Postwar Lionel worm wheels (gears)

[cwburfle]

Having just spent time trying to identify some assorted Lionel worm wheels (gears), I became curious about proper terminology.
I have some worm wheels that are the same diameter, and have the same number of teeth, but the teeth are cut at different angles across the face of the gear.
Is the angle of the cut called the "pitch", or is there another term that should be used?

[cjmeyers]

From Wikipedia:

Pitch is the distance between a point on one tooth and the corresponding point on an adjacent tooth.^[4] It is a dimension measured along a line or curve in the transverse, normal, or axial directions. The use of the single word pitch without qualification may be ambiguous, and for this reason it is preferable to use specific designations such as transverse circular pitch, normal base pitch, axial pitch.

Not the correct term to refer to the angle of the cut.

"Plane of Action" might be the better term.

Regards,

CJ Meyers 

 

 

 

[8ntruck]

Lead is the term you are looking for.  Lead is defined as the distance one tooth will advance in one revolution of the worm gear.  High angle = high lead, low angle = low lead. 

The high angle worm gears will run the driven gears faster for a given input RPM than the low angle worm gears.  The low angle worm gears will give more torque on the output shaft than the high angle worm gears.

Hope this helps.

[cwburfle]

 

Thank you both!

[lionelsoni]

The number of teeth on the worm wheel and the number of starts on the worm completely determine the gear ratio.  The lead is a function of the worm-wheel diameter and the number of teeth.  The lead angle is a function both of the gear ratio and of the diameters of the worm wheel and of the worm.  For example, with the same tooth count, number of starts, and worm-wheel diameter, a large-diameter worm will have a low lead angle and a small-diameter worm will have a high lead angle.

[cwburfle]

 

Thank you.

How would this apply to the case of the Lionel gears I was sorting?
They had the same diameter and tooth count, but the angle of the teeth was different.

[lionelsoni]

The worms that they were meant to mate with had different diameters or different numbers of starts.  Because they have the same diameter and tooth count, their spacing between teeth is the same.  That spacing must also be the spacing between threads on the worms.  But a large worm would have its thread at a shallow angle because the thread has a longer distance to go around the worm, while a small worm would need a steeper angle to advance by the same distance in one pass around the worm.  A worm with two starts would also have a steeper angle, because each thread would advance by twice the thread spacing with each revolution of the worm.