The next animated toy I built from David Wakefield's book was the T-rex Dinosaur.
I ordered some American Cherry from Rockler to use for this project.
Cherry is really expensive. There is probably enough here to do at least 2 toys, so $25 per toy just in wood materials!
I forgot to mention on the previous animated toys projects, that I am using a lot of CA glue versus my normal yellow Titebond II. The CA glue allows me to glue up in less than 15 minutes, versus waiting 2 to 3 hours on the Titebond to set. Since these are small toys, it doesn't take much of the expensive CA glue.
I entered the design into Google Sketchup.
It was a challenge to get the tail curves and body head curves drawn.
I recently starting using Irender, a program that renders Sketchup models into more life-like images.........
The first step was to glue up the cherry blank for the main body. Since it is wider than 5 inches, I first had to glue up pieces to get the right height, then glue up 2 layers to get the 1.5" thickness needed. I used the old fashioned wood clamps so I would not mark the cherry with steel clamps, then have to sand out the marks.
I made a pattern for the main body from 3/16" plywood. You have to pencil on a line 1.5" inches from the bottom of the blank, so you set the pattern on horizontally correct.
Next is setting up the dado blade at 5/8" thickness on the table saw. Then I did pass #1 with blade at 1/2" height, or 3/4" height, then 2nd pass at full height of 1.5".
The blue tape tells me where to stop, so I have full cut through the bottom area of the body.
Next step was to bandsaw the main body using an 1/8" wide blade. I got a lot of wood burn from this operation.
I use a 60 grit drum sander on the drill press to remove the wood burn. I wonder if a different design of 1/8" blade would create less burn? Maybe more or less teeth, or different teeth angles? Will have to research sometime.
I next put the body in my big vise, and made sure the pencil mark for the long 3/8" hole was vertical. I started the hole with a Forstner bit. I had to go to Ace and buy a longer 3/8" bit, that I used in my hand 3/8" drill to finish the hole.
As per the plans, I did not saw the teeth out until after I drilled the long 3/8" hole. If you saw out the teeth first, you will be trying to start your drill in a toothed area, versus a flat area.
I band sawed the teeth and got excessive wood burn that I could not remove with a file or sandpaper. I put a round bit in the scroll saw and basically sanded away the wood burn. On future projects, do not band saw the teeth due to excessive wood burn, use the scroll saw with the round blade.
The next step was band sawing the profile on the tail and the one on the head. I glued on the paper patterns to do this, then drum sanded out the wood burn.
I routed the edges that I could get at with an 1/8" round-over bit on the router table, then drum sanded the body with 220 grit.
I sawed out the head pieces on the scroll saw using the spiral bit. It doesn't follow a line very well, but you are going to sand the head anyway.......so as long as saw outside the line, you are ok. I sawed the teeth with the spiral bit as well.
I did not take a picture of the fixture, but I did use one to make sure the 2 holes were lined up.
I did test the head assy, clamped on, on the head, because of errors on past projects in Wakefield's book. It seemed to work ok.
Small Parts and Head
I made patterns from 3/16" thick plywood for all the small parts.
I did not make the holes in the head 5/16" diameter. That seemed too sloppy to me since 7/32" axles go into the holes. I made them 1/4", then used a fixture with a 1/4" dowel to make sure the 2 head sides were aligned at glue up. I also checked the fit of the head to the body before glue up, and it seemed ok (because there have been errors in other patterns in the book).
I got wood burn on the scroll saw using a regular blade on these small parts. I used a spiral blade to cut the teeth, which does not give wood burn. The spiral blade tends to wander and is harder to cut with. I used the drum sander to sand out the wood burn.
You plug the original center hole with a 1/4" dowel, then drill a new 1/4" hole that is offset 1/16" from the center, to give the T-rex the side-to-side movement. You also drill a 7/32" offset hole to run the legs. You drill these from the flat back side of the wheel. To keep the wheel flat on the drill press table, I sawed out a 1" hole in a 2x4 scrap piece, then set the wheel over the hole. This prevents the wheel from tipping and getting excessive run-out on the wheel.
Finished T-rex before Oiling
Finished T-Rex after Oiling
Sketchup vs. Irender vs. Actual Wood Model
You can watch a Youtube video of this T-rex in action with its loud roaring sound from this link.
I was glad there were no errors in this design There is a lot of work in the main body of this toy. He is really fun to watch him move, with the combination of head movement and leg movement.