Make Your Own Amazing Mechanical Toys by Michael Screen

Author:Michael Screen
Language: eng
Format: epub
ISBN: 9781785005121
Publisher: Crowood

The front and rear wheel assembly, showing the 25mm-diameter axle-spacer blocks used on the front axle to prevent the inside pegs from jamming.

Step 12: Making the front and rear axles

1. Cut a 95mm length of 9mm diameter dowel for the front axle. Cut an 85mm length of 9mm dowel for the rear axle. All wheels are 50mm in diameter. Produce them in the same way as the wheels for the frog toy. The holes for both front and rear axles must be set to a depth of 15mm.

2. The front wheels have a 9mm inside peg set on the interior of each front wheel. Locate the position for the peg for each wheel by measuring 10mm from the circumference to the centre of the hole location for the peg. Remember, the front wheels will need to be synchronized eventually to cause a lift and fall for every rotation of the axle.

3. The rear axle is 85mm in length and made from 9mm diameter dowel. The rear axle requires two spacer blocks placed between the top of the upper rear legs and the dog’s body to project the leg assembly away from striking the dog’s side and jamming. The spacer also causes the lower part of the leg to line up parallel with the wheel exterior. Each spacer is cut from a 25mm diameter dowel to a width/length of 5mm. Drill a 5.5mm hole through the centre of each rear leg spacer. Do not glue the spacers, but let them move freely to help reduce friction.

4. The front axle needs two spacer blocks to prevent the inside pegs that cause the dog’s head to lift and fall, jamming against the edge of the head or body. Take a piece of 25mm diameter dowel and bore out the centre with a 10mm drill bit. Use a bandsaw to cut two 12mm lengths and slide them over the axle.

5. Cut two 9mm diameter dowels to a length of 20mm, and press them into the holes on the interior of the front wheels to form the pegs that will flip the dog’s head up and down.

6. The exterior of all wheels needs a 2.5mm pilot hole for the leg pivot points. Drill the 3mm pilot hole 12mm from the circumference of each wheel. Remember that each pair of axles needs a ‘one up, one down’ configuration to generate the walking action of the dog’s legs.

Step 13: Assembling and fitting the legs to the body and wheels

1. Assemble two pairs of front legs (parts F and G) using an M4 lock nut and 40mm pan-head screw with two M4 washers. The screw/bolt head faces inwards to avoid the screw jamming on the dog’s jaw.

2. Assemble two pairs of rear leg (parts H and I) rear wheels. Again, use an M4 lock nut and 40mm pan-head screw with two M4 washers. The screw/bolt head faces inwards to avoid the screw jamming on the dog’s body.

3. Both front wheel assemblies have an 18mm diameter × 15mm spacer between the upper rear leg and the dog’s body.

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