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Carpenter Automaton

Apparently there are some cities where they hold a contest to see what you can build using just one 8 foot 2x4.

On Youtube, one gentleman, Ben Brandt, made a hammering carpenter automaton.

I decided to build one of these myself, because they look pretty cool.

Google Sketchup
Using the video, I designed my own version of the carpenter automaton.



I was able to design everything ok, except the 2 cams that move the carpenter's head back and forth.  I may have to revise my design after I actually build the model.

Gear Design

I guessed the centerline distance between the two shafts was about 2.25 inches. This means the pitch diameters of the 2 gears must add up to 2.25 inches.  I used 9 teeth for the small gear and 18 teeth for the large gear.  I chose a pressure angle of 20 or 25 degrees, typical for wood gears.

You can use any of several online gear calculators to either create a paper pattern to glue onto the blank, or create a DXF file to load into Sketchup........and then print the paper pattern from sketchup.

One of these programs is GearDXF from Forest Moon Productions.

I used Elmer's white glue to glue the patterns onto the wood blanks. Then I scroll sawed my 2 gears from 3/8" thin common pine.

Cam Design

Once I drew up a model in Sketchup, I could determine the OD's of the hammer and nail cams.  By rotating the hammer arm in Sketchup, I could measure and determine how far the hammer dowel and nail had to move......for the 3 increments of driving the nail.

Base Design and Cams

I didn't take any photos of making the base stand, because it is basic woodworking. I printed out paper copies of the 2 primary cams I designed, white glued them to pine, and scroll sawed them out.

I used hot melt glue to test the design, because I can easily remove it if I need to.

Arm and Hammer Actuation Work the 1st Time

I made a video of trying out the actuation.  A miracle happened, it worked the first time as I designed it!!

 <embed width="440" height="420" type="application/x-shockwave-flash" src="http://v9.tinypic.com/player.swf?file=54xeom&s=9">

 

<embed width="440" height="420" type="application/x-shockwave-flash" src="http://v9.tinypic.com/player.swf?file=xf6rlv&s=9">

 The bad news is...........it worked as I designed it!  I designed it so the hammer and nail rise together after the 3rd strike of the hammer.  In the original Youtube design by the other gentleman, he has the hammer rising quickly........then the nail rises slowly back up again.

This led me to trying different cam designs on a trial & error basis until I got the exact motion I wanted.  Too bad Sketchup won't allow you to easily animate a design to show the motion.....which would avoid all the trial & error in wood. Fortunately, the hot melt glue can easily be pried off with a chisel to try different designs.

Below are the cam iterations I went through until I arrived at the design I wanted.




I also increased the diameter of the hammer cam so the hammer would rise to a higher height after each strike of the nail. I need to move the 2 drive-shafts down a quarter to a half-inch to give a little more clearance in the whole design.


Head Turning Cam Design

These 2 cams are basically cams with a point and an angle on the point as shown below.


 

 

 

The 2 green cams toggle the horizontal piece on the 1/4" vertical head shaft back and forth.  The man looks away when not nailing, but does turn and watch the nailing process.

 Carved Head

I used the Dremel with the green tool to carve out the head, including the safety glasses.

 Completed Assembly

 

 

 

 

I made a YouTube video showing my carpenter automaton in action............





Closing Thoughts

This was a fun project to build, and then see the fun people have operating it. The items that take the most time, once the design is figured out, is scroll sawing the 2 gears, and hand-carving the head.

January 2016 Update

The carpenter's head started to rise and no longer turn.  The 1/4" dowel that controls the head motion needs to be retained in a vertical direction.  The action of the 2 cams tends to make it raise over time.

I added a 1" OD washer and hot melt glued it to the 1/4" head control shaft.  That fixed the issue. 

I also added a dab of hot-melt glue to the nail and the short dowel that raises the arm, so they can not fall out and get lost.


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