153. Circular motion into alternating rectilinear motion. The studs on the rotating
disk strike the projection on the under side of the horizontal bar, moving it one
direction. The return motion is given by means of the bell-crank or elbow-lever,
one arm of which is operated upon by the next stud, and the other strikes the stud
on the front of the horizontal bar.
To design a wood model of this, there were several considerations. One of them
was to figure out how to constrain the sliding element. Another was how to make
this a hand crank toy, yet still be able to see how the two pins and the bell-crank
In terms of experience with Google's free 3D sketchup software, I have now booked
more than 100 hours using it on at least 6 projects. I am still not super proficient at it.
To get the core design work done, I ended up reverting back to a paper model
where I could rotate the elements:
I made my paper model to 1:1 scale and used engineering graph paper for sizes. I used
thumbtacks pressed into a cardboard box below, so I could rotate the elements. Once
I got the core design done in paper, I inputted it into Sketchup. Maybe after I get 1,000
hours accumulated using Sketchup I can do core design work like this on the tube
instead of paper
Here is my Sketchup design of Model 153:
Since the gears turned out very well on previous projects, I decided to make this a
drive unit. This also gets the operator's hand away from the two pins and bell-crank
so he can see how it really works.
I decided to make an animated gif file showing how this model works:
Here is a link showing the animated gif file.
I rotated the elements 10 degrees at a time and took a screen shot at each increment
for 180 degrees (17 files, not 18 because 180 degrees is the same as 0 degrees on this
I then pasted the screen shot into Irfran and resized to 800. I saved as a gif file from
Irfran. I used a free program called UnFreez where you add each gif file to UnFreez
and it creates the animated gif at whatever speed you want.
Here is the finished wood model:
Here is a link to a better picture of the finished model.
Here is a link to a YouTube video of this model in action.
The finished model turned out pretty cool. The wood gears work well and the
whole model has low friction...which is needed to make it run smoothly. The yellow
dyed horizontal slider adds color to the model.