Simran RPU80 Measurements and Calculations for Applying the RPU, Calculation of cylinder volume

Simrad Reversible Pump RPU80/160/300

2 MEASUREMENTS AND CALCULATIONS FOR APPLYING THE RPU

2.1 Calculation of cylinder volume

The RPU80 is recommended for cylinders between 80-250 cm3 (4,9-15,2 cu. in.), RPU160 for cylinders between 160-550 cm3 (9,8-33,5 cu.in.) and RPU300 for cylinders between 290 -960 cm3 (17,7-58,5 cu.in.). These figures will give for a rudder angle of 70 degrees (35°-0-35°) a hardover to hardover time of 6-20 seconds equivalent to a rudder speed of 11,6-3,5 deg./second. Based on experience 6-8 deg./second seems to be the optimum speed for autopilots with proportional rudder control. However, a rudder speed between 11,6 deg./second and 3,5 deg./second should normally cause no problem, particularly not the high speed which will be reduced by the autopilot electronics.

Depending on type of autopilot the rudder speed is automatically or manually adjusted during installation and commissioning. Refer to page 1-1 and the autopilot manual for detailed information.

The cylinder volume is calculated from the formula:

Volume =	L(D2	− d 2 )π
		4
Where

L = stroke length

D = internal cylinder diameter (= outside diameter – 0,6) d = push rod diameter

π= 3,14

(All dimensions in centimeters)

2.2 Minimum rudder time adjustment

(Applies only for Junction units J1000B, J101A and J45A)

The minimum rudder time can be found as follows (see figure 2- 1):

Draw a horizontal line from the applicable value on the cylinder volume axis. Rudder time may now be read on the horizontal axis.

By means of potentiometer RV1 in the Junction unit the rudder time can be increased.

12 20220422N

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