Friction Drive for a Critter

construction sign

NOTE:Click on picture to enlarge. Click back button on your browser to return to this page.

This is my test-bed for a friction drive for "Critters". The idea came from a UK based website. Nigel Lawton has a site were he sells items
of Industrial Rolling Stock in 009/HOn30/HOe. Here is a link to his site: Nigel Lawton 009 The frame is built up from 1/16" and 1/8" brass
flat stock. The motor came from a 40/70 Tonner Bachmann diesel switcher. I turned the little pulley on the motor shaft. The worm shaft
is .094 dia. stock and has two worm gears from a 3 axle Tenshodo truck. I picked up 3 of these trucks many years ago at a train
meet. The brass wheels are also from the same truck. The phosphor bronze spring holds the motor down for a little more friction.

Here you can see that the motor hinges on one end of the frame. I made the hinge with 3 pieces of copper tubing. The X-acto
knife gives scale to how small this drive is. The motor is only temporarily held down with some soft wire twisted around it.

Top down view of the brass wheel set and large friction wheel.

View from back showing the hinge and aluminum bearing retainer.

Bottom view showing the brass worm gears and how the electrical pick-up is accomplished thru contacts
harvested from an ice-cube relay. Some of the contacts are gold plated making for a much better pick-up.

View of what the hinge looks like.

With one side frame rail removed you can get a better idea of how the electrical pick-ups were mounted.

A frame rail and end frame removed and the worm shaft taken out. Note the bearings on the ends of the shaft. These bearings make it easier for
on the motor. There is not as much friction as would be if a bushing was used. The friction wheel with "O" ring is approximately .700" dia. Note
that the hole were the bearing fits in on the en frame piece that the hole is elongated a bit. This allows the bearing to move up and down a small amount.

Here's a picture of the bearings sitting used on the end of the worm shaft sitting on a scale ruler. They are two
different sizes. Both are 3/16" O.D. but the middle one is only 3/16 of an inch wide. The other two are 3/32" wide.

Here's a video of the friction drive running. On the return trip you'll here a ticking noise.
That disappeared after I dissembled the drive to take the picture. After I assembled it
again the noise was gone. Still don't know what it was. Note that this little critter can
push 6 Bachmann side dump cars on level track.

To be continued
Back to Critter page