Differental in speed control

It sounds like they are probably within the +/- 4% speed that MTH claims.

You can change to a custom tach tape in any of them, but this will only get them close.

The reason is that the standard tape is 48 stripes; 24 white and 24 black.

You need to add or subtract stripes in pairs so there is always an even number.

thus if you add 2 stripes or subtract 2 stripes, you are changing the speed by 2/48; or about 4 %.

Before running a lashup I always check the relative locomotive speeds to see if they are close.

I would have thought that 1 foot in 4o feet would be close enough to the same for it to work OK. That represents about 2.5 % difference.

Rod

Well its apparently not close enough.

Last time I guessed (it turned out to be not too far off the average), I decided to use the DCS odometer in the AC6000 to actually measure it.

A lap is just shy of 1/2 a scale mile, so I'll just use .47 (It took about 3 extra feet to get the odo to reach .5 scale miles).

In 2 laps, there was a 30" gap between the 5V and the 3V, and a 15" gap between the 3V and PS3. A dash 9 is about 19", and an AC6000 is 20. So essentially the front of the 5V engine wound up 88" in front of the rear of the last engine. Basically, none of my engines are lashable, which is ridiculous.

Thats a 5.6% difference (front to front of rear engine).

Whether the 5V one is correct, who knows... I dont think it is. But the other two were the ones I had running together, and regardless of MTH's acceptable error range (the second two are technically 1.3% off), the stench of overheating electronics would seem to point at their acceptable range being too large.

So I suppose I could burn one of them up and send it back to MTH under warranty but that seems a rather extreme way to make a point to them, I'd rather just get them to work right (or better yet, they work right straight out of the box).

Based upon your observations, I would have to believe that there's an issue with one of the engines, possibly two.

Without going into a lot of detail, the problem could be:

• Damaged timing tape
• Porous timing stripe paint
• Distance off between the tach reader and the flywheel
• Defective tach reader
• Mechanical issues, i.e., missing or worn traction tire
• Speed control parameter errors in the engine's sound file.

There's a lot of additional detail available in The DCS O Gauge Companion 2nd Edition, pages 170-171.

This and a whole lot more is all in "The DCS O Gauge Companion 2nd Edition", now available for purchase as an eBook or a printed book from MTH's web store site! Click on the link below to go to MTH's web page for the book!

Sheldon;

Further to Barry's points above, you may wish to try a little test as follows, if you have a Z-4000 or some similar way to measure the amps to the track.

When run separately, if one is draws a lot more current than the other, that would suggest it has a mechanical problem.

Then I would run the two engines in question separated, but together at the same time and see what the average combined amperage draw is.

Then lash them up and run them again noting the current this time.

If they are fighting each other you should notice an big increase in current, perhaps double. That would confirm your suspicions.

Just a thought,

Rod

Is these MTH Computers only reading the Tape? And not using the "Back EMF?"

Please humor my question, I have learned something here...

Lee,

Is these MTH Computers only reading the Tape? And not using the "Back EMF?"

Yes, that's correct.

No, I did not change my screen name to boilermaker1 just so that I could complain AGAIN about my issue with speed control!

Kidding aside, boilermaker1 I truly feel your pain!!!!!

- still walt

I dont have a Z4K. At home I have a Z750 brick running through a Rev L TIU. I was running on a modular layout yesterday, they were running on a Z4K on a shared track with a Y6B (not lashed to it) and the three combined (6 motors) were pulling about 5 amps. When the 6000 overheated, I kept running with the dash 9 and about half the train and it was pulling around 2 amps (alone, no y6 either).

I'm still messing with it today. I set up the lashup here at home, with no train and let it run for 15 minutes at 25smph and for 45 minutes at 40. Same thing happened... the midsection of the shell is fire hot, and the rear motor is fire hot (the switch cover is the radiator wings, so it comes off), I cant feel the front motor without pulling the shell. It also smelled of electronics. The PS3 dash 9 running with it was cool.

I let it cool off for an hour and now I'm running the 6000 by itself, same cycle, to see if it heats up. If it does, then I'll be calling MTH for an RA. If not, then I dont know what to do next.

PS - my name isnt Sheldon. Sheldon Cooper is a TV character who said the quote in my signature.

Ran it by itself for an hour, was still running hot, still smelled of electronics. I took the shell off, let it cool down and let it run by itself again without the shell. The boards were still pretty hot, the motors werent too bad. I guess I'll give MTH a call and see if they'll give me an RA for it since it smells like burned electronics... 

When I pulled the shell off, I did notice that everything is kind of jammed in there, and the metal grills in the sides of the shell evidently dont let in enough air to cool it off. 

Ahah; the smoking gun, or I guess electronics.

The first thing I would check is binding in the gears. That could be your problem.

What track voltage are you running at? It needs to be 18 VAC.

Rod

boilermaker1: Rod's comment is SOOOO important!  A few years ago I bought a Railking switcher and it would heat up so much that it would eventually completely stop running.  I had a 4% grade and it would punk out going up it.  My other 8 engines didn't have any issues with that grade.

I came to this forum asking for comments.  I was ready to cut holes for openings because people were thinking that there was no escape route for the heat - just as you stated.

But then one person asked me the question that Rod asked (hmmm, wonder if it was him!) about voltage.  I was running at 14V or 15V and once that I upped it to 18V the engine never got hot again.

I still can't run a lashup with it, but it runs fine.

- walt

Voltage on the track isnt the issue. A Z750 brick puts out 18-19 volts when its direct wired through the TIU (brick to brick seems to vary slightly one brick I have puts out closer to 19, the other closer to 18). My multimeter on the rails agrees with the DCS remote voltage readout, on the track theres a little over 18V.

I would check for binding in the drive train / gears, sounds like something is definitely causing drag.

And drag will slow the engine slightly, enough to cause the error in speed, as well as cause overheating in the motor control circuits.

If you are in warranty, sending it in is probably the best bet.

Be sure to include a note stating the problems in detail inside the box with the engine, sometimes the techs don't get all the info from the RMA. (I speak of all companies, not MTH specifically)

boilermaker1: I owe you an apology for downgrading my thinking on your knowledge of the topic.  Sorry about that.

- walt

Since the OP is returning the AC6000 under warranty this doesn’t apply to him.

But for the DIY troubleshooter, after exhausting the methods described above, you can dis-engage the transmission of the motor/truck without the tach so it free-wheels (i.e., truck rolls on the track).  If not pulling a load, a single-motor has enough power to drive the chassis.  A twin-motor diesel is essentially a MU in itself – both motors receive the same voltage and ideally spin at the same speed.  But if the speeds of the two motors diverge, they work against each other and can draw excessive current causing overheating.  If the overheating and speed error go away running under the single motor, you could have a defective/mis-matched second motor - a relatively inexpensive DIY replacement project.

Separately, when making DCS odometer or stopwatch lap speed measurements, try two reasonably separated speeds like, say, 5 sMPH and 25 sMPH. If the odometer or speed error % changes with commanded speed, it could help isolate the problem.