Understanding Seth Thomas 89 Movement Variations

The Wheel should freely "fall" to the bottom plate when you invert the movement. If it doesn't, one or both of the two pivot holes are either too tight or not parallel. You may wish to very slightly broach each hole aligning the broach to the other side of the plate while the plates are assembled. Being able to move the wheel side to side with finger pressure is not enough. Keep in mind that there needs to be some slop at each pivot to account for any slight deflection of the plates when the mainsprings are fully wound.

That's too slow. What about when the mainspring is fully wound? Make sure you have adequate end-shake before you do anything else would be my advice.

Are there any bushings in either plate? That might be a tale-tell sign as it was with the Governor. It sounds like the rest of the train works well though, right?

Bruce

Edit:

I think it is going to be very tough to get an accurate tooth count from photos. Can you measure the distance between teeth on your warning wheel and compare it to the diameter as well as spacing of the new Governor's Trundles? My biggest question is how well does the Warning Wheel Gear and Governor Pinion mesh?

 

The fact that it runs at all "nearly run down" is a good indication, but 7 seconds between strikes is too long to be considered normal. The Seth Thomas 89-xx warning wheel should normally have 70 teeth. If yours has 85 it is very likely that it is incorrect. Not only would 15 extra teeth over-speed the governor (making the strike slow), the pitch (spacing between teeth) will also be wrong to match the governor pinion Bruce sent you. You can try cutting down the fan (cut the one with the rounded corners, not the one Bruce sent to you) but I think you will not be satisfied until you change that warning wheel for a standard 70 tooth ST warning wheel.

RC

 

The correct wheel would be the best solution but I think it should be possible to get the strike to an acceptable speed with the existing wheel. The difference caused by the tooth count is only 21% and taking into account that most clocks strike too fast, this should be possible to be regulated with the fan size.

Uhralt

 

You could do a simple test to see if changing fan size will help. Remove the fan from the governor, put the governor back in, and, with the spring fully wound, let the clock strike. The strike should be much too fast now. If it is not, then something else is wrong, probably some binding going on.

Uhralt

 

Dave,

If you don't need to broach anymore, don't. If the end shake is so slight that you can't see it, make sure that the plate(s) are fully straightened out and call it good.

I've counted two ST 89 Warning Wheels (including your donor) and both matched RC's 70. If yours is 85, it's a significantly higher ratio as RC stated and would try to spin the Fan faster, which of course it can't, so your train will run slower...and the pitch is off as well.

I can get one with the 70 tooth count wheels out to you Monday. You've already more than covered the postage. Does anything else look "off" to you? The train runs fine until you add the Governor back in, yes?

I think I'll call your movement the 89 - Frankenstein.

Bruce

 

Try the "no fan" first. That will give you the quickest answer.

Uhralt

 

The problem with running a reduced size fan (or no fan at all) is that there will be a greater change in the strike rate between full wind and 8-days run down. Part of the slow strike is likely excess friction at the pinion because of the different pitch. If you measure the wheel diameter and the pinion diameter at the widest point , and divide by the number of teeth (or trundles) you get the pitch in teeth per inch. I would not waste time fooling with it, just accept Bruce's offer to supply the correct warning wheel........... causes one to wonder what else is not original in this 89-FRankenstein.

RC

 

What happened without the fan? was the strike too fast?

Uhralt

 

The Strike Train would have probably run okay with the substituted Warning Wheel/Governor if the repair person had bushed the Governor at the proper depth. He or she probably lacked a Depthing Tool to do the job properly. I still wonder how they let the movement out of their shop with it working this way. Perhaps it was marginally operating before the Warning Wheel Teeth began wearing? Who knows? The fact is that it doesn't operate properly now and it has to be fixed.

 

Agreed, the original Governor Pivot holes would probably have had to be plugged and new pivot holes drilled in the right locations. Either that or one of the larger Bushings might have done the trick. It's hard to know without seeing what the proper depth is. In any case, we'll get it straightened out Dave.

 

Yeah, that tells us that the large fan is not the problem but that binding/bad meshing causes the slow strike. A simple experiment that gives a quick answer. The strike side would probably stop working before the time side has run down.

Uhralt

 

Hi Dave,

From your description, the only thing that has changed is the position of the Pin on the new Warning Wheel. It's approximately 0.080" closer to the edge so it doesn't sound like the Lock Lever is clear of the Warning Pin when the Count Lever is in the shallow teeth of the Count Wheel. Is that right? If so, I think you'll only need to make a slight adjustment to the Lock Lever so that it is clear of the Pin when the Strike Train is running. Does that make sense or am I missing something?

Bruce

 

Dave,

As you probably well know, for the Strike Train to go into lock three things have to happen: The Count Wheel Lever has to be in a deep slot, the Maintenance Lever has to be in the Maintenance Cam Slot and the Warning/Lock Pin has to be captured. The relative change of the Warning/Lock Pin is probably having an unintended effect on your Locking Lever too.

For future discussion, let's refer to Bangster's diagrams found here: Count Wheel Basics

If that doesn't help, you may need to supply us with more photos or a video of what's happening.

Good luck,

Bruce

 

I'm thinking that something may have been thrown out of adjustment when you straightened the plates to re-establish adequate end-shake for your Governor.
Keep after it Dave. You'll get the movement straightened out. You just have to have patience and walking away for a while is the smart thing to do.
Good luck,
Bruce

 

If it consistently snags the tooth with the black mark look at that tooth and the tooth that's on the entrance pallet. Good possability the tooth at the entrance is causing trouble. If it occasionally snags other teeth, then very likely the spacing between the pallets is incorrect. Use a good caliper to measure the pallet spacing, then close the pallets about 0.002"- 0.003" inch and reset the verge depth and see if things improve.

RC

 

While you're tweaking the EW Teeth Dave, if you haven't done so yet, double-check the lift angles on your pallets see:
https://abouttime-clockmaking.com/downloads/Finding%20the%20Lift%20Angles.pdf.

 

First, test the back side of the pallet strip with a file near the saddle to see if the steel is hardened. If it is hard you will need to aneal befor bending anything. Most clock repair books show methods to adjust pallet spacing. One way is to use two needle nose pliers one each side of the saddle and twist the arms to bring the pallets closer. Another method is to place the pallet strip across the open jaws of a vice and use a punch over the saddle and gently tap to close the pallets. There are tools made to do this as well.

Don't worry about the fift angle at this point. Closing (or opening) the pallets will change the lift angle somewhat but you first need to get the escapement working without hanging up. This clock has plenty of power so if it runs OK with a reasonable pendulum swing after you get the pallet spacing right you can probably forget about the lift angles. If the clock runs weakly you can check the lift angle which should probably be about 2 degrees.

RC

 

Weird. I see the instructions for lift angles when I click on the link.

Uhralt

 

Same here.

RC

 

That was my intention to provide LaBounty's instructions for checking lift angles for an Escapement like this one.
It doesn't take long and it can have a profound effect on the performance of an Escapement as well as apparent spacing problems. I've personally seen it.
It's up to you, of course Dave, but I still recommend that you rule out lift angles as a potential source of problems for your escapement. You should take nothing for granted with this movement.

 

Your problem tooth might also be a little higher than the others. You would need a lathe to check it for round, but it could certainly be the issue.
I agree that your lift angles should be secondary to the main issue, which is the tooth being hit by the verge.

 

Dave, the lift angle has nothing to do with the problem of the pallet snagging a tooth tip. However adjusting the lift angle, either by reshaping the pallet strip or grinding the pallet tips will result in changing the pallet spacing. The lift angle is somewhat analogous to shifting gears in your automobile. Lower lift angle is like a lower gear, doesn't take as much power but doesn't move the car as far. Higher gear moves the car further but requires more effort by the engine. In this clock, too little lift will cause a small pendulum swing; too much lift, while resulting in a wider pendulum swing but can exceed the torque available at the escape wheel and the clock will stall, very much like trying to drive up a steep hill in too high a gear.

Without having the movement in hand it can be difficult to know whether the pallets need to be opened or closed. Depends on what has gone before and the number of teeth that are to be spanned. More often than not the pallets need to be closed, but if closing has a negative effect, then try opening. Just be sure to take a base measurement so you can get back to what you already have.

Steve Conover's book, Clock Repair Basics describes how to calculate pallet spacing. Note the strip deadbeat and the strip half-deadbeat setup the same way. The photo shopped picture below shows a ST pallet strip setup.

RC



Shutterbug said; "Your problem tooth might also be a little higher than the others. You would need a lathe to check it for round, but it could certainly be the issue." and I agree, especially if only one tooth seems to be a problem.

 

Dave

I certainly don't dispute the wisdom of RC or SB. I would be foolish to do so, but I know by experience that your lift angles should be checked whether they are secondary to the problem or not and I stand by my recommendation for you to check them. You have the parts easily at your disposal and it will take you 5 maybe 10 minutes to check them if you take your time. Make it part of your routine, just like checking every tooth and pinion when you have the clock disassembled.

Regards,

Bruce


Edit: We've already well established that this clock was "altered" before it landed on your bench. Take nothing for granted with it.

I recently worked on a Seth Thomas Lyre Movement (with the same type of Escapement as the 89). It appeared to me to have a pallet spacing problem. When I checked and corrected the Lift Angles, all problems with the Escapement were resolved, I only had to adjust the depth of the Verge. I was very glad that I checked the lift angles before trying to adjust pallet spacing. Maybe I just got lucky...

 

1.5 to 2 degrees lift should be fine for this clock. Again, changing the pallet spacing will change the lift angle at the same time. Get the pallet spacing right first, then adjust the lift angle, which will change the pallet spacing..... yeah, almost everything with the escapement will affect something else. The first goal is to have the escapement operate, ie. not lockup on one or two teeth. Next you want to adjust the verge depth so every tooth is locking on the dead face of the pallets. Next you want to get the drop off of each pallet to be close to equal and that is accomplished by small adjustment in the pallet spacing and readjusting the verge depth. Once you get the escapement operating and the teeth locking on the dead face and the drops about equal, then its time to assess if and how well the clock runs. You don't have an exact spec. for the lift angle for this ST model so if it has decent pendulum swing and keeps running it is safe to assume that you have a lift angle that the clock likes. If the swing is weak, then do measure the lift angle. But beware, changing the lift angle can sometimes persuade a clock to run when the real problem is a loss of power in the going train. I can only recall two clocks that required a lift angle change to make run. One had been bastardized and the other I could find no mechanical problem but reducing the lift from 2 degrees to 1.5 resolved the problem.

I agree anything is possible with this clock that we know has had other parts switched.

RC

 

This occurred to me as well RC. Distance between the "tips" (edges) of the impulse faces will change in reference to the tips of the Escape Wheel Teeth when the angles are adjusted. The distance will only be marginally affected, but it will be impacted.

In the case of the Lyre movement I mentioned earlier, as I recall, it was the tip of the Exit Pallet which was occasionally hanging up on the EW. In reducing the Lift Angle, the tip (or trailing edge) of the Exit Pallet was widened and shortened slightly. The effect was enough to solve the both the hangup of EW Teeth and it also improved the action of the Escapement. I think doing so also increased the effective Locking Surface.

As you say, it all falls under the Geometry of the Escapement and changing one thing has an impact on the whole. In my case, I'm glad that I didn't try to adjust the Pallet spacing first because the lift angle was off. Perhaps that's less common than a Spacing Problem which should be corrected first if you're following an established procedure of properly adjusting an Escapement. In any case, the Lift Angles will need to be checked either before and/or after spacing adjustments, yes?

BTW, David's procedure establishes a 2 degree lift angle but he describes how to adjust down to a 1 degree lift.

Good luck with it Dave. Problematic movements can teach you a lot more than a "Piece of Cake".

Bruce

 

No, there is no need to measure the lift angle if the clock is running normally. The fact that it is running correctly confirms a correct lift angle. If the clock runs poorly it is a good idea to measure the lift angle unless some other defect is obvious.

RC

 

Okay. Well I guess I'm going to do a lot of unnecessary checking in the future, especially if there is wear to the pallets and the clock is in need of servicing.
Perhaps my experience with the Lyre movement was unusual. I'll have to convince myself of that fact.

Regards,

Bruce

 

I don't want to step on RC's toes.

Adjust your spacing as he recommends and we can come back to Lift Angles afterwards.

If there is any wear to your pallets we most definitely will come back to it.

Regards,

Bruce

 

Unless it is possible to move the escape wheel a bit on its arbor.....

Uhralt

 

I was thinking in terms of rut removal through resurfacing of the impulse and lock faces. I believe that this is the context in which David LaBountry ties his lift angle process into Verge/Escapement work.

Bruce

 

In the process of rut removal it will most certainly be necessary to check the lift angles. I also found that most commercially available replacement verges need some correction of the angles.

Uhralt

 

Good point on replacement verges Uhrait. Along those lines, we don't know what's original on Dave's troublesome 89. I think it's a good idea for him to look critically at everything about it, but first things first...