Caveat: Although anxiety to
see your new gem run on some track may be overwhelming, this may be
dangerous.
In testing over 5000 locos over the last 30 years, 5 to 10% of HO & O showed problems, with brass even higher. N Scale was as high as 20%. Used locos tested for repairs or resale were much worse. Some examples:
- Dirt, lint and other foreign matter.
- Worst of all: Steel wool in motor. The magnet loves the stuff and since no sonic cleaner can remove it, only time consuming hand picking works.
- Loose, worn or oil soaked traction tires.
- Lack of proper lubrication.
- Incorrectly seated motor brushes.
- Bound gears.
- Warped, cracked deteriorating zamac.
- Steam in general: Bent siderods or valvegear. Loose crankpin. Tender truck reversed polarity.
- Athearn: Loose pickup clips. couplings & motors. Wheels out of gauge.
- Tyco, Bachmann etc.: vertical, pancake motors with squeal or frozen shaft.
- Tyco-Mantua: hollowed nylon worm and gear.
- MDC: stripped pinion on step gear
- Bowser: sheared valvegear rivet. 0
- Bachmann: Smoke unit heaters off center, melting stacks.
- Lambert brass GG-1: Shell nose shorting to auxiliary truck frames.
- Alco PRR BP-20: Solder on step mounts shorting to sideframes on 34" radius.
Before starting, check TIPS ON TESTING for some valuable ideas and pointers.
Although these test steps may seem excessive, they will help to avoid irreparable damage. The safer way to start is to examine the loco thoroughly before any testing. Determine whether it is AC or DC and what the maximum voltage is. Most scale locos are 12 V DC, with the exception of some German makes. Lionel, American Flyer and most tinplate are AC with voltages from 12 to 25 V. Move drivers, while feeling for play. If very loose, gears are not meshed properly and may strip. If there is very little or no play, gears or bearings may be bound, which could over heat motor. Check for loose parts, bad connections, foreign materials etc.. Check
When sure, mount the loco upside down in a CRADLE or packing foam to support it, so that all moving parts are clear. Test leads with clips are very useful. Connect these to any simple TRANSFORMER (AC) OR POWER PACK (DC). Although not absolutely necessary, a VOLT METER AND SENSITIVE AMMETER are of great value in evaluation of problems and tuning. Analog meters are preferred, since readings are much steadier. Digitals react too rapidly, causing digits to jump erratically, making them very difficult to read.
Open the throttle to about 5 V and touch lead tips to wheels on opposite sides intermittently. Listen carefully for any noises that indicate the motor is turning or for strange sounds like clicking, grinding, excess hum or squealing. If you hear sparking, crackling or sizzling, remove the tips immediately and look for the cause. When the second tip is touched, watch for bright sparking, which indicates excessive current.
With meters, if voltage swings to 0 and ammeter pins (sometimes audible), a short or heavy overload due to stalled motor is indicated. Since motors vary drastically in STALL CURRENT, the needles may not reach the extremes. If current is 0, there is an open, which is quite frequently due to a dirty commutator segment, worn or incorrectly seated brushes, loose connections or dirty pickups. Find and correct suspected problems, before proceeding.
If all goes well, raise voltage a notch and observe. Motor pitch should rise as well as current and voltage. Some problems do not show up until speed increases, particularly gear mesh and siderod or valvegear binds.
Repeat increases until maximum voltage is attained. I usually go to the maximum power pack voltage of 16-18 v, which will not damage the motor or a well running mechanism. If a loco runs well here, it does not necessarily mean it will run right side up on its drivers.
One case in point: In the middle 50's, I ignorantly disassembled several Mantua Sharknose powertrucks (pre- PM-2) to lube them. Since there were no restraining straps, the armatures popped out. After reassembly, testing revealed a large rise in pitch. Apparently the lube worked very well. Not so. When the locos were tested on some track, they hardly moved. After some retries and head scratching, my 4 years of electronics experience and training in the Navy, with 1000 lb Magnetron permanent magnets, finally popped the answer into my thick head. I had demagnetized the motors! On a short trip to Mantua, I was advised this was an all too common problem. They added retainers and remagnetized all 4 motors for a nominal $1.00, while I waited. I even enjoyed a tour of the factory and picked up some hard to find and obsolete parts.
At this stage, I usually continue testing and run-in on the ROLLERMILL , while working on another project.
Now for the long awaited track test.
CAVEATS:- All locos require "break-in " before loading with
train. After proper lubrication and initial testing, they should be run
light (tender only) at least 15 minutes in each direction at low and high
speeds to thoroughly distribute lube and ease in moving parts. Some,
(notably brass) require longer periods. This is not to be construed as
wearing in poorly meshed gears.
- During extended running, do not leave unattended.
Accidents (Murphy's Law) can happen, which may burn out motors, fry paint or
even cause a PLASTIC MELT DOWN.
- Between tests check for loose parts such as crankpins
that did not fall out. Look for signs of wheel rubbing on adjacent parts
causing shiny marks on paint or other surfaces. Also look for pitting from
arcing. These may cause trouble later, even after testing.
- Digital? command control (DCC) is useless for testing, since the short rise/fall time PULSES drastically increase motor heating thus increasing potential overheating. In addition, control is not consistent and due to the high voltage pulses, good meter readings are not readily obtainable. For more accurate testing, all accessory lights, sound systems and other current drawing devices should be disconnected.
The best test track is a loop of nickel-silver fastened directly on plywood, which acts as a sounding board. Ideally the radius should be at least 2" less than your minimum to avoid that "almost" made it case. A well regulated powerpack with momentum is very helpful for evaluation. Meters can provide invaluable information. At the end, SPEED DETERMINATION is a luxurious extra.
Place the loco on the track and raise the voltage until the loco runs continuously and smoothly without stalling. Run for a few minutes listening and looking for anything strange. Check the current to be sure it does not exceed motor rating. Watch voltmeter for any fluctuations, which may indicate spurious binds in gears, valvegear or siderods. Large, rapid swings toward 0 indicate intermittent shorts such as insulated wheels touching frame, sideframes, valvegear or siderods. In some cases auxiliary trucks are opposite polarity from frame and parts short to it.
Repeat by running backward, then reverse loco heading and repeat both forward and backward. Often a problem only exists when one particular side of loco is on the inside of a curve.
CAVEAT: Running
at high speeds is the most dangerous part of the testing. Murphy is waiting
for crankpins to work loose, valve gear to snag and any other loose parts to
foul. Pay strict attention with all your senses, including your nose.
Raise voltage to 12 V and run in all 4 directions for about 15 minutes each, examining closely for problems. The voltage should be kept at 12 V by adjustment, if pack is not well regulated. Observing the current, the value usually drops considerably as things work in. When it stabilizes at its lowest value, the loco is usually well run in. This is a good time to determine deadhead speed with the methods found elsewhere.
If everything went well, final testing follows, to evaluate performance. This may be fairly simple or complicated depending on your desires and equipment. The important question is: Does it perform the job that you intended it to do on your railroad??? Evaluating a switcher at 10 MPH with a few cars is quite different from testing an express at over 100 MPH or a hog with 86 cars.
The very basics are a decent powerpack, your layout and some cars. Using a plain none filtered, N Scale 90 ohm rheostat or transistorized powerpack will provide a basis for comparison among locos on just about any layout. Filtered DC packs will provide a more rigorous test environment, since even fullwave rectified sine wave PULSES may hide a defect. Electronically generated pulses should be avoided at this stage, since motors and drive trains react very differently to pulse parameters such as width, amplitude, rise and fall time and shape. A voltmeter and a sensitive ammeter should be considered as necessities to avoid overloading and to provide very useful information.
NOTE: Many locos with poor mechanisms may appear to run smoothly at high speeds, but run erratically at slow speeds. Be sure to check low speed operation thoroughly. From observation , a loco that does not run well on filtered DC, will perform worse under the rigors of DCC.
Common to all are the starting and stopping characteristics and the voltage for each. These should be smooth with a voltage around 3 V for a well tuned loco. If more than 5 V, the loco definitely needs tuning. The next is top speed at 12 V, which should be consistent with prototype operation, unless you like using only 1/4 of your throttle's range. Very often this is where the desire for REPOWERING crops up. Because, with all the beauty and detail, the loco just does not hack it in performance.
- Do all locos run through complex turnouts and frogs without stalling or derailing?
- Can your switcher or way freight couple and uncouple with delayed action at speeds less than 3 SMPH?
- Can that freight hog handle 40-80 loads at 40-60 smi/hr?
- Can the high wheeler haul the 10 car limited at 100 smi/hr?
Concerning the nebulous areas of acceleration, deceleration and momentum, smooth transition is the major criterion. Although FLYWHEELS may help smooth performance , none can truly simulate momentum. Only well designed analog electronic circuitry can develop reasonably believable momentum over a wide range. However not all POWERPACKS are created equal. Some perform well with one loco-train combination but not with others. Since most people can not afford to have many different packs to match trains, they must be happy with an acceptable compromise. Taster's choice. Try what you have.
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