How accurate are spur gears?
How accurate are spur gears?
(OP)
Wouldn't spur gears have a tiny variation in mechanical advantage as they go through different stages in where their teeth mesh? Basically the idea is that as the teeth mesh, they have to slide just a tiny amount, probably around 1% of the tooth pitch, but that also means that both gears change their effective diameter by a tiny amount and that effective diameter goes through that change every time a tooth meshes. Theoretically even helical gears would also have the same problem, but it might be much less distinct because the meshing is more gradual.
That being said, would this make spur gears not recommended for high precision instruments? Would even helical gears be good enough?
That being said, would this make spur gears not recommended for high precision instruments? Would even helical gears be good enough?





RE: How accurate are spur gears?
RE: How accurate are spur gears?
RE: How accurate are spur gears?
Actually probably an order of magnitude WORSE inaccuracy is from the required backlash between teeth. THIS is why super high precision motion is done with direct drive (no gears) if possible.
Remember too that repeatability and accuracy are two totally different animals and effect processes differently.
www.KilroyWasHere<dot>com
RE: How accurate are spur gears?
The two gears were on a common concentric shaft, but a spring kept a predictable tension between the two. When the drive motor had to reverse the radar's motion, both of the driven gears were always held up tight against teeth on the drive gear.
RE: How accurate are spur gears?
the torque motors we supplied ((supply) to those missiles for guidance and gyros are all direct drive if possible to eliminate all the gear errors.
Even today we are replacing spring loaded 10-20-30hp servo gearboxes with electronically controlled dual antibacklash servos for same reasons.
There is a use for antibacklash gears but their use is pretty unique, not generic as I assumed the OP was asking about.
www.KilroyWasHere<dot>com
RE: How accurate are spur gears?
Google or search the internet for "AGMA Fine Pitch Tolerances / Quality Grades for Gears"