new ERR TMCC install has lowspeed yips

First thing I would try is to find a screw inside the engine and tie a ground wire to it and the ground wire coming from the tender. If the engine and tender have rollers then tie them together as well for the hot connection.

Pete

Try the engine ground first. The more contact points you have the better. You may not need tender rollers unless you have a lot of switches than can cause stalling.

Pete

I always make sure there's a connection for ground from the engine to the tender in the tether.  While it's nice to have a tender roller or two, the top issue is grounding.

If you do put a roller on the tender, I recommend a 2-3 amp PTC on the wire between them to protect the wiring in the case of derailments.  A tender roller has done wonders for several of my shorter steamers over switches, so I do recommend it, just not for this particular issue.

Thanks Pete and John. I'll establish the engine to tender ground this afternoon and report back.

OK I grounded the loco frame to the tender, but still surges on low speed throttle up.

That looks mechanical, though it's pretty hard to tell for sure.  I'd run it with the shell off and make sure nothing is binding.  Also, turn the flywheel through a complete rev of the drivers and make sure you feel no binding.

What John says. The only time running with ERR cruise was not smooth there was a mechanical issue. Check that the drivers are quartered and the eccentric has not shifted.

Pete

Have to agree with the above. 

Bill

Will take the shell off. This loco has always a silky smooth runner, Maybe I jammed something putting it back together.

Thanks.

Something rubbing is very likely, that's exactly what it would act like if something was binding.  That's why I recommend running with the shell off to test, you can see everything.  Then when you put the shell back on, if it doesn't run the same, you know right were to look.

I took the shell off and it ran the same. I inspected the rods, valve gear ,quartering and side rod play. Everything was good. Lubricated the rods and valve gear and still the same.

But, I did notice a pattern to the lurch. I felt a knocking in the gear box so I'll take it apart and see.

I agree with the guys above, it look's mechanical. But I have to ask a question, Ron what command system are you using. The reason why I'm asking is if you're using Legacy you can set up the engine to run in R100 mode which make's ERR run much much smoother at very low speed. Running in R100 mode compaired to TMCC mode is a huge difference

Thanks,

Alex

I'm running just ERR regular commander. I tested out the gear box and it is smooth. Here is a video of the motor with no load, unconnected from gear box and one can see the surge at low revs.

I'm going to clean the motor out with motor spray and lube the bushings. Then see what it does.

What kind of video is that?

I'd run the motor on a DC bench supply at low speed with the wheels suspended and see if you see any anomaly as it runs.

Are you running 32 or 100 speed steps.

Bill

John, it's a Nikon movie.

Bill, I'm not sure, one or the other. Do you have a suggestion?

I don't think many folks can decode a Nikon specific encoded movie, best to post in a standard video format.

Try it in 32 step mode, also did you set the feature code.

Bill

It seems the loco yips mechanically under the load of the weighted shell. I've done everything suggested.  So now, I'm going to take the transmission out and check it.

If there is nothing wrong then there is something wrong with the ground between shell, the frame and the engine truck, trailing truck and drawbar. I've noticed the headlight only works when the shell is in contact with the frame.

I've also noticed when it yips in reverse the tender lamp blinks in unison with the yip.

If this is meaningful please let me know. I won't tear down the tranny if at all till tomorrow.

Thanks for all the help.

The headlight is most likely using the shell as it's return ground, so that would be normal.  I run brass locomotives with the shell off all the time, there's no reason they shouldn't run.  The only issue I usually have is the heavy lead weight is in the shell, and sometimes the frame doesn't have much traction.

Seems to me you have a ground loop in the system.  The tender lamp blinking is a clue.   Did you electrically isolate the tender from the loco?  If so, does it help??

The video indicates some sort of electrical issue to me, more than a mechanical issue.  However, until you find it - you won't be sure.   Also, try to disable the cruise function (see manual), this will also be a clue, as the cruise will buck mechanical binding.  With the cruise off, you can get a more accurate picture of the mechanics.

OK, the locomotive runs perfect with no drawbar, no engine truck and no trailing truck. Adding any one of these creates the yip.

So, how do I make consistent ground???? I had already installed a plug to wire the loco frame and tender frame and it makes no difference.

It is as though the loco frame does not act as a ground. Or at least it is inconsistent in that any rubbing metal part attached to the loco frame, the trucks or drawbar creates a yip. There is nothing mechanically wrong at all.

Another clue, I just had the shell off and put it back on to show how smooth it runs without the trucks and drawbar, but it now yips. So maybe the internal wiring, headlight, smoke unit ,Seuth, and Seuth on off switch have something to do with this.

Help!!! 

Success at last!!!!! Thanks for the help.

What was the final resolution?

John,

It turned out the motor ground needed to be wired to the chassis.

When I cut off the harness to install the ERR it had 4 wires, apparently somehow the motor ground was wired into the chassis. My ignorance led me to eliminate it.

Live and learn. Thanks again for the advice. At least I inspected every mechanical and electrical system in the loco.

Ron

I'm curious, what is the "motor ground"?  Neither of the motor leads should be to frame ground for the Cruise Commander, they should both be isolated.

Ac motors need a ground and have 4 wires. One for each brush one for field and ground. 

AC maybe, but I'm pretty sure this is a DC motor, or he wouldn't be using the Cruise Commander.  I suspect the "motor ground" is really the frame ground from the locomotive to the tender, that would cause all sorts of issues.

John,

I think you are right. I ran a wire from the negative side of the motor to the chassis. Even though it makes the loco run well it is heating up the command board.

Also, I'm getting a short somewhere.

So my question is , since we know it is a ground problem with in the loco, what should I do next ?

I know it is not the tender for I rigged up a meter to every component including the throttle leads to the loco and everything checked out. No glitches. I did this both with the power coming directly from the third rail and with the positive lead to the loco hot lead. Moved the loco and tender back and forth and no meter glitches.

the drawbar is a metal to metal contact on the loco, screw and spring, but I have it insulated at the tender. However I have a direct ground wire from loco frame to tender frame.

The frame of the tender (and thus the Cruise Commander common) should be solidly connected to the frame of the locomotive.  You should NOT have either brush of the motor connected to frame ground or track power in any way!  This will fry your board in short order!

I think we may need to see a drawing of some kind of how you've wired this.  What wires are going between the tender and the locomotive, and how is each unit wired?

From that description, I'm not sure what's going on.  Try a 1uf 50V non-polarized capacitor across the motor.

John,

What will the capacitor do?

Ron

ERR suggest not using a cap on the motor for the Cruise Commander, only the AC Commander. If the motor wire was grounded to the frame it could have taken out something on the Cruise board. Are you still having problems. 

Bill

Bill, I'm still having problems and it is driving me nuts. I'm using the dc commander, no cruise. It will run fine with the shell off for the most part and glitches with the shell on.

Ron

If you're running the DC Commander, try the cap.  It knocks down the brush noise from the motors.  I've had to add the cap to a couple of units running the Mini Commander 2 boards.  I think I've only ever used one DC Commander, since I automatically select the Cruise Commander for upgrades of DC motored units.

I agree with Bill, grounding either motor lead on the DC Commander or Cruise Commander is a bad thing.

I was assuming all along Ron was using a Cruise Commander. Uneven running at low speed is fairly common without cruise as there is no compensation for small frictional changes. Installing the boiler just increases the load on the motor.

You can try a cap but would be surprised if it made much difference.

Pete

Try disconnecting the smoke unit and headlight. Put the shell on and give a go. Sorry, I thought you were using a Cruise board. Use the 32 speed step and try setting the stall.

  Like John I also install cruise. My first upgrade was a DC commander, my second was a CC and have never looked back.

Bill 

I don't think putting on the shell should cause this issue unless something mechanical is binding when it's on.  Hard to believe this is electronic in nature.

John,

It is not Mechanical, I've gone through every mechanical system and they are perfect. Bill I disconnected smoke and headlight and it did not help. There is some kind of electrical interference between the shell and frame. I tried a direct ground from shell to frame and no luck.

I'll try the cap and if that makes no difference I'll buy a cruise unit. Maybe I have a bad commander board.

If anything else comes to you this morning please advise.

Ron