E-Lawnmower Think Tank

[BrianG]

I've been doing a little thinking on making my own small electric R/C mower and just thought I'd start a thread to get other people's thoughts.

I have a small yard; it takes me around 15 minutes MAX to mow, so I'm thinking an electric R/C mower would be nice. When it gets hot, the last thing I want to do is sweat in the sun pushing around my current ~30lb mower. So, I started thinking about a simple mower I can build. Nothing too fancy. I could probably get a pre-built cordless mower for less than this project will cost, but it HAS to be brushless (of course). And besides, this will be fun; not to mention the neighbor comments.

Anyway, to make it a little easier on myself, I was looking at getting a cheap electric mower (something like this, except from Craigslist or something) and modding it for R/C use. It would already have the deck and wheels, but would take some work to get them geared right and be able to turn it. The one in the link is a corded mower with an 18" deck, 7" & 8" wheels, and 12A @ 120VAC motor. That's 1440w or almost 2HP. Pshaw! That level of power is nothing.

I'd obviously remove the handle, bag, and any other non-essential components.

I figured on running this thing on a 6s?p 20Ah LiFe pack. Should give me about 15 minutes of runtime assuming it needs that full 2HP constantly, which is perfect for my small yard. And if it's not enough runtime, I can always parallel another set of cells.

Couple that with that huge Turnigy 180kv outrunner on a Turnigy 150A 6s ESC should provide enough torque and speed for the blade.

For drive power, a MMPro running another low-kv outrunner geared for 5mph max speed (2mph mowing speed). Might have a little trouble gearing it low enough. I think a worm-drive would be perfect for this to get speed down and to keep the mower from rolling downhill if something happens.

Steering will be tricky. I've seen custom e-mowers with wheelchair/tank style turning, but I don't want to go that route simply for complexity despite the fact it really is ideal. I'm thinking normal vehicle steering will be sufficient; I'll just have to make a turn and back up to do what was missed on the arc. Maybe use 4 wheel steering to reduce the turn radius.

Not sure, but I'm thinking 4WD will be a necessity. Might make the driveline a bit complex, but still doable.

An alternative idea:

I'm wondering if I could simply use a weedwhacker line setup instead of an actual metal blade? Yeah, it will wear faster, but would be cheaper and lighter. My cordless weed eater auto feeds every time you stop and restart it, so a setup like that would work well.

If I did that, the setup would be lighter and less power hungry, but take more work. Maybe even use a Slash/Pede/Rustler rear-end, lock the diff, and use push rods instead of shocks.