Member postings for James Alford

I am currently drawing up plans for a Brocot escapement for this clock, rather than my original design. I have read that the diameter of the pallets should the same as the gap between the tips of the escape wheel teeth, less the drop. What would be the consequences of using smaller sized pallets than this? The main thing that I can see is that it may run out of "operating" surface if the pendulum were to swing too far, so the cut-out part of the pallet tries to engage, rather than the curved face.

Can anyone please advise?

Thank you.

James.

John,

I plan to build a similar spindle and put a request out on Freecycle for an old sewing machine motor. I was offered, quite promptly, two fully-functioning sewing machines to dismantle. It may be worth a try if it can save you a few pounds and reduce someone else's waste.

Regards,

James.

John and Michael: thank youfor the clarification.

James.

I have noticed that some Brocot escape wheels have straight teeth, whilst others have one side scalloped out. Am I right in thinking that the cut-out is to accommodate the pallets if the pendulum over-swings and to avoid recoil?

Regards,

James.

Thank you for the suggestion. I know that, unfortnately, it is not available at our library. I shall contact the Horological Journal to see whether it is possible to buy a back-copy.

James.

Michael,

Thank you. Whilst I found it relatively easy to draw the pallets shown in my design, I do have doubts about my ability to accurately shape them in practice. The Brocot design, with its pins, seems to avoid the problems that I had envisaged with my design.

Back to the that part of the drawing board....... which is why I asked in the first place: to avoid as many pitfalls as possible.

Regards,

James.

I have also bought the plans, but have yet to build it. I plan to do so before embarking upon a clock of my own design (the Basic Clock Design thread). Like you, I found the plans to be encouraging, with some nice, clear guidance.

I look forward to your progres.

James.

Reading through the comments about Brocot escapements and looking at the pictures, I can see the benefits of them, especially with regards to construction. Are they used in clocks with a 1 metre ( 1/2 second?) pendulum? From slide 26 inthe linked presentation, I am not clear.

James.

Michael,

I did not think that it was interfering, but that my original post was unclear! I would prefer your contributions to continue, please.

JAmes.

Michael,

I have found plenty of animations online, but am stuck trying to rotate the wheels in my own drawings. It is possible to animate some elements of assemblies in Onshape, but, so far, my designs have remained stubbornly inanimate. Still, I shall persevere.

James.

Michael,

Thank you for the link to the blog. I have been reading this for a while and have found it very interesting.

John,

My escape wheel has 30 teeth and the arms of the pallets are at 90 degrees. They span 7 1/2 teeth and have an angle of either 1 or 2 degrees (drop?): I cannot recall which I drew. I know that in the drawing below, one pallet hits the teeth of the wheel. This is because I cannot work out how to rotate the wheel in the CAD drawing.

Edited By James Alford on 30/04/2016 09:07:37

Slowly progressing with my drawings. At the same time as designing the clock, I am learning CAD for the first time. I am using Onshape which seems generally to be all right, but seems to do odd things at times, for no apparent reason. I had to draw the pendulum suspension block several times as part way through adding other parts to the assembly, the block split into its components parts and appeared to fall apart.

The width between the frames is currently arbitary and will be set later once I have worked out hw large the winding barrel needs to be. Using the idea of a looped rope with pulleys, I should be able to get seven of eight days running time from a four foot drop.

I have settled on the following gearing. It may not be ideal, but it all seems to fit and look generally fine. I know that it still uses ten leave pinion in the train, but I am struggling to devise a better ratio that fits together.

30 tooth escape wheel followed by:

12:90

12:96

12:120 for the barrel wheel

I have 10:30 and

8:32 for the hour and minute hands.

As mentioned before, the frames are merely shown to hold the wheels and aroburs in place and are not the final design or size.

Thank you for the ideas. I had forgotten about chasers, but have, somewhere, a selection of adjustable half-nut chasers that I inherited from my grandad. They range from quite small to very large.

James.

John,

Thank you. A screw-cut barrel? Well, that will be challenge 73: how to cut a thread without the screw cutting gears for the lathe. I have a small. low geared-high torque 12v motor which I may rig up to the lead screw. Matched carefully, I imagine this could be pressed into use to cut a one-off thread.

Regards,

James.

Russell.

Thank you. That makes perfect sense now. I was thinking along the lines of the clock that I have already which uses a chain which simply loops over a toothed wheel, rather than being wrapped around it, as below.

Regards,

James.

Russell,

Thank you. Do you mean a bit like the second example in following picture for the looping? If so, I am being really dense as I do not see how it increases the effective fall. I can see how it will require a heavier weight due to the compunding effect, but not the running time.

I have modified my gear train in light of the suggestions made and am now trying to work out how long the clock is likely to run for as it stands. Assuming a drop of four feet, I come up with a running time of about three days.

I have been thinking about how to increase this duration and have come up with:

Raise the clock to increase the drop

Possible, but not going to make a huge difference.

Increase tooth count on the driving wheel

Difficult due to size restrictions of my lathe. The maximum comfortable diameter is four inches.

Reduce tooth count on the driven pinion

Possible, although I am trying to avoid really small pinions due to their fiddly nature. I have looked for the ready cut lengths that someone previously mentioned, but cannot find any.

Introduce another gear into the motion between the driving gear and the next wheel

This seems to be the most feasible option.

Some sort of rewinder

Not sure,

Have I missed an obvious method? I have looked at ways of looping the rope or chain over other pulleys, but I still come back to the limitation of the drop.

I should appreciate any suggestions.

Thank you.

James.

Thank you for all of the replies, which I shall study and take into account as I work on the plans.

Regards,

James.

Thank you for all of the replies, observations and suggestions. I need to read them in detail and study some of the links, but I do have a few questions or comments based on them.

Pendulum and Weight in Line

I can see how this could cause problems with the pendulum setting the weight off swinging as well. I had originally planned to use a spring drive, which would not have had the same concern. I shall look at changing the layout to off-set the weight.

Plate or Frame Design

There have been some helpful comments about mounting the frame and the limitations of the design as shown. The frames are only representative at this stage, not the final shape, and I shall take into account the points that have been raised.

Escapement Teeth Spanned

I designed the pallets and escape wheel using the method shown below, which I found in a various forms in different places. The two short lines near the horizontal line and either side of it are the start of the pallets. Why is it better to span more teeth than this?

Remontoires and Maintaining Power Devices

I can see the benefits of these and shall mull them over. I have a commercial long-case clock that has nothing of this sort and it keeps reasonable time, but can see how these devices could improve it.

Tooth Count

Someone commented that using an 11 tooth pinion is not a nice number: there is no 11 tooth pinion in the train. The same post mentions that a 10 tooth pinion is a bad choice. Why?

The Book in the Archive

Thank you for this link. I have started to read it and bits look useful.

Regards,

James.

Edited By James Alford on 21/04/2016 07:19:10

Thank you for all of the comments and suggestions to date. As yet, I am still undecided about a remontoire, but shall study them in more depth before deciding. Although it seems the simplest, I am not keen on an electric device, simply because I do not wish for the clock to be reliant upon batteries or to need plugging into the mains.

I have revised the design, using 0.8 mod as a compromise size between 1 and 0.6 mods. With 0.8 mod, the pinions are large enough for me to have a fair chance of constructing them as lantern pinions. Anything smaller and I doubt that I would have much luck.

I have decided to use weights in the end, not spring.

The attached drawings show the general layout, but the frames are simply representative, but finalised, as are the long arbours at the front.

I plan to use a one metre pendulum with a thirty tooth escape wheel. The tooth count and ratios that I have settled on, starting with the escape pinion are:

10: 75

10:80

10:30

8:32 (the hour wheel)

The wheel on the winding barrel is 120 tooth

Do these ratios and general layout look reasonable?

Next step - pendulum and suspension. Can anyone direct me to any links or sites which cover this area? I can work it out by studying other designs, but some advice is always a help.

Regards,

James.

Edited By James Alford on 20/04/2016 07:31:02

Edited By James Alford on 20/04/2016 07:31:54

Edited By James Alford on 20/04/2016 07:32:49

Edited By James Alford on 20/04/2016 07:57:45