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In many applications, Joyce Bevel Gear jacks are more efficient and faster
than worm gear driven jacks. To determine the suitability of a Bevel Gear
jack for your application, use the steps below to calculate load, travel
speed and duty cycle.
Step 1 - Determine load in pounds.
Step 2 - Determine velocity in feet per minute.
Step 3 - Determine duty cycle in terms of minutes operation (time on) and
minutes resting (time off).
Step 4 - Calculate PV
PV= Load in pounds x velocity in feet per minute/1000
Step 5 - Calculate T
T= cooling time (
from BG 150 Bevel Gear chart) x Time on/Time off
Step 6 - Plot the point on the Joyce Bevel Gear Jack Thermal Graphs for the
calculated values. See these graphs by clicking the desired model below.
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BG 150 and 250
BG 375 and 450
If the point falls below the line the application is satisfactory. If it is
above the line, recalculate T for the next size jack and plot the new values
for the next larger size jack.
Note: T must be calculated for the size jack corresponding to the graph,
since each jack has a different cooling time.
Step 7 - Calculate horsepower required
R.P.M. = velocity in feet per minute x 12 x input turns per 1" travel
(
from BG 150 chart)
Horsepower = Pinion torque (
from BG 150 chart) x Load x RPM/63,000
Sample
A 5000 pound load must be raised 30 inches in 15 seconds. The load remains
in position for 2 minutes. It is then lowered and remains lowered for 30
seconds. The cycle begins again. Determine the appropriate bevel gear jack
and calculate the horsepower required.
Step 1 - Load = 5000 pounds
Step 2 - Velocity = 30 inches in 15 seconds = 10 f.p.m.
Step 3 - Duty Cycle =
.....Time on = 15 sec. up + 15 sec. down = 30 sec. = .5 min.
.....Time off = 2 min. up + 30 sec. down = 2 min. 30 sec. = 2.5 min. off
Step 4 - PV = (5000 x 10)/1000 = 50
Step 5 - T = 38 (for BG 150) x .5 /2.5 = 7.6
Step 6 - The point for PV, 50, and T, 7.6, falls below the line for BG 150-D
and above the line for BG 150-S, therefore BG 150-D is appropriate.
Step 7 - RPM = 10 x 12 x 5.38 = 645.6
Horsepower = [.066 (5000) x 646]/63,000 = 3.38
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