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Movable U-Joint Model


I found a new book with more plans for making wooden models. It is Building Wooden Machines by Bridgewater.


The 2nd model I decided to build is the movable u-joint model. Here is a photo from the book:


As per my usual practice, I entered the model into Google Sketchup:



 This design features 1/2" dia dowels that have milled flats. You glue the milled flat sections together to form the u-joint.

To get a consistent depth of milled flat, I used the drill press and a router bit......


I made a square alignment piece of wood to make sure the 2 pieces of the u-joint were at 90 degrees to each other when I glued them up........


 Cutting the rectangular holes in the base

I decided to use the scroll saw to cut out these rectangular holes.



Removing material from the main stanchions

I decided to use the drum sander on the drill press to remove this material on the side of each stanchion. Then I took each stanchion to the vise, and use the Dremel to hand sand them a little more.




Drilling holes in the wood balls

This is not something I had ever done before. I experimented different clamping set-ups to drill the balls. This first method worked, but was too flimsy...



 This 2nd method was a little more stable.........


 I inserted the horizontal dowel, so I could visually try to keep a good 90 degree angle between the holes.  There is probably a better way to drill the cross-holes in the balls.

 Attaching the 2 main stanchions to the base

I normally just glue items like these stanchions to the base.  The pattern called for dowel pins.  The dowel pins look nice when the model is done.........but they are a pain to put in.  On this model, I decided to glue the stanchions to the base first, then drill the dowel pin holes later using the drill press.



 I ran the 1/4" dowel rod through both balls to make sure everything was lined up ok.  I also had marked the stanchion locations on the base using carbon paper. I had to make the clamp jig shown to hold down the right hand side of the stanchions with the c-clamp.  I cleaned all glue squeeze-out with a wet rag and toothpicks.

 Drilling the Peg Holes in the Stanchions

 I first glued the 2 stanchions to the base.  Then I drilled the 4 holes for the pegs on the drill press......


 Finishing the Model

 I used my usual process of 3 rounds of 220 grit sanding and polyurethane.  I left the model dis-assembled for the first 2 coats, then finished assembly before the 3rd coat......



 The Finished Model







 My daughter Stacy helped me make a Youtube video of the model in operation.

Closing Thoughts on This Project

 The original pattern called for the 2 balls in the drive-train to be split in half.  I intentionally did not want to complicate the project with these sawing operations. I added an 1/8" removable dowel pin on the output shaft, and turned the 1/2" dowel down to 3/8" going thru this ball.  I pinned a short piece of 1/4" dowel between 2 pieces of 1/2" dowel on the 2 stanchions.

Although not specified in the pattern, this model works best if you crank with your right hand, and hold down the output shaft with your left hand. You can then vary the angle while you are cranking. Otherwise, gravity causes the u-joint to fall to its bottom position.

Over-all this turned out a colorful project.  The next stop is to take it to work and let me fellow engineers play with it.









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