|This page shows how the solar dinosaur neck and swing are built and
The dino has a neck that pivots where its attached to the body, and bounces up and down on springs. this makes for a somewhat involved pivot joint, as the neck applies a lot of force to the body as you bounce up and down on it.
The neck is a plywood box beam made from 3/4 inch exterior plywood. The neck is put under quite a bit of stress by the swing and pivot, and the box beam provides a very strong structure. Since the neck is curved, the top and bottom of the box beam has to be made in two sections, each covering about half the length of the beam.
As for the other parts, the sketch on the shop floor is transferred to the plywood and then cut out.
The neck box beam is 12 inches wide, and is assembled using the 2X2 cleats to reinforce the joints just like the rest of the joints in the dino box. The side pieces of the neck are doubled with a 2nd piece of 3/4 inch plywood near the pivot area for extra strength.
On the 2nd picture, note that I miscalculated on the pivot location, and had to move and re-drill it during assembly of the neck to the body.
The third picture shows the finished box beam neck. The top and bottom of the box beam are made from 12 inch wide, 3/4 inch plywood. The top of the neck beam is made from 2 pieces of plywood because it curves too much to be made from one. Likewise the bottom is also made from 2 pieces. The sides are attached to the top and bottom via the same kind of 2X2 cleats as were used for the dino body.
Once the box beam is finished and the glue is set, you could hang an SUV off the end of it.
The neck to body joint is probably he most complex element of the dino. If you bounce on the swing at the end of the neck with a couple hundred pounds of force, it causes a forward acting force on the pipe pivot joint about about 1300 lbs -- so pivot area needs to be strong enough to handle this, and the large forward acting load also has to transferred over to the sides of the dino.
Likewise, the bottom of the neck applies a 1300 lb aft acting force to the dino body at the bottom of the neck. This force is less of a problem, since it lines up pretty well with the drivers platform floor, which is capable of taking a larger aft force.
On the 2nd picture, note that a pocket is formed between the bottom of the neck and the front wall of the drivers compartment. Rubber balls are placed in the pocket to act as springs to give some bounce to the dino neck when you bounce up and down on the swing.
The 2X8 and the plywood piece that goes just above it are particularly important. Without these pieces, the dino top of the dino neck would apply way to much force to the front wall of the drivers compartment, and would break it. So, don't leave these out, and install them carefully.
In the end, this whole neck joint area turns out to be solid as a rock when built as shown.
One could attach the neck to the body without the pivot joint, and this would make the joint simpler, but you still need the same basic structure to transfer the neck load over to the dino sides.
The swing was bought from the play structure parts area and Home Depot. Its a simple platter that hangs from an eye bolt. I installed a 4X4 across the width of the neck box beam to hold the eyebolt. All of the other parts were included in the swing kit.
Gary September 6, 2009