I needed to replace my manual tree trimmer with an electric one, but after checking out the prices decided to make my own by hacking a reciprocating saw. This instructable shows how to hack a Ryobi One+ tool, since all my tools are One+, but I'm sure it can be done with any other brand with a few modifications. You'll need a reciprocating saw that you don't mind cutting up. I didn't want to ruin my everyday saw so I picked one up at a garage sale. Make sure you get a battery operated model. Don't even think of doing this with a plug in 120V unit. The results may be "Shocking!" Also, you'll need a non- conducting extendable pole. I used the one that came with my worn out trimmer. I just removed the cutting head. Again, don't use a metal pole. Don't cut around electrical wires, and wear safety glasses when using any power tool.
Step 1: Getting Started
Take the saw apart. One side will be held together with either philips or torx screws. Remove them and separate the halves. This is a good time to clean up and lubricate the mechanism as well. Cut the red + and black- wires between the trigger/ speed control and motor unit. Shove the wires out of the way temporarily and put the unit back together with a few screws. Cut the housing just ahead of the trigger and at the end of the battery holder. You will now have a control/ battery unit and a motor unit.
Step 2: Prepare the Motor Unit
Disassemble the halves again. Splice and solder flexible stranded wires to the negative and positive making sure to mark which is which. Also, be certain to use the same gauge wire and cover the joins with shrink tube or electrical tape. Make sure the wire is long enough to go through the entire extended pole. Use a rotary tool to clean away all plastic flashing and bracing in the area. Drill out the last screw hole on both halves with a 1/4" drill bit. Line up the inner half of the extendable pole with the holes and drill it to match. Feed the wires through the pole. Use epoxy glue on one side of the pole, install a 1/4" bolt and tighten the nut temporarily until the glue dries. Remove the nut, install the other plastic half with the screws and tighten down the nut permanently. You may wish to epoxy this half as well but if you do, it won't come apart again.
Step 3: Prep the Handle/ Battery Unit
Separate the handle, and solder wires to the - and + from the trigger/speed control. I opted for short wires with speed connectors. Also, you'll need a piece of pipe that will fit snugly inside the larger, lower half of the extendable pole. Easiest way to do this is to cut a piece from the upper part of the pole before you start, but I didn't think of this at the beginning. Luckily I had a short piece of pipe that fit. Again clean away all flashing and bracing from that section of the plastic handle till the pipe fits. Feed the wires though the pipe. Epoxy the pipe inside the handle and re- install all screws.
Step 4: Final Assembly
Put the extendable pole back together, feeding the wires straight through. Connect the handle wires to them observing polarity. Again, I used plug in connectors but you could solder and insulate if you wanted. Finally, epoxy the handle to the end of the pole.
After everything dries, you can try it out. Remember to use a proper blade made for pruning. A construction blade will just gum up. Also, I added a strong 90 degree angle brace to the motor end with epoxy and gear clamps just to make it stronger.
My unit performs fantastically for the small amount invested.