Electric Drive Motor Retrofit

[MossRoad]

Yes, current as in time. :laughing:

One thing I was thinking about. Since the PT425 is all hydraulic, and the gas motor only turns one-way, all you'd need is an electric drive motor and an on-off switch. No reversing circuit would be needed and no speed control would be needed. You could put in speed control for the electric motor, but would it really help anything? You need full flow to create enough pressure to do the steering/FEL functions well. The AUX PTO wouldn't need full pressure, but since it's fed from the same valve bank as the FEL, which is fed from the power beyond on the steering valve, it's gonna get the same pressure anyway.

I suppose you could put in some sort of sensors to only apply the motor when the forward are reverse pedals are pushed, but I think response would be awful. And then you'd have to figure out circuitry to do the same for the FEL and steering. That's why I'd think you always want the electric motor on at speed all the time.

Just some thoughts.

 

[MossRoad]

Also, do you have any powered implements, like a mower, broom, etc... that run of the main PTO?

 

[MossRoad]

Just to shed some light on how the PT425 is set up....

There's a gas engine that turns 3 hydraulic pumps.

Pump 1 is the tram pump, a variable volume pump that supplies the forward and reverse power to the 4 hydraulic wheel motors, one at each wheel. Direction is controlled by a center treadle, right foot forward, left foot reverse, self centering setup.

Pump 2 is the steering/FEL/AUX PTO pump, which supplies power to the steering valve, out a power beyond port to a 3 valve bank that has the FEL lift/lower, dump/curl, and AUX PTO functions. The AUX PTO provides hydraulic power to the quick attach mechanism, or to things like a grapple, power angle snow blade, etc...

Pump 3 is the MAIN PTO, which provides 8GPM @2500psi to a circuit on the FEL arms that can provide power to things such as mowers, tillers, trenchers, stump grinders, etc....

 

[BobRip]

One of my concerns is drain on the battery when doing very little activity. Except for the tram pump the others are flowing oil all the time. If you could slow the motor down you could save some energy. If you could have three electric motors and run only when you need it that would help. It would be nice to know what the no activity energy consumption is. Then you could see if this is really an issue. Just from listening to an electric fork lift I think they shut off the pumps when you are not using them. I am an electrical engineer, but have never worked on this type of project before.

 

[MossRoad]

Yes, the electric forklifts only activate the pump motor for the lift mast when you move the control lever. And it only activates the drive motor when you step on the forward or reverse lever.

 

[MossRoad]

Since gas and electric HP is hard to compare, how would one go about finding a suitable electric motor to provide the same power as a gas engine?

For example, gas engine is rated at 25HP at 3600rpm. Gas engine HP and Torque decrease as a load is applied, while (if I got this right) an electric motor's torque will increase as a load is applied. How do you size an electric motor to provide similar power as the gas engine it's replacing?

 

[cqaigy2]

I could see the motor turning on and off on flat ground, but you might need it to stay running if on a hill, to keep you at the same elevation.

 

[CADplans]

A hydraulic drive machine has to be the worst application for an electric motor,,, WAY TOO much energy is lost,,

The machine needs to be gear drive first, and foremost,, because you have so little stored energy to start with,,,

Intermittent operation of the hydraulics will be marginal,, current electric/hydraulic power sources have VERY low duty cycles,,

The Power Trac is truly a design that needs LOTS of energy,,,

Of course, you could go back to the roots of the design of the Power Trac,, and pull a 6KV power cord,,

If I wanted an electric one, I would drive to the town Power Trac is located in,,
and,, buy a used battery powered one for a few thousand dollars,, it might need new batteries,,,

Of course,, it might be a little low to the ground,,

This one says it is battery powered,, but, that looks like an engine on the back ??

 

[radios1]

Since gas and electric HP is hard to compare, how would one go about finding a suitable electric motor to provide the same power as a gas engine?

For example, gas engine is rated at 25HP at 3600rpm. Gas engine HP and Torque decrease as a load is applied, while (if I got this right) an electric motor's torque will increase as a load is applied. How do you size an electric motor to provide similar power as the gas engine it's replacing?

If you can get your hands on a Baldor motor book, you will see that the torque increased as more load is applied. The torque can increase to 2 to 3 timeç—´ more than running torque. Baldor shows what they call "break-down torque". The torque can increase to 3 times or more than running torque. A motor produces it maximum torque at stall speed, and this is called "locked rotor torque". The motor torque does not fall off as the load increases. This is very simple. Gas engines only produce power every other revolution of the crankshaft. DC brushed Electric motors produce power every single revolution. That is why a 10 hp electric is same as the 20 hp gas this being said, a 20 HP electric motor will need some VERY high capacity batteries, and be VERY expensive to buy, then there's the recurring replacement cost.. think LARGE rechargeable lithium batteries!..

 

[4570Man]

A hydraulic drive machine has to be the worst application for an electric motor,,, WAY TOO much energy is lost,,

The machine needs to be gear drive first, and foremost,, because you have so little stored energy to start with,,,

Intermittent operation of the hydraulics will be marginal,, current electric/hydraulic power sources have VERY low duty cycles,,

The Power Trac is truly a design that needs LOTS of energy,,,

Of course, you could go back to the roots of the design of the Power Trac,, and pull a 6KV power cord,,

If I wanted an electric one, I would drive to the town Power Trac is located in,,
and,, buy a used battery powered one for a few thousand dollars,, it might need new batteries,,,

Of course,, it might be a little low to the ground,,

This one says it is battery powered,, but, that looks like an engine on the back ??

Agreed. To have any chance of working you need to throw away the hydraulic drive motors and use electric wheel motors. I don’t think this is a feasible project the way it is. I really doubt the wind and rolling resistance of electric car is as high as load on a powertrac and they have way bigger batteries than will be possible for this project. The electric forklifts use massive batteries. I had to take my backhoe to go unload a forklift battery and it weighed 50 percent more than the whole PT does. And probably doesn’t use as much energy. The electric forklifts only drive around on on flat ground which with a deep gear ratio doesn’t take much power and lift the mast. Depending on the load that could take quite a bit of power but it’s only momentary.