Remote Controlled Window Lifter by Steve M. Potter "WindowMoto"

MATERIALS

1. Cordless drill. Pretty much any cheap modern one will do.
2. Pulley
3. Spring
4. Strong nylon cord
5. (3) fencepost brackets
6. Small metal bracket
7. Sturdy hinge
8. Sugru rubber glue
9. Hot glue
10. E6000 glue
11. Wood screws
12. Piece of cardboard or thin plastic
13. 12" x 1/4" steel or aluminum rod
14. Roller skate or skateboard wheel
15. Heavy (10 or 12 gauge) two-conductor stranded wire, long enough to reach from where you like to sit to where the window is.
16. Electrical tape or heat-shrink tubing

TOOLS

1. Dremel or Foredom rotary tool and a carbide cutting bit
2. Drill (a second one, or plan your building process carefully ;)
3. Screwdriver
4. Scissors
5. Labeler
6. Battery charger for your WindowMoto
7. Soldering iron or gun and solder
8. File and sandpaper
9. Hot glue gun
10. Wire cutters and stripper

I used the Chicago Electric 18V cordless drill with NiCad battery from Harbor Freight, which was nearly as cheap as this other one they are now selling. Mine has the advantage of a "Turbo" speed setting (see video http://youtu.be/huoiStQ3jX4), not really necessary. The key to success here is revealed when you look inside the drill: both the speed control trigger and reversing switch are electronic, not mechanical. That allows you to separate them by many feet, so the motor can do its job over at the window, while the controller with its battery sits comfortably in your hand at the other end of a wire. Yes, you could get sophisticated with IR remotes, Bluetooth or other wireless schemes, but the wired approach works well and is very easy to build.

Disassemble the drill, careful not to lose any screws. Remove the motor and gearbox from its housing. Take photos to remember how to re-assemble if needed. Remove the speed control trigger and reversing mechanism, and plan where you will cut the handle away from the motor carefully, so that the reversing mechanism will still be functional in the handle. Now with just the outer plastic shell of the drill in hand, one half at a time, use a Dremel with a bit that allows sideways cutting motion (I had the best effect with the one on the right) to carefully cut/saw the handle off the motor housing. Wear goggles as plastic bits will be flying everywhere, and leather gloves may be a good idea too, to protect your hands from the sharp bit if it slips. Use a pretty slow speed when cutting through plastic; the idea is to chip away at it, not melt it. Also, melted plastic tends to gunk up the bit, and may even catch on fire.

After you have cut the handle from the motor body, and removed any sharp flash with sandpaper or a file, cut the 2 wires leading to the motor and solder your 10-gauge 2-conductor stranded wire to those wires. It helps to use a soldering gun here, since many electronics soldering irons don't have enough heat to solder to fat wire well. You will be pushing a lot of amps through this wire at low voltage, so a thicker wire with a good solder joint means a faster motor, with less voltage drop across the wire, and less chance of melting insulation and starting fires. Insulate the solder joints with heat shrink or electrical tape.

Solder the handle's cut wires to the other end of your fat cable, and insulate. You might also want to install some sort of strain relief to hold the cable to the cut top of the handle, in case the cord gets yanked. This could be a large blob of hot glue or Sugru rubber glue.

Cover the ragged cut edge of the handle with a piece of cardboard or flexible thin plastic (like a milk jug) and glue that on with hot glue.

Make a rubber base for the motor with Sugru or silicone rubber by
squashing it down onto glue blobs on wax paper or other non-adhesive surface on a flat table. Be sure not to get any glue stuck in the motor or gearbox, or the moving parts like the chuck and clutch setting. When the glue has set, remove the wax paper and bolt the motor down to the window sill using wood screws and fencepost brackets. I included more Sugru between the motor and brackets to hold it tightly under a heavy torque load.

Mine your garage for those old skate wheels you don't need any more. It's a fine ball bearing with a rubber standoff that is about the same size as the drill chuck diameter. Install a foot-long 1/4" diameter steel or aluminum alloy rod into the drill's chuck and the skate bearing, and bolt the skate wheel to the window sill as you did for the motor, using Sugru to hold it firmly in the bracket. The rod should be level. Do not use tubing. It will buckle. Use solid rod.

With very long wood screws (ideally, with anchors), mount a pulley on a strong spring to the top of the window frame. I used a hinge to do that, but a wide variety of hardware would suffice for this purpose. Choose hardware that is able to tolerate not only the weight of the window, but also to overcome its inertia and static friction when rapidly opened and closed.

Attach a metal bracket to the window that is to be lifted. If the bracket has sharp edges, file them smooth. Since our window frame was vinyl and hollow, I actually glued the screws in with E6000 glue. Be careful not to damage the glass or window seal hidden inside the frame. Mount it as close to the top edge as possible.

Wrap a strong nylon cord (e.g., high-quality paracord) around the bracket a couple times before cinching it down tightly. Loop this cord over the pulley, and back down around the metal rod. Loop it several times around the rod to get a good grip on the rod. Now tie it into a loop, under quite a bit of tension, enough to stretch the spring a bit, and flex the rod a bit. To do this more easily, I first created a slipknot loop in End #1 of the cord. Then I put End #2 through the slipknot's loop, tightened the loop, and used the slipknot as a pulley to add the right amount of tension. Then I tied a few knots in End #2 so it could not slip back through the slipknot. Sailors and boy scouts will have better ways to do this, I am sure. But it works!

Charge your drill's battery, plug it into the controller handle, and let it rip!

Add a label to the remote controller to indicate which way the reversing switch works to move the window up and down.

Adjust the drill's clutch so that it slips when the window reaches full-closed or full-open. That will reduce wear and tear on the cord and reduce the chance of something getting destroyed by the awesome power at your fingertips.

My drill has a locking mechanism when it's not energized, which keeps the window securely shut from potential intruders. So I don't need to use my fancy window latch extenders you may have noticed in the video, which can be locked and unlocked using a long grabber. HOWEVER, if you only actuated one pane of a double-hung window, you need to screw the other pane shut or intruders might sneak in. Again, choose screw locations carefully so as not to hurt the glass or seals in the window, or the counterweight mechanisms in the window frame.

As you can see from my simple drawing, I had planned to include some sort of limit switches for safety. This turned out to be completely unnecessary thanks to the drill's clutch, which works like a charm.

Before I came up with this simple design, I had a lot of fun inventing a much more complicated WindowMoto. Until it failed dramatically.

I created a cheap leadscrew with a long stainless steel 3/8" all-thread rod extending the height of the window, and a brass coupler moving along it, mounted to the window. The rod was rotated by a large Ford car window motor that I had hidden inside the wall below the window sill. You might see the patched hole it used to poke through, as well as two big bolts at the top of the window (by the hinge) that held the upper skate wheel bearing. I controlled it using a Pololu motor control shield on an Arduino microprocessor. It sort of worked for about two or three goes. One problem was resonance in the leadscrew that created huge vibrations and noise at certain points. The pitch of the threads was too fine, so it took a long time to travel at a non-vibrating speed. The motor could be sped up very fast with the controller, but this vibration lead to wear on the brass coupler's threads and the thing suddenly jammed up. Permanently seized. Even though I had greased it up well beforehand. Fail and learn!

Moral: sometimes, simpler is better.

Let me know if you implement my drill-based WindowMoto, or your own improved version, in the comments!