MTH 20-3650-1 4-6-6-4 Z-6 Challenger - Possible Design Flaw?

A few questions:

1) When you say "all 72 in. curves", do you mean 072 diameter curves?

2) Does it depend whether it is a left hand curve or a right had curve?

3) Is an "S Curve" involved?

I have an older MTH Challenger, SPS 902, and the front engine carriage (truck) is very tight.  It sometimes derails on 072 but makes it through 080. It's generally been a PIA and was the last MTH steamer I purchased.  Gone to Sunset Models for steamers.

Can you tell what is limiting the motion? What is making them lift? By suggestions, it sounds like the wiring inside?

I have a similar 2 rail model and I did grind a slight amount of a steel pipe for shorting reasons. It would be easy to see as there were rub marks on the pipe ( raw steel, no black paint left).

https://ogrforum.ogaugerr.com/topic/engine-shorting

Seems strange that this would be happening - this loco has been released before, and I have heard nothing about a "flaw". Of course, mechanical designs do change, though I'm not sure why the basic architecture would. Nothing wrong with a little clearance work on an engine - could a little underneath-filing-work fix it?  

I had to decide between this MTH version and the 3rd Rail version of the Z-6 a few years ago. I reluctantly chose 3rd rail as it already had TMCC/cruise installed, as I don't do PS2/3 very much. I can install TMCC/eyc, but why when you don't have to? I said.

I have often regretted choosing the 3rd Rail model - EOB is a pain and the detail quality is flimsy (and crude on the tender trucks), to say the least. The MTH product feels like quality.

Keep fiddling - you'll get it. Don't fall into the "for this much money it ought to be perfect" hole - it just makes you unhappy.

I should have been clearer? Look at the front drive and see if the middle wheel set is contacting the metal steam pipe when it's turning.

Lay the engine on it's side and see if there something else limiting the swing of that front engine. I'm thinking the wires maybe too tightly wrapped.

Hot Water posted:

A few questions:

1) When you say "all 72 in. curves", do you mean 072 diameter curves?

Yes, I have all 072 diameter curves.

2) Does it depend whether it is a left hand curve or a right had curve?

IT happens either way, left or right.

3) Is an "S Curve" involved?

No "S" Curve involved.  It happened on what I would call a small bend in the track.  I even tried it on a full curve with the same result.

Kerrigan posted:

I have an older MTH Challenger, SPS 902, and the front engine carriage (truck) is very tight.  It sometimes derails on 072 but makes it through 080. It's generally been a PIA and was the last MTH steamer I purchased.  Gone to Sunset Models for steamers.

I also have the older PS-1 Challenger which was upgraded to PS-2 and it has always performed without a problem.

Engineer-Joe posted:

I should have been clearer? Look at the front drive and see if the middle wheel set is contacting the metal steam pipe when it's turning.

Lay the engine on it's side and see if there something else limiting the swing of that front engine. I'm thinking the wires maybe too tightly wrapped.

I've laid it on the side and also upside down in a "maintenance tray" and used a strong light maneuvering the parts and can see nowhere it is binding.

I have an older MTH Challenger as well, it was my demo locomotive at York this fall.  It has no issues at all with O72 curves, and there seems to be plenty of swing in the articulated truck.  I suspect something is binding inside and causing the issue.

TLWhiteJr posted:

....From a close inspection it appears that the front set of articulated drive wheels does not have sufficient free motion to turn but just a slight amount and the drive wheels on the inside of the curve actually lift off the track and they and the front truck derail.  It also appears that the front wheel of the front truck hits the cylinder on the inside of the curve. 

Well, could you take any pictures? (Show that cylinder interfering).

Have you checked the track gauge of the wheels to make sure they are spaced correctly? Maybe the pilot set is out?

I would just check as much as possible as it could be anything. Keep an open mind! Mine was shorting because of a bump in my track work that happened to be on a curve. All things were right and she kept arcing. If I reversed the engine it would not happen on that curve. I can't fully blame the design as it just pointed out where my track work was sloppy.

Did you try putting locomotive on a very flat smooth counter top then pushing the troublesome part side to side and look and feel any binding? When you had it upside down in the service cradle can you put power to it to rotate the wheels.

I'm sorry, but I have to disagree with D500. For the amount of money everyone is spending on a modern locomotive, it should at least perform to your expectations. You shouldn't have to "fiddle" with anything.

For some time, I've been reading one story after another, about the problems people have been having with their Locomotives. It is a sad statement on what people have to put up with to have fun. IMO

PROBLEM SOLVED!  The engine may have been dropped in shipment even though I received it in the shipping box from MTH which showed no damage whatsoever.  Thanks for all your comments and suggestions as they prompted me make another inspection.  On the very front of the engine just above the headlight there is a platform with stanchions for the safety rail.  These were bent over so perfectly that they didn't look damaged but they were hooked over a box which sits on the engine front and limited the movement of the front drive wheels in a turn.  So with a couple of needle nose priers I straightened them and SUCCESS!

Thanks for your responses.

Clarence Siman posted:

I'm sorry, but I have to disagree with D500. For the amount of money everyone is spending on a modern locomotive, it should at least perform to your expectations. You shouldn't have to "fiddle" with anything.

For some time, I've been reading one story after another, about the problems people have been having with their Locomotives. It is a sad statement on what people have to put up with to have fun. IMO

I do agree with you.  In the last two years I've purchased two other PS-3 MTH engines and neither worked correctly out of the box and had to be shipped back to MTH for repairs.  Both were electrical problems.

Mine was shorting because of track work. Shipping it back would have only been a waste of time and money. It would have run fine. There was just one spot on my layout that caused this. Asking MTH to come over and fix that might have been a stretch.

 If you guys wouldn't put up with these problems, don't even try to go to G scale. Almost nothing gets along and everything needs work or mods.

Clem, better idea!

Better learn to live with it because it seems to be an ongoing issue.

From what you described, it sounds to me like it was dropped prior to packaging, and shipped out anyway.

Please don't misunderstand me, I'm confident there are many people happy with their purchases from the start, but, it seems like there is more problems lately.

Glad you found the issue.  Now on to the enjoyment.   I have a NP versions from a few years back and still love running it.

TLWhiteJr posted:

PROBLEM SOLVED!  ... So with a couple of needle nose priers I straightened them and SUCCESS!

Love to see success stories.  Makes sense it was something like that.

I'm going to have to change the tires, which involves pretty much tearing it apart.  Hopefully I see where it binds when that occurs and fix the problem.  Could be tight wires ....