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Diesel / Electric Locomotive Technology

2668 Views 75 Replies 13 Participants Last post by  SeattleTrainGuy
I wish to follow the technology of the diesel / electric locomotive, as I have a 1983 Isuzu P/U with a 58hp, 4 cyl diesel engine, that I would like to have power one of my 10kw generator heads, with a 120v or 240v electric motor powering my rear axle.

My intention is to remove the 5-speed manual transmission and put one of my 10kw generator heads in its place, then idle the engine at the RPM necessary to achieve 60Hz, and direct-wire the A/C 120 or 240V drive motor to the generator head to supply power to the motor.

It doesn't make sense to me to spends thousands of dollars on batteries, along with adding the extra weight, then having to recharge the batteries, when I already have a complete power source.

If anyone knows where I should be searching, please point me in that direction? Thanks!
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I've contacted a friend of mine who is a Conductor for BNSF and have asked him to put me in touch with one of the mechanics who works on the engines.
I doubt that a mechanic will have any understanding of what is going on in the electrical boxes.
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I wish to follow the technology of the diesel / electric locomotive, as I have a 1983 Isuzu P/U with a 58hp, 4 cyl diesel engine, that I would like to have power one of my 10kw generator heads, with a 120v or 240v electric motor powering my rear axle.
As already mentioned, if your generator can only produce 10 kW, then you can't use more than 10 kW of the engine's possible 43 kW output. More importantly, in this configuration with no battery, 10 kW of generator means no more than 10 kW to the motor which drives the rear axle, which is okay for a golf cart and far too little for even a small pickup truck.

So, to just maintain the original performance you need at least a 43 kW generator, and at least a 43 kW motor, and appropriate electronics between them.

My intention is to remove the 5-speed manual transmission and put one of my 10kw generator heads in its place, then idle the engine at the RPM necessary to achieve 60Hz...
What do you mean by "idle"? I actually means to run without producing any useful power, but what you want to do is run to produce exactly the power needed by the vehicle - that's not "idle".

If using the AC output directly from a generator the engine speed does directly determine the power frequency; however, there is no need - or even any reason - to produce electrical power 60 Hz, and there is no reason for that speed (3600 RPM for 2-pole generator, 1800 RPM for a 4-pole generator, etc) to be appropriate for the engine.

... and direct-wire the A/C 120 or 240V drive motor to the generator head to supply power to the motor.
A motor supplied with power at a fixed frequency can only run at a fixed speed; obviously that doesn't work for driving a vehicle, which must vary in speed. The AC power can supply a motor controller (called a VFD for "variable frequency drive" when supplied with AC power) to run the motor. If using a VFD, there's no need for the power from the generator to be at a fixed frequency.

You might want to start with the Wikipedia page for Diesel locomotive, Diesel–electric section, for a description of what is actually involved. You might note that typically the power from the generator to the motor controller is DC. Also, locomotives change engine speed with changes in the power requested by the operator's control actions (moving the "throttle" lever), rather than running at constant speed.

It doesn't make sense to me to spends thousands of dollars on batteries, along with adding the extra weight, then having to recharge the batteries, when I already have a complete power source.
Without a battery, the entire system just replaces the transmission with an electro-mechanical transmission system which is continuously variable (which is nice) but much less efficient than any conventional automotive transmission... and that doesn't make much sense.
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Seriously? This is your understanding of a mechanic who is charged with the maintenance and repair of diesel / electric locomotive?

You might visit with one to learn that they know everything from bumper-to-bumper. This is why they are the go-to people when a locomotive fails.
Mechanics do maintenance (change lubricants, etc), diagnose the location of faults, and replace faulty components. Just as the mechanic who services a car has no idea how anything inside any of the car's electronic components work (but can replace a failed ECU), the train mechanic probably has no ability to design or even functionally describe the control systems of a locomotive. Maybe you'll find one who has a personal interest in the technology...
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OK, probably a really stupid thought here, but I'm pretty sure if this was the case, trains would use massive versions on automotive transmissions.
Heavy mining trucks commonly use diesel-electric powertrains, much like trains, and some of Caterpillar's heaviest models do use a mechanical transmission (check out their Mining Trucks - "AC" models are diesel-electric and other models are diesel with mechanical transmissions). These are big (the 797F has rated gross machine weight of 623,690 kg, of which 364,000 kg is payload), but trains are heavier, and relative to their mass they are much lower-powered. That means the trains spend a long time at very low track speed and a hydrodynamic coupling (such as the torque converter in a traditional automotive automatic) or clutch would slip a lot; effectiveness (torque to the wheels) and durability are more important than optimal efficiency. Trains have requirements that even heavy trucks do not, and pickup trucks certainly do not.
Forget for a minute the 10kw Harbor Freight piece--assuming you got one that actually had a reasonable output, then it would adjust for how much power was actually being USED by the system.
Yes, the output of any generator will be determined by the speed at which it is driven and the load on it.

I suspect brian_ would want one battery at least, to help with regen braking, and also so that the power has somewhere to go when you're sitting at a stoplight not using much/any power.
Yes, but not to allow idling... the solution for idling with a battery is to simply stop the engine when power isn't needed from it. In any hybrid the battery, in addition to supporting regenerative braking, allows the engine to stay within its range of efficient operation instead of having to follow either the highest peaks of demand or the lowest levels.

I don't know what "one" battery is intended to mean, since batteries come in all sizes and the number of batteries is irrelevant. But not much battery capacity is required for the benefits of hybrid operation - typically less than 1 kWh of capacity per ton of vehicle mass.

With the generator setup you can set the load such that the engine is in whatever torque peak (most efficient points in an engine's power curve--lower ones in the rpm band generally take less gas and usually make a little less power) it needs to be to make adequate power, and will be most efficient at WOT, so if you can get it to run at like 1200 RPMs and WOT, and make enough power for your needs, then it should run well and get like 50 mpg (assuming you have an engine that is a good size for the application). Additionally, if you put that much load on it, it should require little to no cooling, as it won't be losing much energy as heat when you lug it that much.
All of that is a good description of why a continuously variable transmission is good. Just realize that - without a battery - the engine must follow the power demand, so it will be required to run at far higher and much lower power than the most efficient point as the vehicle is driven. The result is that in the real world the electric transmission scheme doesn't have any advantage over any other continuously variable transmission... and they don't do much better than traditional transmissions with a reasonable number of ratios.
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when speeds were much lower and bodies likely quite lighter altogether there actually used to be just a few unusual buses in the northeast usa which were basically a genset engine under the hood paired to trolleys-borrowed (not surprising given the similar axle sizes) traction motor .. somewhere around the 1910-1930's timespan that is

I unforuantely can't find any examples right now due to the way the web is (even an exact search for 'diesel-electric bus 1920' still dumps a lot of modern non-electric bus photos all over, oh well) but I do know at least two different ones had made their appearance in station-related photos in the usa 'classic trains' magazines for one thing tho
Sure, I can believe that was done, especially back when mechanical transmissions were relatively crude. More recent examples of series diesel-electric buses are hybrids... with a battery.
I'm talking about utilizing my already 44mpg 4cyl diesel engine to direct-power a 20kW 240V generator head, and then wiring through a controller, directly to a 240V motor that will produce at least the same 58hp as my diesel engine does.
No, the motor can't produce 58 hp (43 kW) from only 20 kW of input power. Without a battery, you need a generator which can produce all of the power needed by the motor.

And what do you mean by "direct to a 240V motor"? If that's a DC motor, you have what trains use. If that's an AC motor, it won't work without a controller... so it's direct to a controller, which feeds the motor.
My intentional gain is MPG. I don't know how true this is yet, but with an electric drive, I should see upwards of 75-80MPG because the diesel engine will for the most part, just be idling, (1000 - 1200RPM?), to achieve the 60Hz needed to produce the 240V A/C power.
It is absolutely not true. You seem to think that running slowly means "idling", and not consuming fuel. An engine turns fuel energy into mechanical energy, and you still need the same amount of energy to move the vehicle, so running the engine slowly to run a generator gains nothing compared to running the engine slowly (in a high enough gear to get the engine as slow as desired) through a mechanical transmission.
I just checked the tag on the generator head. It says that it produces single phase, 20kW, 240V, 60Hz, 83.4Amps at 1800RPM.
240 V multiplied by 83.4 A is 20 kW with a power factor of 1, so that makes sense.

So that would be my operating RPM if I am reading this right.
That's the design speed, intended to produce 60 Hz. As I said before, there is no reason to run at specifically 60 Hz; it could produce more power at higher speed if it doesn't overheat, and less at a lower speed... and less at 1800 if the load is lower.
No reason at all for the RPM's to be all over the place, because I can go outside right now and start it up, hold it at whatever is higher than idle, and it doesn't raise or lower in RPM's all by itself. That makes no sense anyway.
As I said before, if you are running an AC motor without a controller, the AC frequency must change to match the motor speed... and while no one would do that, it would mean that the whole system would act like a single-speed transmission (but heavier, more expensive, and less efficient). If you use a motor controller, then there is no reason to fix the motor speed at 1800 RPM.
I don't have a tach on this truck, so I don't know what 1800RPM sounds like...
My suggestion is that you get a tach, learn to drive, and achieve your fuel economy improvement at nearly zero cost.
Remember this when you're thinking about offering information; I am building a 20kW generator that will produce 240V A/C power, to supply that electricity to an electric drive motor. That's it. The generator just happens to be bolted in my pickup and it has wheels. This would be nothing different than you buying a 20kW generator to provide emergency backup power for your home. I'm just using it in a different application, and regulating the speed of the electric drive motor with a controller. That's all.
The huge difference is that your home is not a vehicle. Everything that uses electricity in your home to turn a shaft controls its own speed, yet you wanted to plug 240 V AC power directly into a motor without any controller like the "engineering" crew on the Enterprise plugging in a "power conduit" and everything just works... but the real world is not Star Trek.

Now you are accepting that you need a controller. Okay, that works, but that home backup generator is very inefficient because it is forced to run at 1800 RPM all the time; a dedicated generator set driving a vehicle can be controlled much more appropriately. Even common Honda "inverter type" gasoline-engine generator sets vary their speed so that the engine doesn't run faster than required to produce the required power.

And at this point you were still planning on a generator with less than half of the required capacity... like putting 5 kW generator on your house and wanting to run 12 kilowatts of appliances at the same time.
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With a 20kW generator you're still short more than 2 times on power. Is your generator single phase ?
Good point... a single-phase AC motor would be a terrible choice, although a VFD could run a proper 3-phase motor from a single-phase source. Rationally, of course, it would be a 3-phase inverter running from a DC source.
So then your setup would look something like

1PH generator [3PH AC -> DC -> 1PH AC] -> VFD [AC-> DC -> 3PH AC] -> induction motor
No, I think he's planning on
1PH generator [1PH AC] -> VFD [AC-> DC -> 3PH AC] -> induction motor
because the generator is a 4-pole alternator driven at the required speed (1800 RPM) for 60 Hz.
I do know that in the locomotive, the A/C power is rectified to D/C, and then back to A/C power going to the drive motors.
Then if that's what you're copying, why not do that? In this locomotive design, the engine does not run at a fixed speed, and so the AC power is not at a fixed frequency.
You're limited to 20kW right now from your power source. You can't get 58HP (43kW) from a 20kW power source, regardless of the type of motor you hook up to it. What am I missing ?
You are missing absolutely nothing. :)

This frustration is the problem with trying to help someone design a system when they do not have even the most fundamental understanding that the power into anything must be at least as much as the power out, and that all of these components are transferring and transforming power. The average person probably does not understand that... but the average person doesn't try to design a powertrain.
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So I need to go after a D/C motor, as I see those readily available at 60+hp. Yes/No?
No. Whether the motor is DC or AC, the power input to the motor must be greater than the output power (because it is not perfectly efficient). All modern EVs use AC motors, but some DIY projects still use DC motors, and this has nothing to do with the amount of power needed from the generator.
And tell me if I am reading all of this wrong, but a battery bank in sufficient size that would power a D/C motor that would produce 60hp would be in the neighborhood of 96V?
Size and voltage of a battery are unrelated. The choice of voltage and choice of controller and motor (and generator and its controller in this case) are tied together. Valid choices using available components can be as low as 48 V and as high as 800 V.

Battery size is related to energy capacity, and safe power output is proportional to energy capacity for a given battery type.

Assuming 5C maximum rate of discharge, to pull 40kW you'd need at least 83Ah at 96V or say 166Ah at 48V.
To explain this, "C" rate is the ratio of power (in watts or kilowatts) to the energy capacity of the battery (in watt-hours or kilowatt-hours), so discharging at 5C means using up all of the battery's capacity is 1/5 of an hour.

In his example, cricketo is dividing the required power (40 kW) by the "C" rate (5) to get the required energy capacity of the battery (8 kWh), and providing examples of charge capacity and voltage which come out to that energy capacity. To put a scale to this size, it is on the small end of the range of battery capacities used in plug-in hybrid cars.
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Shouldn't this thread be put into the "perpetual motion" section?
No, the intention is not perpetual motion (or "over-unity gain"); the original poster is just working toward understanding that.
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Looks like you’ve got some decent background on your conversion idea. Locomotives generally use two stage ac-dc electric motors to manage the enormous torque, speed (and braking) requirements needed for modern train weights and acceleration requirements. Also locomotive applications have substantially different traction characteristics than EV’s. Coefficient of friction and train resistance are entirely different than automotive applications. Sounds like you don’t necessarily want to closely model a freight locomotive configuration in your conversion, but are more interested in the general concept of mating a traction motor with your existing diesel engine. You could explore the miniature train hobby to find the answers you seek. is the go to website for 1/8th to 1/3 rd scale train builders. Lots of people there have vast experience building small scale diesel electric drive chains. These would all be very similar to what you wish to accomplish.
Great tip! (y)

I can save people a few steps of run-around - this is presumably the target forum:
Live Steam & Riding Scale Railroading
(a forum for trains within a larger forum of "The Home Machinist!")
and within that more specifically
Riding Scale Railroading

Except that most people do so with a ICE. Diesels have different power curves and speed requirements than ICE engines.
"ICE" means "Internal Combustion Engine"; both gasoline-fueled and diesel-fueled engines are internal combustion engines. You are referring to the difference between a gasoline engine and a diesel engine, not between an ICE and a diesel engine.

Yes, diesel engine control is a bit different from gasoline engine control, but externally it is fundamentally the same: changing throttle valve opening of a gasoline engine and changing injection setting (pump rack position or electronic input) of a diesel engine have essentially the same effect.

Most of the difference in power curve shape between typical gasoline engines and typical diesel engines is simply that in most applications diesels are turbocharged and gasoline engines are not. Of course each engine has its own operating characteristics, not the same as every other engine burning the same fuel.
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