Parts for Ground
For the ground board and chair base, I bought a 4 foot by 8 foot
- 23/32" exterior grade plywood from Lowes. It is large enough
for the two pieces needed. An option is to have the hardware store
cut both pieces for you.
1. For the groundboard cut a 40"
by 40" piece of plywood and draw lines from corner to corner
to locate center:
2. For the large sprocket, I used
the gear assembly from my son's discarded bike. You can buy sprockets
online or for a better deal, stop by your local bike shop. They
should have many old sprockets they can sell you for a buck or
3. Fasten the large sprocket to
the "Seat Mount For Boat Pedestal" with 2 inch 1/4-20
screws, washers and nuts. I later added two more screws for a
more secure mount (see first photo in step 4)
4. Attach the "Seat Mount
For Boat Pedestal" with gear to the center of the plywood
for ground board with four 1/4-20 by 1.5 inch screws, washers
5. Cut 4 - three inch long pieces
from the 2x4 for the groundboard legs and attach with 9X2 wood
screws to all four corners:
6. Cut foam
board with a utility knife 30 inches in diameter with a square
hole in center for the "Seat Mount For Pedestal Base".
The foam board will act as a spacer to help support the bike chain
and keep it from drooping since the chain will be mounted horizontally.
7. Fasten the small sprocket onto
the drill arbor using nuts and tighten
in place. I ground flat sides on the round shaft of the arbor
for a more secure fit in the drill chuck to avoid slipping. Some
arbors already come with flat sided shafts. I bought the used
small sprocket unit below from my local bike shop for $1. There
are actually two sprockets screwed together that I had difficulty
separating, so I just left them together and use the chain on
the smaller sprocket.
8. Tack or staple the foam board
from step 6 onto the ground board. Here is a photo of the completed
ground board with bike chain and small sprocket:
The Groundboard is complete!
Page - Component No. 2 - Construction of Chair Base
Big Astronomy Binoculars - Large Astronomy
Detailed procedure for drill-powered
astronomy binocular chair.
Binocular mount for Apogee 25X100 large
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Reclining chair for large astronomy binoculars.