Hi Bach Man,

Are there any differences between the older 4-8-4 motor and the newer Niagara motor? I recently did some load testing on the two motors and found a number of differences; particularly, in stall current (mA) and rpm.

New motor -
Stopped and running off track in air, both positions - 0.1
Running on level track, no cars or tender - 0.25
Stall - 0.4
RPM of drivers - 300

Old motor -
Stopped and running off track in air, both positions - 0.1
Running on level track, no cars or tender - 0.4
Stall - 0.55
RPM of drivers - 500

The RPM numbers are approximate as I could not get the reflective tape to stick to anything and had to focus on a connecting pin on the rearmost driver.

Thank you,

John G.

Hi Willis,

Thanks for your response. Yes, the worm on the new motor was different; however, I removed the worm from the old motor and put it on the new motor in order to keep the gearing correct.

John G.

Jeffery,

Hi jward,

I also have some locos, by Bachmann and others, both steam and diesel, all of which have been converted to DCC by me, that can pull cars over the 2% grade on my layout. These locos include one Bachmann 4-8-4, converted a couple of days ago. However, the Bachmann 4-8-4 under discussion can barely pull itself a 4 cars over the grade.

The question is why not this one? The chassis, drive gearing, and running gear on both 4-8-4s are the same vintage; thus, any recent upgrades to the running gear do not apply. The only difference is the motor. I am waiting for Bach Man to advise if there have been any rpm or torque changes changes to the new motor. He did indicate improvements had been made, but did not indicate if the improvements made changes to the motor torque and rpm ratings.

The primary drive gear on the NIagara motor is much smaller in diameter than the older gear. Assuming the gear changes did not affect the final speed of the locomotive; either, the motor rpm and torque had to be changed or the intermediate gearing was revised.

I choose the Niagara motor for my upgrade as it was the only one I found that was the same size as the old one. I could not find any torque or rpm specifications for either motor, so I took a chance that the Niagara motor would work. If this was a bad decision, I would like to know, then I can put this loco on display.

Thanks for the response,

John G.

Thanks for the reply Bach Man,

So you are saying the new motor should perform better than the old one. Does this mean that the new motor should have the same or better torque output and the same or better rpm range? I have looked for these specs and could not find them.

Regards,

John G.

I am still working on this loco and have eliminated or corrected all the suggested problems. I have discussed the decoder and its tuning with the folks on the Digitrax forum.

However, the performance problems remain.

Bach Man - is there a possibility that the original motor, 1999 or 2000, had different specs than the new Niagara motor I purchased for this loco?

Thanks,

John G.

Thanks Terry,

As a new product, I am hoping someone has operational use of one of them and can answer the question about outputs for signals.

Does anyone have experience with these decoders?
In addition to outputs for the solenoids, are there outputs for signals?
I have a number of model power turnouts that I wish to convert to DCC.

Both trucks have springs; however, I did try running the loco with the trucks removed, no change in operation. I did try more weight and traction tires, but this improved traction enough that the drivers stopped slipping and the motor stalled.

May be the 4-8-4s came in sets and are not the same quality as the non-set locos. These locos do not have speed or pulling power. I would have thought these locos would have had one or the other. The 2-8-2 pulls well and is one the fastest locos I have; just the opposite of the 4-8-4.

Both the DC and the DCC 4-8-4s that I have are, apparently, weak pullers. By contrast, a Bachmann 2-8-2 and a Rivarossi 2-10-2 that I have can each pull 11 hoppers and a caboose up the same grade; albeit, with drivers slipping, but they make the grade, NPI. Maybe the difference in driver size or weight distribution causes the difference.

When I replaced the motor, I had to modify the motor mounts  a bit. I found that the new mount had come loose and allowed the motor to lift a silly millimeter or so in forward, enough to disengage the gears allowing them to bind tooth to tooth and stall the motor. In reverse, the geometry of the gears pushed the motor back into place, so the loco seemed to operate much better. The random stopping problem appears to be solved. It is just regrettable that the loco is such a poor performer on a grade. Oh well.

rbturner - Thank you very much for your assistance with this problem. The answer was binding; I was looking in the wrong place.

I did not know that installing the dummy plug would reset the loco to DC. I will try that.

I had three of the 2-8-2s, one had a non-functional pancake motor and I gave up trying to fix that that one. the second loco had a burnt motor and that is the one we are working on. The third loco is still DC and I have run that one. It has the same motor and gearing as the one we are working on. It does not randomly stop or cause track faults, but has the same problems negotiating the 2% grade. It does not have the brake rods that the the second loco has.

I did notice, while checking the brake rods, that the drivers wobble a bit more on the second loco, the one we are working on, than on the third loco. The quartering seems OK, but maybe the driver shaft journals are worn and that is causing binding.

The new motor for the second loco was sold as being for a Niagra and came with suppression capacitors. It had the same dimensions as the old motor, but came with a flywheel and a different main gear. Due to space constraints in the chassis, I had to remove the flywheel. I installed the main gear from the old motor on the new one and the motor and complete loco bench tested OK. However, when I put the loco on the track and tried to run it, the random stops started.

I have not yet removed the caps, but will try to get to that today.

With this one loco running, the ammeter reads about 0.4 to 0.5 amps just before a stop. There is a time lag between the ammeter updates of a few seconds, due, I suppose to the time lag incurred between reading the current at the DCS and then displaying the reading on the laptop screen. During the stop, the ammeter reads 0.2 amps which seems to be the background load with no locos running. While this loco is stopped, the headlight is still getting power. The only time the ammeter reads close to 1.0 amp is when four locos are running.

I did read that loosening the screws that hold the frame, that holds the drivers and the trucks in place, helps the loco run better. I did try this with some success; so, I took the next step and removed the screws entirely. The loco did run much better; especially, on the curves. Better meaning the drivers slipped at a faster rate than before on the upgrade, but 4 cars was still the limit.

This particular model of the 2-8-2 has brake rods and shoes, attached to the frame, that drop down between the drivers. It is possible that the drivers, when under load up the grade, are rubbing against these rods and loosening or removing the screws holding the frame allows the rods to move out of the way. Needless to say, testing this would require the permanent removal of the rods and I am hoping to avoid that as I doubt I could ever get all eight of the rods glued on again.

As for the throttle, I only have one DT and it has not been plugged into the LocoNet while testing this loco.

The DCS52 reports amps at the control station to JMRI. When on the upgrade, train motion stopped, but drivers turning, the reported amps are 0.4 to 0.5. The decoder in the loco is rated at 1 amp.

The 2nd motor did not have caps.

When I disconnected the caps on the 4-8-4 motor, I only disconnected the cap wiring soldered to the motor frame. At this point, I could try removing the caps entirely.