The three main components that will make the Robo Laundry Pole.
Living a self-sustaining lifestyle off grid in the country requires a good amount of DIY ingenuity, along with careful consideration of power usage. Obviously, a clothes dryer is not something we would have out here considering it is one of the most power hungry beasts as far as appliances are concerned. Our goal is to be completely off-grid someday.
Currently, we use an outdoor clothesline, and although it is powered by free sun energy, it’s somewhat small for our needs and requires a hike up and down 15 stairs with several heavy laundry baskets. Yeah, when you work the land, you go through a lot of clothes! DIYers do not settle for off the shelf solutions that often fall short of expectations, so I decided to dig into my scrap pile and create the ultimate laundry drying solution for our needs.
Being able to hang laundry from the top of the stairs was the first goal which would require a long line between some type of pulley system. That’s pretty much standard for our country living. Since I like a challenge, I decided to take the concept a lot further and make it automated.
The Robo Laundry Pole will still use a cable between pulleys, but it will be driven by an old powerchair motor that’s powered by a 12 volt battery charged by the sun. This way, the line can be driven like a conveyor belt in either direction when hanging or collecting bulky laundry. The powerchair motor also includes a plastic wheel, so it should be compatible with standard clothesline cable.
I went into the back of my robot parts shack and found the three main components that will make up this project: a powerchair DC gearmotor with wheel, a half decent car 12 volt car battery and 300 feet of plastic coated heavy laundry line. Ok, let’s get this project going!
A powerchair DC motor with gearbox and plastic wheel.
Power wheelchair and scooter motors are very powerful and well-built DC motors that include a gearbox and an output shaft that is easy to mount to a wheel or pulley. This 20-year-old motor is perfectly functional and is rated for 24 volts, 300 watts, and 150 RPM at the output shaft. The included nylon wheel will also make a good drive pulley for the clothesline wire, although I will probably need to wrap the wire twice around to create enough drive friction.
I will run the motor at 12 volts instead of 24 volts, so it should turn at around 60 RPM, a good speed for the clothesline. Even at half the voltage, the torque on this motor is incredible; therefore, drive power won’t be an issue. As a testament to the power and efficiency of this motor, I connected it to a 1.5 volt flashlight battery and could barely hold back the wheel even at the slow speed it was turning.
300 feet of plastic coated heavy duty clothesline cable.
My clothesline will need to span 75 feet in one direction. I found the heaviest gage of stranded cable available at the hardware store. The longest roll they had was 300 feet that would easily make the 150 foot round trip with plenty to spare. This type of clothesline duty cable is also plastic coated, so there will be no interaction between the metal and the clothes, and friction will be much better on the nylon drive wheel.
The hardware store also had cable joiners, but they looked like junk. I’ll fabricate my own later using whatever parts I have in my scrap metal bucket.
Plastic coating prevents oxidization and cable fraying.
Another important job that the plastic coating around the wire will do is to protect the metal from oxidizing and to ensure that no strands come free over time. A wire rope like this made of many strands can be very dangerous if it unravels, especially when working around it with your bare hands. The rubbery plastic coating should also introduce some good grip between the cable and the smooth surface of the wheel being used as a drive pulley.
A few baskets of wet towels can easily weigh 100 pounds. Drive friction is as important as the cable’s ability to span 75 feet without sagging all the way to the ground.
A large 12 volt car battery in half decent condition.
I intend to power the robot laundry line from solar energy that will charge up a 12 volt battery. This older 60 amp hour lead acid car starter battery is a beast, but still holds about half its capacity, which is probably enough to run the powerchair motor nonstop for 24 hours or more! Since the motor will be idle for most of the time, a very small solar panel like the ones you find on outdoor LED lights should keep the battery topped up. This will be explored near the end of this project.
The 10 inch drive pulley mounted to the motor shaft.
With the tire removed, the total diameter of the pulley will be 10 inches, which would result in a total line travel speed of 1.8 miles per hour if the motor did yield a 60 RPM shaft speed. This is about walking speed which is certainly in the ballpark. If I find the line does move too fast, I can simply add series ballast between the battery and motor to reduce the current. A 12 volt headlight bulb would work nicely for this.
Powerchair motors include a normally closed magnetic brake.
For safety reasons, you will find a magnetic brake on the primary motor shaft on all power chair and shopping scooter gear motors. This brake is fully engaged when there is no power applied so that in the event of a total power loss the vehicle will stop in place rather than coast out of control.
To disengage the brake, 24 volts is applied to the magnetic coil that moves the braking plates away from each other. Unfortunately, this brake will not engage with only 12 volts, so I will remove it completely. Back driving the motor does take some amount of force; I’m hoping no brake will be needed. I will deal with this later if necessary.
The magnetic motor brake removed from the motor shaft.
A few cap screws fasten the brake assembly to the motor shaft, easily removed as shown here. The brake consists of a flat electromagnet that pulls to plates apart when engaged. When idle, the friction introduced between the two plates prevent the motor from turning. These parts will come in handy for some future project – back in the stock pile they go!
Spinning up the motor for a speed test.
With the magnetic brake removed, I connected the motor directly to a battery for a quick test to make sure it’s in good working order and to verify the total RPM.
The motor spun up the wheel at the expected 60 RPM. My failed attempt to hold it back by hand only reduced the speed by a few RPM at the most. Hey, don’t get your hand caught between the wheel and motor if you are working with these components, measured in foot pounds of torque; there is more than enough power to break your fingers or wrist here!
A pair of 6×6 wooden posts will support the line at each end.
Knowing that the clothesline may be required to support 100 pounds or more, it’s important to create a solid support system at each end of the line. Those cheap cast aluminum pulley kits just bolt to the front of the house with a few small woodscrews, but there is no way I am doing that!
The Robo Line will have 6×6 treated posts at each end – one fastened to my home built front stairs, and the other bolted to the woodshed using large lag screws. I leaned the poles in position to verify the total run and angle between them.