Thread: Spacers in FIRST gearboxes
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Unread 31-01-2003, 07:51
jskene jskene is offline
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Axial thrust load for helical gears
You need to be aware that helical gears like the ones supplied for the gearbox generate considerable side (axial) thrust. That is, the gears try to slide sideways along the shaft when they are subjected to a load. The equation for this axial thrust (from Boston Gear's website: ) is:
Axial thrust load = (126,050 x HP) / (RPM x Pitch diameter)

So, for the large gear when driven by the drill motor in low gear, RPM = ~450, HP =~ 250watts/746 watts per HP = .34, Pitch Diameter of the 1224 gear = 2"
Axial thrust load = (126,050 x .34)/(450 X 2) = 190 lb. This suggests that you would be wise to use the aluminum tubing provided, and not PVC pipe.