Electric motor for 1/8 scale electric engine

[Mr Ron]

I've built 3 locomotives powered by DC motors and storage batteries. The problem with DC motors is, I can't find inexpensive ones to use. One of my engines uses 4 DC motors. As I'm starting work on another engine, I'm investigating alternative means of power and would like to hear your comments. Small universal AC/DC motors are easy to find and cost much less than DC motors. One thought I had was to use a DC to AC inverter, storage battery, universal motor and a variac variable transformer. I could also use a variable control made for universal motors as used in routers. Vacumn cleaner motors look like a good candidate with gearing. Your thoughts?

[Fender]

Mr. Ron,
What size motor/motors are you looking for? I see quite a few DC PM motors for less than $100, so don't understand what the advantage would be in going to AC or universal motors.
http://www.electricscooterparts.com/motors24volt.html
The more expensive part may be in the controllers.

[steamin10]

With power losses in the conversion from batteries to AC inverter and , blah-blah, you will have a heavy loss. Inverters and such are very good, when you can access them such as third rail, or overhead wire. That, of course isnt happening here.

No, I believe the drives worked out and inservice already, similar to Golf cart, and wheel chair power is the way to go. Surplus motors are available to make in-truck power, two motors per truck, with one or two trucks powered, can move you, and a small load. You will always bump your head on amp-hour storage, thats the nature of the beast. So wringing out the amps without waste is the goal, and converters are very wasteful in their smaller forms.

Follow in the footsteps of the proven, and dont try to re-invent the wheel, for your best success.

Cheers!

[FredR]

I'm not going to hijack the thread but talking about third rail and overhead wires..... Since most of the electrics run at 48v, would it still be a safety issue using a low voltage? I suppose the current is what is actually going to be an issue....

FYI, don't yell at me about this, I am just simply asking

Fred

[Fender]

No comment on the safety question, but here is a prototype example of overhead DC catenary
http://www.youtube.com/watch?v=unhXEQQk8G8

[FriscoJim]

I worked with 48 VDC for years and never received a shock from it. However, shorting a battery pack would generate arcs beyond stick welding proportions! The real danger wasn't electrical shock, but getting burned by an arc or a glowing orange wire on a shorted circuit. But that's just my experience with it... as they say, "Your mileage may vary."

[FriscoJim]

No comment on the safety question, but here is a prototype example of overhead DC catenary
http://www.youtube.com/watch?v=unhXEQQk8G8

WOW! Not only was the "catenary" an eye-opener, but how about that switch and the rotary dumper? In at least one shot, you could see sparks from the "pole" and between the wheels and rail all at the same time!

[Fender]

Yeah, this video gives new meaning to the term "pulse width modulation". I notice that the engineer wears a hard had, at least part of the time.

[steamin10]

OMG! I was talking about full sized as it related to power distribution giving it full availability for the relative unlimited power available. Not just batteries, a limited source. Apples and Oranges diference guys. Like the south Shore RR, or the elevated trains in Chicago. Ya know the Elevated lines were created in Chicago, to be more modern than New York, with its ground level horse cars. chicago took to steam on the elavated lines, and when the engineering came about, went electric above, while the Herd in New York dug tunnels for the subway.

Chicago had a small gauge underground railroad that hauled coal and packaged goods to the donwtown area, and took away ash and trash. It is documented in the book,'Thirty Feet Down'. It was suddenly abandoned in 1956 I think. Cars and electric locos were left where they were. Only a few made it to the light of day. It was powered by an ovehead bar, and some locos were either all battery, or battery augmented. I dont have the book, nor have I read it. Some years ago, this relic of a system caused havoc, when a piling was driven through the tunnel, forcing a collapse. The pilings were seen on the side of the collapsed tunnel, and burocracy daudled until it flooded and ran into the lowest levels of the huge buildings. Ya, the piling was driven into the Chicago river, in a project to protect a Bridge, whose pilings had rotted away on the surface.

The engineer in the lignite episode can be seen tapping the wire to get partial power and speed. Even in this crudest ( and scary to me ) video, it shows how much work a tiny rail operation can do. The other amazing one is the Chinese steamer, leaking everywhere, pulling a gaggle of cars over trackage a cartoon would be hard to imitate, with a happy brakeman, ( or whatever he was) waving and bobbing happily along on this swale filled road. Supposedly it is an operating mine, shipping coal to be processed, on the other end.

Before this thread got lost in the sideplay, I was only trying to contemplate a limited amount of power with a battery unlike having a continuous source, allowing a diferent control system to waste energy to accomplish the work. When we run a motor , we do work. How much and how long are part of the equation. Dropping resistors, relays and such are energy wasters, and must be avoided, with battery power, to get the better deal on efficiency.

I was not suggesting hanging wire in scale, or any such fantasy. Thanks, ya know how to hurt a guy.

[Mr Ron]

Mr. Ron,
What size motor/motors are you looking for? I see quite a few DC PM motors for less than $100, so don't understand what the advantage would be in going to AC or universal motors.
http://www.electricscooterparts.com/motors24volt.html
The more expensive part may be in the controllers.

I'm aware of the scooter motors; it's just the $100 cost that deters me. I already have an engine that is powered with a "scooter' motor, but I need two motors for my next engine. It will be a model of a DD1 electric as used by the Penn and LIRR's. They operate by a jackshaft between the motor and the drivers using conventional conn rods. It is listed as a 2-B + B-2; two unit engines run back-to-back.

[kc6uvm]

Mr. Ron,

Thinking from an engineering point of view, you might want to research what GE and EMD have done to produce locomotives using AC traction motors. Start with a AC motor(s), figure out the maximum power (plus a safety factor) you'll need considering for the ocasional power spike for times when an engine is moving from a dead start and what will be your power source (ie a generator) and electronic controls.

I heard of just a few doing this. But, the tried and true method has been either battery electric or gas/diesel hydraulic motor power. Good luck.

[BClem]

If you're not opposed to scrounging for these motors (I used to thoroughly enjoy scouting around scrap yards!) there are some very powerful DC motors in exercise treadmills. Either remove used motors or buy replacement reconditioned ones would be reasonable. Commercial DC motors are very expensive and usually designed for rectified and filtered line voltage - 90 or 180 volts so would basically be of no use to you. The lower voltage DC motors are very specialized and very expensive as you know.

A possibility would be to use engine starter motors since they are low voltage - 12 or 24 volts but they are brush phased to run at maximum speed/ maximum torque. The brush phasing can be changed for better low speed control when used with a PWM speed control. There are permag starter motors being used on some vehicles as well. That would be a plentiful source if a specific starter motor could be used.

I am also in agreement that an inverter is not the way to go with what you need to accomplish. Most basic AC motors are designed to run at 60 Hz and do not function well in a variable speed application. Once the 60 Hz 'sync' is out of balance, the efficiency is drastically reduced so to run slow speed, the motor would need to be sized upward by three or four times. Besides, there is much more constant torque available with DC motors at varying armature speeds.

Good luck!

Bill