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Model 131 Rack and Gear

Here is the concept drawing and description of operation from the book 507 Mechanical Movements:

131. On rotating the disk carrying the crank-pin working in the 
slotted arm, reciprocating rectilinear motion is imparted to the 
rack at the bottom by the vibration of the toothed sector. 

 
 When I first designed my model in Google Sketchup, I wanted it to be relatively
big in size. When I went to print the paper patterns, it way too big.
Fortunately, Google Sketchup lets you scale your drawing, so I scaled it to 1/2

scale. Here is the Sketchup design:
 
 

I also created an animation of the design to make sure everything worked ok 

before I built it:
 

 Here are photos of the model as I built it:

The black plastic square I bought from Rockler sure is handy making the bases of these models! Before I bought it, I would have to adjust the clamps by trial and error, using a metal square to check the 90 degree angle.

The vertical dimension from the yellow rack to the quarter gear is critical to smooth operation of the model. I checked the fit as I glued up the 2 bearing assemblies. I tried to use the 2 tapered block support method for the bearings to position them, like on the steam engine model, but there is not a big enough gap below the bearings to use them. Patience is a virtue building these models


And here is the finished model:

 


Here is a video of the model in action:

 

This was a fun model to design and build.    The rack and quarter gear run smoothly on the finished model.  The yellow dyed straight rack adds color, plus the red padauk quarter gear.


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