I've been kicking this idea around for awhile and thought I'd draw some comments (and spears) from the tinkerers here.
This is a long post that describes a harebrained project that won't interest most people at all.
Overview: The project is a small ride-on lawnmower (approx 40" wide cut) that would have an onboard gasoline-powered 5500 watt generator (13 HP). This would power two drive motors, one for each rear wheel. Front wheels are free castering, steering is by differential drive of the rear wheels. The grass is cut by two or three rotating blades directly connected to AC motors (just like a plug-in corded lawnmower).
Layout: (I wish I knew Sketch-up!) Generator is at the rear of the vehicle, driver sits in front of it and low. The rear wheels are located outboard of the driver and generator, The mower deck is directly below the operator's legs. Castering wheels are at the front corners. The mower deck could be free-floating with its own adjustable wheels.
Below is a picture of the ($5000+ ) Zeon rechargeable ZTR mower. The layout I'm envisioning is similar, but with a generator back there in the bustle in place of batteries and a slightly lower seat. The "lap bars" would be replaced by a forward/stop/reverse handle on each side. And there would be a canopy and fuzzy dice. The Zeon has electric motors directly spinning the blades and two drive motors that operate through transmissions to power the rear wheels.
Power Factors: We've got 5500 watts max continuous at 120 VAC = 45 amps available. Standard corded AC lawnmowers with a 21" cut are typically rated at 13 amps max, so we'd need 26 amps total for two similar motors. That leaves 19 amps (2280 watts) for our two drive motors. That converts to a little over 3 HP total, or 1.5HP per side.
Estimated Weight: 750 lb
-- Generator: 170 lbs
-- 2 drive motors and 2 cutter motors: 60 lbs
-- Wheels and axles: 40 lbs
-- Frame, mower deck, blades, seat, wires: 300 lbs
-- Operator: 180 lbs
Cost of components: No good estimate possible. The 5500 watt generator is about $425. The mower deck could be salvaged from an old riding mower, mount the electric motors where the blade spindles used to be. The frame would need to be welded up, but without any steering components or suspension, it would not be complicated.
As a plus, during development all the sub-parts can be tested and run from the house using a (beefy) extension cord.
Why do it?
- Fun project
- Compared to a regular gasoline version this has no clutches, complicated transmission, steering mechanism, etc.
- If the generator gives me trouble I can easily remove it from the chassis and have it serviced--or replaced.
- A "real" small ZTR mower starts at about $2200
- It might actually mow the lawn faster than me and my push mower
- If we lose electricity, I've got a mower that can power my well pump or my fridge and furnace.
- I can add a small electric string trimmer to a front corner and trim the borders as I mow
- I've only got a few years left on my term life policy--this is a chance to make DW rich!
- I'm thinking there must be a way to get federal money for this. It's a hybrid! And, it could be "zero emissions" (Add the optional ballast weight in place of the generator, order the optional 2 AWG extension cord that conveniently plugs in where your clothes dryer gets power). Virtually silent mowing! Get Green bragging rights, a tax credit, and probably some sort of carbon offset payments.
Unknowns:
1) Are 1.5 HP drive motors (one per side) enough? I'm not building a racing machine, but if I can't go up a moderate grade or accelerate to 3-4 MPH (about 5 FPS), then this might not work. I've heard a lot about the fantastic low-end torque of electric motors, but is that only high $$ DC permanent magnet types? 3 HP doesn't sound like much. But, here's a 3/4 HP (4.5 A at 110VAC) electric winch that lifts 220 lbs (straight up) at 33 FPM. At our approx 750 lb all-up weight, a 1:5 slope, and 3 HP available, that would give a vertical lift rate of 5.6 FPM (which is faster than the vehicle's target speed on level ground). Obviously, that's just a back of the envelope approach, (I didn't do the MGS math) and there will be lots of other losses, but maybe these motors will be enough.
2) Source of drive motors/associated controllers: I'm guessing the optimum motors won't be the cheap motors. There are some (big) plug-in hand tools that could be pressed into service in the hillbilly approach: electric impact wrenches, etc. These come with their own gearing and controllers, just take the power from that 1/2" square drive and rig up a mechanical linkage to the trigger, plug 'em right in to the generator. Be sure to buy the extended warranty.
3) Brakes: I'll probably need some. Maybe a set from a small motorcycle would do okay.
"What do you do all day?" indeed.
Okay--ready for the darts!
This is a long post that describes a harebrained project that won't interest most people at all.
Overview: The project is a small ride-on lawnmower (approx 40" wide cut) that would have an onboard gasoline-powered 5500 watt generator (13 HP). This would power two drive motors, one for each rear wheel. Front wheels are free castering, steering is by differential drive of the rear wheels. The grass is cut by two or three rotating blades directly connected to AC motors (just like a plug-in corded lawnmower).
Layout: (I wish I knew Sketch-up!) Generator is at the rear of the vehicle, driver sits in front of it and low. The rear wheels are located outboard of the driver and generator, The mower deck is directly below the operator's legs. Castering wheels are at the front corners. The mower deck could be free-floating with its own adjustable wheels.
Below is a picture of the ($5000+ ) Zeon rechargeable ZTR mower. The layout I'm envisioning is similar, but with a generator back there in the bustle in place of batteries and a slightly lower seat. The "lap bars" would be replaced by a forward/stop/reverse handle on each side. And there would be a canopy and fuzzy dice. The Zeon has electric motors directly spinning the blades and two drive motors that operate through transmissions to power the rear wheels.
Power Factors: We've got 5500 watts max continuous at 120 VAC = 45 amps available. Standard corded AC lawnmowers with a 21" cut are typically rated at 13 amps max, so we'd need 26 amps total for two similar motors. That leaves 19 amps (2280 watts) for our two drive motors. That converts to a little over 3 HP total, or 1.5HP per side.
Estimated Weight: 750 lb
-- Generator: 170 lbs
-- 2 drive motors and 2 cutter motors: 60 lbs
-- Wheels and axles: 40 lbs
-- Frame, mower deck, blades, seat, wires: 300 lbs
-- Operator: 180 lbs
Cost of components: No good estimate possible. The 5500 watt generator is about $425. The mower deck could be salvaged from an old riding mower, mount the electric motors where the blade spindles used to be. The frame would need to be welded up, but without any steering components or suspension, it would not be complicated.
As a plus, during development all the sub-parts can be tested and run from the house using a (beefy) extension cord.
Why do it?
- Fun project
- Compared to a regular gasoline version this has no clutches, complicated transmission, steering mechanism, etc.
- If the generator gives me trouble I can easily remove it from the chassis and have it serviced--or replaced.
- A "real" small ZTR mower starts at about $2200
- It might actually mow the lawn faster than me and my push mower
- If we lose electricity, I've got a mower that can power my well pump or my fridge and furnace.
- I can add a small electric string trimmer to a front corner and trim the borders as I mow
- I've only got a few years left on my term life policy--this is a chance to make DW rich!
- I'm thinking there must be a way to get federal money for this. It's a hybrid! And, it could be "zero emissions" (Add the optional ballast weight in place of the generator, order the optional 2 AWG extension cord that conveniently plugs in where your clothes dryer gets power). Virtually silent mowing! Get Green bragging rights, a tax credit, and probably some sort of carbon offset payments.
Unknowns:
1) Are 1.5 HP drive motors (one per side) enough? I'm not building a racing machine, but if I can't go up a moderate grade or accelerate to 3-4 MPH (about 5 FPS), then this might not work. I've heard a lot about the fantastic low-end torque of electric motors, but is that only high $$ DC permanent magnet types? 3 HP doesn't sound like much. But, here's a 3/4 HP (4.5 A at 110VAC) electric winch that lifts 220 lbs (straight up) at 33 FPM. At our approx 750 lb all-up weight, a 1:5 slope, and 3 HP available, that would give a vertical lift rate of 5.6 FPM (which is faster than the vehicle's target speed on level ground). Obviously, that's just a back of the envelope approach, (I didn't do the MGS math) and there will be lots of other losses, but maybe these motors will be enough.
2) Source of drive motors/associated controllers: I'm guessing the optimum motors won't be the cheap motors. There are some (big) plug-in hand tools that could be pressed into service in the hillbilly approach: electric impact wrenches, etc. These come with their own gearing and controllers, just take the power from that 1/2" square drive and rig up a mechanical linkage to the trigger, plug 'em right in to the generator. Be sure to buy the extended warranty.
3) Brakes: I'll probably need some. Maybe a set from a small motorcycle would do okay.
"What do you do all day?" indeed.
Okay--ready for the darts!
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