Crutch and Arbor Question

[Richard Barkey]

The pictures below are of an arbor / crutch from a Chinese wall clock movement. I regretfully said I would take a look at this clock which is owned by my neighbor. It had a broken spring that I have replaced and so far the movement is running, but I hope I have seen the last of it.

After working on this movement I had a couple of questions that I am hoping someone can give me an answer and/or opinion on. First, (see the pictures), the crutch is connected to the arbor using a friction fit. The crutch is loose until the c-clip is installed at which point it will move on the arbor with little effort. Is this arrangement designed so the clock will self adjust the beat? The crutch is made of stamped steel and cannot be formed or bent to adjust the beat. Or should the crutch be tight enough on the arbor so that I adjust the beat by moving the crutch on the arbor and it should stay put?

I hope I have explained the questions but let me know if you need clarification. I would appreciate any information as this is a learning experience for me.

Richard.

Crutch and Arbor 1 (http://static.flickr.com/99/265562272_70c30a5b6f_b.jpg)
Crutch and Arbor 2 (http://static.flickr.com/120/265562275_b4fceca9f0_b.jpg)

[Scottie-TX]

Difficult to say for sure;
You're well aware of the three possibilities and eliminated one.
1. Self adjusting
2. Friction fit for permanenet adjustment
3. Bending the crutch is not an option
Looks like a half deadbeat escapement.
I see either a self-adjusting crutch I don't like or a friction adjusted crutch that has become too loose. I'd shoot for squeezing that spring even tighter to hopefully result in a friction fit that won't be self adjusting.

[Richard Barkey]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Scottie-TX:
I see either a self-adjusting crutch I don't like or a friction adjusted crutch that has become too loose. I'd shoot for squeezing that spring even tighter to hopefully result in a friction fit that won't be self adjusting. </div></BLOCKQUOTE>

You are keeping me honest here. Thinking it is a friction fit and too loose, I tried squeezing the clip tighter but ended up breaking it (it is made of spring steel). It came to me then that this must be a self adjusting arrangement as it appears there is no other way to adjust the beat. Lesson learn to observe first and adjust later... What can I say? I found a new clip at an automotive supply shop of all places and tried that and it seems to work okay. The movement is running.

Question though, is this a typical setup for a self adjusting beat crutch or would it normally look different? I don't think I have ever seen a self adjusting movement before.

Richard.

[Scottie-TX]

Nah!
Just some nipponese bovine contrivance.
Others - most notably Hermle just use a conventional collar between arbor and crutch. I recall reading about problems occuring with it after introduction to cleaning solution so perhaps they use some sort of mild bonding agent also.
Glad you were VICTORIOUS!
http://static.flickr.com/80/246209370_885331df88_o.gif

[shutterbug]

The self-adjusting verges are not very popular with repairmen :smile:
You should not try to clean them or oil them and if you do, the damage is usually not reversible. I think Scottie had the best solution, make it act like a friction fit and adjust it manually. I say this because I just have a hunch this baby will be back to haunt you :biggrin: