Botsford "grasshopper" escapement question.

[Jeremy Woodoff]

I have a clock with the Botsford so-called "grasshopper" escapement in a "PARIS" front case sold by Jerome Manufacturing Co, also seen with a label of Coe & Co., New York. See pictures and video. In the lever escapement there is an upward pointing pin attached to a brass disc on the balance wheel arbor. This pin interacts with the lever fork. Fixed to the bottom of the lever is a vertical pin that points down towards the brass disc. As the disc rotates, the pin doesn't quite touch the edge of the brass disc. What is the purpose of this pin? Should it be in contact with the disc?

There is an occasional problem with the clock, especially when fully wound, when the pin attached to the balance wheel ends up on the wrong side of the fork, stopping the clock. I don't know how that happens. The clock easily ran for two days on a winding for many years. When it began to stop before the end of the second day, I cleaned and oiled it. Since then it won't run for more than a day, as if it's losing power near the end of the run. The bearings for both the balance wheel and lever are both adjustable up or down with a screw, and I've tried many different adjustments. I'm wondering whether the pin described above might have any relation to the current problems.

 

[gmorse]

Hi Jeremy,

In the lever escapement there is an upward pointing pin attached to a brass disc on the balance wheel arbor. This pin interacts with the lever fork. Fixed to the bottom of the lever is a vertical pin that points down towards the brass disc. As the disc rotates, the pin doesn't quite touch the edge of the brass disc. What is the purpose of this pin? Should it be in contact with the disc?

The vertical pin pointing downwards in the lever next to the fork is the guard pin. Its function is to stop the impulse pin in the balance roller, (the 'brass disc'), from swinging past the lever fork when the fork is in the wrong position. There should a small cutout in the edge of the roller in line with the impulse pin, usually crescent-shaped, (the 'passing crescent'), which should only allow the guard pin to pass at that point when the impulse pin is safely in the lever fork.

It should be set so that it touches the edge of the roller in every other position, and it seems from your picture that it doesn't reach the disc at all. In fact, it appears that the roller is too low on the balance staff.

It would help if you could post a clearer picture of this area, preferably with the escapement at rest and without it being partly hidden by the back plate, because the roller appears to be too low, or the pin has been shortened. In normal use, the guard pin should be held away from the roller against the lever bankings and only touch the roller if it receives a jolt, which I'd have thought would be less likely with a clock than with a watch which is always in motion.

This would cause the problem you're seeing, of the fork ending up on the outside of the impulse pin.

By the way, is 'Grasshopper' the model name of this clock? This isn't a grasshopper escapement but a detached lever.

Regards,

Graham

 

[Jeremy Woodoff]

Thanks for your helpful reply, Graham. I put "grasshopper" escapement in quotes because I know it isn't really a grasshopper escapement. But it's been called that, I think because the large lever makes such a noticeable, jerky motion. The clock is often called the "Paris" model. The word "PARIS" is embossed in a cartouche below the dial. But there's another model with a papier mache front in the same shape that doesn't say "Paris." The Jerome catalog from around 1853 has a few clocks called "Paris" or "Paris Style," but they're not this clock.

Here are some more pictures. It's very difficult to photograph this escapement. The last picture shows the lever after I adjusted it slightly to lower the position of the banking pin. I don't believe the balance roller has been moved, but the position of the banking fork and banking pin could well have been changed, since they bend easily. The pin now extends below the roller. It clears the crescent cutout and seems to contact the roller outside the crescent. I can't tell what this would do besides add friction to the escapement. It doesn't seem to change the motion of the fork, the side-to-side motion of which seems controlled by the action of the pallets with the escape wheel.

 

[gmorse]

Hi Jeremy,

These pictures are much more informative, thanks. The escape wheel and pallets weren't visible before, and the nature of the escapement is now clearer. It's an interesting variant of the pin pallet escapement, with all the lift on the pallets rather than the escape teeth. In a lever escapement, the sideways movement of the lever is limited in various ways, and the pallets and teeth are usually designed so that each pallet is pulled deeper into the tooth once it contacts it, (the 'draw'). This is the 'run to the banking' and keeps the guard pin clear of the roller unless some jolt disturbs that. In this example, I can't see any banking pins or other arrangements, so I think this design uses the pallet frame striking the escape wheel teeth as banking, to keep the guard pin clear of the roller after impulse is given.

You do have another problem with the balance spring which will be impacting the action to some extent, because it should be flat and level.

Regards,

Graham

 

[Jeremy Woodoff]

Thanks again, Graham. Did you look at the video that was attached to the first post? I think that has a clear view of the escapement. The hairspring is a problem, but I'm not adept enough to get it straightened out. It's better than it was--at least the coils aren't coming in contact with each other or anything else. It lies flat when unpinned, but inserting the pin to hold the end of the spring invariably causes it to distort.

 

[shutterbug]

That's a very interesting escapement, but yeah - not a grasshopper.