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Author Topic: Steam loco 4-8-4 rebuild  (Read 2676 times)
crosswire

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« Reply #30 on: June 13, 2021, 09:09:28 AM »

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.
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the Bach-man
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« Reply #31 on: June 13, 2021, 10:53:59 PM »

Dear John,
This loco has undergone continuous upgrades since it was introduced decades ago.
The latest motor is very likely improved since 2000.
Good luck!
the Bach-man
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crosswire

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« Reply #32 on: June 14, 2021, 09:32:32 AM »

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.
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jward


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« Reply #33 on: June 14, 2021, 10:02:05 AM »

Keep in mind the motors would not be the only improvements made over the years. The drive train may be improved as well, with unnecessary friction engineered out of it. AS I've mentioned before, I have several Bachmann locomotives that will pull at least 20 silver series freight cars up a 4% grade with 18r turns.
 
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Jeffery S Ward Sr
Pittsburgh, PA
crosswire

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« Reply #34 on: June 15, 2021, 08:52:52 AM »

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.
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willis

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« Reply #35 on: June 15, 2021, 11:31:22 PM »

hi John G,
were both motors identical except for the worm gears?
if so the gear mesh is way off and probably slipping.
Willis.
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crosswire

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« Reply #36 on: June 16, 2021, 08:50:39 AM »

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.
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crosswire

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« Reply #37 on: June 19, 2021, 08:41:02 AM »

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.
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