Meccano Gears  1Wednesday, 8 June 2016  Admin Meccano Gears  1Simple Gearing.Meccano has long been associated with basic mechanical principles and none more fundamental than gearing. Gears are used to increase or decrease the rotation speed of a shaft, decreasing or increasing the torque at the same time. They will also reverse the direction of rotation for pair of gears used. The change in speed of the shafts depends on the ratio between the teeth on each pair of gears. The picture below shows the 4 common types of gears found in Meccano. The holes in the plate are ½" pitch, so you can see the left and centre pair of gears mesh at 1" (25.4mm) centres, the right hand pair of gears mesh at ½" (12.7mm) centres. The left hand pair of gears give a 2:1 ratio  the upper pinion will rotate twice, whilst the lower spur gear will rotate once. This is calculated by 50/25 = 2. In most applications, you need to reduce the rotational speed and increase the torque. If the input is connected to the upper gear, and the output connected to the lower gear the rotational speed will be halved, and the torque roughly doubled. Additionally, the rotation direction will be reversed. The centre pair of gears have a larger size difference, these will give a 3:1 ratio. The large spur gear has 57 teeth, and the small pinion 19 teeth. 57/19 = 3. This will give a greater torque increase (and a greater reduction in rotational speed) in roughly the same space. Finally, the right hand pair of gears both have the same number of teeth (19), so there is no change in rotational speed or torque, but the rotation direction will be reversed. 

Meccano Spares 