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 Posted - November 08 2014 : 12:14:28 PM
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I have a large collection of old Mantuas and started to rebuild the motors with rare earth magnets. Just what I have found. I have an amp and volt meter on each of my main lines. When I tested the locos I did so on each track. Both are powered by a MRC Sound and Power 7000, all DC.
First I converted a Berkshire and a Pacific. Results were basically the same with each. Replaced the magnet with 8 1/8x1/4x1/2 magnets (two stacks). Note that the gauges on my panel may not be accurate to compare to anything but themselves.
Prior to upgrade:
70% throttle was required to start the locomotive.
60% to maintain minimum speed.
Amp draw between 2 and 3.
Amp needle 'jumped' frequently as the loco ran.
Once moving the throttle could be decreased to slow the speed but not to the point that the updated motors ran at.
Post upgrade:
40% throttle required to start the locomotive.
40% required to maintain speed.
Amp draw between 1.5 and 2 amps.
Amp gauge remained steady.
Start point was as low as the throttle could be operated.
Top speed was the same.
Easier throttle control due to the range that the throttle can be moved through.
Easier switching since the starting speed is less and better throttle control.
The cost to do this was ~$35 for 50 magnets on EBay, enough for 6 locomotives.
Time is about 15 minutes to change the magnets. Rest of the time is whatever is required to dismantle the locomotives. I am happy with the results for the cost. There is no flywheel action but there is a momentum option on the transformer I use that can simulate this.
Note that even though the locomotives were in good working order prior to changing the magnets since I had them apart I did a complete clean and lube job. I the past the clean and lube did not make this much of a change but did provide some improvement.
I have ordered a can motor replacement and when I receive it I will compare it with the rare earth magnets. The can motor did run $35. We will see if the cost difference is worth it.
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Posted - November 08 2014 : 12:54:27 PM
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how hard would it be to put a Rare Earth Magnet in a Tyco/Mantua 4-6-0 motor?
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Posted - November 08 2014 : 2:32:36 PM
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| Many of the Mantua or Tyco/Mantua motors are essentially the same (e.g., 4-6-0, 0-6-0, what have you) and they all can use 1/8 X 1/4 X 1/2 Neodymium mangnets (takes 3 to occupy the space of one of the standard Mantua magnets) . . . part #N42 from www.kjmagnetics.com . On the older motors you can take out a screw to remove the magnets; on the newer ones (the 4-6-0), you have to remove a rivet. You can then put a screw in place of the rivet.
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Posted - November 08 2014 : 3:36:07 PM
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On the riveted motors, I usually don't bother drilling out the rivets. I just pull out the old magnet and stick in a stack of either two 1/4 x 1/4 x 1/2 inch magnets or four 1/8 x 1/4 x 1/2 inch magnets. The magnets end up a little farther from the armature than with the screwed together motors, but the motor seems to work well enough, anyway.
By the way, when you pull the old magnet out it's permanently weakened by doing so, but the rare earth magnets can be taken out and put back in with no degradation.
Carpe Manana!
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Posted - November 08 2014 : 4:34:55 PM
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tkruger:
I love the NdFeB upgrades too. Easy to do, and I've gotten similar results to yours, though I have a question about the current draw. That's stall current, right? Is this the PM-1 or the MG-81 motor?
I also use a through-bolt and nut to replace the rivits, only because the riveted frames always seem to have a deathgrip on the magnets, and I don't want to warp the frame prying on it. I use a brass bolt to avoid short-circuiting the magnetic flux path.
Edited by - Autobus Prime on November 08 2014 4:36:22 PM
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Posted - November 09 2014 : 01:12:30 AM
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quote:
I also use a through-bolt and nut to replace the rivits, only because the riveted frames always seem to have a deathgrip on the magnets, and I don't want to warp the frame prying on it. I use a brass bolt to avoid short-circuiting the magnetic flux path.
Originally posted by Autobus Prime - November 08 2014 : 4:34:55 PM
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That's why I was surprised to discover that Mantua used a steel rivet on red box era MU-2 when I disassembled one with shorted windings. All that does is weaken the magnetic field around the armature.  I always assumed they were aluminum. Pittman style open frames are always held together with brass screws. I'd like to try replacing the steel rivet on a good motor and see if it makes much of a difference.
The Tyco Depot
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Posted - November 09 2014 : 01:31:44 AM
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quote: quote:
I also use a through-bolt and nut to replace the rivits, only because the riveted frames always seem to have a deathgrip on the magnets, and I don't want to warp the frame prying on it. I use a brass bolt to avoid short-circuiting the magnetic flux path.
Originally posted by Autobus Prime - November 08 2014 : 4:34:55 PM
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That's why I was surprised to discover that Mantua used a steel rivet on red box era MU-2 when I disassembled one with shorted windings. All that does is weaken the magnetic field around the armature. I always assumed they were aluminum. Pittman style open frames are always held together with brass screws. I'd like to try replacing the steel rivet on a good motor and see if it makes much of a difference.
Originally posted by NickelPlate759Â -Â November 09 2014Â :Â 01:12:30 AM
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NKP:
Was it magnetic steel? There are some grades of stainless that arent' very magnetic.
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Posted - November 09 2014 : 4:51:19 PM
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AB, the rivet sticks to every magnet I have like glue. I'm sure it's just plain steel, so what were they thinking? 
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Posted - November 09 2014 : 10:29:44 PM
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tk,
thanks for posting your experiment. I always heard there was an improvement with rare earth magnets but, I haven't seen any real numbers until now.
Unspoken expectations are premeditated failures.
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Posted - November 10 2014 : 09:35:29 AM
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This is an excerpt from another post I made on another forum (MRH) about rebuilding 2 Aristocraft 4-4-2s. They had the open frame motors.
"I began checking things out and all motors ran albeit some better than others. At 12 volts the amperage draw for the 4 motors was .65A to 1.19A. Stall amperage was just under to just over 1.5A for all motors. More web searching and I ended up ordering 3 neodymium magnet sets from Proto:87. Each set consists of 5 magnets plus a metal shim. After putting these into the 3 best motors (Picture 3) I was amazed at the difference in performance. I ran test measurements again on the motors and chose the 2 with the best numbers. At 12 volts the amperage draw was down to .55A and stall draw was down to .8A. The motors were all cleaned, oiled, commutators were cleaned and brushes filed flat."
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Posted - November 10 2014 : 09:36:16 AM
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The Amps draws listed are not accurate per say. My amp meters are more accurate to say 'out of 1-6 you get X'. But to say it draws X amps I would not rely on. They are consistent though. For comparison, what I am concerned with they work well. If I need accuracy I can use my multi-meter if I need to pinpoint the exact value. At this point I think the wrong scale was silk screened on the meter.
So far it is worth the cost. I have started to do this on motors that were running well and still saw improvement.
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Posted - November 10 2014 : 6:56:25 PM
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Yes, I suspect your meter scale is wrong, too. I doubt your motors draw 2 amps.
But, as you say, still a good comparison. For example, to maintain minimum speed adding the Neo. magnets gave you a 33% reduction in required power. That's significant.
At $5.83 per locomotive (not including labor)I would say that's a good performance value.
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 Posted - November 11 2014 : 09:02:39 AM
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quote:Yes, I suspect your meter scale is wrong, too. I doubt your motors draw 2 amps.
But, as you say, still a good comparison. For example, to maintain minimum speed adding the Neo. magnets gave you a 33% reduction in required power. That's significant.
At $5.83 per locomotive (not including labor)I would say that's a good performance value.
Originally posted by NC shortlines - November 10 2014 : 6:56:25 PM
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You say not including labor. Actually since I enjoy working on these does that mean I can subtract the labor cost? By using that math did I make money on this purchase? Can I more importantly use this line of logic to justify buying more train stuff? :)
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 Posted - November 11 2014 : 2:23:39 PM
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Tim,
Have you ever heard a dedicated fisherman ask how many bass he would have to catch to pay for his $18,000 bass boat. of course not! It is not about cost but fun and satisfaction.
Regards, John
A ship is always referred to as "she" because it costs so much to keep one in paint and powder. <> Chester W. Nimitz
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Posted - November 26 2014 : 2:39:14 PM
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Great info - thanks. Nelson did a create write up with pictures back in '12. Would you consider doing one for a fee?!
http://www.tycoforums.com/tyco/forum/topic.asp?TOPIC_ID=12192
rich p
Edited by - richard p on November 26 2014 2:49:41 PM
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