Looking for advise from clock bilders

[marklazarz]

Don:

Here are a couple of photos showing the pendulum-crutch arrangement that Art mentioned.  In this case (Clayton Boyer's Clock #6), the crutch is attached to the pallet shaft and is a tight fit so it's adjustable.  The pin extending from the crutch goes through a slot in the pendulum with only about .010" slop between the slot and pin.  The driving force on the escape wheel rubs against the pallet faces and gives a tiny push to the crutch pin with each beat, thereby keeping the pendulum going.  A lot of new clock builders think that the pendulum drives the escape wheel when, in fact, it's the other way around.  I highly recommend that you purchase a proven design plan and build it.  Consider the money spent as tuition on learning how all the parts go together.

Mark

[ArtF]

Mark:

  That IS truly nice work, makes me want to drop everything and build another clock. :)

Harnden:

As to tooth counts, you dont worry about them, you worry about ratio's. All thats important is ratios..

SO lets say you know the escapement wheel goes around once in 1 minute. You then know you need
a gear somewhere to hang a minute hand on that is 60:1 ratio..it has to turn once per 60 minutes.

  SO using the gear train calculator, you can tell it how many gears you wish to use, and what ratio to get..
it will then give you all the gears you need to make that 60:1, you can then place a minute hand on the
shaft of the final gear. Make another at 12:1, and you have the final train leading to the hour hand..

  Mark makes a good point, a professional design is one where the designer has gone though all this
in hundreds of permutations and working various placements so its a great clock..

On the other hand, if your like me, you wont go that sensible, smart and learned way, lol, you
will instead design a gear train and place it on to see how hard it is to drive a minute hand.. Youll
be amazed to see it seems to work well and proceed to change your pendulum to a crutch as Mark showed..
  at which point youll begin to see why Mark suggested a full design.

  At some point in this process you will begin to see just how sensitive a device a clock is, and just how
much its a marriage between art and physics. Most have absolutely no idea. Until you've built one,
and experienced it, I dont think one can appreciate just what a miracle they are,moreso when made from wood.
. But your doing it right, and its a great journey..

  In the end, of all the things Ive seen built since I started Mach3, nothing has impressed me more with
a persons craftmanship than clocks. Make a 6 hour and you did well, 12 hour and one should be proud,
24 Im envious, and a week , well, I bow in your direction and welcome our new overlord...

Art

[John T]

Hi Mark
I totally agree with Art.  In my case, I build with wood, nearly always with Baltic Birch because it is dimensionally the most stable I can get. The one thing I always watch is the mod. I want biggish teeth because they are more forgiving to build. I like about 4 teeth per inch because its just plain friendly.    Having said that. As Art said make some and see what you like.

John

[marklazarz]

This is a good discussion because we arrive here at different points in our clock building endeavor.  I happened to find Gearotic after I built a clock then studied it and decided I wanted to design my own.  I understand what is happening but the math is too complex for my feeble brain so thankfully Art wrote this wonderful piece of software that figures out gear ratios and shafting and lets you position things the way you want.  I'm glad I arrived here after building a clock because I don't think I could progress without actually seeing how others approach spacers, shafting, bearing points, hanging a pendulum, going trains, timing trains, etc.  To each his own I guess but I gotta admit, it's a rush seeing the tree move.

[ArtF]

Mark:

  It IS a rush isn't it? It hooked me immediately. I came from the other direction, figuring..how hard can it be..
LOL.. "VERY" was the answer. As you said, spacing, shafting..wow.. it was a lot to consider. I wrote gearotic to help me make another. I'm very pleased so many have found it useful.

    Now that Auggie is running my laser and I'm happy with its outputs, Ive moved back to making more tools for
graphics and design, Im leaning toward a clock face designer... We'll see what the future brings..
Art

[John T]

Hi Art
Something that I do very empirically is designing the crutch on a pendulum clock.  I've gone from mounting a pendulum directly on the pallet arm. Ie no crutch at all to all sorts of arbitrary lengths. All work. But is there a "best" length ?  Mostly I've just looked at clocks from the 1800's but that's hardly more that just copying.
Any ideas?

John

[HARNDEN88]

Thanks guys for the input. Mark I did get the plans for the #6 in dfx for my cnc but like I thought already having some issues to print the plans I have to load this program that he suggested delta cad and when I follow his instructions it prints like 4 pages for one gear and none of the gears tell me how thick they are and I have to tape all the pages together got to be something I can do easer then all that . and when I load them in vcarve they all load as one file so I have to pick the gear I want and close all vectors then go to tool paths seams like a lot to do just to cut I tried one of the gears closed vectors tried simulation and got error check for duplicate lines and when I go back to close vectors it tells me one open vector but will not let me close it. Just wondering is you used cnc for yours and did you have any problems. any help you can give me would be great also Art was right I would like to learn gerotic so that is why i started with what he said to put one on a board to see how things work. with being said I have some questions regarding my escapement. first it has 30 teeth so does that mean it takes 2 revolutions to get one min and if so would my first gear train be to reduce that gear to a gear that would rotate one revolution.SO is the escapement gear the second hand or do I have to have another gear to put the hand on that rotates once. Second question is why do most escapements I see in plans have 30 teeth is there a purpose or is it their preference. Third when using gerotics art said number of teeth was not important just ratio so how do you decide how many teeth. last could one of you set up my next gear train from escapement so I know what numbers to plug in I think once o see the order of things it will make more sense, Something like I know first step is ckick on circular gear next pick number of teeth on wheel and pinion next pick gear type Epicylcoidal but after that do I go to calculate and pick gear size which changes my dp and mod and then to to auto pick 2 pair search pick the last neg number before pos start then pick add to project if this  good ware to after that. so I guess if someone could plug in the numbers so I csn see it I could move on from there should be easy for you gearheads but not for the confused wanta be clock builder Don.

[ArtF]

>>Something that I do very empirical ly is designing the crutch on a pendulum clock.  I've gone from mounting a pendulum directly on the pallet arm. Ie no crutch at all to all sorts of arbitrary lengths. All work. But is there a "best" length ? 

Im no expert on that, but the longer the crutch the more it slides up and down the pendulum, but..the more torque it has to
push the pallet.. so it'd be a balance of getting it just long enough to get the necessary power, and short enough that the friction of rubbing up and down is reduced to a minimum. Often, youll see no difference, it can only be measured..many of these types of things, in terms of how much weight it takes to run it.. its a good measure of efficiency..

Art

[ArtF]

Don:

  How many teeth depends on the pendulum in terms of how much per minute. If you put a 2 second period
pendum on it, the 30 tooth gear will take 1 minute to rotate once. If you put a 1 second pendulum on it, youd
need to make a 60 tooth, or gear it down for the second hand.

  So, drop a 2 second pendulum on it, and put a second hand on the shaft of the escapement gear itself.

Now, as to tooth count, it could be anything. With your escapement on the screen, go to the circular gear panel,
select "autotrain". In the ratios box, select "minute to 60 minutes" , then hit the search button.

What comes up is a list of gears pairs that will do that conversion. Select "Two gear pairs" instead of 3, and hit search again,
these are the sets of dual gears that can go from a minute to 60 minutes. Pick one and select "Add to project",
when your back on the projects screen, select the shaft of the escapement gear. You now how a train that
ends with a gear that rotates once every hour..

Etc..

  As to size, you have to reduce the mod to make them smaller. Mod is the size of a tooth in mm's , so reducing
the mod reduces the gear sizes. Select a mod that works for you when you begin a project..

Art

[marklazarz]

Don:

I think Clayton included a Word document on how best to print from DeltaCAD.  As for importing into Vectric, yes you get the whole model so you should close all open vectors with a tolerance of .02 or so and don't worry if some remain open because there may be some text or lines that won't close.  My next step is to pick a board that will fit on my CNC table with the appropriate part thickness and set it up as the starting point in Vectric.  Then import the model and move as many parts to the material that will fit nice, making sure to pick the same size thickness as your material.  You don't have to delete the remaining parts, just leave them in Vectric off the the side of the material so you have access to them.  I like to do this and "save as" HalfInchParts-1, HalfInchParts-2, QuarterInchParts-1, etc. as many time as necessary to cut all the clock parts.  If you "save as" a few times, it's easy to go back and re-load HalfInchParts-2, for example, if you need to re-cut some parts without having to start from scratch and move all the parts around again.

There should be a PDF document included with your plans that provide detailed assembly instructions and drawings.  Print this out in it's entirety because you will refer to this document many times during construction and assembly.  Initially it will look very complicated and confusing, I know it did when I first started.  I then remembered what one of my bosses said to me years ago when I was faced with an enormous task - "How do you eat an elephant?  One bite at a time!"  Being basically cheap, I was determined not to waste the money I spent on the plans.  So I got a knife and fork...

[kit]

Now that Auggie is running my laser and I'm happy with its outputs, Ive moved back to making more tools for
graphics and design, Im leaning toward a clock face designer... We'll see what the future brings..

I'm sure we'd all love a clock face designer, but something simple like the ability to design a fork for the pendulum or cut holes out of the plates would also be very welcome. At present these things require another CAD program (easy) and another CAM program (expensive). My No.1 wish for the next improvement would be the ability to import shapes into the gearotic 3-axis CAM page and cut them out at the same time as the rest of the clock.

Getting back to the original purpose of this thread: I'm having trouble persuading a Graham escapement to work. At present I'm using the default 1/2 degree lock angle. On my next day off work I'm going to try a new palate using 2 degrees. Any comments on this from those who know?

Kit

[ArtF]

Kit:

  Request noted.. I have been mulling having GM load the DXF's to be put out by Auggie in order to generate the Gcode.
Auggie is pretty good at it, and I think can be expanded. So you may see that request fulfilled in due course as part of
the clockface generators output.

  As to the Graham, you need to figure out exactly why its failing to see what may help. Lets look at tit this way,
you have a wheel, it has a weight on its pulley. Pallet is tilted to right and tooth is locked. Describe what happens
as pendulum swings.. does the tooth on the wheel press properly on the pallet lock face? It is that which adds
power to the pendulum to keep it swinging.. does it properly hit the lock on the other side, and on return how does the
tooth drag on the surface. The angle at which the two hit is the most important thing..  Ive only built a couple grahams,
both worked right away, even if the pendulum was direct connect, so I dont have much experience personally on
whats up when they fail, mine DID fail, but it turned out I had it upside down, wrong pallet face direction...

Art

[HARNDEN88]

Mark thanks for the advise I was playing around in vectric and did what you are saying. but had a problem I started with center gear closed vectors, did toolpath and when I run simulation it only cuts everything but one of the pockets any ideas what I can do thanks Don

[HARNDEN88]

Art thanks I will try what you said for the gear train. You know what my next question is going to be lol.How do I make this 2 second pendulum ? remember I need to know in detail thanks Don.

[marklazarz]

Don:

I'll answer your last two questions.  Send your Vectric .crv file to my e-mail address and I'll take a look at your toolpath.  It looks to me like you didn't select the last cutout when you defined the toolpath.  As for the two second pendulum, a pendulum's period is a function of it's length.  In Gearotic under Indicators, there is a button called Pendulum Calc.  You can enter the period you want, in your case 2 seconds, and it will tell you how long to make the pendulum from the pivot point to the center of mass of the bob.  Entering 2, returns a result of 39.112 inches, simple as that!  Remember this is a theoretical number assuming that the rod has no mass and that there is no friction.  Best thing to do is add 5 inches including a 2 or 3 inch adjustment screw and you should be able to dial it in.

Mark

Art, if you read this, be advised that the Pendulum Calc button seems to take about 5 seconds for the dialog box to appear after clicking on it.