Ve6fi Amateur Radio
This Capstan Winch will be used to lift tower sections when building new towers and will be used to install and remove antennas used for Amateur Radio.
Requirements are that it can lift 500 pounds at a rate of 25 feet per minute.
500 lbs X 25ft/min = 12,500 ft lbs/min
12,500 ft lbs/min X 1/33,000 ft lb/min X 1/.50 efficiency = 0.75 HP
This means that a gear box, coupling and motor must be capable of handling approximately 3/4 horsepower.
The motor would draw how much current?
3/4 HP X (746 watts/HP)/120v = 4.6 amps at 120 V AC or .75 X 746/12 = 46 amps at 12 volts DC.
Go with the 120 V design and use a 1 HP motor.
What ratio gear box is required?
Motor RPM is 1800 rpm and gear box ratio selected is 60 to 1
1800 rpm X 1/60 = 30 rpm.
The Capstan turns at 30 rpm and since it has a radius of 1.5 inches to the center of the rope, the speed of a
rope on the capstan will be 30 rpm X 6.28 X 1.5/12 = 23 ft/min ( Circumference is 2 phi X Radius)
Go with a 3/4 HP rated gear box at a 60 to 1 ratio and rated for max load of 80 ft lbs torque.
Checking the 80 ft lbs of torque in terms of pull on the rope: 80 ft lbs X( 1/1.5/12 ft radius) = 640 lbs pull
on the load line so it meets the 500 lbs requirement stated above.
The coupling is used to transmit power from the motor to the gear box. It is used to avoid any misalignment
between the two units. The coupling spider size and material must be capable of transferring this power. Use
Hytrel spider with L090 lovejoy end pieces which are rated at 3 HP.
Use a foot switch to control the motor to pull a load up the tower. Release the pull rope with the motor
stopped to move a load down the tower. The schematic for the control is shown below. Insert some
Quench arcs and MOV across the main contacts on the 120v relay.
Use a sailboat type rope lock to hold the pull line when the motor is turned off and there is a load on
the load line.
Start off with a 5 inch diameter piece of Aluminum and turn it down in the form of a saucer and install
the necessary key ways or purchase a ready made Capstan drum.