OT What type of welder transformer?

Railroads

Active member
Evening, I have a somewhat crazy idea and I would just like to ask a few questions.

Sometime in the near future I am thinking of building a working 7 1/4" gauge ride on New York Central Railroad http://www.railpictures.net/images/d1/7/9/1/8791.1176411600.jpg 3rd rail electric. If I decide to go for a working live third rail I am thinking of running 48 volt motors on the locomotive and up to 60 volts DC on the third rail at what ever amperage a welding transformer could deliver.

So my question is what sorts of older type welders would have a large transformer with taps? Ideally should I be looking at 120 or 220 AC line voltage for a welder transformer to use as a third rail power supply?

I am very familiar with electrical projects. But, I have never messed with welding equipment before and really don't know what I am looking for if I decide to find a older welder to tear apart to use as a power supply for my DC 3rd rail system.

My only welding experiences are with stick welders made from old car alternators and microwave transformers.

To build my lokey I am going to buy a older stick arc welder to build my behemoth. Or maybe hire a buddy to do the welding of the frame parts.

Robert
 
I believe that 48V is the highest voltage that can be left exposed without safety shields and who knows what other rules might apply.

Bob
WB8NQW
 

Railroads

Active member
Original plan was to use 24 or 36 volts. But I was afraid that losses in the conductor rails would be higher resulting in a loss of power on steeper inclines with a decent load behind the locomotive.

Nominally 50 Volts supply sounded about right for a set of 6 traction motors.

Robert
 
First of all let me say I think this is a very cool idea. I've made some assumptions, first it will be outside second it will be run somewhat infrequently. As akuna mentioned I fear rust/corrosion will always be a major problem. You may have to build a rail polisher to clean them each day before you can run it. Another issue will be the duty cycle of the welder, most welders will not have a high enough duty cycle to run long periods without getting hot. How about using parts of an electric golf cart: batteries, charger,controls, and the motor with additional gear reduction. Good luck!
 

Weld Engineer

Subscriber
You will need a constant voltage welding power source but will find difficulty getting a single phase 230 volt machine to put out 48 Volts. A Stick only machine is constant current but you will not be able to set a voltage so those won't work. If you look at the OCV of many CV machines (GMAW aka MIG) it won't typically be high enough as most processes other than large high power processes take place less than 40 Volts typically not more than 30 for general applications. No idea what your amp draw is but you will need to consider duty cycle too. If you are maxing out the voltage it affects duty cycle too.

I think you will find it tough to use 48 Volts from a reasonably priced unit.

Max OCV is 42V from a standard industrial unit Miller had made for many years.
https://www.millerwelds.com/equipment/welders/mig-gmaw/deltaweld-302

Sounds like a cool project and I'm sure there is a solution.
 

oldgoat 47

New member
I guess you should work out the current draw of your traction motors and then look for a suitable supply. If you use 3- 48v X 1000 watt motors you wold only be dragging a bit over 60 amps from the welder and the duty cycle at that current should be 100%
 

Railroads

Active member
Thanks to everyone who has responded. I am only doing research right now and thus the questions on a suitable power supply for the third rail. The outside third rail would be the power and the two running rails the return.

I know no one has done such a setup before. At least none that I can find examples of. I did find this discussion though. http://www.sevenandaquarter.org/forum/?/Engines+and+Rolling+Stock/External+electric+power/&cat=5&topic=587&action=view_topic

Any real construction is a ways off due to many issues and the high cost of the track it's self. The rail is not cheap by any means and could take a couple of years just to get enough rail to build even a short section of track.

Robert
 

pegasuspinto

Active member
I am going to chime in too and say you CAN NOT expose the public to these kind of voltages. That is enough voltage to be very dangerous. If you have a derailment, will you short out the track? What happens if someone falls onto the rail? Manages to get a watch or necklace bridged on it? With 7.5 gauge track you can only get the 3rd rail 3.25 inches away from the others. Even as an outside rail I can't see it being very far away.
 

dkamp

eMail NOT Working
An ordinary AC buzz-box welder will work just fine. Yes, it's constant-current, not constant voltage, but with the load you're running, neither will matter. OCV on it with the tap setting very high would be upwards of 75-80v with NO LOAD, but once you're drawing current, it WILL sag substantially. Under full current load, expect it to level off around 40, as under arc service, it sits around 25 or so.

Don't put DC on the rails- instead, put a rectifier under your loco's hood, and switch the polarity there in order to reverse your direction.

Yes, you'll have resistance at the contacts. No big deal, the more you run it, the cleaner it'll get.

For safety, get a wireless remote control switch from your local hardware store, and set it up to control a contactor that shuts the welding transformer down.

As for people getting shocked, we weld with stinger, on grounded surface, in the rain all the time. I get shocked all the time. It hurts and makes me jump, but much to my wife's chagrin, it has never killed me very much... the voltage is simply too low for the circumstances.

BTW... my name is Dave, and I used to teach electric railway propulsion. I had many students who were members of the 700 club. Some didn't survive, but most did. Not pretty, not safe, but knock one order-of-magnitude off that voltage, and it's actually very tame.
 

pegasuspinto

Active member
Problem with fluctuating voltage and motors is they do not like it. That is why they are rated at a particular voltage. If voltage was not a problem, then they would not be rated differently.

Load an electric motor at less then the rated volts and they can and will burn up. Low voltage and high current burn up lots of auto starter motors.
Not quite true. DC motors run slower and less amps with less volts. Starters don't typically burn up from low volts unless someone grinds them to death trying to start something that just needs more RPM. AC synchronous motors run high amps at low volts, because they try to spin the same RPM and put out the same horsepower. That is why old elevators, cranes, golf carts, mine locos, etc used DC driven motors-they were very easy to control speed by just dropping voltage. Now with VFD's it's much easier and more efficient to control the frequency fed to the motor.
 

Railroads

Active member
Nothing seems very safe if one stops and thinks about it? A garden railway with a 48 volt 3rd rail not open to the public is no more dangerous than any other activity we carry out on the day to day bases. Hell, I've almost got hit a dozen times just trying to get the mail or walk my dogs. Hell, How many times have you heard about someone getting shot just walking down the street??? Too many around here to count anymore.

Electric railways have been one of my interest for decades. But, I have never seen much on a smaller scale done before. Probably stands to good reason that not many people are savy enough to pull it off.

With a good track and realistic speeds is a 3rd rail anymore dangerous than riding atop a working steam engine model? Or how about a mower engine running a hydraulic pump and motors for those who model diesel locomotives?

I've been shocked by AC and DC up to 120 volts many times and while it hurts like heck. I am still non the worse off.

Robert
 
It is not the voltage that will kill you. It is the current and the body path it takes. One hundred milli-amperes ( .1 amp) across the chest area is 100% fatal. Data from the annual mandatory safety course that IBM service folks were required to take. Skin resistance and contact area make all the difference in the world as to outcome.

Bob
WB8NQW
 

Railroads

Active member
It is not the voltage that will kill you. It is the current and the body path it takes. One hundred milli-amperes ( .1 amp) across the chest area is 100% fatal. Data from the annual mandatory safety course that IBM service folks were required to take. Skin resistance and contact area make all the difference in the world as to outcome.

Bob
WB8NQW
.1 amp at what voltage? Seems for males it was .5 amps and .3 for females the last time I took any electrical safety courses. :shrug: Baring the fact it has been 15 years or more since my go round with electrical education.

UK third rail practice is to have the full 3rd rail exposed most of the time as the clearances are different and the trucks or bogies would rip the wooden protection boards up. Thats way they are only found in the station areas now. 1500 volts DC fully exposed down through the country side. :eek:

Robert
 

dkamp

eMail NOT Working
In order to get dangerous current through critical body path, the path needs to have low resistance... but the critical path ISN'T low resistance... the skin layer is lower... and regardless, the welder's output voltage is simply not high enough to pass that level of current. Connect an ohmmeter from one leg to one arm, and you'll find that dry, you'll have over 100,000ohms' path resistance. At 80v, 100K results in less than one milliampre. If you're wearing dry clothes, you can sit on those rails, and never get a shock.

IF you contaminate your skin with sweat, grease, and water, that path resistance will fall, however, the path will no longer be through middle-body-mass, it will be at skin level, again, rendering it painful, but not through lethal path. If it was high enough to be lethal, I would have expired long, long ago... any guy who's had to weld in the rain, or in the water, has been through it.
 
One tenth of an amp through the heart lung area will be fatal no matter what the supply voltage is. If the skin is punctured a very small voltage can easily pass .1 amps through the body. Voltage does not kill. Current does.

Bob
WB8NQW
 

Railroads

Active member
Ok, ok. Like I said, I was only interested in a feasibility study. Instead of a powered rail I think I will opt for a set of marine batteries if I decide to have an electric loco. This being the most common method of powering a electric loco. The other is using a engine driven auto alternator.

Those fair trains that used to give kids a ride around a circle of track had both rails powered. One was the hot side and the other ground. The voltage was 110 DC in the UK. I will see if I can find the site I saw about these some time ago.

The fair train I'm thinking of dates from the early 1900's. I just can't think of who owns it currently?

Robert
 

dkamp

eMail NOT Working
How is it, that after all these years, that men who weld in the outdoors, sweat, rain, snow, sunshine and dark-of-night, that millions of men haven't died from being zapped while changing a welding rod?

It's because there simply isn't sufficient potential to pass the current. One tenth of an amp doesn't come through your body with 80V applied.

Bob, You're at much higher risk of getting bit by a 50w HF tranceiver by the mic shield becoming part of the counterpoise... the RF voltage coming through has the potential to go much higher, and that's because under AC harmonic circumstances, Kirschoff was wrong. The ONLY time a welder will approach enough voltage to cause a serious problem, is when the welder has an HF arc starter integrated in... like a TIG supply, and he's not gonna be forking out the coins it takes to put HF arc stabilization into his downsized railway. An ordinary AC or DC welder is not going to present a hazard in the OP's application.

Consider two kids walking down a rural railroad track: There's greater hazard for an individual to get shocked by stepping on the head of BOTH rails of a NON_ELECTRIFIED rail segment... for FOUR reasons:

A ) track signalling is done at somewhere between 40 and 150VDC. If there's a track signalling segment (like crossing gates, block protection signals, a movable bridge span, etc), the wayside station applies voltage between the rails to detect presence of a rail vehicle)

B) Train-to-wayside signalling injects LF, and frequently modulated LF into the rails to both broadcast (to the train) things like block speed limits or stop conditions.

C) The rails, being a contiguous long-distance conductor, and the right-of-way, also being used as an easement for telecom and electrical power, becomes a 'coupled network' where magnetic lines of force developed by the utility current conductor induces current into the rails, thus, making it a 'sympathetic' conductor...

D)... as well as a long conductor generally slightly better than earth conductivity, and although sitting on wood or concrete ties, is somewhat insulated from the ground (technically, it's regularly shunted with extremely high-value resistance), but still, extremely susceptible to carrying ground-currents.

The simple presence-of-rails already electric in nature. Using a welding transformer is NOT a substantial hazard, and it sounds like he's got a pretty good idea of what he's doing. He's more likely to roll a railcar over his foot, than get shocked from a welder. Under these premise, he should build his railway with plastic rails, or no rails... at which time, he could electrify the rails however he'd like.

Robert- What you're considering doing, has been done as commonplace for over a century, both in industrial, commercial, entertainment, and private. I just moved seven narrow-gauge railcars weighing about a ton each (including one very, very fancy replica turn-of-the-century trolleycar) running on 240vac, with combination of catenary and third-rail. The trolley ran a quarter-mile straight track from a 'station' by the road, to a 'platform' by the house, and every morning, the kids rode the trolley from house to the 'station', and waited for the school bus. Nobody ever got hurt from it. If your property includes even the slightest modicum of common sense, there's absolutely nothing to worry about.
 
My reference to .1 amps had nothing to do with welders. IBM mainframes had some serious power present inside. They had water cooled 1.2 V DC supplies that ran continuously at 900 amps to supply the ICs in the processors. The AC input was 208V at 400 hertz from a 208V 60 hertz motor generators on the computer room floor. With that kind of capacity, electrical safety was always part of everything we did when the covers were open. The annual safety course was general in nature. There were thousands of small pins on the printed circuit boards where we could measure voltages or scope signals. If you managed to break the skin and came in contact with any of the low voltages present all over inside the machine it would most likely ruin your day.

Bob
WB8NQW
 

dkamp

eMail NOT Working
So then I'll reiterate the OP's original title "...What type of WELDER TRANSFORMER?"

Using an ordinary AC buzz-box welding transformer will work fine, and pose no more danger than any other aspect already extant in his downsized railroad.

Use AC on the third rail, and a rectifier in the locomotive, along with a series of resistors with switches in series steps... you could use 8 'positions' on your lever, just like a real-life electric railroad locomotive, and a genuine reverser handle to flip the polarity of either the armature or the field, and you'll be a full-figure style like the real thing.

An excellent source of make-work parts for this would be the control box, motor, an drive axle from an electric golf-cart. The CitiCar I owned many years ago used a ruggedized version that had a 5-element resistor for 6 positions (one stop, one full, and four partials).

You'll have no problem running something like this with a 'cheap' department-store welder... if you were close by me, I'd give you a Sears unit that was given to me from a friend who was cleaning out his uncle's estate (I'll never use it, and if you saw my other welders, you'd understand why). You'll likely never see the upper side of 50A, and since they're a saturation-limited transformer, you won't have to worry about the duty cycle being insufficient for your train... set it at about 25% and it'll be fine.

You could tap off the rails at regular intervals of your track and run lighting and signals... 12v LEDs with current-limiting resistors where necessary, or you may even be able to make inexpensive 120v 'decorator' type lamps (80 lumens, etc) glow sufficiently for pleasant effect.

For ersatz 'crossing' signals, mount motion sensors on the signal stands, and wire them to truck windshield-wiper motors striking gong-bells from old school 'recess' ringers. You could affix a simple drag-clutch to the wiper motor's spinning arm, tied to a lever on the crossing gate to pull it down, and when the motor stops, the crossing gate's counterweight, or an old worn-out gas spring, will pull it back up.

A tap off the rail shoe supply line, rectified to DC, and fed to an appropriate charging controller and lawn-garden battery will run your on-board lights and A 12vdc air inflator with enough pressure and volume to pump up a reservoir hidden in one of your passenger cars to toot a whistle. Find a well-versed electronics/ham-radio guy to find build the supply, probably need a switching-type regulator in the charge controller to tolerate the incoming voltage. FWIW, many of the new 'wall-wart' supplies are switchers, and tolerate much wider voltage range than the old transformer-units, so you MIGHT find a workable one after some experimentation.
 
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