Electric Lawn Tractor Conversion??

[sean]

So I have about an Acre lot to maintain, and i have an OLD 1972 Bolens 1556 Hydrostatic Tractor. This is about the same size as a large riding lawn mower but weighs about twice what one would at around 800lbs. It has Hydraulic lift, shaft drive front and rear PTO.

Not mine but similar:

Maybe my end result?

of course with a motor and batteries as ballast

Currently it has a 15 hp Tecumsuh ICE POS with a 4 belt pulley on it 2 belts driving the hydraulic pump and 2 belts driving the PTO when engaged. The engine is on it's way out and has been getting progressively worse, I have been thinking that rather than putting a honda or other ICE engine in there I could convert to Electric. There is room enough I think I could put enough batteries in there, and the weight wouldn't be a negative feature for a tractor as it is just added traction.

I plan to get a Hydraulic "12V power unit" such as This one:http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_200329764_200329764 available from Northern Tools with a trasducer set to trigger the solenoid and run the pump when pressure drops. Or make it work on pedal actuation and lift use. Anyway just not running the hydraulic pump all the time unless you are driving and when it is necessary.
I still need to find the hydraulic demands for the transmission on the tractor and ensure that the power unit I get matches the pressure and rate demanded.

What I want to know is what size and type of motor should I plan on using to drive the PTO? The impliments I currently own are a 42" belly mower a 36" rear tiller and a 54" sickle mower. I imagine that the tiller would of course take the most power to drive, it would be REALLY handy to be able to control the PTO speed independently of the drive speed...

So I currently have a full size car battery in the tractor and have room for probably another 3-4 deep cycle 12V batteries, where the engine is if I can manage to fit the hydraulic power unit and use a compact motor such as an E-tek in there. Maybe even 5 if I shifted the motor very low.

I think it would be wise to refab the PTO to accept #50+ chain and/or use a dual roller drive, I need to find the load specs for the chain and determine what would be the load.

Would going from Belt to chain be a wise choice here? I think I might start with Belt for Ease of Installation but I know the frictional Loss will be Horrible.

In general I think that I could run the Hydraulic Unit without a controller but rather some sort of switching wiring that would allow it to only come on when the ignition was on and when there was a demand for hydraulic pressure. The impliment hydraulic Lift will remain in place without pressure being generated.

So What type of Controller would be desirable to control the PTO motor? I would like to be able to control the speed of the PTO and I need to again confirm the RPM that the PTO operates at and choose my motor and voltage accordingly.

I have been looking here at parts..:http://www.evparts.com/shopping/mainpage.php?id=3

So what are some problems to my plan?? I know there must be some...


I am thinking if I got a Etek for 300-500 and a hydraulic unit for 2-300 then I could get enough batteries and controller for another 500 and have an electric conversion for about what it would cost to do a Honda conversion... Electric would of course be a HELLUVA lot slicker than a honda!!

Thanks for you constructive input!

 

[TylerDurden]

Hi Sean,

That's a lot of power to supply. With 15hp original, I'd guess you need two Eteks.

Most decent walk-behind tillers have at least 5hp...

 

[sean]

So I was checking on GE Elec-Trak tractors made in the 70's and 80's and they run a 14HP motor for the Tiller and another for the Traction. Check them out at Elec-trak.org

I would think that for the traction since the tractor isn't particularly fast and the range needed isn't too far that the hydraulic power unit would deliver enough pressure for driving and lifting impliments.

The PTO will suck some HP when mowing I think it's said that each mower plade takes 1-2HP so I would need 3-6HP for the mower. The Tiller on the Elec-trak was a 14HP motor, I don't see why an E-tek wouldn't be able to put out that amount of power also. The main disadvantage I see is that driving through the PTO output inherently presents some loss to friction.

What kind of power can I expect from an Etek at 48V-72V x 150 Amps??

I know my engine currently is putting out NOwhere near 15hp and still will pull stumps and do wheelies, the Hydrostatic drive is a very nice way to deliver power...

 

[fechter]

That looks cool. I have an old International Harvester Cub Cadet tractor around somewhere that looks very similar.

I think an Etek would work. The power rating of a gasoline engine is not exactly comparable to an electric motor. Mowing or tilling will really drain the batteries in a hurry though. I'd plan on cramming as many batteries as you can fit in there.

The Alltrax would be good. You can program it to change features. You might consider forced-air cooling (a blower) for the motor, since there won't be any wind generated from speed.

I have a 24v hydraulic pump sitting around somewhere. It's not real powerful, but it has no problem lifting a 1000 lb load with the right cylinder. It's just not real fast. You could just run the hydraulic pump when you need to move a cylinder. If you want to run it off the main battery, it might need its own controller just to reduce the voltage. A cheap scooter controller might work OK. This would probably be cheaper than a dc-dc converter. If you don't run the hydraulic pump often, you might just tap it into one battery with a relay. The battery that runs the pump will be drained a bit faster than the others, so separate charging for at least that one battery would be a good idea.

 

[sean]

Fetcher:
I would have to have a pretty decent hydraulic pump that would deliver at a good enough speed so that I could drive as the drive is hydrostatic (read hydraulic) it has a pedal that pivots forward or back and that switches the valve and will go forward or reverse and as you press the pedal further you go faster.

I need to crawl under it and see the current hydraulic pump and determine if maybe I can just run an extra Kol motor to it @ 24V.

I am definitely going to be cramming it full of batteries, I may make a box for the rear to hold additional batteries once I have it built and tested..
Now to find an Etek for a reasonably price!!

 

[fechter]

I see. It sounds like the hydraulic pump is going to need an Etek also.
Can a single motor run the PTO and the pump at the same time? I would guess that's how the original ICE was setup.

 

[lemmiwinks]

Personally, for your application I think a permanent magnet motor such as the etek is a poor choice. For any given current a series wound motor produces the greatest amount of torque, and that's what a garden tractor is about - torque. If you investigate the elec-trak's further you'll see they used a shunt wound motor (if I recall correctly anyway) which is similar to a series wound.

You can pick up a small is (8" diameter) series wound motor out of a small forklift, aero tug or golf cart pretty cheap. A permanent magnet motor might be a good choice for the hydraulics, but for motive power I'd choose a series wound motor.

Just my $0.02 anyways, good luck with the project whatever you decide. Don't forget to keep us posted of your progress, photos are good 8)

***EDIT***

Actually, I just reread the thread a bit closer (duh!). I didn't realise the mower was propelled hydraulically. I guess an etek could be fine, I really have no idea so I'll just STFU now :wink:

 

[sean]

I see. It sounds like the hydraulic pump is going to need an Etek also.
Can a single motor run the PTO and the pump at the same time? I would guess that's how the original ICE was setup.

Yes the engine currently runs the Hydrostatic and the PTO with 2 sets of 2 1/2" belts each. However if I used it this way I have no independant control of the PTO and drive motor seperation. To run the Hydraulic pump/hydrostatic I will need 2-3 HP MAX probably would be fine with .5-1hp. I looked at it just now and I will need to use a pump mounted to the current Hydraulic pump as it is integral to the transmission/rear end. However there is LOTS of room to put one there especially if I eliminate the Engagement levers to push the pulleys against the Belts and replace with a PTO switch and throttle...

I wonder if the PTO could be driven with an extra Kollmorgen BLDC motor I have. Or I could get a longer bodied larger DC motor as there is about 6" x 12" shaft space to mount a motor.

The Etek I was thinking of would drive JUST the PTO as that way I could have lots of PTO power (important on a non-pulling tractor) and speed adjustable PTO power. The adjustability of the speed of impliments would make this a much nicer machine as currently you have to change the motor RPM.(consequently changing the Hydrostatic drive sligtly which you compensate with the infinitely adjustable pedal valve)

For example when tilling it would be perfect to be able to adjust the speed of the tines and drive very slowly. Currently w/ hydrostatic and no cruise instead of a gear tranni, when tilling you have to try to consistent with the speed which can be difficult.

Anyway, the configuration I am speaking of would give the tractor it's best efficiency and productivity, in my opinion and is very doable.
It will probably require 2 controllers and obviously 2 motors.

I do have a line on an old 8 HP electrak with bad batteries and paint and no mower deck, I could get theis whole tractor for $300 or less (too much) but it's too small for the larger impliments and wouldn't have a tiller ability.

What engine size and type would you recomend instead of the E-tek to have High torque at different motor speeds? for the PTO that is I don't have much of a space restriction...


Input appreciated!!

Sean

 

[jackatfsi]

Can't add much info as my yard tractor is long gone.......BUT......I remember that I needed (and had to make) two 100+ pound cast concrete wheel weights on the rear........no reason not to replace that weight w/ heavy batteries.........could be 4800WH right there !