Meccano Gears - 8 - Helical Gears
Tuesday, 14 June 2016 | Admin
Meccano Gears - 8
Helical gears were a late addition into the Meccano system. They allow a right angle drive with the output shaft offset from the input shaft.
These gears a very different to standard gears, and they will only mesh together as shown. The larger gear (211b) has 35 teeth, and the smaller gear (211a) has 14 teeth. This pair will give a ratio of 35/14 which is 2.5:1. The teeth are cut at 45 degrees to the gear face. There gears won't mesh with other gears in the Meccano system as the teeth are cut to a profile of 24DP, as opposed to 38DP. The teeth on these standard gears are cut 'right hand'.
If you have one right hand cut gear and one left hand cut gear, they will mesh on parallel shafts, as shown below. This give a much greater contact face compared with standard spur gears, so a greater load can be applied.
The small gear is a standard RH cut gear with 14 teeth, the larger gear is a LH cut gear with 35 teeth.
To mesh correctly at 1" pitch, the total number of teeth on both gears needs to be approximately 48. If the gear cut is different (ie 1 LH and 1 RH) they will mesh in parallel as above, if the gear cut is the same (ie 2 LH or 2 RH), the gears will mesh at 90 degrees,
There are a number of reproduction gears available with different numbers of teeth and LH/RH configurations. The LH cut gears have a letter 'L' appended to the part number, ie 211aL.