Pictures for the ultra-light and portable observing chair
The chair was modeled after the one made out of oak by KC Woodsmith, but
mine is made of 1 1/2" x 3/4" poplar, a lightweight hardwood.
If you don't care about light weight or you weigh more than 200 pounds, you
probably want to use oak.
All of the bolts (except where noted) are 1/4x20 because the
threaded inserts and the furniture bolts are 1/4x20
threaded. The three front leg struts are 36" long and the two back leg
struts are 19" long.
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This picture shows the chair all taken apart. The struts are made from 1 1/2" x 3/4" poplar. The two top struts are for the seat (12 1/4"). The next The aluminum tubes are 3/4" diameter and have |
The most tricky part of the chair is the place where the back brace, which holds the back legs together and sits directly on the ground, attaches to the back legs.
As shown on the left, the bottom of the back legs are cut at a 60 degree angle and a 3/8" hole is drilled through the wide face 3/4" from the bottom to accommodate the furniture nut (shown on the right). A 5/16" hole is drilled through the narrow (3/4") face, parallel to the long edge of the wood (this is the trickiest part) to accommodate the 2"-long 1/4" bolt used to attach the back legs to the back brace (see next picture).
This end is cut at a 60 degree angle and two holes, at right angles, are drilled to meet. A furniture nut with a 1/4x20 thread in the side.
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The furniture nut is available at good hardware stores. It is threaded for a 1/4x20 bolt to come in at right angles and the slot on the furniture bolt is used to help align the bolt and nut during assembly, which is very helpful.
The furniture nut slips into the hole in the leg.
The 1/4x20 bolt attaches the back brace to the leg.
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There are two back legs (left) and the front (3 legs) and back legs are spread
apart 16 1/2" (center to center)
and held from going further apart by a canvas belt bolted to the back brace
(right) and the center front leg (next picture - left - note the chair is
upsidedown)
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The picture on the right shows how the three front legs are held
together at the top. The bolts at the top of the front legs (right) need
to be countersunk and set flush with the wood since the seat assembly slips over
here. The width of this front leg assembly is 8 3/8".
Each of the aluminum tubes is about 2 15/16" long.
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The seat is constructed separately and is made from
two struts of 1 1/2" x 3/4" poplar, 12 1/4" long. A
rectangle of 1/4" thick baltic birch (12" x 7") is bolted (#6
bolts) onto the struts via 6x32 brass threaded
inserts set into the narrow (3/4") edge of the strut and provides the
spot to sit on. As shown in the picture on the right, through 1/4" holes drilled into the struts 1
1/4" and 3 13/16" from the back end, 1" long 1/4x20 bolts are used to attach the
3/4" aluminum tubes (8 1/2" long) which have threaded inserts in
their end. You can use vinyl electrical tape on the aluminum tubes to
create more friction with the wood to keep it from slipping. However, I
found that Tygon (#3603) tubing 1/2" i.d. 3/4" o.d. works even better.
Unfortuanately, most people will find this difficult to find. So use
electrical tape.
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Importantly! There is a #8 bolt that
passes vertically through the strut about 3/8" from the end. The nut on
this bolt needs to be kept tight at all times as the function of this bolt is to
prevent splitting of the poplar strut (which will happen if this nut loosens).
So use a lock washer.
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On the bottom of the baltic birch seat is glued a piece of 1/4"
baltic birch about 3/4" wide and 8 1/2" long (left). The purpose of this
strip is to prevent the thin plywood from breaking when you sit on it.
The pivit point of the chair (right) is 17 1/8" from the bottom of the front
legs and 1" from the top of the back legs. A 1/4" hole in each allows the
1/4x20 threaded rod to pass through and the front and back legs are held fairly
tightly with wingnuts. Use lock washers here or it loosens quickly.
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The seat height is adjusted easily by lifting the seat and putting it
wherever you wish. It stays put by friction.
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