[mattstrike]

I'm working on a Ford LGT-17 lawn mower, that I'm trying to convert to 4x4.

So not a full electric conversion, but I need the front wheels to be powered when I'm using the snow-blower. The tractor has a manual gearbox that powers the rear wheels, wheels are weighted, but without getting crazy I can't put enough weight on the rear wheels to get traction when the blower is up or down, just too much weight over the front axle between the blower and the engine.

Not really knowing a lot about electric motors my first thought was to find something I can mount to the front axle hub. There is no room to mount anything between the front wheels, the belts run through that open space as well as the front wheels steer and the axle articulates over bumps, etc...

The engine drives the belt pulleys off the front, and a driveshaft into a pinion and ring gearbox on the back. The gearbox drives a belt, which has the clutch mechanism (depress the clutch to disengage the belt idler). That belt drives the transaxle at the rear wheels.

My initial system design/thought process is to not use batteries. I'd keep the existing drivetrain in tact for normal use, adding a generator to the input or output of the ring and pinion gearbox. If I drive the generator off the output side, I could skip out on most of the controls, because the only time the front wheel motors would get power is if the belt was driving the rear wheels?

Some of the other questions I have are how to appropriately size and select a generator and motors. The motors won't be turning all that fast, I think the front tires are about 10" diameter, and depending on how deep the snow got I would have to move at a snails pace to not over-load the snowblower. And how well the system will work in higher and lower gears because the gearbox output wouldn't change speed during normal use.

I was thinking that I should select motors that were capable of moving the tractor by themselves at maybe 2mph, any faster would just be the result of the rear wheels depending on what gear it's in. But in the crawling gear (0.5mph), would I be overheating the motors on the front wheels if I didn't have them on a controller?

I wanted to keep it simple and cheap, at most I would want to put a basic control on the clutch pedal to cut out the electric motors with the clutch.

The tractor currently has a two cylinder 18hp Kohler, so it should have enough power to handle some additional drivetrain load.

Any thoughts on what to look for in a wheel mounted electric motor for this application? What kind of power supply should I be looking for? I'd like to keep it simple without requiring added attention while using it.

 

[major]

Hi there,

Welcome. Electric wheel motors will be difficult to do. Maybe you can find something in a steerable wheel drive from a forklift, scissors lift or the like. Or go hydraulic. Many scissor lifts use hydraulics. Be cool if your tractor has a pump on it now.

Maybe we'll see someone chime in with an idea.

Regards,

major

 

[Karter2]

Easier to do this i suspect...
That should solve your grip problem

 

[electro wrks]

This is the same problem you would encounter if a bucket loader were put on the front. Weight has to be added to the rear to counter balance the load. These small to medium size garden tractors are just not designed to have that much weight on the front. You could find a non driven, heavier duty, hydraulic power steering(probably needed for practical steering) front axle, but the frame would probably have to be reinforced to handle it.

As for as a practical, driven(electrical or otherwise), steerable front axle that's "simple and cheap" for this application: forgetaboutit.

 

[brian_]

I'm not familiar with the LGT 17 specifically, but I agree that equipment such as a snowthrower is hard on a small tractor. But that doesn't mean a project isn't worth trying...

The front axles of small to mid-sized 4WD tractors often use an interesting drive scheme, like the Kubota in this discussion, which has a drawing of the axle end: Need Help w/ Kubota L3710 Front Axle Bevel Gear Housing Lesak (post #2). Ignoring the problem that the Kubota owner was asking about, these axles have a near-vertical shaft on the steering pivot axis (labelled "15" in the drawing), a bevel gear drive into it, and a reduction drive to the hub.

If you can find a small enough front axle of this style as salvage, perhaps you can mount electric motors onto the tops of the steering axis shaft, which would place the motors over the axle beam and would give them some gear reduction. Whatever drive hardware is in the middle of the beam would be deleted, as well as the horizontal shafts. This would take substantial fabrication, and might not fit, but it's the only scheme which immediately occurs to me other than the good ideas already supplied by major, or building up a completely custom front axle with hub motors.

The front wheels on these tractors are very small, which is a challenge for in-wheel motors, but presumably the goal is not for very much power. Perhaps the bigger challenge is to get them geared low enough, but perhaps a hub motor intended for higher-speed use with a much larger wheel will work out.

 

[Karter2]

I suspect the biggest problem will be to find motor/s that can drive at such a low speed with sufficient torque ....without some complex form of multiple gear reduction., And fit in the space available.

 

[mattstrike]

Thanks for the ideas. And yes, it's not going to be super easy or cheap. But if I could stay below $500 it's worth it to me. I can't even get a 4x4 tractor locally for less that $3000 anyway, and it's not like my tractor hasn't already been invested in. And the more I can salvage from other things the better.

So far I haven't been able to locate a front steering/driven axle. Nothing used or for parts on CL and haven't found a suitable tractor salvage yard near me (haven't really looked that hard either). That's why I started thinking about electric motors mounted to the wheel. The other benefit to wheel mount was that I don't have to worry about one wheel slipping and the other not turning as happens with front axles. But if I did find something like that Kubota axle I would have to cut it down to fit anyway, so could still come up with a way to drive each wheel individually.

If I went with a custom axle route that wouldn't be so bad, I've got a TIG, a lathe, and a few other tools that make it possible. And that would be well within my ability. But I'd have to source materials from a salvage yard to keep costs down, hopefully no custom parts that need a mill, etc.

Another idea I had looking at some off-the-shelf gear reduction boxes with a 30:1 or so ratio, might open up some options with the motor selection. With a 3000rpm motor and the 8 in diameter tires that would get 2.3 mph. I'm thinking with a right angle gearbox I could mount the motor vertically above the wheel such that it rotates with the knuckle and drive it with a chain or belt.

 

[Karter2]

Something like a pair of wheelchair drive motor/gearbox units ?
But you will need controllers and i doubt you will be able to produce the power butsts needed without a battery also.

 

[mattstrike]

So I guess I really need to know more about picking the right electric motor. Lets just for arguments sake say that I have figured out how to get power to the wheels, but the drive ratio of that depends on what I need to look for in a motor.
More about the tractor: 670lbs wet, blower is another 100lbs, and I'm less than 200lbs. So ballpark it at 1000lbs.

DC vs. AC, does it matter?
Bi-directional control for FWD/REV -how is that done?
Power rating and duty cycle (would have to be close to 100%)

Some of the things I've been looking at are electric winch motors, golf cart motors, drill press motors, etc.

So if my end goal is to be able to drive somewhere between 0 and 2mph, and I have the flexibility on gear ratio from 2:1 up to 30:1, which is the best way to pick a motor? I'm thinking that a 1/2hp motor would be sufficient for what I want, to move 1000lbs at no more than 2mph, though I think I need to have a way to protect the motors if I run the rear end in 4th gear (6mph or so). So I think I should design the system to operate whatever motor at 6mph; but that would require a controller to regulate speed in lower gears (and how does that effect the duty cycle?)


So what I'm thinking for the drive hubs and front axle is make my own unless I get really lucky and find something at a salvage yard that I could modify. I have a simple DIY metal casting setup for aluminum/brass already, and have used my 3D printer to make molds for casting parts before. I've been meaning to really put that to the test with some functional aluminum parts. The axle could be simple box channel steel, so I don't permanently maim the factory parts.

So I have come up with a basic design for a hub using standard parts from McMaster Carr (Bevel gears and tapered roller bearings) that I could potentially 3d print, make molds, and cast myself. And I have a lathe to make input and output shafts. So finding a fairly accessible motor that is readily available makes it easier to modify my design to have that motor bolt right up. However the design is already at $400 for components to make two hubs (hardware, standard bearings, seals, and bevel gears). That leaves me $100 for tires/wheels that bolt or spline fit a hub, two motors, and a controller. So I'll have to find another way to optimize the cost like cheaper bearings or less of them if I continue down that route.

 

[brian_]

DC vs. AC, does it matter?

Yes. Among other things, it determines the availability of motors, the type of controller needed, how practical regenerative braking is, and how reversing is done.

Bi-directional control for FWD/REV -how is that done?

Yeah, about that difference...

• An AC motor is reversed by the electronics which control the inverter. You tell it to turn the other way, the motor gets AC power in opposite to the forward phase order.
• A brushed DC motor (assuming it is series wound, as is the typical practice for brushed DC motors used in DIY EVs) is reversed by replacing the usual direct connection of the field winding to the motor input terminals, and routing it (or the input to the brushes) instead through a reversing switch (typically a set of interconnected contactors). It only works in reverse if the brush timing is not advanced too much (so now you need to find out what advanced timing is... )

 

[stevegates01]

It is a very good tractor but I don't know if it is worth to make the front electric. Moreover I'd better leave it like it is. My friend have a tractor from Japan and it is kind of plug in electric vehicle, can't remember the name but it looks great and it is very powerfull. Besides that, it is times bigger than a garden tractor, my friend is using it as a lawn mower on big fields and he's finishing the work very fast because the tractor is very powerful. Also he have an attachment for snow and it is kind of the best snow blower combination. Wish there were more electric vehicles, they have more power and make less pollution.