Diesel-Electric Models

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keyrouteken
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Diesel-Electric Models

Post by keyrouteken » Mon Apr 17, 2017 12:06 pm

Hi Everybody:

A friend of mine asks the following question...

"Are there any true miniature diesel-electric locomotives that are exact miniatures of full-size diesel-electric locomotives?

I am asking because I do not know, and because the miniature diesels I have seen on videos at various live-steam meets may just have fairly simple power units in them, and I cannot tell at all if any of them are true miniature diesel-electrics just exactly like their full-size sisters.

If there ARE any TRUE miniature diesel-electric locomotives, please let me know. I would LOVE to see videos of them."
This person is a member of the GGRM at Niles Canyon-- Fremont, CA.

I don't know of any , say, a Model 567 8-cylinder diesel engine. How 'bout you guys ??

Ken Shattock
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cbrew
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Re: Diesel-Electric Models

Post by cbrew » Mon Apr 17, 2017 12:12 pm

I have not heard of any in "true" form. but i have seen some use 2 and 3 cylinder diesel engines coupled to both hydraulic and electric systems. may be the right "smell" using one of these engines, but the sound will not be on point. because of this, I when full electric with a high end sound system. the sound is on point, just not the smell :)
If it is not live steam. its not worth it.

Kimball McGinley
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Re: Diesel-Electric Models

Post by Kimball McGinley » Mon Apr 17, 2017 2:13 pm

I have seen an SP GP-9 in 1/8 scale (7-1/2" track) that was a true diesel - electric. It visited the OCME track here in So Cal. This is done in smaller scales too, they call them "Live diesel", I think.

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BigDumbDinosaur
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Re: Diesel-Electric Models

Post by BigDumbDinosaur » Tue Apr 18, 2017 12:13 am

keyrouteken wrote:Are there any true miniature diesel-electric locomotives that are exact miniatures of full-size diesel-electric locomotives?...I don't know of any, say, a Model 567 8-cylinder diesel engine. How 'bout you guys ??
I've not seen such a thing. Modeling the 567 with any number of cylinders (six was the smallest version) would be cool but probably disappointing. Diesel engines and the noises they make don't scale very well. Also, the 567's design would involve modeling internal design features that are not simple by any measure (e.g., the connecting rod big ends). I won't even get into the blowers and fuel injectors...

Electric propulsion using an internal combustion prime mover, whether gasoline or Diesel, is problematic if one is attempting to model reality—electricity also doesn't scale very well. Complicating matters is the general behavior of generators, which are square law machines, unlike naturally aspirated two-stroke Diesels, whose power output at fuel throttle is roughly proportional to RPM (neglecting mounting pumping losses as the engine speed increases). Much of the complication in Diesel-electric propulsion is in reconciling these differences. That's why I took the approach I did with my F7.
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BigDumbDinosaur
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Re: Diesel-Electric Models

Post by BigDumbDinosaur » Tue Apr 18, 2017 12:14 am

cbrew wrote:I when full electric with a high end sound system. the sound is on point, just not the smell :)
If you burn out a traction motor you'll get a prototypical "smell," though not of burnt Diesel oil. :D
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ALCOSTEAM
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Re: Diesel-Electric Models

Post by ALCOSTEAM » Tue Apr 18, 2017 6:46 am

There was (or is) a member here on chaski from up in the northeast that built an 1 1/2 locomotive using one of the Harbor Freight 10K generator heads. I don't remember about the traction motors, could of been DC and he used a 120ac to DC controller. Its been many years ago that he posted info about it and so far the search function has not done me any good finding the posts.

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cbrew
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Re: Diesel-Electric Models

Post by cbrew » Tue Apr 18, 2017 6:56 am

ALCOSTEAM wrote:There was (or is) a member here on chaski from up in the northeast that built an 1 1/2 locomotive using one of the Harbor Freight 10K generator heads. I don't remember about the traction motors, could of been DC and he used a 120ac to DC controller. Its been many years ago that he posted info about it and so far the search function has not done me any good finding the posts.
That would be Bill,
I also have all the hardware for this setup but never used it for reasons i stated above
If it is not live steam. its not worth it.

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BigDumbDinosaur
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Re: Diesel-Electric Models

Post by BigDumbDinosaur » Tue Apr 18, 2017 1:49 pm

cbrew wrote:
ALCOSTEAM wrote:There was (or is) a member here on chaski from up in the northeast that built an 1 1/2 locomotive using one of the Harbor Freight 10K generator heads. I don't remember about the traction motors, could of been DC and he used a 120ac to DC controller. Its been many years ago that he posted info about it and so far the search function has not done me any good finding the posts.
That would be Bill,
I also have all the hardware for this setup but never used it for reasons i stated above
The behavior of Diesel-electric propulsion can be modeled in fluid power, although it's not a simple matter and definitely not inexpensive to achieve. Noises are an altogether different problem. The only thing that is going to sound like an EMD 567 at full throttle is an EMD 567 at full throttle. Acoustics don't scale, and to my ears, the sound systems used in battery-electric models sound like recordings—which, of course, they are (samplings, technically speaking). ALso, the noises made by a locomotive emanate from a variety of locations, not one, as would be the case with a sound system and its loudspeaker.

Despite being an electronics type with a lot of experience with electric propulsion systems, I would not invest any time in trying to do it in a 1-1/2 inch scale locomotive. For me, the sticking point would be the traction motors. The permanent magnet motors that are used in battery-electric locos do not behave anything like the wound field motors used in real locomotives, and are nowhere near robust enough to sustain a heavy drag on a grade.
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cbrew
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Re: Diesel-Electric Models

Post by cbrew » Tue Apr 18, 2017 2:27 pm

BigDumbDinosaur wrote: The behavior of Diesel-electric propulsion can be modeled in fluid power, although it's not a simple matter and definitely not inexpensive to achieve. Noises are an altogether different problem. The only thing that is going to sound like an EMD 567 at full throttle is an EMD 567 at full throttle. Acoustics don't scale, and to my ears, the sound systems used in battery-electric models sound like recordings—which, of course, they are (samplings, technically speaking). ALso, the noises made by a locomotive emanate from a variety of locations, not one, as would be the case with a sound system and its loudspeaker.

Despite being an electronics type with a lot of experience with electric propulsion systems, I would not invest any time in trying to do it in a 1-1/2 inch scale locomotive. For me, the sticking point would be the traction motors. The permanent magnet motors that are used in battery-electric locos do not behave anything like the wound field motors used in real locomotives, and are nowhere near robust enough to sustain a heavy drag on a grade.
having had a one lunger growing up, I have zero interesting is riding a lawn mower around the track all day, or even 10 minutes for that matter.
as for the fear of using PM motors, yes they are not as good as wound field motors. but with the proper setup, they have proven to be successful in the hobby.
i am running four 500watt PM motors, one per axle. on a 900lbs locomotive, it has more then enough power to slip the drives on dry rail
and sound. i agree. most of the sound systems are very "lacking". but again, if the sound system is designed right. it can and will sound very convincing, at least that is what i have been told about my creation.
being a steam guy, i have always had the opinion that it most sound right or no sound at all.
the coolest thing about a sound system, if i want quite. its a button push away and all you hear is the click and clack of the rail
the only functionality i have not been able to do is auto sense the load of the loco and adjust the primer tone and volume, but i am happy as it is.
If it is not live steam. its not worth it.

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BigDumbDinosaur
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Re: Diesel-Electric Models

Post by BigDumbDinosaur » Wed Apr 19, 2017 1:05 am

cbrew wrote:having had a one lunger growing up, I have zero interesting is riding a lawn mower around the track all day, or even 10 minutes for that matter.
Who said anything about running a one-lunger?
as for the fear of using PM motors, yes they are not as good as wound field motors. but with the proper setup, they have proven to be successful in the hobby.
I think you may not be understanding what I'm getting at.

The full-sized locomotive can also spin the drivers if the engineer gives it enough throttle at start-up. However, as soon as slippage occurs the build-up of counter electromotive force (EMF) in the motors will act to limit current flow. Where the problem arises is when continuously applied power at low speeds (drag conditions) is at or immediately below the point of incipient wheel slip. Under such conditions, motor current will be very high due to low counter EMF and rapid temperature rise will occur. This is usually what causes traction motor burnout in full-sized units.

Most permanent magnet motors use electronic commutation, with slip rings feeding current to the armature. The electronic commutator is a solid state device that rapidly alternates armature polarity like a double-pole, double-throw switch. Motor current at stall or very low speeds is limited only by the DC resistance of the armature, the wiring connecting the motor to the power source, the power source itself and the forward drop of the semiconductors in the commutator. Those semiconductors cannot withstand that maximum current for very long, which means the motor can be destroyed if subjected to a sustained load that keeps the armature speed low. Such conditions will occur when pulling a heavy train on a long upgrade at drag speed.

Aside from durability issues, PM motors used in conjunction with an engine-driven generator will not be as efficient in using the available prime mover power as wound-field motors of an equivalent horsepower rating. You don't see PM motors in full-sized locomotives because they don't produce the sustained low speed torque that a series-wound DC motor can produce. Nor will the PM motor utilize generator output efficiently at higher train speeds, as the methods used with wound field motors to limit the high counter EMF caused by high armature RPM can't be applied.

It is for these reasons, as well as some others, that when I designed my locomotive I decided to use hydrodynamic propulsion. The propulsion system didn't have to be electric. It only had to behave like it was electric. And, it can withstand a sustained hard drag on an upgrade that would likely burn out the motors in many battery-electric units.
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JR May
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Re: Diesel-Electric Models

Post by JR May » Fri Apr 21, 2017 6:35 am

An interesting topic, one that has intrigued me since I first saw an article maybe 30+ years ago about a Gauge 1 live diesel electric, although it was a model airplane motor that was used as the prime mover. The concept seems rather popular in Gauge 1, actually.

With the growing popularity of internal combustion powered locomotives at the club tracks, why has no one produced a casting set or ready to run model of an EMD or ALCO prime mover? Visit Cabin Fever or similar shows and you tend to see miniature Chevy V8s or hit 'n miss engines in operation. Some years back I recall seeing a casting kit for the V8 on the market. An EMD locomotive at the club track would probably generate a lot more respect if powered with a scale model of its proper prime mover. Its doable. Would it have the exact sound? Probably not, but then live steam locomotives generally don't have a prototypical bark either.

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dnevil
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Re: Diesel-Electric Models

Post by dnevil » Fri Apr 21, 2017 7:39 am

The closest I've seen to a true diesel electric model is Stan Galloway's 1 inch scale diesel. It used a 4 cylinder Elmer Wall gasoline engine, which was about the right size for 1 inch scale.

http://ibls.org/mediawiki/index.php?title=Stan_Galloway

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Daris
Daris Nevil
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