Cantilevered Loads Simplicity ® Plain Bearings
Counterbalance If holding the 2:1 ratio is not possible, one method of preventing binding problems is using a counter balance. For efficient counter balances in horizontal applications, use this formula: M • Y = W • Z Note: To avoid problems when running without mass: (M) Z = 1-1/2 s W can be calculated. Load on bearing will be: M + W # of bearings
Y
W
Load or Force
M
X
Z W
Y
Load or Force
M
X
Example: 50•24=W•Z(Z=1-1/2•6=9)
W = 50 • 24 = 133 lb. 9
24"
W
50 lb. Load or Force
Load per bearing: 50 + 133 = 45.75 lb. / bearing 4
6"
General Rules: 1. Drive Force Ratio (D) should never be larger than 2. A Drive Force Ratio (D) larger than 2 can cause the slide to lock up. 2. Load Force Ratio (L) can be larger than 2, but as this ratio increases, the drive force required to move the slide increases dramatically. A Load Force Ratio (L) larger than 4 is not recommended. 3. If the slide is occasionally operated unloaded, use the distance to the slide’s center of gravity as the distance to the load ( l ). Vertical Applications: 1. If L is between 0 and 2, the lowest drive forces occur when the value of D is about 90% of L (D = .9 • L). However, D values between 0 and L will work fine. 2. If L is between 2 and 4, use this equation: D = 4 - L Horizontal Applications: For best results, the drive force should be applied as close to the shaft as possible no matter what the value of the Load Force Ratio (L) is.
Cantilever Loads and Drive Force Location without Counterbalance d = distance from shaft to Drive Force
l = distance from shaft to the load center of gravity s = center-to-center spacing of the bearings on the shaft (If non-self-aligning, then outside to outside distance should be used.)
L = l / s = Load Force Ratio D = d / s = Drive Force Ratio
Shaft
l
Load
s
Drive Force
d
Hanging or “Top Heavy” Horizontal Applications with High Acceleration Rates: If your application will have high acceleration forces, use this formula for the value of the Drive Force Ratio: D = 0.8 • L x a where a is acceleration in g’s.
Drive Force
Load
144 Round Shaft Technology • pbclinear.com
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