teeth and pinions and everything was in good shape. Could the mainsprings be causing this? Or could it be the suspension spring? I really don't know what else to look at. I will post some pictures later.

    Thank you!

    Pat
     
  2. R&A

    R&A Registered User

    Oct 21, 2008
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    Does it regulate to a plus and a minus or fast and slow ??
     
  3. Ravens_Time

    Ravens_Time Registered User
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    It has the regulator at the 12 o'clock position that you turn with the small key. It was so bad I watched the back of the movement as I turned that arbor and it doesn't move too much but it's also not very smooth.
    I took that geared arbor out and checked it but it seems ok. Just when I think I have it regulated it will speed up and when I tweak it it will slow down. Cant seem to find that sweet spot but I think there's something not quite right with it.
     
  4. Willie X

    Willie X Registered User

    Feb 9, 2008
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    How much pendulum swing and how long does it run?? Willie X
     
  5. R. Croswell

    R. Croswell Registered User

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    First of all, mainsprings, set or otherwise have gradually reducing power output as they run down. When regulating without a timing meter, fully wind the spring after each adjustment so that you know you have the same power.

    Second, These regulating devices are rather crude. When turning the regulator to go faster the suspension spring is raised as the screw turns, however, when turning the regulator to go slower frequently the weight of the pendulum bob is not enough to pull the suspension spring down through the chops so is remains where it was and/or gradually works itself down over time causing the rate to unexpectedly change. I believe that the original suspension spring on some of these had a small indentation above and below regulator fork into which it slips so the regulator can drive it up or down but even so there will be some slack.

    Solution, as inconvenient as it may be, when you turn the regulator to "slower", give the pendulum a downward tug to make sure the suspension spring actually moved down and is seated.

    There are other things that can affect time keeping as the spring runs down so make sure the clock is "in beat" by raising one side then the other to see if there is a position where it beats more evenly. Check that the drops onto each pallet are equal (the escape wheel moves ahead the same amount on the "tic" and the "tock". This clock should have at least 1" total pendulum swing, preferably a bit more. Small pendulum swing indicates a mechanical problem and can cause the clock to be unstable.

    "Set" springs are seldom the problem and even set springs will usually run the clock OK when fully wound. Pictures are always helpful.

    RC
     
  6. tom427cid

    tom427cid Registered User
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    In the column marked FWIW once in a while I have encountered this issue. Making sure that every thing is ok I will start to experiment (unless it is obvious the bob is incorrect)with a heavier bob. What seems to be happening is that a light bob has greater amplitude but the amplitude is not consistant. Increasing the weight diminishes the amplitude but it will become more consistant. Also check the thickness of the SS it can also have the same effect if it is to thin.
    Hope this helps
    tom
     
  7. Rockin Ronnie

    Rockin Ronnie Registered User
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    I have a 30 hour New Haven that ran fast despite what I did. It had a 1 oz pendulum. Going to a 1 1/2 oz pendulum solved the problem.
    Ron
     
  8. Ravens_Time

    Ravens_Time Registered User
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    Willie, its approx an inch of pendulum swing...best I can tell. It will run until the springs wind down. 10 days has been the longest before rewinding it.

    Thanks for your reply!

    Pat
     
  9. Ravens_Time

    Ravens_Time Registered User
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    RC,

    Thanks for your reply. I have not been rewinding each time I make an adjustment. That seems to make good sense. I agree the regulating mechanism is quite crude. I have great difficulty speeding this movement up. As I turn the adjustment arbor I watch the suspension spring and it does shorten it but the effect on timing is very slight if at all. As adjustments continue all of a sudden it will be running fast. I shot a short video of the pendulum for whats its worth. I will say right after I put the movement in the case and got it in beat if I moved the clock it would fall way out of beat. Thats when I found the pendulum leader was rubbing against one end of the crutch loop. I adjusted that and that seems to have fixed the beat issue.
    Here is a picture of the suspension unit:

    Sessions_Suspension.jpg

    And the video:

    Thanks for help,

    Pat
     
  10. Ravens_Time

    Ravens_Time Registered User
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    Tom,

    Thanks for your reply. It has a Sessions bob but unknown if original. I have another clock just like it that I have yet to work on with an identical movement and it has the 6 sided bob. I have a bunch of spare bobs and will experiment and see what happens.

    I measured the thickness of the SS and compared it to my clock and they are the same. Scratching my head here. It'll probably end up being something simple...I hope,

    Pat
     
  11. Ravens_Time

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    Thanks Ron, I'll try another bob and see what happens.

    Pat
     
  12. R. Croswell

    R. Croswell Registered User

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    The pendulum swing looks a little weak. A better assessment is the amount of recoil at the escape wheel. It should be very obvious.

    RC
     
  13. Willie X

    Willie X Registered User

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    I agree with RC. I think I hear some 'soft ticks' in there too. Do the 'slow roll' test. This may bring your problem to light.

    The slow roll test is where you remove the pallet arbor and wind the spring just a couple of clicks. This should maintain a slow roll of the escape wheel for a minute or two. Try the normal position and both positions with plates in plain with the floor. Stop and start the
    E-wheel with your finger tip repeadedly. This can often point to a small or intermittent power loss problem.

    Are the pallets flat with a good polish, no grooves or pits? Pallet arbor free but not sloppy?

    And finally, do you know that this clock is notorious for keeping an eratic rate.

    Your regulator assembly is the best (latest) one they made. It is probably not your problem. Pendulum is probably original to the clock and likewise not the problem.

    Question, are you adjusting the rate each time you wind it? If yes, what is the closest rate you have so far in a week? These clocks are difficult to rate day by day, it has to be done week to week.

    WIllie X
     
  14. Ravens_Time

    Ravens_Time Registered User
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    Thanks for your replies gents,
    You’ve given me some homework for the weekend. Willie, I was adjusting it day by day and it was all over the place. The owner of the clock said it hasnt run in years. There was slight grooves in the pallets and they were polished out using 2000 wet/dry and then semichrome. I will check the pallet arbor for looseness and get back to you guys.

    Thanks for the help!

    Pat
     
  15. Ravens_Time

    Ravens_Time Registered User
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    Willie, I heard the soft ticks as well. I tried RC's suggestion of tilting the clock one way and then the other and sure enough if was slightly out of beat.
    Made a very small adjustment to the crutch and the ticks are even and its keeping time. 1 day in and hasn't lost or gained as of yet. Guess my ears aren't as good as I thought. Would a slight out of beat escapement cause regulation issues like this but still continue to run?

    Every clock is a learning experience. Thanks guys,

    Pat
     
  16. Rockin Ronnie

    Rockin Ronnie Registered User
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    Not sure if this was mentioned. Do you have enough of a gap in the crutch loop for impulse. Could not see any impulse in your video. It should be minimal but a gap just the same.
    Ron
     
  17. Ravens_Time

    Ravens_Time Registered User
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    Thanks for your reply Ron,
    I will check. How much room should there be? Is it like a piece of paper width like 400 day clocks or larger?

    We finally had nice weather here this weekend so I didn't get to spend much time inside working on it. I will say that its actually keeping very accurate time since I wound it on Friday. I think that slight out of beat condition may have been the culprit.

    Pat
     
  18. R. Croswell

    R. Croswell Registered User

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    The smaller the clearance between the leader and crutch loop the better as long as it is not zero. Check that there is some clearance in the entire loop and that it isn't zero at either end.

    Sometimes in a case like this the culprit turns out to be the sum of several issues rather that one single issue. You can only evaluate time keeping over a full run period, in this case 8-days without resetting or winding or changing anything including the location of the clock.

    RC
     
  19. Ravens_Time

    Ravens_Time Registered User
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    Thanks RC,

    I wound the clock Friday morning and it remained accurate until yesterday it has lost 2 minutes. I will let it run the full 8 days and see where its at. I will then examine all these areas mentioned by everyone and see whats what. Without a timing aid it seems like it just suddenly lost power after 3 days. I believe you're right about it being several issues. I just need to pin them down.

    Thanks again,

    Pat
     
  20. R. Croswell

    R. Croswell Registered User

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    #20 R. Croswell, Jun 25, 2019
    Last edited: Jun 25, 2019
    It can be helpful to make a graph and plot how many minutes the clock is off from correct time every day (or every 12 hours if you have the time) to learn if time keeping gradually accumulates or if it really does fall off sharply after 3 days. If it really is flat for 3 days and falls off sharply there is still something mechanical robbing power. Springs are seldom the problem but that is a possibility, especially id they have been replaced at some point with inferior or under size springs. How thick and how long is the time side spring? Is there any indication (unusual or "hand made" look at either end) that may indicate that the spring had broken and was shortened? The duration of the run is largely dependent on the length of the spring.

    You mentioned that you do not have a timing device. If you have an Android "smart phone" there is a decent app called "Clock Tuner" available in the Play Store. The cost is $4.99. It works well but the documentation is poor and some of the terminology is unusual. First, it will only work for 30 minutes as a free trial then you have to upgrade to the paid version which at $4.99 is well worth it. Just start the app and place the phone's microphone hole as close as possible to the clock and in 10 seconds (the default scan period) it will display the BPH and a graph showing if the ticks are evenly spaced. It has a box that displays "Beat Error" but it isn't really beat error but timing error in minutes and seconds but that function will NOT work correctly until you do a few setup things. The app has a table of preset beat rates and automatically selects the closest one, which for most clocks isn't the correct target rate so the beat error will also not be correct. Your sessions bim-bam likely has a beat rate 9724 BPH. With the app open and stopped, touch the "Target Frequency" box, then touch "Add" and enter 9724. Everything should now work OK and the "Beat Error" box will display the minutes and seconds the clock is fast or slow. The "Up" and "Dn" buttons allow you to manually select the target beat rate but the selection is limited to rates in the table, so to rate a different clock you first need to make sure the rate is in the table or add it. One can usually fine the correct rate from Jeff Hamilton's "The Clockmaker's Beat Book", and of course by disassembling the clock and doing hear tooth counts and some math.

    With this app you can easily get the timing error each day (or half-day) to plot your graph. One thing that has not been mentioned, this clock has a "passing gong" on the half hour. That means that power is taken from the time train to lift and drop the hammer on the half hour. A smaller load is imposed to release the strike on the hour. "Clock Tuner" (or Microset or time Trax) will allow you to measure the beat rate a minute or so before the strike point and just after so you can see just how much the clock movement slows down at the strike point.

    RC

    Here's a shot of Clock Tuner on a Sessions Bim-Bam that I have.

    clock-tuner.jpg
     
  21. Ravens_Time

    Ravens_Time Registered User
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    RC,
    Thanks for your reply. I downloaded this app on my wifes phone. Haven't had a chance to check it yet cause I cant get it away from her long enough to try. This thing is constantly losing time now. With the little bit of time I have had to work on it, it appears the exit drop is minimal. I double checked the space between the leader and the crutch loop and there is definitely a gap but the leader is getting a weak impulse from the crutch. More on one side than the other but both seem to be weak. I pulled the SS and checked it under a microscope and it has some rust on it that is barely visible to the naked eye. Other than that it appears to be ok with no cracks or splits. The dimple at the top where it hangs at the regulator is very slight and doesn't seem to hold it all that secure. Should I reshape the dimple or make a hole in it and install a wire? The other Sessions I have with the exact same movement has a wire. I think I'm going to remove the movement from the case and put it on the stand and really study the escapement.

    Thanks again for all the help!

    Pat
     
  22. R. Croswell

    R. Croswell Registered User

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    Pat, always take care of the obvious first. If the suspension spring is slipping past the dimple, then yes by all means put a hole in it and a wire. The easiest way to make the hole without a carbide drill is to use a small punch and support the spring against the end grain of a piece of hard wood.

    It is a simple recoil escapement but it has to be adjusted correctly to work well, and there is a good possibility that you are losing power from wear some place in the gear train. With the movement out of the case, move the verge closer to the escape wheel little by little (very, very, very small amounts) then move the crutch by hand until you reach a point where the escapement will not operate. Then back off just a bit until the drop off of each pallet is about equal (the escape wheel moves the same amount on the tic and the tock). If the drops are large and the lock is small you may need to adjust the spacing between the pallets (do research on how to do this in most good clock repair books - the verge is hard or should be and you can bust it if you don't do it right). Next "level" the movement until it runs "in beat". You can't visually evaluate the action of the escapement if the clock is not running in beat.

    RC
     
  23. Ravens_Time

    Ravens_Time Registered User
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    Thanks RC,

    I have Steven Conover's book on Escapements so I should be able to nail this down.
    Thanks for this description...makes sense. I will do this and let you know how it goes.

    Pat
     
  24. Ravens_Time

    Ravens_Time Registered User
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    Hello again,

    I removed the movement from the case and first did the slow roll test. Seems to be ok and the EW turned after a few clicks. Checked in multiple positions and the movement passed. I then reinstalled the verge and checked drops. The drop onto the entrance pallet was excessive. I followed RCs advice and closed the distance between the pallet arbor and EW until the escapement wouldnt work and then backed it off. This seemed to help but the pendulum swing still seems weak. One thing I noticed that I had not observed before was slop in one of the verge arbor pivots. I shot this video. Sorry it runs so long but it was shot in slo mo.
    Do you guys think this is enough to cause weak recoil? Should I bush this cock? I will also include a video of the recoil after adjustment. It appears to me that there is recoil on the entrance but very little recoil on the exit. Should there be recoil on both?
    As usual thanks to everyone for taking the time to look and offer your help!
    Pat

     
  25. Willie X

    Willie X Registered User

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    That looks close enough.

    A thinner longer mainspring will usually help this condition, 120" long and..0165" thick. But, as already stated it's an inherent problem with short pendulum Sessions clocks. You will usually see a rate improvement though

    Willie X
     
  26. R. Croswell

    R. Croswell Registered User

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    The drop onto the entrance pallet (off of the exit pallet) is still a bit excessive. Moving the verge ever so slightly closer should reduce this drop (and increase the lock and the pendulum swing). If the verge snags the EW teeth then likely the spacing between the pallets id off a bit. Make sure that the verge isn't hardened before adjusting this. Conover's book explains how to do this. The slop in the verge cock is robbing some power and I would probably bush those cocks. It does look like to me like there is some recoil at both pallets. If there is still some recoil after 8 days running then it will probably run OK but with only a small amount of recoil it will be very sensitive about being level (in beat). The loss of power from the spring to pendulum is sum of the losses of all the places that are not just right. Each issue that you bring up to standard will improve the drive to the pendulum a little more. It becomes a question of how good is good enough, or is "good enough" as good as you want?

    RC
     
  27. Ravens_Time

    Ravens_Time Registered User
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    Thanks Willie & RC. I disassembled again and bushed the front plate pallet cock. I had already done the back plate. I also tested each wheel alone and with their corresponding pinion and found the bushings for the T2 pivots were a little tight. I addressed those with smoothing broaches. Checked all of the gears for bent pivots and wheels and everything was true. I assembled the time side only and made one last adjustment moving the pallet arbor slightly closer the the EW arbor. The lock has increased a lot and the recoil is obvious. Pendulum swing is now 1.8 inches. Here’s another video.


    Now I’m just wondering if I should replace the spring or put it all back and see how it goes.

    Thanks again for all the help.

    Pat
     
  28. R. Croswell

    R. Croswell Registered User

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    Looks pretty normal now. Go with it. If you really want to test the springs, and everything else, fully wind it and see if it will run 10+ days before stopping. Expect time keeping accuracy to fall off after 7 days. I doubt that there is any problem with the springs.

    R
     
  29. Ravens_Time

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    Sounds like a plan! Thanks RC!

    Will update when it’s all back together.

    Pat
     
  30. Willie X

    Willie X Registered User

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    That looks good. I hope you report back after a few weeks and fill us in on the rate thing. Willie X
     
  31. Willie X

    Willie X Registered User

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    Rave,

    That last slow-mo video should be archived somewhere. It's a good example of what a good running Sessions escapement should look like. Well done!

    Wilie X
     
  32. Ravens_Time

    Ravens_Time Registered User
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    Thanks Willie! Just followed your guys advice. I will definitely update and let you know the results. I hate to get too excited because I’ve had more than a few run great on the test stand and you put em back in the case and they go downhill from there. Thanks again for all the help from everyone.

    Pat
     
  33. R. Croswell

    R. Croswell Registered User

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    Always check that all four mounting feet are flat against the case so the movement is not twisted when the screws are tightened

    RC
     
  34. Ravens_Time

    Ravens_Time Registered User
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    Thanks RC,

    Set the movement back in and everything is squared and leveled and running again. So far so good. I will report back when I have some running data.

    Thanks again to everyone for your help.

    Pat
     
  35. Ravens_Time

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    Hello all,
    After 5 days running the beat rate is 161.9917 (according to clock tuner app) to the target of 162 BPM. Keeping good time without any variation so far. I'm gonna let her run and see how long she'll run. Thanks again for all the help!!!
    Pat
     
  36. Ravens_Time

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    Final update: Still running after 12 days! As RC predicted time keeping fell off after 7 days and it started losing time. Strikes are still synchronized and functioning. I’m very glad I followed your advice and didn’t replace the mainsprings.

    Thanks again,

    Pat
     

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