Building a Strasser Regulator Clock

Discussion in 'Clock Construction' started by Allan Wolff, Jan 28, 2013.

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  1. Allan Wolff

    Allan Wolff Moderator
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    Mar 17, 2005
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    Dial Pan

    The dial pan is made from .04" thick brass sheet. The diameter was rough cut oversize with a tin snips and then flattened by hand. Gloves are recommended due to the sharp edges. A 7/16" hole is drilled in the center of the pan where the hands will pass through. For now, this hole will be used to mount the pan on an arbor for turning in the lathe. The pan is too thin to turn by itself, so it was sandwiched between an aluminum plate and the small wood disk used to turn the bezel.
    DSC_3824.jpg


    Even though it was supported on both sides, the pan would flex slightly as the edge was machined. The diameter was then reduced until it fit inside the lip on the back of the bezel. The front plate of the movement was then used as a template to drill holes for winding arbor, second hand and dial feet. Six holes were drilled around the edge of the pan to fasten it to the bezel with 0-80 machine screws. I placed them close to the edge to allow drilling into the thickest part of the bezel. After all this work, I sure did not want to drill too deep and go through the bezel, so I measured carefully, used a depth stop on the drill press AND marked the drill bit just to make sure I did not go too deep. The holes in the bezel were then tapped with 0-80 threads.
    DSC_4606.jpg


    The dial pan feet need to support the pan 1/2" above the front plate to allow space for the motion works. It was actually quite nice to get back on the small Taig lathe to make these parts.
    DSC_3827.jpg


    The feet are attached to the pan with silver solder and to the front plate with taper pins. The taper pin holes are spaced to allow for a small washer between the taper pin and front plate to protect the front plate from scratches. I don't like seeing scratches on the plate where the pins have been inserted. The washers also raise the pins above the plate and makes them easier to insert and remove. To make sure the holes are all in the same location and centered on the pin, I made a gauge from drill rod that was center drilled and has a small cross-drilled guide hole. With the gauge held in a vise, the pin of the dial foot is inserted into the center hole of the gauge and held by hand while a drill bit is run through the guide hole. This worked really slick and made quick work of the drilling operation.
    DSC_3832.jpg


    The small pip that goes through the pan can actually be left a little bit long so they can be filed and sanded flush on the front of the pan. Since the dial will be glued directly to the pan, we don't want any high or low spots that will show through the paper. When the feet were soldered to the pan, the pan warped in the area around each foot. Most of the warpage disappeared when the pan cooled, but I still had to do a little hand straightening to get it flat again.
    DSC_4609.jpg
     
  2. Allan Wolff

    Allan Wolff Moderator
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    Dial

    I thought I would take the easy way out on the dial, but as usual it turned into a learning experience; meaning problems occurred.


    The dial was drawn to scale in CAD. Here is a low resolution image to give you an idea of what the dial looks like.
    dial.jpg


    The diameter of the outer time track is 8 inches; just large enough to cause problems. I tried printing the dial on my dot-matrix printer and on a laser jet printer at work. The result was rather dull looking when printed on regular paper. I tried some photo paper in the dot-matrix printer, but the results still were not that impressive.


    Then I got the idea of saving the drawing as an image and having the dial printed as a photograph. I use DraftSight for CAD and it is capable of exporting drawings to an image file. No matter what resolution or file format I used, the image was pixelated when viewed close up, especially on the curved lines and signature. Exporting to PDF format worked great, resulting in smooth lines and great detail. Unfortunately, I could not find a photo printing service that would accept a PDF format. Now what?? Quite by accident, I found that the PDF viewer I use was also capable of exporting to image files. (PDF-XChange Viewer - Recommended if you are tired of Adobe's constant upgrades, huge downloads and poor performance.) The dial was exported to a 1200 dots/inch TIFF file and sent off to the Sam's Club photo website. I ordered an 8X10 for $1.46 and an 11X14 for $2.87 and picked them up the next day at the local store.
    The 8X10 looked fantastic! It was printed on Fuji photo paper with a nice matte surface. The image was sharp with no jagged edges and great black & white contrast. The white background was maybe a little too white, but this could be corrected with photo editing software and reprinted. The outer time track was exactly 8 inches which unfortunately was clipped off at the edges of the 8X10 print. I had anticipated this might happen; that is why I also ordered the same size image printed on 11X14.
    Sam's must use a different machine for 11X14 printing. There was no manufacturer's information on the back of the paper and it was clearly lower quality. It had a flat finish instead of matte and a yellowish color. The lines were obviously jagged, especially on the curves and signature and the scaling was off. The outer time track measured 8.25 inches. Argh...foiled again.
    Reducing the image slightly so it fit on an 8X10 print was an option, but I thought it would leave too big of a gap between the time track and bezel. Before giving up on the photo idea, I decided to try a different printing service; one at the other end of the scale. I put the image on a thumb drive and took the Sam's photos to The Camera Gallery in Tulsa. I showed them the 8X10 and 11X14 photos and asked if they could provide the quality of the 8X10 on an 11X14 print. "Sure, no problem. Come back tomorrow," said the young man at the counter. Success!!! The dial was printed on Kodak Royal paper with a beautiful matte finish and the image was very sharp. The outer time track was about 1/16" over size, but this still fits nicely in the bezel and is not a problem for the hands since they will be made to fit. The 11X14 print cost $9 instead of $2.87, but this is still very reasonable for a 8" dial. I guess in this case, you get what you pay for.
     
  3. Tinker Dwight

    Tinker Dwight Registered User

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    Re: Dial

    You always need to understand the difference between
    pixelated and vector drawn.
    There are shops that make negatives for PC boards that
    can handle vector drawing formats.
    These can then be transferred to B/W photo paper.
    The other option would be to have them put it on 35mm
    film. You could then use an enlarger to set any size
    you desired.
    Many ways to skin this cat.
    Tinker Dwight
     
  4. kdf

    kdf Registered User

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    Re: Dial

    Nice work. I have made a few dials in Corel Draw, and printed it on different papers. Best results for me was on ordinary 300 grams paper, and over the print I glued transparent self adhesive matte foil for protection. This dial was big so it was printed on A3 laser printer.
     
  5. Allan Wolff

    Allan Wolff Moderator
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    Motion Works

    I am always amazed at how many parts are needed for the motion works, and the works for this clock has a few more than usual. The typical motion works serves 3 functions. It turns the minute hand clockwise once per hour, turns the hour hand clockwise once in 12 hours, and provides a clutch mechanism to allow the time to be set. Most clocks use gear ratios that result in one of the arbors turning clockwise once per hour so the minute hand can be driven directly by the arbor. This clock does not have an arbor that rotates once per hour. The closest we have is the second arbor that rotates clockwise once in 3 hours (1/3 RPH.) I will explain the overall solution and then show how the pieces fit layer by layer.


    Typical motion works have a 12:1 gear ratio that drives the hour hand from the minute hand. For this clock we will split the ratio into 2 parts. The first is a 1:3 ratio that multiplies the 1/3 RPH second arbor to get 1 RPH to drive the minute hand. The second is a 4:1 ratio that divides the 1/3 RPH second arbor by 4 to get 1/12 RPH, or one revolution in 12 hours to drive the hour hand. It is easy to derive gear sets that provide 1:3 and 4:1 ratios. However, the center distances of the 1:3 set must equal the center distance of the 4:1 set of gears. If they are not equal, the gears will not mesh properly. By plugging various combinations into a spreadsheet, I came up with these gear combinations.
    A 60-tooth wheel (pitch radius=15 mm) drives a 20-tooth wheel (pitch radius=5 mm) to provide a ratio of 1:3 and a 20 mm center distance.
    A 16-tooth wheel (pitch radius=4 mm) drives a 64-tooth wheel (pitch radius=16 mm) to provide a ratio of 4:1 with the same 20 mm center distance.


    Here is a build up of the assembly. The second arbor protrudes through the front plate. A metal disk is made with 2 shoulders that attaches to the arbor with a taper pin. The metal disk serves as half of the clutch.
    DSC_6088.jpg


    A 60-tooth wheel slips over the larger shoulder and is held against the metal disk by a brass spring. The spring provides pressure on the wheel so it rotates with the second arbor during normal operation but can slip and allow the time to be set. This photo also shows the posts that support the hands and intermediate wheels. The hand post is threaded into the front plate. The intermediate post is fastened to the plate with a screw so its postion can be adjusted slightly to obtain the best mesh of the gear teeth. Slop in the gears will show up as unwanted hand movement, so we want the mesh to be as close as possible while not binding.
    DSC_6102.jpg


    The clutch wheel drives the 60-tooth intermediate wheel in a counterclockwise direction. The intermediate wheels are made in 2 pieces and pressed together to form a single unit. A taper pin and washer will hold the intermediate wheels in place. The minute hand arbor is one piece, with a 20-tooth wheel on one end and a square on the other where the minute hand is attached.
    DSC_2456.jpg DSC_6105.jpg


    The hour hand arbor and 64-tooth wheel slip over the minute hand arbor and is driven by the 16-tooth intermediate wheel. The hour hand arbor is stepped so a collet carrying the hour hand will slip over the smaller diameter until it bottoms out on the larger diameter, setting the height of the hand above the dial.
    DSC_6097.jpg


    A drawing is attached as a PDF file so you can zoom in on the various components without losing resolution. The drawing shows several sub-assemblies that were used to determine how the parts would fit together.
    View attachment Motion Works.pdf


    Since there is no strike mechanism requiring a snail or trip pins, the hands can be turned in either direction to set the time.
     
  6. Allan Wolff

    Allan Wolff Moderator
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    Hands and Dial Assembly

    The hands were made using the same process as the Pinwheel clock described here, so there is no need to cover it again. The design was developed by importing a photo of the dial and hands of an 1845 Laterndluhr into CAD and "tracing" them. Once drawn, the photo was removed and the hands were touched up and scaled to fit my dial. The hour and second hand are rivetted to their collets which are a friction fit on their associated arbor.
    DSC_6865.jpg


    The minute hand is long, very thin and easily bent so I made a knurled knob that serves as the minute hand washer. The time will be set by turning this knob rather than pushing the minute hand around the dial. Hopefully this will also save the dial from becoming dirty and scratched. The knob and minute hand are held in place with a finely-threaded recessed nut and this entire assembly is retained on the hand post with a brass washer and taper pin.
    DSC_6862.jpg DSC_6860.jpg




    I taped the dial to a window so I could see the alignment marks through the paper. I then placed the pan on the dial and drew around the holes and outer rim for reference lines when the dial is actually attached. The dial is glued to the pan with Scotch Photo Mount spray adhesive. This adhesive is supposed to be permanent and safe for photo paper. After the adhesive is dry, the dial is trimmed with an Exacto knife and the bezel is attached to the pan. A grommet was turned from a piece of brass for the winding hole. This adds a little extra detail and hopefully will protect the dial from the crank. Here is the dial, bezel and hands.
    DSC_8465.jpg


    All parts of the movement are now complete and it is mounted to a board in my office closet and has been running for about 2 weeks. The movement has gone through several adjustments that I will describe in my next post. I have made no attempt to regulate it yet; I'm just thrilled to have it running reliably.
     
  7. John MacArthur

    John MacArthur Registered User
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    Re: Hands and Dial Assembly

    That looks terrific, Allan. Has the movement been running in test mode, while you made the dial? I'm very curious about the escapement action and reliability.

    John MacArthur
     
  8. Allan Wolff

    Allan Wolff Moderator
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    Re: Hands and Dial Assembly

    Hi John,
    The movement has been running non-stop for 2 weeks now, but it did not start out that way.
    I had it running in the shop bolted to the leg of a metal shelf assembly. The weight required to keep it running was 15.3 lbs. The entire movement was disassembled for final finishing. Everything was cleaned thoroughly and finished with either 600-grit sandpaper or polished for appearance such as the bob. After putting it all back together, I mounted the movement to a temporary board in the main house because the environment is cleaner and I can keep a better eye on its operation. After putting the pendulum in motion it began to settle down to its normal swing (which takes several hours). At some point, I heard the escapement rattle off a burst of 3 or 4 clicks and then go back to its normal 1-tick per second. About 30 seconds later, it did it again. This continued until I stopped the pendulum to see what was going on. Things move pretty quickly during the burst, but it appeared that he escape tooth was hitting the impulse pallet hard enough to bounce the pallet up so the tooth missed the locking pallet. This continued until the pendulum swung a little further from center and there was enough tension in the suspension spring to overcome the bounce. I assumed that the final cleaning must have removed some rough edges on the wheels, perhaps the escape wheel had some burrs that were adding friction to the time train. It just looked like there was too much power on the escape wheel. To test this theory, I removed about 2 lbs. of lead from the weight. This eliminated the chatter, but now the pendulum was stopping, as if there was not enough power in the impulse. The only option for increasing impulse power on a Strasser escapement is with stiffer springs on the impulse side of the suspension. I added an additional piece of spring steel to one of the impulse springs. This created a new problem where the escape wheel tooth would intermittently not be able to fully push up the impulse pallet to reach the lock pallet. The clock ran, but the ticking sounded terrible. Even adding back the lead I had removed earlier did not provide enough power to fix the occasional week impulse. While watching it run, I thought I saw a slight movement between the crutch fork and the pin that connects to the impulse side of the suspension spring. Perhaps this was enough to allow the chatter to occur, or was wasting power so there was not enough left to keep the pendulum going. I squeezed the fork together in a small vise so there was virtually no clearance left. While I had it apart, I removed the extra impulse spring that was added because it did not seem to help anything. Everything was reassembled and the weight was set to 13.5 lbs. The clock ran for a while, but as the pendulum amplitude decreased, I noticed the beat was off slightly, so I lifted the movement slightly on one side by slipping a business card under the mounting board. After these adjustments, the escapement no longer chattered while it still had a very crisp, strong impulse and lock. After running a few days, I reduced the weight further to 12.5 lbs. The clock has been running strong for 2 weeks now at this weight. I will reduce the weight further when I shorten the weight tube. Enough lead has been removed that there is now 2.75" of empty space in the tube.
    This frustrating exercise taught me a few things, about the Strasser escapement. It is very sensitive to being out of beat. Tilting the movement by the thickness of a business card makes a very noticeable difference in the beat. The escapement is also sensitive to the amount of power it receives. Too much can make it bounce and run away, while too little may prevent it from impulsing correctly. I may experiment with lowering the weight further, but it sure is running well at 12.5 lbs.
    Allan
     
  9. John MacArthur

    John MacArthur Registered User
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    Re: Hands and Dial Assembly

    Hi Allan -- Thanks for the thoughtful and thorough reply. It seems as if you have solved the initial problems. I (going on intuition alone) would have suspected at least the beat and "bounce" problems. I have heard over the years that this escapement needs to be perfectly set up, but operates very well when it is. It sounds like you are over the hump. My #4 regulator is roughly half done, and I'll post some pics in its own thread when I get closer.

    John MacArthur
     
  10. Allan Wolff

    Allan Wolff Moderator
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    Adjustments

    The movement is still running without a hitch while we work on the case, but I wanted to go over a few modifications that were made. Nothing major, just a case of one thing leads to another.
    Most of these changes were related to the weight.


    The initial design assumed the weight cord would be anchored to the front plate. This caused 2 concerns. The cord moves to the back of the winding drum as it is wound, causing a greater force to pull the cord over on top of itself. Also, the weight pulley would be skewed quite a bit near the top of its wind; more of an aesthetics issue than anything. To correct these issues, a stud was made that fastens to the front plate and anchored the cord at the center of the winding drum.
    DSC_0172.jpg


    A new problem quickly arises to replace the previous. Moving the anchor point of the cord back also moves the weight back and now it hits the bob. Since the bob is already very close to the back of the case, the only solution is to move the movement towards the front. New mounting brackets were made 3/4" longer. The crutch also needed to be lengthened by 3/4".


    Bringing the movement forward also required the case design to be modified. At least this was still in the design phase and nothing had to be rebuilt.




    I originally planned to use 85 lb fishing line for cord. I even found some nice braided brown line. With the line installed and holding the weight, it just looked so thin that I did not trust it to hold the 15 lb weight, even though it was well under its rated load. It twanged like a guitar string. I decided to go with a heavier cord and found some 200 lb kevlar spear-fishing cord. It looks much better with the heavier cord, but now I can only get 18.5 turns on the winding drum. 21 turns are needed to run for 32 days. This problem was solved by modifying the winding drum to make it 1/8" longer. The 1/8" front shoulder was turned off and a brass plate was silver soldered on the arbor to form a new shoulder. Of course the hole for the cord needed to be redrilled and the old hole filled in. The winding drum was already pretty close to the front plate and I was only able to pick up 1/16" in that direction. the other 1/16" was gained by moving the great wheel back 1/16". The modified drum with the new cord is shown in the photo above.


    Apparently, it is against the rules to fix a problem without creating a new one.
    Moving the great wheel towards the back plate caused the slip washer screw to interfere with the second wheel.
    DSC_5756.jpg


    This issue was easily fixed by recessing the screw into the washer. All issues finally appear to be solved. I'm not changing anything else unless it breaks.
     
  11. John MacArthur

    John MacArthur Registered User
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    Re: Adjustments

    It looks great, Allan. I'm glad to hear that it is running well. In any project, it seems that unexpected problems of greater or lesser degree crop up at the end. It's good that there was nothing insurmountable.

    John MacArthur
     
  12. jhe.1973

    jhe.1973 Registered User
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    Re: Adjustments

    Hi Allan,

    Thank you so much for showcasing your terrific workmanship here!

    Your clock looks beautiful and inspiring.

    Any chance you would consider taking it to a National Craft Exhibition/Competition? It sure is worthy of honoring the NAWCC that way!
     
  13. Allan Wolff

    Allan Wolff Moderator
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    Re: Adjustments

    Thanks to everyone for the kind words of encouragement.

    I have thought of entering a clock in the Crafts Competition. Then I start calculating the cost of travel, lodging, etc. for 3-4 days and it gets pretty expensive. I'll make it there some day.
     
  14. Allan Wolff

    Allan Wolff Moderator
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    The Clock is DONE

    I have not posted for several months because the case took longer than I thought, but now it is finally DONE!!!




    I let my friend take the lead on the case since he is a woodworker by trade and has a much better woodworking shop than me. I drew up a set of plans for the case so it fit the key dimensions of the movement such as the bezel diameter, pendulum length and so on. The case is approximately 59 inches tall and 14 inches at the widest point. He was amused when I dimensioned the drawing the same way as the movement; to the thousandth of an inch. We kept having to convert to fractions so I adjusted the units in the CAD drawing to 1/32 of an inch. This was still more precision than we could cut with a table saw, but at least the marks were on the tape measure! I have attached a PDF file with the case drawings for anyone brave enough to build one. I would like to caution that many of the parts are very close to the dimensions shown but many also need to be cut to fit, so do not expect to cut out all of the pieces and have everything fit perfectly. We may have also improvised on occasion and these modifications were not captured on the drawings. We both agree that this was a very challenging case to build.




    The case is made from 2 different woods. Black limba was used for the backboard and stringing and jatoba was used for everything else. The black limba is actually yellow with black grain. These woods were recommended by my friend because he had plenty of it and it was nice to work with. If we were to build another case, I would use maple for the stringing for better contrast. Our cases are made of identical material, but we decided to part ways on the finish. My friend wanted to highlight the grain pattern in the limba backboard and keep more of the natural color of the wood. He finished his with boiled linseed oil. This darkened the wood slightly and really brought out the grain patterns in the wood. Here is a photo of his case after 2 coats of linseed oil.
    Toms Case.JPG


    I wanted to go with a darker backboard to make the bob, weight and other brass parts stand out. The backboard was first dyed with a mixture of VanDyke Brown and Brown Mahogany Mohawk Ultra Penetrating Stain (but it is a dye.) This turned the backboard almost black, so I rubbed it out with mineral spirits and steel wool and now it is similar in color to very dark walnut. The entire case and backboard was then finished with Watco medium walnut Danish Oil. Paste wax was applied to both cases to protect the finish and give them a little luster. Here is my case mounted on the wall and ticking away.
    DSC_0001.JPG

    I may report back later if I ever run time tests on the clock. Right now it stays within 10 to 20 seconds per monthly winding.


    This has been a long project; much longer than I anticipated. But I learned a lot and made a great friend in the process. Thanks to everyone on this message board who provided ideas, comments and encouragement. You guys are great!
    Allan
     

    Attached Files:

  15. caddwg

    caddwg Registered User

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    Re: The Clock is DONE

    Allan:
    Beautiful job! I really can't say enough in congratulating you on a simply magnificent job that you'll take pride in for many years to come. My regulator clock is currently on hold for now, while I take a short break and work on some other machining projects; converting mill to CNC and making a zero dial for my lathe + misc. others. Again: Congratulations Warmest Regards: Larry
     
  16. ccwk

    ccwk Registered User
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    Re: The Clock is DONE

    Well Done Allan, definitely worth all the effort and thankyou so much for sharing your journey with us all.
    Cheers Conwae

     
  17. burt

    burt Registered User
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    Re: Dial

    Outstanding clock and through "presentation" of its inception and build. An excellent "learning opportunity" for those of us who are not necessarily clock makers but appreciate the craftsmanship and skill required to complete such a project. Thank you very much for sharing.
     
  18. gmeyer4

    gmeyer4 Registered User
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    Re: Dial

    Amazing Allen, Top notch work!
     
  19. Steven Thornberry

    Steven Thornberry User Administrator
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    Re: Dial

    Allan, the only flaw I see in the completed clock (and I suppose it could be considered a minor one) is that it is not hanging on my wall!Nutjob
     
  20. Hessel Oosten

    Hessel Oosten Registered User

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    #120 Hessel Oosten, Feb 1, 2018
    Last edited: Feb 1, 2018
    Dear Mr. Wolff, dear Allan, others here,

    Please, could I ask you a (probably a lot more..) question, about your marvellous PPU shown here ?

    But first, let me introduce myself shortly.
    My name is already shown in the message menu. I'm 65 and retired oncologist.
    Did for a long time in my life, Boeing home-cockpit-building (1:1) in a spare bedroom, but since 2 years I'm completely hooked to clock-building-attemps.... Closed the cockpit-door...:).
    So, I'm especially interested in the technique (not, the collecting).

    Joined a local clockbuilding-club (www.klokkenbouwen.nl) and made my first small clock. See attached photo. The club offers a great building course (both theory and practice).

    Although I have great doubt about the magnitude of my technical skills at this moment, I did read your Strasser thread here several times; collected Strasser information everywhere on the internet etc.
    Yesterday I made a visit to another Dutchman, who did build a Strasser too (the only one here, as far as I know) and even better..., "she" already runs (on my tablet I registered ("ClockTuner-app") 3600,0.
    He offered very friendly help (which will be necessary), if I should decide to start with such a big project. Well, a lot more could be written, but may be not at this moment.

    My question is about the "Graham deadbeat wheel" in the clock:
    Yours is 1.198" = 30.429 mm with an offset of 0.094" = 2.387 mm, which is a 8,92 degrees offset and a 7,5 tooth-span. Intended pendulum swing 2 degrees.
    Your fly-cutter has 24 degrees side angle.

    I bought the nice book of Mr. Peter Heiman: Regulator Clock Construction.
    His Graham wheel (but NOT a Strasser escapement !) is 1.875 = 47.625 mm with an offset of 0.098" = 2.489 mm which is a 5.97 degrees offset and a 8.5 tooth-span. Intended pendulum swing :???: degrees.
    His fly-cutter has a 26 degrees side angle.

    * I presume the difference in offsets's above have to do with the difference in teeth spanned and so indirect with the degrees of pendulum swing.
    The difference (8.92 v.s. 5.97) is remarkably great. My knowledge at this moment is not sufficient to calculate it myself, so please can you advice how to do that ?
    The dcr_deadbeat_calc.xls spreadsheet did not help me with this (I think).
    I can construct a Graham wheel and anchor in CAD, but is it necessary to do that for every trial ?

    * I presume it's right that the "oblique position of the tooth" is in fact completely determined by the magnitude offset ?

    * Has the difference in cutter angles (24 v.s. 26 degrees) a relationship to the values above or is it based on something else ?

    * Your escape wheel is much smaller than the other, both clocks are 1 sec pendulum clocks.
    What are the considerations for smaller or bigger diameters ? (Aside from the fact that bigger is sometimes some more easy) ?

    I hope you have time for an answer. In the mean time a continue my drawings.
    Have attached too an already completed 3D-part of your drawings/clock.

    Greetings from Holland,

    Hessel Oosten

    P1260952kl.jpg Screenshot Strasser 1.png Screenshot Strasser 2.png P1270130.JPG
     
  21. Allan Wolff

    Allan Wolff Moderator
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    Welcome Hessel,
    First let me say what a great job you did on your first clock. We would love to see more pictures and details so feel free to start a new thread for your clock!

    I'll see if I can answer your questions.
    Regarding the offset and angle of the escape wheel cutter. The good news is these dimensions are not critical in the escape wheel design. The offset determines the tooth front slope angle, or how much the tooth leans forward. You want only the tip of the tooth to contact the pallet, so a few degrees is all you need. More front slope angle is fine as along as you do not get too carried away and lean the teeth over so far that they are practically laying down. The angle of the escape wheel cutter determines the tooth back slope angle. This provides clearance so the pallet does not hit the back of the tooth after it passes. More angle will give you more clearance but thinner teeth. You will want to have enough material in the tooth to give it strength so is does not bend from the impact of hitting the pallet. Again, the angle is not critical so you can lay out the wheel in CAD so it looks right and determine the angle from your drawing.

    What are the considerations for smaller or bigger escape wheel diameters ?
    I used the same spreadsheet you refer to for the Graham escape wheel and then made the pallet anchor to fit the wheel. You can certainly make the escape wheel smaller or bigger, just adjust the length of the pallet anchor arms. As described back in post #8 the length of the arms was made to span a certain number of teeth. You can also span more or fewer teeth, adjust the arms accordingly. The pendulum swing is primarily determined by the settings of the lift and lock pallets. These are adjustable so the escapement can be fine tuned for best operation. A tiny movement will make a big difference in pendulum swing so this can be a tedious process to adjust.

    You CAD drawings look excellent and you should have no problem drawing these parts and then rotating the escape wheel and moving the pallets to make sure everything fits correctly.
    Allan
     
  22. Phil Burman

    Phil Burman Registered User

    Mar 8, 2014
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    Just a couple of points regarding the Strasser escapement I have built. Because of the pallet design they do not penetrate very far into the tooth “valleys” so the teeth do not have to be so tall. This improves tooth strength (I had problems with bending teeth during manufacture of the escape wheel), reduces the mass/inertia of the escape and allows for manufacture with a standard endmill. The picture shows the profile of my second attempt at the escape wheel.

    The second point is very important and is much more critical on a Strasser escapement than it is on a standard graham. On a Strasser the locking length should typically be only of the order of 0.15mm, smaller is better. The larger this value is the lower the impulse on the pallet. In addition it seems that it is more important than normal that the concentrically of the escape wheel teeth is as “perfectly” concentric as possible, otherwise the escapement may stop on the “high” tooth or not receive any impulse on the “low” tooth.

    As Allan points out adjustment of the pallets can be a tedious process to adjust. I developed a procedure of several months. It is important that you have windows in the front plate so that you can observe the action of the escape wheel/pallets and that the pallet assembly is capable of being removed without disassembly of the movement in order to allow for adjustment of the pallets.

    Phil escape wheel rev 2.JPG
     
  23. Hessel Oosten

    Hessel Oosten Registered User

    Apr 26, 2017
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    #123 Hessel Oosten, Feb 2, 2018
    Last edited: Feb 2, 2018
    Gentleman, Allan, Phil,

    Thanks you very much for these -usefull- comments ! Greatly appreciated.
    Developing/awakening insight here.

    Will continue reading and drawing first.
    Found "the Kummer book".

    When the cutters go into the brass.., I will continue in a separate thread.

    Allan:
    Where to ask further building-questions about -your- Strasser ?
    Here or in a new, separate "Strasser-like" thread ?

    Hessel
     
  24. sharukh

    sharukh Registered User
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    Oct 10, 2011
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    And what book would that be ?

    Sharukh
     
  25. Hessel Oosten

    Hessel Oosten Registered User

    Apr 26, 2017
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  26. sharukh

    sharukh Registered User
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    Oct 10, 2011
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