Been thinking about a robot lawn mower for about 40yrs
Made a few chassis using windscreen wiper motors decades ago.
Ok on the flat but old second hand wiper motors don't last that long.
The electric scooter craze meant low cost DC motors are now easier to get.
We use these at work as general purpose equipment.
For reasonable speed a wheel speed of 50-100RPM would determine the gearbox reductions needed.
Even the geared DC motors will need an extra stage.
The worm drive wheel chair motors have more reduction but cost more.
Smaller window winder motors also can be used for the smaller bots.
https://www.parallax.com/product/arlo-r ... orm-system
For long life Brushless DC motors would be the best type.
These are just starting to be used in cordless drills etc
The RC model plane motor can get high power in those outrunner types.
But they have high RPM which means large reductions
12volts means high currents, 24V systems would allow for lower current and higher efficiencies.
Higher efficiencies means longer battery life = more lawn mowed.
The latest battery electric push mowers are now 36- 56volts etc
The people designing these have spent a lot of money.
To get more power you need more batteries, but most are designed around the cheapest Li-ion cell.
Which is the 26650 or 18650, ie 18/26mm diameter 65mm long cell.
You can put them in parallel or in series, series is more common hence the increase in cordless drill voltages.
Batteries are the issue.
Lead acid/gel cell are the lowest cost but heavy and if you discharge them too low they don't last that long.
Lithium-ion are lightweight but need good chargers and battery protection.
LiFePO4 are in somewhere between.
The two wheel drive with two castor wheels seems like a good chassis type.
But if I am going to spend so much money on an electric mower why not make general purpose machine.
Electric motors have very good low speed torque so you can use them for mini plows, tillers etc.
This design is the best I have seen so far for a GP electric drive system
And this one has gearbox designs for those DC motors
Making them autonomous is a much bigger challenge, but google Deep learning.
I think it is nearly within reach, especially if you do something like paint the edges orange or something like that
Most have a RF sensor that detects a cable dug in around the edges.
The walk behind tractor is actually the worlds most common tractor design.
An electric autonomous version could change the third world and my backyard
Lead acid batteries are fine as the extra weight helps with traction.
Spend a bit more for the deep cycle type.
Grab some solar panels for charging, get some LED lights and you have a backup lighting system.
Useful if blackouts are common in storm season.
You can make a smaller mower that just mows parts every day instead of doing it every two weeks which requires a heavier cutting blade. Use a kids ride on plastic car for bits?
Or make a dozen tiny ones and have a robot swarm.
Teach a drone to fly upside down? Have a tethered version so battery life is a none issue.
Wheels, inflatable? foam filled trolley wheels?
Seen some for those robot mowers use rigid plastic with teeth for traction.
Robocut was the best of the kits but seems to have gone.
http://hackedgadgets.com/2008/09/14/rob ... -platform/
http://forums.parallax.com/discussion/7 ... -lawnmover
Push mowers have rigid wheels.
Real RC mowers with tracks
http://www.mcconnel.com/remote-control- ... 0/robocut/
Steep slope mowing kills people which is why these are becoming popular.
Plastic saves weight, steel is strong, wood is cheap.
Foamed PVC board about 12mm thick is easy to work and glues well.
Or save yourself a lot of trouble and just go out and buy one
Ouch, 1/4acre block mower is nearly $2000, go get second hand ride-on.
$2000 could buy a bunch of bits to DIY mower.
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