Martin_gsxr
Veteran
Location: Montreal, Canada
My Posts This: Topic Forum | Hi Bert, 48 is near but not perfect.. here is a post by CUDABOY:
i'd measure if i was near a heli. but, 'module' and 'pitch' are not some arbitrary values assigned by a standards board. you can actually measure them for yourself.
z = number of teeth in gear
Mn = normal module
PD = pitch diameter of gear (diameter in mm of the gear if the teeth were all stripped off)
OD = outside diameter of gear (diameter in mm including the teeth)
Formula
Normal Module:
Mn= PD/z
If you measure the PD to be 70mm and there are 140teeth, then the gear has a module of 70/140=.5
similarly, pitch is the 'english' measurement system. pitch is defined as the number of teeth a 1" wheel would have. so, 48P is a 1" diameter* gear with 48 teeth.
so, 48P is roughly (25.4mm*Pi)/48=1.66 module** (25.4mm = 1 inch)
*pitch is vastly more complex to calculate because it is calculated off of the "pitch circle" rather than the inner or outer diameter as 'module' measurement does. i won't go into the gory details of pitch circle---but, it involves a lot of trig...suffice to say, if you do calculate the pitch circle, you can find the pitch by dividing the pitch circle circumference by the number of teeth....or (D*Pi)/Teeth (where D is the pitch circle diameter of the gear)
**in the example above, the module would actually be less than 1.66 as the pitch circle would be slightly larger than the 1" since the module calculation uses the ID of the gear. |
