Hey There Mr Bachman, a question for you

[chuckger]

Dear Mr Bachman,

  I have taken notice of the thread on the question of lubing the gears on the K 27. Is this loco really shipped with a dry gear box??  Can you tell me how to lube the gears and what is the recomended lube.

  Thanks, Chuck

[Jon D. Miller]

Chuck,
I've only had seven K-27 locomotives opened up prior to their being placed in service.  I'm sure this number pales by comparison with the numbers that others have worked on.

Of the seven, all had well lubricated gear boxes.  They were not shipped "dry." 

I do remove the boiler in order to lube the motor armature shaft and while inside the locomotive the gear cases have been checked.



The cover for the top of the gear case is just under the brass strap to the front of the motor.  This brass strap must be removed to gain access to a very small plastic cover.



Once the brass strap is removed then the small plastic cover can be removed. Once that small cover is removed you can see the worm gear, as in the above picture.  You can add lubrication at this point.  I use Super Lube or Bachmann's EZ Lube gear grease.

You can also gain access to the gear box by turning the locomotive upside down and removing the bottom gear case cover.  Be advised that this cover will only fit one way so note its orientation.  The cover must be reinstalled lined up exactly as it was removed.

Sorry, but I don't have a photo of the bottom cover.  But if you turn the locomotive over the cover is obvious mounted over the third driver.

To put your mind at ease you may want to check the gear case lubrication on your K-27.  It's probably not necessary when placing your locomotive into operation.  If you do go inside by removing the boiler then make sure to lube the motor armature shaft.


One of the "Enthusiastic Children"

JD

[chuckger]

Hi JD,

  Thanks a bunch.

  Chuck

[Barry BBT]

Just one observation, there is no need to lube the Pittman armature shaft.
It is a ball bearing motor with a thrust bearing between the "flywheel" and the motor housing.  The reason for the quotes is the uselessness of the flywheel, it has no effect on the performance of the motor, beside slower response.  The purpose of the flywheel is to provide an optical tape to be scanned for DCC.  I tested flywheels in the course of trying to solve a surging problem many years ago, larger flywheels than found on this loco and a smaller (8000 series) motor.

Not being able to actually lube the bearings in a Pittman is frustrating, but ineffective.

Barry - BBT 

[StanAmes]

Just one observation, there is no need to lube the Pittman armature shaft.
It is a ball bearing motor with a thrust bearing between the "flywheel" and the motor housing.  The reason for the quotes is the uselessness of the flywheel, it has no effect on the performance of the motor, beside slower response.  The purpose of the flywheel is to provide an optical tape to be scanned for DCC.  I tested flywheels in the course of trying to solve a surging problem many years ago, larger flywheels than found on this loco and a smaller (8000 series) motor.

Not being able to actually lube the bearings in a Pittman is frustrating, but ineffective.

Barry - BBT 

Barry

You appear to be a little confused.  Let me try to clear up this confusion.

In the smaller scales the most common use of a flywheel is to is to act as an energy store to power the locomotive across small sections of dirty track.  To perform this function the mass of the flywheel must be sufficiently large to be able to store this energy.

In a locomotive with the mass that exists in the K27, to perform a similar function the mass of the flywheel would half to be quite large which is not practical.

So you are correct that if this is what you expect out of a flywheel then indeed such a small flywheel will have no measurable effect.

But that is not its purpose.

Nor is the purpose of the flywheel for an "optical tape to be scanned for DCC"

The purpose of the Flywheel in the K27 and other emerging Large Scale locomotives is to significantly improve the slow speed operation of the locomotive and in the case of the K27 this works exceptionally well.

To gain this benefit you will need to use a modern generation motor drive control circuit. 

Hope this helps

Stan Ames
http://www.tttrains.com/largescale/

[glennk28]

They'll run quite nicely on ordinary power packs--I tried mine on a Marnold, and some older MRG's, as well as a homepbuilt one.  All very slow and smooth.  An interesting demonstration--push the loco along a piece of track--with no power connected--and see the class lamps light up

[Barry BBT]

Mr. Ames,

I don't appreciate your condescending attitude.

You don't seem to understand either.

A slow moving flywheel will have little effect on anything, even with a mystery motor control unit.

Barry - BBT 

[StanAmes]

Mr. Ames,

I don't appreciate your condescending attitude.

You don't seem to understand either.

A slow moving flywheel will have little effect on anything, even with a mystery motor control unit.

Barry - BBT 

Barry

My humble apologies.  As one of your customers I have marveled at what you have been able to accomplish with improved mechanical designs.   I have great respect for your opinions in the areas you have expertise in and It was never my intent to be condescending nor do I believe it would be appropriate to do such a thing. 

The motor drive hardware and software now used by many of the top end model railroad electronics manufacturers is also a marvel.  When great electronics is combined with excellent mechanical designs the results are pronominal.

Normally the electronics are retrofitted into existing locomotive designs.  Several years back manufacturers begin to build locomotives the other way around by making specific mechanical improvements solely to improve the ability of the electronics to control the locomotive.  Locomotives designed this way are beginning to show up in a variety of scales.

So while it is indeed true that the K27 flywheel has little effect as a traditional flywheel, it does indeed provide a significant improvement when used with a hi frequency back emf motor drive circuit.  You do not need much mass to smooth out the motor back emf between high frequency pulses.  This concept is now being applied to locomotive designs in a variety of scales by a number of manufacturers.

As both electronics and locomotive design evolve I fully expect to see further improvements in the future.

Hope that helps.

Stan Ames
http://www.tttrains.com/largescale/

[Greg Elmassian]

OK, so I assume the laws of physics still apply to G scale trains? (just being a trifle sarcastic)

If a given flywheel has little effect at higher speeds (because it's rotational momentum is not much different than the motor itself), then it is obvious that the same flywheel has much less effect at slower speeds, since it's inertia is that much less (due to the slower speed).

I need some help understanding why you want additional mass to help the BEMF circuitry/ algorithm. (It's really a computer program in a decoder).

Actually the flywheel can "mask" what the BEMF signal is trying to tell you. One use of BEMF is to correct the rotational speed of the motor against erratic frictional losses. A flywheel would "delay" the signal due to it's inertia.

Also, "high frequency" PWM should be pretty darn independent of the mass, BECAUSE of the high frequency, much higher than the fundamental/resonant frequency of the rotating mass.

A low frequency PWM system would "need" a flywheel more, since the lower frequency pulses have a better chance of altering the motor speed in a "non smooth" manner.

(I've wondered why Aristo bothered to put "flywheels" between their modular gearboxes, but I suspect it's just weight to help keep the center of gravity low.)

Anyway, help me understand if I have missed something in the laws of physics or basic kinematics or electrical theory above.

Regards, Greg

[Barry BBT]

Greg,

I don't think you have missed anything.  But, in fact have stated what needed to have been said better than I could have, thank you. 

Barry - BBT

[StanAmes]

Greg

I have learned over the years the internet communications has its limitations.  Generally if you cannot convey your  information in two email exchanges the chance of doing it further emails diminishes greatly.  If this topic is of real interest to you give me a call and I will put you in touch with Rutger, Bernd, Peter, Jurgen or one of the other manufactures of high end motor drive circuits who can go into the theory of this in whatever depth you desire.

If we were talking about brushless motors then indeed the flywheel mass would be way too small to serve a useful purpose.  Indeed a brushless moter is the gold standard. There are a lot of brushless motors in model railroad applications and they have a very big advantage of extremely smooth and uniform operation over the full 360 degrees of operation.  A brush motor is different.  The operation between poles is not uniform or smooth.  If you measure the stall current using the resistance test you will also generally find a difference in each pole.  When you rotate the motor you can feel the poles.  It all adds up.

Do the math.  When you have a PWM of 25-35KhZ even a 9 pole motor will have a very uneven operation when measured from the time one pole energizes the motor to the time the next pole energizes the motor.   When you pulse and measure the motor at 30khZ using a modern microprocessor, the time between poles from the perspective of the micro is a very long time, especially in slow speed operations.

A flywheel, even a very small one will tend to integrate these difference and present a more unified operation over the rotation of the motor.  From a simplistic standpoint it makes the brush motor appear more like the brushless one.

As you can see this topic has wondered far from the initial questions and is beginning to get into a depth not of real interest to most of the readers here.  Again if you have a real interest in this topic give me a call and we can work through it or get you in touch with the right people who can explain the theory better than I can.

Stan
www.tttrains.com/largescale