Meccano Gears - 7 - Bevel Gears
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Meccano Gears - 7
Bevel gears the second most useful gear type after spur and pinion gears. There are three standard bevel gears in the Meccano system, 26 Teeth (Part 30), 16 Teeth (Part 30a) and 48 Teeth (Part 30c). These are shown below.
These gears are used in Meccano because they produce a 90 degree drive with both shafts on the same plane. The gear teeth are cut at an angle, which is made by a line drawn between the centre point of the the two shafts, out to the meshing interface between the two gears. If the two gears have the same number of teeth (as in the 26 tooth gear), the line (and therefore the teeth) are cut at 45 degrees. This allows maximum contact between the teeth of the two gears.
If the bevel gears have a different number of teeth (as in the 30a and 30c shown in the upper example), the angle will be different for each gear, therefore the teeth are cut at a different angle on each gear, to maintain the maximum contact between each gear.
Bevel gears will only mesh correctly as a matched pair, so part 30 (26 teeth) will match with a similar part to give a 1:1 ratio, and parts 30a and 30c (16 and 48 teeth) will match giving a 3:1 ratio.
As with contrate gears, the meshing shaft centrelines just needs to pass at right angles to each other. If you think of one bevel gear as a clock face, the meshing shaft can exit the clock face at any point.
There are a number of different pairs available as reproductions, two of which are shown below :-
The lower pair 30g (12 Teeth), give a compact 1:1 ratio.
There are also some other reproduction bevel gear pairs available.
30h (16 Teeth) - Meshes to give a 1:1 ratio