Motor to drive train coupling failure on MTH PS4 Engine

What is the MTH Catalog number of this engine please?

The item number is 20-3466-1

Well first, the list price is 899? It was delivered in 2013.

http://mthtrains.com/20-3466-1

Was it used?

Has it been modified?

Do you keep throwing traction tires?

Are you pulling long trains?

If you turn the sound off does the drivetrain sound smooth?

Do you hit the estop or is the engine exposed to slamming stops or super fast starts with long trains or consists?

If you take the shell off turn the flywheel by hand to fully rotate the running gear all the way around a cycle to check for any binding.

 I have several of their steamers and have not had any failures of the drives but I'm sure it can happen. I run two rail so the tires will just spin if overworked.

 I would expect that an axle is out of quarter or something major to cause this.

To answer your question, no I have not seen any dog bone failures.   Occasionally one might be worn.

I would question is the alignment of the motor and gearbox correct.  Must be something wrong with the engine.  Worthy of discussion with service manager.  G

I don't find a parts blowup on the MTH site. Can you take a picture of the part? You can probably replace it with metal part(s). Plastic driveline parts have a history of failing. Just another example of penny wise and pound foolish. 

Pete

Pete, High strength plastic dog bone drive shafts have been used since the 90s in MTH Engine. Let alone other manufactures.  I Have not had but one replacement over all my years of servicing engines.

MTH HO big boy had a production run issue, but that was resolved.

If an MTH O engine is snapping dog bones drive shafts, something else is at issue.  I would not go to metal until I found out why I am snapping a drive shaft.  Especially 4 in a year.  G

I had one fail in a Weaver steamer anout 16 hears sgo.  Keep them well-greased.  Check motor alignment.  If gearnox covrr opens, check inside for foreign mstter.

Engineer Joe - Thanks for your reply.  By the time I bought the engine, 5 passenger cars, Z4000 transformer, and DCS system, it totals $1500.  This is my first MTH, so I had to buy the whole kit and kaboodle.  PS4's do not play well with Lionel transformers, so that is why I had to buy the Z4000.  I was a Lionel man before this, and with the luck I have been having, that may be what I have to stick with.

1.  This is a new engine

2.  No, I do not throw any traction tires

3.  The Southern Crescent Limited and/or Southern has a 5 passenger car combo to go with it.  I bought that, but the coupling on one of the cars kept disengaging, so I just use 4.  

4.  Yes, drive train does sound smooth

5.  No, I use the DCS system to slowly start and stop.  With the sound effects of the PS4's that is part of the fun of owning one to here the sounds in time with the speed changes.  It starts and stops smoothly with no jerking motions.

6.  Last I checked, there was no binding, but to tell you the truth, I will need to double check to be 100% sure.  It has been over a month since the last failure and I'm not as young as I use to be.  I agree that there must be something causing the failure.  The tips are what is wearing off.  The slots in the metal shaft that the tips slide up in have sharp edges, they were not machined smooth from the manufacturing.  I am suspecting that is part of the problem.  I have had problems with the slide rods connecting the wheels on base Lionels getting slightly bent causing binding, but do not see that here.  Again, I will double check that tonight when I get home to see.  

One thing that is frustrating is this train has been back to MTH 3 times within one year and you would think that would all be checked out before sending it back to the customer, especially repeat failures.

Again, thanks for your help in trying to trouble-shoot the problem.

Do you know where I can get these "dog bones"?  Surely they can't be too expensive and MTH did not have any in stock the last time I had this problem.  After a month I hadn't heard from them, so I called them to remind them I still had not received a part and they had to take one out of one they had at their shop.  

I can make one out of something besides plastic, but fear that may cause me more grief by stripping gears or burning out a motor.  Looks like I may have just gotten a lemon.

Contact GGG, whose email can be found on his data listing.  He'a good tech and stocks many parts.  MTH has a high shipping charge.  If you call MTH tech support, ask to speak to someone above the tech.

Thanks,  there is a train show in Nashville this weekend:

My son and I will be going to it this Saturday and I am hoping I may get lucky and find someone there that may have several of these and some advice.  But then, they should not be failing at this rate.  

Anyone near Nashville - this is a good train swap meet/show.  I went 2 years ago.  You may want to pay it a visit.

"If you take the shell off turn the flywheel by hand to fully rotate the running gear all the way around a cycle to check for any binding"

I went home for lunch to check it out.  Rolling forward rotates several rotations very smooth, then a catch, but then it rolls out of the catch for several rotations and repeats.  I can't get it to roll in reverse by hand.  Not sure if this is normal or abnormal rotating by hand.

So, what is your advice?  

1.  If this is in the gears, it is beyond my capabilities

2.  If I send it back to MTH again, how do I prevent this whole cycle from reoccurring for another year?????

3.  If I have had this much trouble with a train over the past year since taking it out of the box new and I indeed do have a lemon, what are the chances of MTH replacing it with a new one and how do I go about doing that????????

Pictured is the plastic "dog bone" or drive coupling.  Tips are worn off on one end.  part of one tip is well worn on the other.

You should now be able to turn the input to the gearbox with your fingers. Try it and see if you can feel any binding. If this was mine I would measure the diameter of the plastic pins, then get some music wire at the hobby shop. Cut off the pins then drill a hole so you can replace the plastic pins with the metal wire.

Pete

I will try turning the wheels by the drive shaft instead of by the wheels to see what happens.  Seems like I tried that last time and it rotated with not problems.  I will report back.

How is the fit of the dogbone into the slotted cylinder? I could imagine if it was loose it would apply to much pressure to the ends of the pins or allow too much side to side movement. Maybe MTH has only been replacing the dogbone and not the receiver.

Pete

Well, it is loose now.  I replaced it the last time and honestly could not tell you how loose of a fit it was.  Currently I have no new one to replace it with in order to see.  I sent MTH an email last week and last night, but still haven't heard back from them.

Got home and turned the drive shaft by hand.  Absolutely NO problems forward or backwards.

What now?  See Pic of drive and drive coupling "dog bone" below where I am pointing.

Does anyone else notice what looks like wear in the metal sleeve on the motor drive side?????  Is this normal????  I've had nothing but plastic dog bones in this thing and I bought this engine new............

What appears to be wear is in the "forward" direction.  This time it failed on the wheel drive side even though there is wear on the "dog bone" on the motor side too.

Click on the picture to get a larger view.

I don't see any grease on it.  Did you read my suggestions above?  Try any/

This part is also used in RC boats.  For a better price/source, try googling RC boat parts.

1.  Screw drive box is well greased with no foreign matter that I can see.

2.  Motor and gear box shaft appears to be aligned well.  No adjustment if they were not.

3.  There appears to never have been any grease on this part.  Again, MTH has worked on it 3 times and they did not apply any grease directly on the "dog bone" but I'm willing to try anything once I get another "dog bone".  

4.  I Haven't started looking on line yet for an alternative supplier for the part, but I will search them to see.

Thanks a bunch for your suggestions.  Just trying to explore all possibilities for failure.

Google "dog bone coupling". Lots of hits. You will need to know the shaft diameters and length of the dog bone.

Pete

Thanks, I'll give it a try.  In the mean time, anybody see or think of anything else that may be causing this failure about once a month?

So you are doing this by rotating the flywheel?

It won't turn in reverse? Is the catch happening as the running gear is in the same location?

then you state there are no problems in either direction?

I'm sorry, this is hard to follow.

Could he have an axle that's one tooth off on a gear? or one is out of quarter?

When I went home for lunch, I was trying to turn the wheels by physically pushing on the bottom of the wheels.  But when I came home after work, I tried turning forward and reverse by turning the drive shaft.  

When I turn the wheels with the drive shaft it is very smooth and will turn the wheels in forward and reverse with no problems at all.  Pushing up on the wheels to turn them may have put the whole system in a bind possibly????  

Anyhow, there was no problem turning in forward or reverse when turning the drive shaft just like the motor would.

Sorry for the confusion.  Hope this clears it up some.

If had had a loco that went back to MTH for the same repair three times and now is going bad again, I'd call MTH and insist on talking to someone higher up in the company than a basic tech.  Obviously there is a root cause that the techs haven't addressed, and I suspect that some person at a higher echelon would want to know if there were repeated unsuccessful attempts to repair a problem.

That is interesting, and it is possible the wear in the sleeve has a sharp edge and is cutting at the tit of the DB.  How is the thrust play of the motor.  Does the Flywheel push fwd and pull out significantly in the opposite direction?

If the drive trains is smooth, and the alignment looks ok.  I am not sure why the tits are breaking off unless it is wear via the sleeve, especially if the thrust is significant.  It could be acting like a saw.   G

Thank you for taking the time to explain. I do understand the frustration.

My next hunch would be that the motor is out of alignment with the drive then?? There must be some extra stress on this shaft for it to wear out so fast.

 Norton and others here have more experience than I do. I tear stuff apart all the time to get to the root of the problem. I have repeatedly bought used stuff that was abused. It helps to learn the goings on inside all the engines.

 Metal replacement joints are a known cure for some shafts that get extra stress. I believe that 3rd rail switched to metal u-joints because of some failures in their old diesel?

 I just find it odd that this loco doesn't pop up more as a troubled model. I'm left guessing that you have a 1 off??? I'm wondering if it was damaged in original shipping throwing something out of whack?

 BTW, I explained to turn the flywheel so I thought that's what you had done. I don't think these engines freewheel? ( the wheels shouldn't turn?)

Interesting. (OK, "infuriating" to Jblovel; sympathies.) The sleeve acting as a saw seems most likely, and that would be good, because the inside of that sleeve can be filed or ground by something. It will be awkward, but I'd give that a go, if I may suggest it. A set of small files is priceless in this hobby.

Is it always the same end that breaks? That could be important.

The drive system is a proven design, used pretty much by everyone, almost universally successfully. The design is kind of a u-joint type to allow movement of wheels and motors independently of each other (though with unsprung drivers I don't see that happening much), and to reduce the need for all sorts of fixed-length driveshaft variations and inventory. I suppose that it could also be a fail-safe stress point to protect other components; never thought of that.

Thanks everyone for the input.  

MTH contacted me today via email and stated that they suspect that the last batch of dog bone couplings were made of the wrong plastic material.  

They are shipping me one of those now and will ship me one of the correct material later after it has been made.

I will make sure the edges of the slots are not sharp this time before I re-install.

To D500 - I can't remember if the failed end is the same this time, but one of the tips on the other end is almost gone and the other is worn and if I recall correctly, that was the case last time.

Well, I'm going to the Nashville train show and swap tomorrow and try to forget about this for a while.

Again, Thanks to All.