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Robomower Part 8 - Mowing something...

A couple of posts ago, I promised a reciprocating saw. Today I discovered that somewhere in that whole “Measure Twice, Cut Once” thing, I seem to have missed something: The mower deck was just a bit too long to fit within the length of the frame. The way I saw it, I had couple of options. First, just ditch the deck altogether, and spend $25.00 or so on a used one off of a gas-powered motor. Since gas mowers don’t need to accommodate batteries, the decks are a little bit shorter, and I was confident I could wedge it in just fine. With that in mind, I figured I had nothing to lose by attacking the current deck with a reciprocating saw, and, drawing inspiration from Michelangelo, cut away anything that wasn’t a mower deck. As it turns out, once I was able to let go of the idea of hanging the mower deck from the frame by the deck’s axles, I just shaved a couple of inches off of the front, and a little off the sides, and it fit just fine. Of course, making any part of this thing smaller is a good idea! The problem was that the mower in its pre-reciprocating saw configuration had a built-in height adjustment system. I really wanted to keep it intact, but it was squarely in the way of the frame. Also, the physics of the system meant that the entire deck would move fore and aft as the height changed, which meant that it would require even more room in an already cramped environment. So away it went. I still wanted some height adjustment, even if it was pretty basic and required some work to get it set up just right. There were some holes in the bottom of the deck, and I drilled one more. I then ran some 5/16″ threaded rod through the holes. I then attached a cross member made form 1 1/2″ angle iron at the rear, and one made of 1″ flat bar stock at the front. I drilled hole in these, and ran the threaded rod through. The mower now hangs beneath the robot frame, and by tightening or loosening the nuts attached to each rod, I can adjust the height of the mower deck.

Mower deck install

The mower deck installed in the robot frame. The threaded rods provide a point of attachment as well as a method of height adjustment.

Now it was time to put it all together and see if this thing would actually cut grass!

As of right now, I am still waiting for a relay that I need in order to create a remote control switch to turn the mower blade on and off. For now, I just hooked up an ordinary 15A light switch to give me at least some control over when the business end would be swinging.

I also figured it would be good time to neaten up the wiring on the main bot battery box, and keep all the control logic from sliding around on top of that relatively slick surface. I re-used a nylon webbing retaining strap from the wheelchair to keep the main batteries in their tray, and the nylon carry straps from the sides of the battery case to keep a 1/4 piece of wood scrap in place. This scrap became the main electronics panel. I attached the B.O.S. to the wood with drywall screws, and the Sabertooth with some small brass wood screws I found lying around (So far there hasn’t been a heat problem, but I suspect in the future I will be putting in some stand-offs for better air flow around the Sabertooth. The BR6000 was just tucked under the retaining strap. I’ll think of something do do with that sooner than later, likely involving an Altoids tin.

The "Control Panel"; A 1x4 scrap and some screws...

So armed, I called out Mrs. Zennmaster and daughter Maile, and went to go show some weeds who’s boss. I flipped on the light switch and the B.O.S.. The mower spun up, and the bot was moving. Mowing was happening! Unfortunately, the mower batteries turned out not to be in the shape I thought and hoped they were, and so the blade didn’t really get a lot of juice behind it. The bot, however, worked great! With everything battened down a little better, it was just as fast, but a lot less “loose” looking and sounding. All the connections stayed together, and the thing just looked happy.

After deciding against further use of the mower blade until a better power source and switch could be added, I removed the light switch and the mower batteries, handed Mrs. Zennmaster the camera, and away we went!

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