Gary's Motorized Big Binochair

Version II - With Speed Reducer

by Gary Honis


The electric drill used for direct drive of the binochair, as detailed on the previous pages 1 through 7, is operated at slow speeds when slewing. Since the drill used is a variable speed drill, just a slight pressure on the drill trigger will rotate the binochair. One advantage of this is that there is almost no noise at these slow drill speeds. A disadvantage is that the rotation control is course; and fine adjustments are best made by not using the drill but rather by rotating the binoculars slightly. Another disadvantage is that there is horizontal pressure placed on the vertical electric drill when slewing.

An alternative is to use a speed reducer (gear reducer) between the drill and the small sprocket. In shopping for gear reducers, I found that most are for industrial applications and expensive, costing around $150. Lower priced gear reducers are for hobbie projects and robotics and tend to be to very light duty; not hefty enough for rotating the binochair. After searching for gear reducers, I decided to use the gear reduction afforded by an electric ice cream maker we were no longer using. I found its gear reduction to be ideal for controlling the rotation of the binochair. The gearing is very robust since it was designed to mix ice cream as it hardens....if you ever hand cranked a non-powered ice cream maker, you understand the torque required.

I decided to install the gear reducer so that I could easily return to the "drill only" version if I wanted. I have found that I prefer the binochair using the gear reducer. Operation of the binochair is noisier than with the "drill only" method but not more offensive than the noise made by a Meade LX 200 (that I also own). Slow speeds of the drill provide a slow motion control for my 25 X 100 binoculars. Faster speeds of the drill allow slewing to new sections of the sky. The gear reducer provides for smoother operation of the binochair when slewing. My recommendation to anyone planning to build a similar motorized chair is to use a gear reducer (ice cream maker).

Parts for Speed Reducer:

Construction Details:

1. Remove the closet door rollers previously installed in Step 12 of Page 3.

2. Drill a 5/8 inch hole next to the existing hole (see photo). The location of the hole is determined by measuring from the center pivot out to the center of the drill arbor that was used for mounting the small sprocket. For my binochair this location was 17.5 inches from the center pivot. Be sure to get the hole's location as precise as possible so that the chain is not too tight nor too loose when it is mounted.

3. This is the electric ice cream maker motor/gear unit that I used. Electric ice cream makers are readily available on ebay. I bought one on ebay for $10.50 to have as a spare.

4. This is the ice cream maker with plastic cover, wires and fan removed from the motor shaft. The drill will use this motor shaft to drive the binochair:

5. The ice cream maker has a 8 pointed large gear that drives the ice cream bucket paddle. I found that a 1/2 inch square head bolt fits into it perfectly. The bolt with washers, small bicycle sprocket and nuts are shown below:

6. Use a 1/2" X 5/8" steel spacer as an insert through the chair base plywood. I cut the spacer below to the same thickness of the plywood with a hacksaw:

7. Use a slow curing high strength epoxy (I used JB Weld) to secure the spacer and washer to the hole in the chair base plywood:

8. Drill holes in the plastic arms of the ice cream maker to attach to chair base plywood with 3-inch wood screws. I just keep the ice cream maker attached to the chair base and don't remove it. If you want it to be more easily removable; use bolts and wingnuts.

9. Cut a hole in the plastic cover a little larger than the diameter of the drill chuck:

10. Saw plastic cover in half with a hack saw:

11. Screw one half of the plastic cover onto the ice cream maker using two original screws. Use a rubber band to hold the other plastic cover half in place . This rubber-banded half can then be easily removed to tighten/loosen the drill chuck.

12. I kept the original wood blocks installed in Step on Page for holding the drill. Instead of replacing them, I added two pieces of wood and styrofoam to adapt the drill holder for the new hole position:

13. Cut two small pieces of 1/8 inch panel board (or other material) as shown and superglue rubber grippy material where contact will be made with the drill battery:

14. Completed unit installed on chair base - The drill is higher now and easier to reach:

Side View:

Top View:

Transport and Setup:

I found that for transport, the two wooden parts: chair base and groundboard, could be left attached together. Their combined weight was still easy enough for me to carry and lift into my van. To keep the chair base from rotating on the ground board while carrying and during transport, I installed three hand knob bolts through the chair base plywood and into metal T-nuts on the ground board. I keep the ice cream machine on the chair base and only remove the drill during transport. When I arrive at an observing site, my setup steps are as follows:

1. Lay down chair base/groundboard, undo transport hand knobs and level.

2. Install drill in its holder and tighten drill chuck onto ice cream machine shaft. (Front half of ice cream machine cover is held on with rubber band)

3. Place chair on chair base and install bungee cords.

4. Install binoculars on sliding computer tray.

5. Relax and enjoy observing the wonders of the night sky:

If you found these construction details helpful in building your own binocular chair and would like to let me know how it went for you; you can contact me at the following email address:



To My Astrophotography & Digital Imaging Home Page


Detailed procedure for drill-powered astronomy binocular chair.

Binocular mount for Apogee 25X100 large astronomy binoculars.

Comfortable observing with big astronomy binoculars.

Reclining chair for large astronomy binoculars.

Ice Cream Maker - Gear Reducer used from Ice Cream Maker