Tractor Conversion Help

[mikedefelice33]

I've got a 1970s Case 646 garden tractor shell I'd like to convert to electric. The engine caught on fire which has been pulled, but all the other components seem good including hydraulics. It's a little different than other tractor conversions and posts I've seen on here and YouTube as it's fully hydraulically powered, as in there's no clutch or transmission. The engine, which is an Onan 16.5hp 3600rpm, only spins a rather small looking hydraulic pump. All controls, including driving, are powered with hydraulics.

I'm looking for some advice for what size/type motor I'd need or if anyone has insights as to whether I actually need something with as much power as it originally came with seeing as electric motors have different rpms and torque compared to size.

Ideally, I'm looking for a really simple set up. Am I wrong to think that this could be a really simple setup? I'd love something as simple as an upcycled motor, speed controller as the throttle, and batteries (with some charging setup.)

Any insights towards motor type/size, voltage, etc? Thanks for any help. I'm looking for a cheap-ish option.

 

[Hillhater]

If all systems are hydraulic, including the traction drive, you probably wont even need a motor peed cotroller.
a constant speed motor to drive the pump and a simple on /off relay from a suitable voltage battery. (48v ?)
You could even cosider simply installing an aux hydraulic motor and pump from a fork lift truck…..if the pump pressure and flow rate is similar,

 

[amberwolf]

16.5hp x 750w per hp = 12375w so to match the power out0put youd need 13kw+ at 3600rpm (rounded up power). if it doesn't run at full power much or often you could use a smaller motor / etc thta can handle peaks of this intensity for as long as you do need that full power.

if you're not sure how much power it really needs, you can use simulators and calculators to make some guesses about the power required to do the work you need it to do under the conditions you need it to happen unde.r

presumably the engine always ran at that rpm and didn'thave a throttle to vary it's output, just valve controls for the hydraulics to vary their flow / output.

if so, then finding the right electric motor is much easier than finding one that has to vary itself. you can look for motors that are designed for that speed and power directly first. if you can't find one, find one that can do at least that power level, at whatever rpm, and then use gearing or pulleys to change the rpm it actually spins at to the rpm the hydraulic pump expect.

it would be simplest to use a brushed motor, since yhou don't need to vary the speed the controller can be simpler; but you'll still need one to run the mtoor as a switch or contactor to handle that much power is likely to be huge and expensive, vs a controller to do the same thing. then you can use the cotnroller to start the motor and run it, and limit the current drawn from the battery to keep from damaging that or your wiring.

brushed mtoros can have more intial startup torque if tha'ts needed, but if you want a more efficient motor you can use a brushless type, usually 3-phase bldc, and a suitable controller. a dumb controller would work fine if you don't need to vary the speed or have any kind of motor braking, etc, no foc controllers required.



if the system typically ran at or near full power much of the time you'll need a battery that can sustain at lesast that ful power of 13kw, continuously. how long does it have to run? mulitply the 13kw by how many hours it has to run and that's how many kwh the pack has to be.



it's fairly ,likely you could get an old forklift motor and controller to run it. battery you can buy modules from batteryhookup or greentecauto or similar places and make the battery you need; it'll be cheaper and a better battery than if you try to buy one from typical battery pack sellers

 

[mikedefelice33]

Thanks for the reply.

In terms of how fast the motor NEEDS to run, it weird. The RPMs of the motor control the speed of the hydraulics, unlike what you implied, that a valve controlled the flow. It's a very odd setup, but works extremely well. At low throttle it drives slow, the bucket raises slow. At high throttle, it drives faster. There's only one "speed" for the drive mechanism. The bucket does have variable flow when delicate on the controls.

I'll start searching for motors and battery setups. I'd love to run it for at least 30 min to do small jobs and then have its unburnt twin with an ICE for longer stuff.

 

[amberwolf]

In terms of how fast the motor NEEDS to run, it weird. The RPMs of the motor control the speed of the hydraulics, unlike what you implied, that a valve controlled the flow. It's a very odd setup, but works extremely well. At low throttle it drives slow, the bucket raises slow. At high throttle, it drives faster. There's only one "speed" for the drive mechanism.

Then you'll definitely need a controller for the motor, even if it's brushed. But you can use a cable-operated throttle box and run the cable from your existing throttle to it, so you don't have to change any of the mechanics of how the user operates it.

Now you have to decide which technology to use (brushed or brushless), and judge how much power it will really need to do the jobs it has to do, and then pick which motor and controller to do it with. then find or build a battery to supply that power.

I'll start searching for motors and battery setups. I'd love to run it for at least 30 min to do small jobs and then have its unburnt twin with an ICE for longer stuff.

If all you need is half an hour, then whatever kW is needed to operate it, you can divide by two to get the kWh capacity of the battery pack required.

I recommend at least half again as much capacity as you need so that as it ages it will still be able to do the full job.