Gina

@tekkydave and anyone else interested...   Thinking about this again.  The Z drive on the Concorde is working very well now and would be a simple Z drive for the Giant printer.

Decided on timing belts instead of clock chain and sprockets.

On 20/01/2021 at 14:59, Stub Mandrel said:

The critical thing is how small (tooth count) a pinion can you use? You might consider using 1 mod gears?

Considering I'm printing GT2 timing pulleys very nicely I see no problem with mod 1 spur gears.

ATM I'm trying the deadbeat escapement as that need far less work.

The anchor didn't fit so redesigned it.

I've printed the deadbeat anchor and the escape wheel and now reassembling the clock, having stripped it down to try the gravity escapement.

Decided to have another go at the deadbeat escapement and see how it goes.

TBH I'm not sure.  It's proving pretty difficult to work out how the gravity escapement is going to fit in.  Also, as you say there's a lot to re-design whereas I already have a lot of the parts made for a standard escapement.  I might be able to get the deadbeat escapement working in appearance if I drive the pendulum separately.  Rather like a slave clock.

Maybe I should have another go at the deadbeat escapement.

I've worked out that I should be able to get away without an extra gear pair but with higher ratios - though I have to test that out. 

6:1 from chain wheel to centre wheel with the chain wheel going faster (can do this because the auto-winding can keep up with the faster chain drive).  Then two stages of 10:1 give the overall ratio from centre wheel (60m) to escape wheel (6s) of 600:1.  Or do you think I'm being too ambitious?

Do you like it Neil?  I think the deadbeat escapement is a dead duck!  To difficult to get right so I'm trying a design for the gravity escapement..

I have a pretty fair idea of how it's going together in two dimensions but the third I'm not sure of yet for the escapement.  The pendulum is behind the escape wheel yet the arms are in the same plane.  I guess the arms (or are they legs) have to bend back to reach the pendulum.

So far it seems that I shall be replacing all the spur gears!

With a gear ratio of 150:1 the nearest ratios work out at 12.5:1 and 12:1.  With a size limit just over 200mm this gives 8t and 100t at mod2 for the first pair and 8t and 96t mod2 for the second.  This would seem to be just about the limit.  I'm happy with mod2 - it's what I used in my Moon Dial Clock but I would rather have 10t pinions rather than 8t.  One solution would be to increase the ratio of chain wheel and centre wheel.  This would only mean reprinting a couple of gears - the 20t gear is attached to the chain wheel with a dog clutch constantly engaged.  I could keep the clear acrylic sheets that form the clock case if I keep the spacing the same.

Spacing is 113mm.  Some new calculations :-  From the Centre Wheel rotating one an hour to the new escapement rotating once in 6s we have a ratio of 600.  It would be nice to use 6x10x10.

This seems pretty good for the Great to Centre Wheel ratio.  ie. chain wheel to minutes wheel.  6:1 ratio and mod2 with gears of 16t and 96t.   Why this shows "design failure" I don't know - maybe an Autocad expert might know.  But it seems to work anyway.

Had the clock apart and done some measuring.  I may be able to get a gear of 170mm or even 200mm diameter on the chain wheel.  This might enable me to get the required 150:1 gear ratio to the escape wheel in 2 rather than 3 stages.  Currently, the 60:1 ratio from minutes to escape wheel seconds uses 80:10 and 75:10 gear pairs.

Copied from the previous Blog, this shows how I had designed the gears around the minute shaft.  One error - Great Wheel should read Centre Wheel.  The Great Wheel refers to the chain wheel.  This shows part of the striking mechanism which I shall think about.

Some calculations :-

Centre wheel has 80t, chain drive wheel has 20t so chain wheel takes 15m per revolution.  The gravity escapement shaft takes 6s per rev. so if we start from the chain wheel, the overall gear ratio required is 15x60/6 = 150:1.  150 factorises into 2x3x5x5.  Suitable gear ratios would be 6x5x5 - easy to implement.  This is assuming I do without a seconds hand.

This shows the design as far as I had got before including most of the striking mechanism (green and pale blue levers etc.).

The pink and purple gears are the intermediate minutes to hours and can be swapped with the going train gears (red and blue in this model).  The striking system could probably moved a bit higher to reduce clutter.  The auto-winding system, starting with the green motor gear at the bottom, will be replaced with something simpler.  Maybe worm drive.  I hadn't got as far as the chain drive for the striking mechanism.

Actually, I'm wondering now if the striking mechanism doesn't make it all too cluttered.  Anyway, I plan to get the main timepiece working first, then add any extras.

The Gravity Escapement would not depend on any critical 3D printing and it would be different.  The clock is already pretty different from a "normal" longcase clock - they don't have all their works on view.  As those who know me know, I like to be different.

The escape mechanism would be below the main gears where it can be seen rather than behind.  Everything would be rearranged.  The hour gears would go centre top where the current escapement is, instead of at the side.   I shall need to have a good think about the rest.

This escapement turns once in 6s rather than the 60s of the deadbeat or anchor escapement so will need more gearing.

I think the deadbeat escapement stands a good chance of working if I can get my printer to behave.  Otherwise, it would seem that the Gravity Escapement has little to go wrong.  It would need a serious redesign of the whole clock though.  It would certainly be different and that makes it appeal to me.

I wonder... 

@Stub Mandrel  What do you think Neil or anyone else?

Hopefully the deadbeat escapement will work but otherwise I might have to try something that's more tolerant of conditions such as used in tower clocks.   Gravity Escapement.

Deadbeat escapement, showing: (a) escape wheel, (b) pallets showing concentric locking faces, (c) crutch.

Now printing the parts to see how the fit together.  I'll make up a test rig.

Been designing the escapement.

I've seen it before somewhere.  Well, it's a sort of clock... 😀

Hi Neil.  Yes, that's how it works.  Great to see you here.

Start of a design for a deadbeat escapement.