[HO] steam engine open frame motor RPM question

It seems pretty slow. However, another check for starting speed voltage and at 12 volts would give us a better indication.

4000 rpm or higher might be reasonable at 12 volts.

The scale maximum speed of the loco should be in the 60-100mph range. (between 1' and 1'8" per second aproximately)

You measured the rpms at 6.7V which is a partial speed and may or may not be that relevant. Try again with the voltage at 12V for the axle speed and see what it does. There were a number of locos done by the importers that were trying to slow down the high speeds that many locos ran at. Often, they were not good sellers due to the much slower speeds that they ran at. You may have one of those locos. For some reason, many people think that locos should all be able to run at more than 100mph. In truth, very few locos were able to run at that speed and many locos were unable to run at anything much more than 1/2 of that speed. Even many of the road diesels of today have trouble running more than 80mph or so and generally don't unless the train is well "overpowered" by most standards. I'd more consider 65mph to be a decent standard for diesel locos to run at when at 12V as this will not only make the speeds look better but will also improve the low speed characteristics of a loco as 5mph won't be so close to the minimum speed at which the motor will keep running at. Even better is to have even lower max. speeds to let the distance between stations seem even further apart - those that travel on a commuter train can have a good idea of how long it takes to go from one station to another and those are local stations rather than a full town to another town in the countryside.

-- Bob May Losing weight is easy! If you ever want to lose weight, eat and drink less. Works evevery time it is tried!

Use caution!

Methyl Alcohol (or any common alcohol) is highly flammable. Any sparks from the motor could easily start a fire. If the motor is TOTALLY submerged this danger would be lessened (no air), but don't try to to put it into, or out of, the alcohol while running. I'd also take good precautions against fire. Do it outdoors, wear face protection, use long tongs or pliers, have a good fire extinguisher handy (plain water is not very good for fighting alcohol fires), etc.

Also, some older motors may have the armature coated with a varnish that MAY be soluble in alcohol (shellacs). You MIGHT wreck the motor.

There are other cleaners available that may be safer, depending on what you call safe. Freon was one such, but it, and many other solvents are ozone destroyers. Others may be toxic.

Probably better just to spray the running motor with a NON-Flammable motor or contact cleaner (auto, shop, and elecronics parts suppliers) designed for such use (in a well ventillated area). Then re-lube the motor as the cleaning will destroy any lube in the motor.

Dan Mitchell ==========

JCun>

The advice is appreciated even though somewhat confusing as there seems to be some skepticism as to safe cleaning solutions. I have digested the info and will pick my own poison. Thank you.

One party asked for further data. First, before posting the original note, I oiled the bearings, both the trucks and the motor, gear box inspected and space between commutator segments cleaned and buffed the commutator with a soft eraser. Rotating the rotor with my thumb, the feeling is that it is free running. (The motor and gear box is coupled with flex tubing). Now the new data:

Start voltage: .7 (will continue running at .5 volts) RPM @ 12V: 2196, 1836 & 1908 = 1980 RPM avg. (Rather erratic running!) 12V current: .2 to .3 ma.

The current is questionable as quotes from other threads say .5 to 2 amps is typical.

My goal is to find out if the motor is faulty ! ! !

Thank you, Vern

Sounds like you have a can type motor rather than an openframe motor. 0.3ma of current is also very low for such a motor as they usually take at least

10ma of current. If you mean 0.3Amps of current then the motor can indeed be one of the smaller openframe motors. The low current indicates that the motor doesn't have a weak magnet on it so you don't have to worry about that. In addition, the low starting voltage indicates that also as weak motors won't start readily. I'd suspect that the motor was just wound for a low rpm level and that is pretty much the way it is. You may wish to replace the motor if you desire higher speeds and there are a lot of sources out there for motors. The KTM motors have been available in several speed ranges (you will probably see a KTM mark on the top frame of the motor near the magnet) while the Pitmann motors seem to have had only one speed range. For the smaller motor, the DC-195 is the motor while the larger motor is the DC-70. The DC-90 is also available but not generally used for steam as there were few engines that could handle the width of that motor. You may also want to check the brushes and armature for running qualities at speed as the KTM or it's clones just weren't made as well as the Pitmann motors. All Pitmann motors have the name on the frame of the motor in the magnet area.

-- Bob May Losing weight is easy! If you ever want to lose weight, eat and drink less. Works evevery time it is tried!

=> Now the new data: =>

=> Start voltage: .7 (will continue running at .5 volts) => RPM @ 12V: 2196, 1836 & 1908 = 1980 RPM avg. (Rather => erratic running!) => 12V current: .2 to .3 ma. =>

=>The current is questionable as quotes from other threads say .5 to 2 =>amps is typical. =>

=>My goal is to find out if the motor is faulty ! ! !

Doesn't look faulty to me. Looks pretty good, in fact.

The motor rpm doesn't mean much. What you really need to know is whether the engine is running at something like a protoypical speed at 12V. To find out if the engine is running within its proper range of speed, do a timing test. Mark off a section of track that's a multiple of 5ft, making sure you can see the beginning and end of the timing section clearly. 10ft or more is good. Time the loco running thorugh it at 12V. Start it a couple of feet before the beginning of this section If the loco is running at 1ft/sec, it's running at

60 scale miles per hour - which is about as fast as these locos ever went. (A scale mile in HO is 60.6ft) If it's much faster than this, say 1/2ft/sec, it's running too fast. At 1.3ft/sec, it's running at 45scale mph -- a little slow, but not unduly so.

BTW, an eraser is not a good thing to use on a commutator. Use a cleaner - lubricant like Aerocar's Conducta Lube (part # ACT-3003). You'll be amazed.

Also. what kind of oil did you use? Reoiling the motor and gears with a different oil than was used by the mfr may actually make things worse. 1st, the oil may be the wrong weight (esp. if you used the same oil for all parts of the mechanism.) 2nd, there may be too much. 3rd, the oil may dissolve the gunk and turn it into grease. 4th, a synthetic oil may not mix properly with a petroleum based oil. All of these things can add drag, and slow down the engine. IOW, don't reoil without cleaning first. If you don't want to use methyl alcohol (I've never had trouble, but YMMV), use a cleaner recommended for electronic parts.

And never, never use household type oil such as 3-in-1. Use synthetic oils made for small mechanisms.

HTH&GL

That sounds like a fine motor to me. Electric motors are pretty simple. Long as it turns under power and the armature spins freely its likely OK. If it doesn't vibrate while running at full speed your armature is balanced. About the only other thing that can happen is one armature winding sometimes opens up. Then the remaining two windings sometimes can keep the motor turning, but it looses about a third of it's torque with only two out of three windings are pulling. You can check for this with an ohm meter. Just measure the resistance from brush to brush as you turn the armature with your fingers. If you find one spot that's open check your windings. But from what you have posted here, it looks like a good motor. The starting voltage is good. There is something wrong with your current measurements, no HO can motor draws that little current. A good one might run at 100 mA (0.1 A). Open frame Pittman style motors draw more like 0.5 to 1 amp. Current draw is proportion to mechanical load on the motor. As you load the motor down it will pull more current trying to keep it's speed up. If you stall a motor and give it full voltage it will get hot. David Starr

=> There is something wrong with your current =>measurements, no HO can motor draws that little current.

Recent reviews in MRR show that typically motors in recent engines draw 0.2 to 0.3 amps under load, and 0.5A or less stalled. Current draw is a function of the mechanical precision of the motor's parts, the resistance in the current path, and, most importantly, the strength of the magnetic field. Modern super high intensity magnets result in very low current draws compared to earlier motors, even in opoen frame types.

Oh, in them olden days we had moterrs what wuz moters, let me tell ya. Why, I recall one moter that drew 1-1/2 amps runnin' light. And it got pretty warm, too, yer had ter let it cool off a bit arter five minutes running. Almost burned it out onct, the smoke was pouring out of her, but I thought it was just a smoke generator I hadn't noticed before. Till I smelled it, it stunk wuss than a burnt hamburger. Hee, hee, hee, hee, koff, koff splutter, uggh.

Motors have come a long way.

HTH

I trust my current measurements on this motor. It was remeasured again this evening. While I was at it I checked the stall current @ 12V. It was 1.0 amps. A measurement of continuity of the rotor segments showed no open windings.

I did the 5 foot timing test suggested by a responder. It is painfully SLOW. About 30 seconds. That is unrealistic!

I want to do two things. Purchase a replacement open frame motor and a set of brushes. I have NOT removed the hardware supporting the brushes and it is possible that there is insufficient pressure of the brushes on the commutator.

As a check, the new motor would be installed and the engine tested again.

However, in my long search on the Internet I have come away with a goose egg on sources for the two items. Maybe I am a poor 'searcher'. Question? Any hints where one might find these items?

Thank you, Vern

Actually those numbers sound pretty good. If you had a problem with the motor, then the current would be HIGHER, not lower.

Don

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=>However, in my long search on the Internet I have come away with a =>goose egg on sources for the two items. Maybe I am a poor 'searcher'. =>Question? Any hints where one might find these items? =>

=>Thank you, Vern

Northwest Short Line

Lots of sizes -- don't limit your self to an open frame motor, all you need is one that fits. You also need a gear/wheel puller, so that you can use the existing gear on the new motor. You'll have to do some calculating to figure the correct motor, but NWSL has help on that, too.

Good luck!