Dark Lady Clock

[Michael GilliganParticipant @michaelgilligan61133]

Posted by John silver on 06/09/2016 22:32:35:

I'd like so find some info on making a lathe tre-panning tool

.

This looks a very useful little tool grinding jig, John.

**LINK**

http://bbs.homeshopmachinist.net/threads/45764-Homemade-trepanning-tool-grinding-jig

MichaelG.

[John silverParticipant @johnsilver78232]

Thanks for the link Michael – something to study…

[Ian S CParticipant @iansc]

To make the tool, grind up a bit of HSS (size it to suit the size of the work) a bit of 1/4"sq would do for most stuff. With the cutting end away from you grind the left side to a bit past half way, now this side needs to be tapered in to accommodate the circumference of the circle. In use be careful as you near penetration as it rarely goes through in one go, and if the tool catches up it can ruin a good bit of metal, and make one say bother. looking from the front, it looks like a parting tool with one side vertical, and the other with clearance.

There you are, I know what I mean, I'v got to make one tomorrow.

Ian S C

[John silverParticipant @johnsilver78232]

Ian,
Maybe you could post a photo when the tool is completed? It would be a great help and information is pretty sparse on this tool??

[john carruthersParticipant @johncarruthers46255]

I used a 55 deg HSS thread cutting tool as I had one handy. Light cuts from each side of the V not just plunged in.
The brass sheet was stuck to a bit of ally waste then both stuck to the faceplate with carpet tape.
I gave it a polish first to get a 'satin' finish on the brass.

[John silverParticipant @johnsilver78232]

All finished, it only runs for a little bit then stops. But i haven't added any clock oil to any pivots or the foliot???

Edited By John silver on 12/10/2016 15:39:24

[James AParticipant @jamesalford67616]

Looks good.

[john carruthersParticipant @johncarruthers46255]

Brian told me they take a while to run in. A drop of light oil helps on the rubbing faces. Mainly round the verge bearings.
What weight are you using?
I ended up with 3.5 kg on a double fall, with a ball race in the weight pulley.

I also fitted a smaller adjuster on the foliot. One turn of the original weight was too coarse.

Edited By john carruthers on 13/10/2016 08:37:17

[Neil WyattModerator @neilwyatt]

Well done John!

[John silverParticipant @johnsilver78232]

Thanks chaps not too shabby fir a first metal working project i need to shave a little off the curved part of the pallet as it just fouls on the escape wheel on one tooth – time to get the file out

[SillyOldDufferModerator @sillyoldduffer]

Good work. Very impressive for a first project.

Dave

[John silverParticipant @johnsilver78232]

Greetings all,

I'm a bit stuck trying to get the clock to run OK. Lifting the verge causes the gears to spin as the weight falls as expected so I have been looking at the profile of the pallet.

I took the photo in Brian's notes and drew around it scaling to the correct diameter around the bolt head. This is shown in red.

The blue shows the layout of the various lines on the 14mm wide metal strip and the purple basically what comes from it.

As you can see there is quite a difference between the position of the 3mm curves to the threaded hole on both variants.

I'll post this to Brian for comment too

[John silverParticipant @johnsilver78232]

[john carruthersParticipant @johncarruthers46255]

I have a shorter radius, so a deeper curve in the working faces.

[roy entwistleParticipant @royentwistle24699]

John If the pallet fouls one tooth of the escape wheel, might I suggest that the fault lies with the tooth rather than the pallet

[John silverParticipant @johnsilver78232]

The pallet isn’t fouling on any tooth. But because my two curves are further away from the axis, the swing on the foliot is greater and struggles to come back the other way.

[roy entwistleParticipant @royentwistle24699]

Sorry I was reading what you posted on the 14th

[John silverParticipant @johnsilver78232]

Well with a 3kg weight attached from the ratchet assembly only I get this…

 

Edited By John silver on 26/10/2016 17:20:04

Edited By Neil Wyatt on 26/10/2016 18:13:10

[Neil WyattModerator @neilwyatt]

You can hear it speeding up and slowing down, it definitely is hesitating on some teeth, its as if the shape of the edge of some teeth gives it a 'kick' while others hold it back?

Neil

Edited By Neil Wyatt on 26/10/2016 18:13:30

[John silverParticipant @johnsilver78232]

Indeed. I did cut the teeth accurately and filed the rear of the teeth to a curve. The front of the teeth just have the sharp edges filed slightly. I do wonder if my pallet shape is the problem? It’s certainly different to the profile taken from Brian’s photograph. I guess i’ll make a new pallet and see what happens

[Neil WyattModerator @neilwyatt]

Watch the video carefully. The first time it nearly stops the tooth at the left looks much rounder in cross-section (looking at the tip).

Neil

[John silverParticipant @johnsilver78232]

Hi Neil,

I think I see what you mean, the teeth that are more curved on the edges are allowing the pallet to wing further round, making have to travel further back the other way losing momentum all the time.

I wondered if the pallet was re-made with the curved sections closer to the shaft then the pallet movement would be reduced and more likely to return the other way to complete the cycle. To be fair the teeth were all square on the leading edge and I thought easing the sharpness of the edge would help in operation but I still think the pallet shape is the problem, especially when you compare Brian's extrapolated pallet (from photo) to the one I certainly started with using the starting cutout from the dimensioned drawings.

At least my experience with wooden clocks has shown how critical the escapement is for reliable operation

All the best

John

[Russell EberhardtParticipant @russelleberhardt48058]

John,

From your video it is clear that there is too much friction in the escapement. To minimise the friction the working surfaces should be highly polished and the pallet should be very hard. I don't know what you have made the pallet from but if it's mild steel (lead free) it could be case hardened. Better still to use gauge plate and harden it with no tempering.

The design of the pallet looks wrong to me.

Assuming very little friction the impulse force provided to the pallet by the escape wheel tooth will be perpendicular to the working surface of the pallet. To maximise the effect of that force in maintaining the swing of the foliot that force should act perpendicular to a line drawn from the centre of the pivot to the contact point. That is far from the case with your design. At first thought it would seem to imply that the sliding surface of the pallet should be radial to the pivot. Perhaps a bit of playing about with the operation on a CAD program (or on paper) would help with understanding it?

Russell.

[Neil WyattModerator @neilwyatt]

Posted by Russell Eberhardt on 27/10/2016 17:09:30:

At first thought it would seem to imply that the sliding surface of the pallet should be radial to the pivot.

It can't be truly radial, or there wouldn't be any impulse?

Neil

[Russell EberhardtParticipant @russelleberhardt48058]

Posted by Neil Wyatt on 27/10/2016 18:09:53:

It can't be truly radial, or there wouldn't be any impulse?

Neil

That would be true for an anchor type escapement but not for this geometry.

If the surface of the pallet is radial to the vertical pivot of the foliot then the impulse vector, perpendicular to the pallet surface, will give the maximum moment to that pivot. With John's design the impulse vector is almost in line with the centre of the pivot just before release so provides virtually no energy to the folio.

Russell.

[Author]

Posts