A Different Set Up

[Marc]

This is a new one on me.

 

 

This is the engine room from an AS1171 bumper auto that I'm working on.

Has anyone else seen or worked on this arrangement before?

Apart from the fact that it is all very dirty (this shot is pre-cleaner) and the mainspring is well and truly set, can anyone spot what is out of the ordinary with the set up?

[Geo]

The spring winds anti-clockwise and it has a slipping clutch.

Edited January 13, 2015 by Geo

[Mark]

Can't remember seeing one of these. Does the ratchet wheel have friction/slipping. Because the mainspring looks like it is hooked.

[Marc]

Well spotted George.

 

Like I said, it's from an auto-wind movement, but rather than a slipping bridle on the mainspring to limit the build up of torque when the spring is at full wind, this uses a manual wind spring and barrel, but incorporates a slipping clutch (the domed star shaped washer) to couple the arbor to the ratchet wheel (which has a round hole rather that the normal square hole).

As I said this is a new set up to me and had me scratching my head when it came to dismantling it, and here's the question; how should this be lubricated?

 

After a fair bit of google I have been unable to locate any information on this arrangement, in fact all of the details I can find on the AS1171 show the more usual auto set up.

When I took it apart the whole thing was dripping in oil which can't be right. I have tried a touch of 8213 breaking grease on on the four points of the star and it is just too slippy, although this could be due to my use of a slightly stronger than spec mainspring, and I have tried it dry, but this just results in the balance galloping. This too could be down to the over strong spring so I have the correct spring on order, but if anyone knows what the correct lubrication is for this part it could save me a bit of faff when I install it.

[Marc]

Correct Mark, the ratchet wheel has a circular hole, the domed star washer has a hole with two flats which correspond to two flats on the arbor, the four points of the star washer friction couple to the top of the ratchet wheel. Any thoughts on lubrication?

[Mark]

Hmm... My first thought would be to use a high friction grease like 9501 and check it's performance from there.

[Geo]

I've not seen one myself Marc, but I think if you can get the correct strength of spring one of the braking greases will do the trick.

[anilv]

Reminds me of the friction dampers on vintage bikes and cars...!

[Geo]

Reminds me of the friction dampers on vintage bikes and cars...!

I had one on my 1931 Royal Enfield, that's how I recognised it! :-)

[bobm12]

Hi Marc,

 

I haven't seen this before either but then again, I haven't seen much I guess. :)  In any case, I can't figure out the function of the cross shaped part! I'd love to see a picture of the whole assembly put together.

 

@Geo: very interesting you bike, Geo! I wonder if a picture won't be much to ask? Thanks mate!

 

Cheers,

 

Bob

Edited January 14, 2015 by bobm12

[Geo]

It's a small clutch unit that sits on top of the ratchet wheel and allows slippage when the spring is fully wound by the automatic wind mechanism.

Edited January 14, 2015 by Geo

[bobm12]

mmm, I see now it makes sense! Thanks for the explanation Geo.

[Marc]

Hi Bob,

here you go;

 

 

The screw on top is threaded into the top of the arbor and forces the points of the star down onto the ratchet wheel whilst engaging the hole in the star washer (which has flats) with the top of the arbor (also has flats). The ratchet wheel hole is round so there is no direct coupling between the wheel and the arbor. Torque is transferred from the ratchet wheel to the arbor through the friction contacts at the points of the star. When the spring is fully wound the auto wind system continues to turn the ratchet wheel but the friction couplings slip preventing any damage to the winding set up that would otherwise result as the mainspring is fixed to the barrel with no slipping bridle.

 

To dismantle this arrangement you have to immobilise the star washer with heavy tweezers so that you can undo the screw. If you don't hold the star washer the whole thing just spins. 

[bobm12]

Thank you Marc,

 

very interesting and now that I see it somehow in my mind it looks familiar from something I saw many, many years ago (kind of fuzzy in my mind now) It must have been some big chunk of machinery back then (I was a kid). I completely understand it after your perfect picture and explanation.

 

Very much appreciated,

 

Cheers,

 

Bob

[Geo]

It would appear that the original Rolex Bubbleback had a similar clutch system.

[Marc]

Is that one that you're working on Geo?

[Geo]

Is that one that you're working on Geo?

If only!

I came across a movement being sold on EBay and immediately recognised the clutch system. I posted it purely out of interest. :-)

[Mark]

I love the bubblebacks.

 

You may have seen this one

 

 

unfortunately it was when I thought it was OK to speed up the footage, the assembly is out of shot sometimes, but it was one of my earlier vids.

[jdrichard]

Very useful