Do the old Samsonite gears (above) work with current Technic gears (below)
LEGO bricks tend to be backward compatible with older bricks, but since I don't own any Samsonite gears I cannot tell.
Image credits belong to Technicopedia.
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The first gear wheels, or cog wheels, were designed by Knud Kristiansen around 1964 or 65; the original Danish design patent was filed on March 1, 1965.
Under licence by LEGO, Samsonite manufactured and sold these gears in the USA from 1965-1972, and in Canada from 1965-74. The gears had studs on the top and tubes on the bottom. They could be made turnable by fixing them to wheels with studs or turntables. These gears were never available in European sets.
A different type of gear, incompatible with Samsonite gears, was produced by LEGO in Europe between 1970 and 1975. Although the gears themselves are incompatible with technic gears, the axles that held them in place had the same cross-section as the axles for technic gears. This means that mechanisms can be constructed that use both types of gears.
Interestingly, the gears had a small circular spring in them to help them grip the axle. If I remember correctly, the ends of the axle had a groove that aligned with this spring, making the gears a slightly more stable fit at the ends of the axles than in the middle.
Modern Technic LEGO was then introduced in 1977.
They are not compatible, the teeth are completely different.
Notice that the red old gear has 9 teeth and is the same size1 as a current 24-teeth, as illustrated by below:
The axle hole however is compatible, so you could have a construction using both types.
1. Actually, the distance between axles to have two of these red gears mesh is the same as the one required for two 24-teeth ones (60 ldu).