MTH HO NYC Empire State Express 4-6-4 Hudson Center Driver Wheel Lifting Problem

Model Railroader General Discussion (Model Railroader)
1

I have just acquired a New Old Stock (built in 2013) MTH HO scale NYC Empire State Express 4-6-4 Hudson engine with tender. Everything functions great on it except at the same point in every driver wheel rotation the center drive wheel, both left and right, lifts up and off the rail, see picture.

Center Drive Wheel lifts above rail
This causes jerky motions in both forward and backward directions along with derailments on turnouts and curves. Only this center drive wheel has traction tires and is gear powered from the motor. The front and rear driver wheels are powered from the center wheels by rods.
MTH Customer Service with only one month before extinction, was gracious enough to list possible causes for me to test:
#1Q. Electrical pick-up pins on the front and rear driver wheels could be out-of-position.
#1A. I verified electrical pick-ups were in the correct position.
#2Q. Driver wheel bushings could be seated incorrectly.
#2A. I verified that all driver wheel bushings were in the correct positions and orientations.

2

Your photo isn’t showing in my Google drive and I know this may seem like a very long shot but I had a similar thing with by BLI Dryfuss Hudson. It wobbled slightly on the track but on the rollers it was very obvious so like you I had a dig around and couldn’t see anything out of place. I ordered a new wheelset from BLI on the off chance but before I fitted them it was on a shelf at eye level and every time I walked past I was bugged by the fact that in the position the centre drivers were now rotated to that wheel was quite obviously very slightly higher than those before and after. Finally i had to just look under the hood and whilst i can’t remember exactly how i noticed the bushing was in place but the housing on that particular driver is in 2 pieces and it’s very difficult to spot this but the secondary element wasn’t installed properly from the factory. Once identified it was very easy to rectify and hey presto it now runs perfectly. Also this set-up is only on one side of the axle and this is the only locomotive model i have ever seen this arrangement on.

I know we’re not comparing apples with apples here but it sounds like a very similar issue and that you have eliminated everything else so may be worth a look.

Good luck because if you’re a mechanical hypochondriac like me these things spoil the enjoyment no end.

3

I’d add at the time - 2 years or so ago - there was a guy running the same model on the same rollers on YouTube and it shook in the same way so i was thinking it was a manufacturing defect as in the wheels weren’t perfectly round which seemed unlikely but it was the installation of the component that is the problem.

4

Eccentric rotation usually means the axle is not dead center. This creates a tiny cam out of a round wheel.

I don’t quite understand quartering but it seems to me that the driver connecting rod (I can never remember what it’s called, it’s not called the connecting rod as that connects the imaginary piston to the main driver) might not be centered accurately on one of the outer drivers. It seems to me that all the drive pins on each driver need to be perfectly lined up or some slop needs to exist in the center driver connecting screw or the driver set will hop.

5

This may be a symptom of a split gear on the axle. Not a very pleasant outcome.

This has happened to me on a few occasions.

IMG_2787 by Edmund, on Flickr

These happen to be from a PRR I1, Broadway Limited.

My MTH Empire State Hudson came with a spare driver (with or without traction tire) I believe it had the gear on the axle.

That would sure be an aid in making the repair. You mentioned that you already changed the gear though with no improvement. (could both gears be split?)

It may be possible the main rod going into the cylinder is binding? Removing the motor, or at least raising the worm high enough to disengage from the gear on the driver will allow you to roll the drivers enough to detect where the bind is.

Good Luck, Ed

6

It’s a long shot, but have you tried contacting Scale Trains? They bought some of MTH. I don’t know how much, or if any MTH employees moved over to Scale Trains.

7

Pretty much everything has been mentioned. Quartering, a side rod or a main rod not bored in the correct place/spacing for the pin distances, bent axle, axle not centered in the wheel, wheel not perfectly round…

The traction tire could have been it, but you replaced the axle with a regular metal tire and found it does the same thing.

Split gear is a distinct possibility.

Are you sure none of the rods, levers, and their pins/retaining screws are making contact once per rev? Nothing bent or extraordinarily sloppy and loose in the running gear?

8

Agree with everyone on this. Basically could be almost anything. If it were me at this stage I would do a couple of things.

Disconnect the drive and push it so that you can feel for any binding through your mk1 fingertips. You’ll also be able to feel whether or not there is vertical movement. It’s often in my experience the identification of where the anomaly lies relative to which position the driveline is in that drops you onto the issue.

Something you may try that helped me with an irritating noise and slight hesitancy at low speed on my Hallmark Blue Goose was to video it on the rollers if you have any and look in slowmo to see if anything looks amis. Looking at these things on a large screen definately helps. In my case the main rod was brushing the access ladder slightly but i couldnt see that 1:1

Fingers crossed.

9

You can check quartering visually without taking anything apart. Otherwise, I agree with the above, I would disconnect the tender, remove the boiler and disconnect the motor. Then manually roll the drivers and see what could be the cause. I think that the problem lies with a spring or a driver bearing.

Simon

10

Checking quartering ‘visually’ may not be enough. It has to be consistent side-to-side on all three drivers – it does not, of course, have to be exactly 90 degrees of quarter, as cylinders don’t really drive the wheels, but they have to be at identical angle within the clearance of the rods… which ain’t that much. And you can’t open clearance up as the side rods are actually driving the forward and back driver pair.

What I’d speculate is that this is actually a two-parter (assuming the replacement gear didn’t crack too, which I find possible but unlikely). That is that there is a bind in one, perhaps both center driver bushings as they slide, with some component of rod thrust causing the axle to move unevenly in reaction. Did we confirm that both sides of the driver pair move the same amount vertically? Possibly not…

11

Thanks everyone for your recommendations.

I put the picture showing the center wheels lift on Imgur. Hope the below link works:MTH Empire wheel lift. Note that I did verify using sheets of paper under the wheels, that both sides (left and right) center drive wheels lift the same height at the same time.

I did look for a split gear and did not find even a hairline crack on both of the center drive wheel sets (with and without traction tires sets).

Unfortunately Scaletrains bought only tooling from MTH, no parts, and no service people (according to several MTH service personel). I am hoping that Scaletrains will make an Empire State Express Hudson in the future. One of many nice features of this engine is there is no wiring cable dangling from engine to tender. The draw bar to the tender has leads built into it, with conections on the tender post.

Some new information about this problem that maybe useful. The center wheels lift when the right side connecting rods are at the 9 o’clock position when the engine is moving forward. When the engine is moving in reverse the center wheels lift when the right side connecting rods are at the 3 o’clock position.

Before getting to involved with removing the motor and other … I contacted the seller and explained that this appears not to be an easy fix. He was gracious enough to accept return of the engine as it never functioned properly. I have given him this disscusion page info and he will keep tabs on it for ideas.

Thanks again for everyones input.

12

Thanks for the update. I was wondering if you had found a solution .

13

In British parlance, the rod from the crosshead to the main driver is called a ‘connecting rod’ and I think the rods from the main to the other wheels are ‘coupling’ rods. In America we do call a piston-to-crankshaft component in IC engines and even multiple-cylinder steam (as in ships) a connecting rod, but not on reciprocating steam locomotives. There we call that component a ‘main rod’ and the others are ‘side rods’ respectively.

14

Hi OP, I’ve thought about this alot in an attempt to help.

It’s clearly not the drive train, the gear and axle box wouldnt cause the center wheel to lift. A cracked axle gear wouldnt cause the wheel to LIFT, it would simply cause the motor to spin freely. If anything, misaligned gears push the wheel DOWN.

Its clearly not the pistons. I previously thought it could be resistance in the connecting rod (between crosshead and main driver), which is pushing the wheel up during motion, but you said its at 9 and 3 oclock, which eliminates this possibility.

Therefore, the only remaining option is the coupling rod and two other wheels causing this. Most likely, one of the three drivers is out of quarter and causing the center wheel to lift.

In fact, if you look at the two separate diagrams I’ve shown below, you can see what I mean.

The first diagram shows what I mean. Having an out of quarter center driver would cause the center driver to lift. Since the wheels are sprung, there is vertical play inside the drive. Note in the drawing all three pins are at the same vertical level, since the stiff, straight coupling rod will enforce this.

There are many ways to push DOWN on a wheel, but this is the only way I could imagine for the drive train to LIFT a wheel.

The second photo shows a rough estimate to each wheel’s quartering. Obviously accounting for human error and distortion in the photo, this may be less pronounced, but it does appear to be out of quarter drivers. But note how the first and third wheel have parallel lines, whereas the second driver is clearly off.

Then again, this could simply be the center wheel having less rotational play since its the only one connected to a gear.

However, this woud be my best guess as to what is going on.

Fixing out of quarte

15

Here’s the same diagram but with the top drawing resemble the photo.

16

Charles, I think you nailed it.

17

Agreed, there is a pretty clear 6-7 deg difference and, even in our comparatively sloppy toy rods, that presents a problem, as we now know.

18

Charles I think you have indeed reasoned it out. At first I thought there maybe a flaw in your answer, as the wheels only lift at one position with each rotation not at 2 positions. However as the forward travel center wheel lift postion is only at 9 o’clock and in the reverse direction lifts only at the 3 o’clock position, these 2 positions correspond to the maximum vertical upward force for each travel direction.

I have sent a message to the original seller telling him you have likely defined the problem and given a fix. Again my compliments to your deductive power.

19

Anytime!

The fix is very simple, just use the twist method on the center driver. No Additional parts should be needed for repair.

No additional parts are available anyways, since MTH has more or less shut down their parts department.

Good luck,

Charles

20

Before you twist the wheels around their axle, see if you can simply re-cog the axle. If it is possible to slip it by one tooth and then reseat it, you may solve the problem that way…maybe. It’s worth a shot. On the other hand, if the wheels really are out of 90 deg quarter, yes, you will have to correct that on that one axle.