Galileo Wooden Escapement Mechanism

instructables

Galileo Wooden Escapement Mechanism

by andrea biffi

Teaching physics to teenagers is for sure one of thebest jobs I've ever done. If you are touched by aproject there are many chances that students will beexcited too. I think this Instructable gives you a goodexample of that.

Assembling a kit composed by pulleys and gears,and based on a so essential and common in our lifephysics law, that is harmonic motion, could be anaffective experience for both teenagers and adults.

This will also give you a perfect tool to let studentsplay and experiment with gears ratio, relationsbetween forces and movement, and understand howa mechanical clock can be set changing pendulumlength.

You can find the Italian version of this tutorial onWeMake.cc fablab website here(http://wiki.wemake.cc/Orologio_di_Galileo_(vers.1)).

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Step 1: Galileo Galilei Design

The project takes inspiration from a video by Ken Kuowhich explain how an Escapement design by Galileoworks:

//www.youtube.com/embed/v2sQF0UFVVE

You will see that basic parts of my design maintainanimation's original shape (thanks, Ken Kuo!), andare quite similar to Galileo drawings.

The escapement is a mechanism which preventsmechanical clocks to discharge in a big hurry, youcan find very different types of escapements, but theyall are based on the same principle. In a few wordsthey take advantage of inertia of a pendulum andpotential energy of a weight, so that at eachoscillation a small portion of that energy can betransferred to the pendulum to help him keeping

same amplitude forever, and another portion goes togears, to move hands.

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Step 2: Simpler Design

I tried to make the simpler design I could, so that alsochildren can assemble it. On the picture right side yousee my first version, and on the left is the secondversion, which makes a single charge last more thanten minutes. If you search for Galileo escapement onthe web you can find many different designs, amongthem also a nice Lego version.

You probably can make gears by hand with a verticaldrill and a jigsaw, if you have good patience and youalready practiced quite a lot. I decided that lasercut isa good choice to obtain nice parts in short time,although it's not so praiseworthy in comparison withhandwork.

Step 3: Materials

Materials needed are very common, cheap, and easyto buy. You need some 8mm and 4mm thick plywood,a piece of 8mm and a little piece of 10mm smoothwooden bar, a pair of little brass or aluminium pipes,one bearing (with code 6000), a 6mm threaded rodand some metalware. I also used a sheet of thin

plexiglas, and I cut two circles of plexiglas about 3-8mm thick, but they are not essential. See next stepsfor more details about materials, dimensions, andsizes.

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Step 4: Metalware BOM

Other than wooden rods and plywood and plexiglasplates, keep ready these metalware parts:

one 6000 ZZ or 60002RS (10x26x8mm) bearing

one M6x30mm stainless steel coupling nut

two small pieces of aluminium or better brass pipe 10mm (OD) x 8mm (ID)

a 25mm DIN-933 M6 hex cap bolt

a 1m stainless steel M6 Threaded Rod

two 6x25mm M6 penny repair stainless steel washer

three M6 nuts (one hex nut, one cap nut, and one wing nut)

a short screw for wood

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Step 5: Tools

Actually you don't need many tools to assemble this mechanism. You should have an hammer, some finesandpaper, vinyl glue, a little bit of cyanoacrylic glue, and a wooden block with two holes, 8mm and 10mmdiameters, but this last one is not essential. You need also a fine saw to cut wood rods.

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Step 6: Lasercut Materials and Procedure

You can cut most parts from a 58 x 18 cm plywoodboard, 8 mm thick. Then you need a smaller 4 mmthick plywood board and a small plate of plexiglas(about 50 x 100 mm), which can be from 3 to 8 mmthick. Find at least a small piece of good quality 4 mmplywood for the teethed washer. Use a 0.5 or 0.6 mmplexiglas plate to obtain thin washers.

Open the attached file which contains an .dxf

drawing, upload it in the laser cutting machine, andchoose the parts to cut referring to the notes on thered layer.

For detailed lasercut procedure please follow someother my tutorial, like the complete stamps instructable.

https://www.instructables.com/ORIG/FC7/MSWG/JBMJY95J/FC7MSWGJBMJY95J.zip…Download

Step 7: Diagrams and Blueprints

Follow blueprints in attached PDF to assemble parts together, you will see top and front views there, with numbersand letters defining pieces. Look top view to determine gears and spacers order. Besides I drew a nice 3D modelof the Escapement mechanism, to better explain the steps.

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https://www.instructables.com/ORIG/F36/DW8C/JBMJUHNO/F36DW8CJBMJUHNO.pdf…Download

Step 8: How to Use the Straightener

I call it straightener, but it's nothing more than an MDF or wooden block, with perfectly perpendicular sides. If youinsert the 8mm or 10mm pivot in the matching hole, while hammering it into the gears or the plywood base, you willbe sure to keep it straight.

This is quite essential in this project, but you also can verify the perpendicularity with a small set square.

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Step 9: Rear Panel and Pivots

First of all use the sandpaper to smooth every pieceof wood, both gears (pay attention to every teeth),plates, and also extremities of wood rods you alreadycut at the precise dimension. Sanding is most usefulespecially where parts touch one each other.

With the straightener and the hammer insert all five

long 8mm pivots into their holes, with a small amountof vinyl glue. Then glue in place the four 8mmspacers as in the image. Check the pivots arevertical, with a set square and also placing in positionthe top cover, but don't hammer it.

Step 10: The Ratchet

The ratchet is needed to charge the mechanismeasily, that is to raise the weight with no need todisengage the gears. The saw-toothed part #20should be a made by a good quality plywood, since isexposed to some friction with the plastic fins we'll seeafter. The circular transparent washer is made by thinplexiglas, and should be glued with cyanoacrylate.

Other pieces may be glued with vinyl glue perfectlyaligned one each other. To do that I suggest to useone of the aluminium pipes, place parts on it for firstminute while the glue are drying, then take them off,and clean the pipe.

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Step 11: The Pendulum Hook

The pendulum is made by a 6mm threaded rodbecause it's easy to take on and off, and also lets youhang on something as weight at a certain distancewith a nut, and easily change it.

The nut which keeps the rod is crowned by three

plywood layers, labeled from 17 to 19. Look at theimage and pay attention to glue everything in the rightorder. On the rear side, in the piece #19 you willinsert the head of the bolt which will keep the hookclasped to another part (the "finger" #4).

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Step 12: The Main Gear

You should also have 12 rivets, to be cut at the rightlength, that is about 8mm of stem. With assist of anhammer beat them in the tiny holes. Pay attentionthey don't lean or stick out from behind.

Then glue 8mm spacer and small gear on the rear

side of the main gear, insert the aluminium pipe in theholes, and let it protruding 1mm on the rear. Alwaysverify that wood rods rotate freely inside the pipes.Also verify that gears, especially the big ones, don'tswing at all in the rotation around the pivots.

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Step 13: The Fingers

In the detail from the bottom side you see there are two reference cuts on parts 4 and 5, and they have to stayaligned so to glue parts in that position. Between those two parts remember to glue spacer 13. After the vinyl glueis dry, push the bearing in the bigger hole, placing the pieces on a planar hard surface, making sure the bearingwill be perfectly flat. Then you can push the assembled piece on the 10mm pivot marked as "f".

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Step 14: The Multiplier Gear

This gear has the function to multiply the time neededto unroll completely the weight cord, even if you needa bigger weight to move the main gear. The cord hasto be rolled around the racket, and it has to be a thintwine since it must not roll on itself.

Push the aluminium pipe in the gear hole, leavingonly 1mm of tube outside the gear's bottom edge.You can also glue the tube to the gear but it'snecessary, the only important fact is that this gears

like the others, must not swing while it turns.

Place the little plexiglas fins in the grooves, as in thepicture, then glue the extremity which is further fromthe center, with a drop of cyanoacrylic glue in thegroove. leave the glue drying completely beforesliding the racket on the tube. You see that over thebigger plexiglas washer ther is a free smaller spacer,needed to reduce frictions.

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Step 15: The Arm and Counterweight

This long arm must rotate quite loosely around theshorter 8mm pivot, and as you can see in thepictures, you should place two thin washers betweenfixed 8mm spacers of the base and the arm. The lastspacer (#15) should have a tight hole to keep the armin place.

The metal washer at the arm extremity acts as

counterweight, anyway it is not always needed. Youwill understand that you need it if the gearssometimes speed up and make two or three teeth at atime. Anyway if you keep a light counterweight or ifyou don't use it at all, the clock weight can be a littlesmaller.

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Step 16: Slide Pads

Now, to reduce frictions, you must glue a three little Plexiglas pieces where parts slides one over each other. Thisis between arm and one finger, on the other finger extremity, and on the extremity of the arm where it touch therivets gear, like in the pictures. Glue pieces with cyanoacrylic glue, or other strong glue.

you can do that also after closing the cover, but it's simpler that you take note of position, and glue them now.

Step 17: The Cover

Before hammering the cover in place, you must pushthe circular windows in the holes. Take off anyprotection from the plexiglas before inserting thediscs, and look if you can determine the face a littlesmaller than the other. This is usually because thelaser ray is not exactly cylindrical, but a little conical,

and so the pieces. Place smaller face down, andinsert discs in the holes. Then, cover them with a rag,use the wooden block and hammer them in position,until the upper face is at same level of wood surface..

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Step 18: Tollerances

Before assembling the pieces together and closingthe cover, you should well understand where to placeevery thin spacer, as you'll never be able to open thecover unless you'll cut the rods.

Gears have to move very softly, but they must nothave play more than half or one millimeter. Washers

are not essential but they help to reduce frictions.Insert one #18 washer at every extremity of the gearspivots, as in the images. In the animation you onlysee the top ones, but consider you need also twomore spacers below the gears.

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Step 19: Hang It

Now that assembling is mainly completed, it's time tothink how to hang the pendulum mechanism, andwhere. It's easy to use holes to screw a board on therear side, as in the photo, so that you can place itunder some books in your library. Another option is touse the two holes to fix it on the wall.

Once the mechanism is vertical, you can screw in thethreaded bar which acts as pendulum. At the lowerextremity screw also two bolts (one should be abutterfly bolt), and a washer between them. You'llneed them to attach a mass to the pendulum.

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Step 20: Give It Power

Wrap the ratchet with a thin rope, in clockwisedirection, and knot a metal washer on the rightextremity.

Then you'll need a nice weight on the other extremityof the rope. Since Mechanism is quite flat the weightcannot be too big. I suggest a metal pipe, made from

aluminium or brass, maybe one inch diameter and20cm long. You can close bottom face and put somegravel inside. Actually you should not have too muchweight, it depends on the construction quality of thepieces and assembling. Try with an empty pipe, thenadd more weight if you're not able to make it working.

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Step 21: Setup and Details

Setup is not simple, but follow instructions and you'llbe able to make it working like a Swiss clock!Furthermore, if you're a lucky person, you couldalready have it working without setup at all.

Now you can charge the ratchet, and push thependulum. The fingers should touch alternatively thearm and one rivet, between one oscillation and theother. If this is not happening, you must loosen thebolt which keeps the pendulum bar, and vary theangle.

The two elements which act on the rivets wheel,should touch gently it in one position or the other (onteeth or rivet), when the pendulum is steady andvertical.

Try changing angle with very small adjustments, thenwhen mechanism works for a while and you'resatisfied tighten the bolt quite hardly.

Step 22: Show It!

Time to show the Galileo escapement mechanism to your friends! I hope you'll share and make this project, whichis so much enlightening for physics phenomenons and mechanics operations!

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Amayzing mechanism with an extra amayzing tutorial. really thanks that you made it so easy for us.

You're welcome!

I'm glad you like it!

An impressive construction and a very well written instructable.

Thanks!!

Very well done and very interesting! Thanks for sharing.

Great instructable, I did not know about this escapement mechanism. I've tried to download thevideo but it does not work...

You're right... I removed it for the moment, I'll try to make a better and working video. Thanks!

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