K-Line Hudson Motor

The "stock" K-Line Hudson uses the Mabuchi RS-385 motor.  Note that TWO of these are used in many diesels, especially Weaver and MTH models from the 1990s.  This motor simply doesn't have enough power to haul significant-length trains, regardless of what locomotive it's installed in.  (The twin-motored diesels do quite well, though.  On my layout, an MTH passenger GP-9 from 1994 pulled 7 full-scale passenger cars at 80 smph with ease, while a Weaver Baldwin Shark from the same era pulled 15 average freight cars at 50 smph comfortably.).

There's not enough room inside the K-Line boiler shell to install a larger motor in the same position and orientation as the factory-original.

Many of us have chosen to have Pat (Harmonyards) perform a chassis swap on our K-Line Hudsons.  He replaces the K-Line chassis with an MTH one, which reorients the motor rearward and, with Pat's modifications, accommodates a much larger Pittman motor.  He will also replace the electronics, if you desire that.  Pat has provided extensive posts on this forum regarding his conversions.  My K-Line Hudson is in his shop at the moment.  The conversion is not inexpensive, but, if you acquired the basic engine inexpensively (as I did), the resulting total cost will likely be less than that of a new Hudson that may not have as much detail.

@KarlDL posted:

The "stock" K-Line Hudson uses the Mabuchi RS-385 motor.  Note that TWO of these are used in many diesels, especially Weaver and MTH models from the 1990s.  This motor simply doesn't have enough power to haul significant-length trains, regardless of what locomotive it's installed in.  (The twin-motored diesels do quite well, though.  On my layout, an MTH passenger GP-9 from 1994 pulled 7 full-scale passenger cars at 80 smph with ease, while a Weaver Baldwin Shark from the same era pulled 15 average freight cars at 50 smph comfortably.).

There's not enough room inside the K-Line boiler shell to install a larger motor in the same position and orientation as the factory-original.

Many of us have chosen to have Pat (Harmonyards) perform a chassis swap on our K-Line Hudsons.  He replaces the K-Line chassis with an MTH one, which reorients the motor rearward and, with Pat's modifications, accommodates a much larger Pittman motor.  He will also replace the electronics, if you desire that.  Pat has provided extensive posts on this forum regarding his conversions.  My K-Line Hudson is in his shop at the moment.  The conversion is not inexpensive, but, if you acquired the basic engine inexpensively (as I did), the resulting total cost will likely be less than that of a new Hudson that may not have as much detail.

Hi Karl, thanks for the reply! I looked at a thread of Pat's work and it looks fantastic! How can I get in contact with Pat about the chassis swap? I really want to give this engine the works and make it as great as it can be. Thanks again!

Tyler

It’s easy, his info is right here on the forum: @harmonyards; and there’s @Norton, with sound and power options such as his Blunami controlled Hudson!  We all hand a grand time at Hudsonfest…

I believe you can also just fit a bigger motor into the K-Line Hudson, (I’m a big fan, BTW and have three).

thanks!

- Mario

@CentralFan1976 posted:

It’s easy, his info is right here on the forum: @harmonyards; and there’s @Norton, with sound and power options such as his Blunami controlled Hudson!  We all hand a grand time at Hudsonfest…

I believe you can also just fit a bigger motor into the K-Line Hudson, (I’m a big fan, BTW and have three).

thanks!

- Mario

Hi Mario, thanks for the reply! You've given me more options now! I'll have to look into all my options and see what would be best on the wallet. Those Hudsons in the video are spectacular! The one using Blunami is very intriguing and has me interested. The K-Line Hudsons are very nice I really want this to run as good as it looks! Again, I'll have to look at my options. Thanks again!

Tyler

Having spent considerable time in Blunami conversion, I'm skeptical about doing it with large steamers.  You are betting that the motor current will seldom exceed the Blunami card's (2A or 4A) maximum current rating.  But a Pittman's stall (locked rotor) current is published as 15A.  Maybe OK with a flat layout and short trains.  Long trains of 21" passenger cars uphill?  Perhaps not.

I've suggested to Soundtraxx that they ought to make a 10A Blunami card, which I would readily use in non-DCS/non-TMCC steamers with can motors.

Blunami and larger motors for a K-Line Hudson are two different subjects. I have installed a larger motor in the K-Line engine in the same location as the Mabuchi motor. I can only estimate torque is maybe 30% greater. Nothing close to what harmonyards Pittmans can produce but it can pull 13 18” passenger cars for a short distance and 10 cars for about 20 minutes. I have yet to do a longer test using more cars so I don’t know what max is yet.

As for the Blunami, I have one in an MTH Hudson powered by a 9433 Pittman. It also pulls 10 cars with ease rarely exceeding 2.5 amps and never stalled…..yet.

I am not sure what stall current is as I can’t get a constant reading across the brushes with an ohmmeter but understand Lionel drives these same motors with boards rated at 8 amps pretty reliably.

Pete

@KarlDL posted:

...a Pittman's stall (locked rotor) current is published as 15A.  Maybe OK with a flat layout and short trains.  Long trains of 21" passenger cars uphill?  Perhaps not.

I've suggested to Soundtraxx that they ought to make a 10A Blunami card, which I would readily use in non-DCS/non-TMCC steamers with can motors.

If a loco is designed, weighted, and geared correctly it should not encounter a "locked rotor" condition at full current in normal use.  When the loco is overloaded it should not stall, the wheels should slip.  If you're already doing a motor swap and have any doubt, subsituting a 24-volt Pittman for the factory 12V motor will reduce the current draw by HALF, at the expense of reduced top speed.

Where 3-rail O gaugers have gotten themselves into trouble, is the combination of rubber tires AND tall gear ratios.  No tires--the wheels spin.  Low enough gear ratio, and even with tires the wheels spin.  Unfortunately, the way many of our locos are made, the motor might stall if the loco is overloaded (probably not at 15 amps though.)  Removing the tires, or swapping in a 24V motor is a straightforward way to reduce the maximum current likely to be drawn in actual use.  On a small layout, the loss of top speed with a 24V motor might not be an issue.

My Kline berks have the same motors as the Hudson.  For some odd reason the Kline berks are very slippery and I'll get spinning wheels before a stall.  So I've never had issue with burned up motors or fried electronics due to heavy loads.  If I want to run a long train I Lashup two Berks.  Now if someone can tell me why the Kline Mikado has better traction than the Kline Berks with the same wheel base for the most part?  Only thing I can think of is the weight distribution between the two engines.

I find this discussion very interesting, the Hudson is designed was supposed to be a runner. With extremely tall drivers, the engine is not built for heavyweight, but to move things out at a very quick clip. The original K-Line Hudson will pull 8 to 10 heavyweight cars without a problem This would be prototypical

@Ted S posted:

If a loco is designed, weighted, and geared correctly it should not encounter a "locked rotor" condition at full current in normal use.

This is correct and the probability of a full stall is low, IMO.  Nevertheless, the stall current is a guide to the current that the motor may draw when heavily loaded.

For example, the RS-385 motor stall current is 4A at 8-9 VDC.  That voltage achieves adequate loaded speed in twin-motored diesels and, therefore, series wiring of these motors is practical in a Blunami application.  The maximum observed motor current when pulling 15 freight cars up a 3% grade was just below 1A.

While Soundtraxx recommends that the motor's stall current not exceed the Blunami card's stall current rating (2 or 4 A), some may choose to ignore that based on measured current draw under maximum load conditions as they may exist on their layouts.  The Blunami card and software will alert the user if its current rating is exceeded, I'm told. 

FWIW and as a reference point, the ERR Cruise Commander motor drivers are rated at 8A - half the Pittman stall current.

Absent measured data, there is an element of risk in driving a large motor from the 4A Blunami card.  When I return from travel, I'll see if I can measure some "hard" data on a Pittman-equipped locomotive pulling a good-sized train uphill.

My approach for managing the stall currents is to add a PTC in the motor leads.  If you have it sized right, it'll be invisible in normal operation, but still protect you from cooking the drivers in a motor stall situation.  I started doing this when I was beta testing the Cruise Commander Lite boards, I fried one when the locomotive hung up on a switch and stalled the motors.  I added a 1.6A trip PTC in the motor leads to protect against the stall, that has protected things so far for years in a number of installations.

John I'm not familiar with a PTC or what it stands for, is that like a fuse?  Seems easy enough to do, and a good idea.  Rewiring dual-motored diesels in series will also reduce the current draw (and the speed/rpm at any normal voltage) by approximately half.  You could think of it as a poor man's 24V motor swap.

Of course Lionel has taken a different approach to protecting the OEM electronics- if the motor encounters an overcurrent condition, the loco just stops and blinks the cab lights.  It seems as though the threshold is set pretty low, because sometimes operators encounter the motor overcurrent shutdown in normal use.

Karl, when you do your tests, please make a note if the drivers slip or stall at max load.