Zero Turn Radius Electric Riding Lawn Mower

40580 Views 50 Replies 15 Participants Last post by bennettdan, May 19, 2011

TheRedBaron

Discussion Starter · Jan 31, 2011

Hey everyone:

I am looking at doing a zero turn radius riding mower conversion. However, as been mentioned in other posts, a hydrostatic transmission is inefficient when used with an electric motor. My idea is to use two hub motors, one for each drive tire, instead. Then I would use another electric motor for the operation of the blades.

This is 3 electric motors however, which adds a degree of complication to the design.

So my main question is if that is too complicated a set up?
Comments, Questions, and Concerns are more than welcome!

(basic mower stats: 16hp mower briggs and straton engine, 48" deck, zero turn steering)

21 - 40 of 51 Posts

PhantomPholly

· #21 · Feb 9, 2011

Nice lawn Major!

major

· #22 · Feb 9, 2011

ruckus said:
Will you give us some specs? Series or shunt wound? Controller or hard-wired? If series, do you have to limit speed or do the blades provide enough limiting force?

It is from this thread http://www.diyelectriccar.com/forum...ions-deck-motor-riding-lawn-moweri-45125.html

Glad you like it

And in case it is not in the referenced thread, the motor is compound wound and controlled by a single contactor.

And Pholly, I'll tell Tony you like his lawn. Mine never looked so good

major

TheRedBaron

Discussion Starter · #23 · Feb 13, 2011

major said:
Here's a deck I did a while back

That is a pretty nice set-up. Interesting idea to mount the deck in the front. Have any performance issues due to that? Also, is that the motor situated under the seat? I would then guess that the batteries are under the hood.

@ruckus -> I will post pics as soon as I can

major

· #24 · Feb 14, 2011

TheRedBaron said:
That is a pretty nice set-up. Interesting idea to mount the deck in the front. Have any performance issues due to that? Also, is that the motor situated under the seat? I would then guess that the batteries are under the hood.

I helped Tony build the deck to replace the original Electrak deck which was also front mounted. Tony likes it out there. He has a flat yard. Don't know how it would handle on hills.

He runs the tractor with a generator. Got tired of replacing batteries. He's run that thing for like 35 years. See that thread I referenced for details.

major

TheRedBaron

Discussion Starter · #25 · Feb 15, 2011

After looking at a couple of threads it looks like using one motor for the blades is more efficient than using three separate ones for each individual blade.

It also looks like having the belt system in place is still a good idea though that reduces efficiency so that the blade system can deal with individual blades slowing down.

Any idea on the efficiency of a belt system or where I can look that up?

Also, what is a good place to look for motors? I am trying to find one in the 3.5 HP or 2.25kW range and haven't been happy with the selections.

Thanks!

Jimdear2

· #26 · Feb 15, 2011

If you are going to use belt and need to search out a motor, look for one like a that won't run away if the belt breaks. Look for something like a Seperatly Excited (SepEx) or I think Perm. Magnet. There are some others as well.

Ask the experts about what you might want.

Jim

major

· #27 · Feb 16, 2011

TheRedBaron said:
Any idea on the efficiency of a belt system or where I can look that up?

Hi TheRed,

Median efficiency of the surveyed industrial and agricultural
belt types and constructions is 96 per cent. Within
rated and application power levels, efficiency ranges from 90 to 99 per cent depending on belt type

from: http://www.cptbelts.com/pdf/misc/energy_loss_and_belt_efficiency.pdf

Regards,

major

TheRedBaron

Discussion Starter · #28 · Mar 14, 2011

4

Hey Guys:

Here are some pics of the lawnmower. We have already removed the engine and if anyone is interested in a 16hp Vangard Briggs and Stratton (still runs) shoot me an email ([email protected]). (I don't know why you would be interested considering the forum we are on but....)

Anyway the transmission of the thing is all jacked up. The engine runs and the blades will turn on but the mower doesn't actually move. This inclines us to think we should just rip everything out and go with a motor for each wheel running off the chain final drive rather than try to fix up the transmission. I have also read a couple articles describing the issues these cone drives had so going with a technology proven to go bad doesn't give me a good feeling.

On the battery front, it looks like we will probably go with a thundersky or HiPower 100ah LiFeSO4 battery

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PhantomPholly

· #29 · Mar 14, 2011

TheRedBaron said:
Hey Guys:

Here are some pics of the lawnmower. We have already removed the engine and if anyone is interested in a 16hp Vangard Briggs and Stratton (still runs) shoot me an email ([email protected]). (I don't know why you would be interested considering the forum we are on but....)

Anyway the transmission of the thing is all jacked up. The engine runs and the blades will turn on but the mower doesn't actually move. This inclines us to think we should just rip everything out and go with a motor for each wheel running off the chain final drive rather than try to fix up the transmission. I have also read a couple articles describing the issues these cone drives had so going with a technology proven to go bad doesn't give me a good feeling.

On the battery front, it looks like we will probably go with a thundersky or HiPower 100ah LiFeSO4 battery

Oh my gosh, it's an old cone drive. What a blast from the past! I remember helping my boss put one of these on display 36 years ago when the technology was brand spanking new and I was working as a bicycle repairer at a lawnmower sales & fixit place....

TheRedBaron

Discussion Starter · #30 · Mar 14, 2011

PhantomPholly said:
Oh my gosh, it's an old cone drive. What a blast from the past! I remember helping my boss put one of these on display 36 years ago when the technology was brand spanking new and I was working as a bicycle repairer at a lawnmower sales & fixit place....

Wow! Dinosaurs ran on cone drives? Who knew?

TheRedBaron

Discussion Starter · #31 · May 1, 2011

Update on the lawnmower's status. We currently have both of the wheel motors working! That just shows us testing one of them, but we did the other one as well.

Below is a picture of the current status of the mower. As you can see the new drive system of the mower is a lot different than the old cone drive. We are using a BLDC 500 Watt, 1000 rpm motor for each of the wheels. For the blade motor we will be running a 8 hp, 16 hp continuous brushed dc motor.

Our current issue is figuring out how to set up the control sticks. The controllers for the drive motors accept 0-5 volts. However, trying to get that sort of behavior mounted to the sticks is an issue because we still want to be able to have the reverse capability of the zero turn. The controllers have a switch that must be enabled in order to reverse the motor.

In other words we want some sort of functionality that looks like this:
+5v (full forward) ---- 0 Volts (stationary) ----- +5v (full reverse)

We were planning on using some sort of potentiometer set up but nothing we can think of would allow us to map this sort of behavior. If anyone has any ideas, that would be awesome because we are a bit stuck on this issue!

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GizmoEV

· #32 · May 1, 2011

TheRedBaron said:
Our current issue is figuring out how to set up the control sticks. The controllers for the drive motors accept 0-5 volts. However, trying to get that sort of behavior mounted to the sticks is an issue because we still want to be able to have the reverse capability of the zero turn. The controllers have a switch that must be enabled in order to reverse the motor.

In other words we want some sort of functionality that looks like this:
+5v (full forward) ---- 0 Volts (stationary) ----- +5v (full reverse)

We were planning on using some sort of potentiometer set up but nothing we can think of would allow us to map this sort of behavior. If anyone has any ideas, that would be awesome because we are a bit stuck on this issue!

Either a circuit board to interpret the signals or maybe a simpler thing might be two pot boxes. One for the forward direction and one for the reverse direction. Hook the arms to a spring so that when going forward the spring connecting to the reverse potbox stretches and vice versa. Hook up the micro switch in the potboxes to enable forward/reverse as required.

major

· #33 · May 1, 2011

TheRedBaron said:
In other words we want some sort of functionality that looks like this:
+5v (full forward) ---- 0 Volts (stationary) ----- +5v (full reverse)

Hi TheRed,

Check out wigwag controls. They are dual direction input command devices used on handicap carts. I repaired one (installed a small Curtis controller) for a friend. Might be available on the Curtis web site.

Likely those won't connect directly to your motor controllers, but may give you some ideas. I have seen a couple of examples of homemade devices which function this way. IIRC, had 2 pots, microswitches and relays with a spring centering device.

major

JRP3

· #34 · May 1, 2011

Here are some wig wag pots, they also have hall effect versions:
http://www.tecknowledgey.com/catalog/default.php?cPath=54_55&osCsid=f9dc9165cb26880b4ce3de251a48d6b0

Anaerin

· #35 · May 1, 2011

You might want to look at this, I think it's pretty close to what you're looking for, done with a regular pot:
http://www.diyelectriccar.com/forums/showthread.php?p=1674

mizlplix

· #36 · May 1, 2011

Greetings to all. this is my first post here on the site.

By a strange coincidence, I am a mower mechanic for the local school district. I keep up a fleet of 20 riding mowers of all sizes and types. But, 14 are the zero turn type. 10 are the Hustler 72" Super-Z and 4 are the 64" John Deere Z-Trak type.

Both types use individual fixed displacement hydraulic wheel motors, but one has a unified double pump and the other has two/single pumps.

Not to start any bad feelings, but either would be easy to do a single DC motor to drive the hydraulic pumps and mower deck, (which is direct-belt driven).

The hydrostatic pumps are of the positive displacement, variable volume type with a swash plate to adjust the output. There is no torque converters or slippage involved. they would be a great match for DC power.

The electric motor would need to be RPM controlled automatically by the controller. The deck is always an electric clutch. the variable displacement pumps would take care of for/rev and speed settings.

Turn on the key, and the DC motor starts at a set RPM. drive off trailer to mowing location. start the deck with a toggle switch. A sensor would be needed to throttle up and down with load to stop over speeding when suddenly unloaded.

Oh, well , just dreaming.

MIZ

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GizmoEV

· #37 · May 2, 2011

MIZ,

A permanent magnet motor or a shunt wound motor would be perfect as they keep a fixed RPM. If they are forced to spin faster then they regen and if slowed they pull more current to maintain speed. I have heard that shunt wound motors are better for this purpose because they handle the heat better. Another alternative is a SepEx motor. The controller on my Gizmo has a speed control mode rather than a torque control mode so it should be able to do the same thing and not have issues of over speeding when suddenly unloaded.

TheRedBaron

Discussion Starter · #38 · May 2, 2011

mizlplix said:
Greetings to all. this is my first post here on the site.

By a strange coincidence, I am a mower mechanic for the local school district. I keep up a fleet of 20 riding mowers of all sizes and types. But, 14 are the zero turn type. 10 are the Hustler 72" Super-Z and 4 are the 64" John Deere Z-Trak type.

Both types use individual fixed displacement hydraulic wheel motors, but one has a unified double pump and the other has two/single pumps.

Not to start any bad feelings, but either would be easy to do a single DC motor to drive the hydraulic pumps and mower deck, (which is direct-belt driven).

The hydrostatic pumps are of the positive displacement, variable volume type with a swash plate to adjust the output. There is no torque converters or slippage involved. they would be a great match for DC power.

The electric motor would need to be RPM controlled automatically by the controller. The deck is always an electric clutch. the variable displacement pumps would take care of for/rev and speed settings.

Turn on the key, and the DC motor starts at a set RPM. drive off trailer to mowing location. start the deck with a toggle switch. A sensor would be needed to throttle up and down with load to stop over speeding when suddenly unloaded.

Oh, well , just dreaming.

MIZ

That may be more practical idea than you think. Considering the price of gasoline and where that is headed, starting to convert some of those mowers (both zero turn and standard) to electric may not be that bad of an idea. Considering the amount of mowers you have to maintain, do you live in a more populated area? I ask because if there is a decent college nearby you might be able to get a class full of engineers interested in doing such conversions. Plus with college funding you might even be able to get the entire thing paid for.

I say this due to direct knowledge. I am a Senior in a Big 10 school in the electrical engineering department and we are currently converting this lawn mower to electric drive for the city's maintenance department. As a community outreach program, we have received quite a bit of school funding that has allowed us to pretty much pay for the entire project ourselves.

In any case, I wish we had gotten a hydraulic system instead of a cone drive. The drive system setup would have been a lot less difficult though the hydraulic system may not have been as efficient as the direct chain drive we are using now.

As of now, we may just mount multiple over sized pots to give us the functionality we need instead of some sort of wig-wag pot. We have also thought about using string pots to map the behavior as well. If I have time, Ill post a drawing of what we are thinking about doing.

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mizlplix

· #39 · May 3, 2011

My biggest concern on a mower conversion would be batteries.......where to put them and getting enough to run about a realistic 3 hours per day. Lithium for certain....

A zero turn is a lean and bare animal. I will measure a Hustler Super 72 today to get a size for the front and rear packs.

They are running the 31 HP Kawasaki V-Twin motor at present. what would be a good electric replacement?

JRP3

· #40 · May 3, 2011

That might be a good application for a swappable pack so you don't carry around excessive amount of batteries. How many gallons of gas does a mower use in three hours? That should give you an idea of the kwhs you need in a pack.

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