Lashing up two locos with a slight speed difference

No way to control the speed, unless you change the stripes. I don't think a sound set swap will help.

If the 2 engines are close in speed, they'll be ok. You could run the fastest one in front uncoupled and and see how much you need to speed up the slow one to keep up. If you run around 35 mph and have to speed the slow one more than say 36 mph, I would look into why it's so slow and not couple them.

 If it catches up and you have to put it back to 35, they should be OK together.

I used to pair up engines that were exact speed matches. I have to admit that I don't check them regularly. In 2 rail there's no rubber tires so it doesn't matter as much. The G scale engines seem to do OK unless there's something wrong.

They don’t have to match speed exactly, as long as the faster loco is not spinning its wheels when coupled with the slower loco.

The faster one will pull a bit harder on the train than the slower one, that’s all.

There are 24 stripes on a standard PS/2 tach wheel.  If you drop one stripe, you can increase the speed by about 4% for the same throttle setting.  Conversely, if you add a stripe, you'll slow the locomotive down about 4%.  Obviously, if you take away a number of stripes, the math changes, but hopefully you get the basic idea.

If they're running 1-2% difference in speed, just run them.  The locomotives will tolerate that much imbalance in speed without an issue.

Rich Melvin posted:

They don’t have to match speed exactly, as long as the faster loco is not spinning its wheels when coupled with the slower loco.

The faster one will pull a bit harder on the train than the slower one, that’s all.

Sorry, I got extra " wordy" with my reply. I like this example. The problem with posting publicly on something like this, is everyone has a different definition of "slight speed difference".

 If it's slight, there won't be any problem and they will work as a team. If one engine has to really drag or shove a much slower engine constantly, there's something wrong and it will cause an issue in my experience.

 That said, I lash-up er um, I mean I build large consists all the time with all types (& brands) of MTH controlled engines without causing issues.

Thanks everyone for your replies.  I can now proceed with more confidence.  And, if I notice any wheel slippage, I will add or subtract a stripe from the loco that is determined to be "out of spec".   Tom

I've burnt out a few engine just because of speed differences,   Missing the watch dog  signal . . WE finally gave up on lash-ups,,,,,, Tooo risky for my budget. Occasionally          we'll give two engine the same ID and test run them before coupling them together, This sway it Eliminates the watch dog problem. (better than  nothing)

Gregg posted:

I've burnt out a few engine just because of speed differences,   Missing the watch dog  signal . . WE finally gave up on lash-ups,,,,,, Tooo risky for my budget. Occasionally          we'll give two engine the same ID and test run them before coupling them together, This sway it Eliminates the watch dog problem. (better than  nothing)

What exactly did you burn up? ....can you elaborate more? I’d like to learn what exactly burned up. Was it electronics, or motors, or D all of the above......Pat

Gregg posted:

This sway it Eliminates the watch dog problem. (better than  nothing)

I'm somewhat confused how the WD comes into play here once you have them started up.

I have 2 IDENTICAL RS-3 Erie Lackawanna PS-2 engines and couldn't get them to run the same speed!  5 SPMH difference.  When I wanted to lash them I would start them, slower one in front but still unconnected, and get them moving.  I knew what speed setting to use on each to make them run the same.

So I would let the faster one slowly catch up (I had the front coupler open on it and the rear one open on the slower one) and when they coupled up I would quickly change the speed of one or the other so that each was running at the speed that I knew made them run the same.

Not exactly a lashup but it looked nice and did provide twice the pulling power

- walt

Walt, at a difference that large, you could use a custom tach tape to match them.  But, I do have a question.

Is the 5 SMPH difference constant at all speeds?  If so, that's pretty odd!

gunrunnerjohn posted:

Walt, at a difference that large, you could use a custom tach tape to match them.  But, I do have a question.

Is the 5 SMPH difference constant at all speeds?  If so, that's pretty odd!

John: I ran a bunch, and I mean a BUNCH, of tests at different speeds.  You are correct, the SMPH difference changes with speed.  I said '5' because of the speed that I like to run my trains '5' worked.

That was at 50 SMPH.

BTW: I tried replacing the tach tapes on BOTH engines with no improvement.  But I used the recommended ones, not alterative ones.

- walt

OK, that would be a 10% speed difference, significant and too much to handle without adjustment.

You would obviously have to use alternative tapes with a different stripe count to affect the speed.  I'd first measure the scale MPH of each locomotive over a measured distance and calculate the speed error.  I'd suspect that one will probably be the offender, but it's hard to say.  In any case, once you have that data, you can then set about correcting the issue with a new custom tach tape.  Let's say that one is running too slow at 45 SMPH and the other one at the correct speed 50 SMPH speed, this is probably the easiest situation to address.  Since you can only affect the speed with whole increments of a stripe, at 50 SMPH, each stripe accounts for about 2 SMPH.  A good place to start would be a tape with 19 stripes to replace the 24 stripe "standard" and see where that gets you.

Here's a link to a set of custom tape images: Custom Tach Tape Image Post In DCS Documentation Thread.  The easy way to do this is to print these on 1/2 page gummed shipping labels using the "label" print paper type, that's how I do it. 

In order to pick the correct one, just take the exact image of a stock tape for your size flywheel and print the images on plain paper at first at full size.  Match the exact length of the 24 stripes from the stock tape to a 19 stripe image in the custom tape files.  Get as close as you can, you should be able to get pretty close.

Print that file on the gummed label paper using the "label" setting and cut it out for your custom tape.

I converted that USA Trains GP engine in that video to MTH PS. Not only was the conversion to command made, I also replaced the stock small wheels with larger NWSL ones. So I had to fine tune the tach tape to get the speed correct. It matches the stock MTH engines very well. So matching can be done on different engines.

 Walt, being that yours are stock MTH matching engines, I'd have to be inclined to say something is wrong with one of the engines. 5 MPH at 50 is something that tells me this. On brand new G scale engines, I found that several (3 or 4) needed to have the tach moved closer to the flywheel. I don't think this is from the truck design. I believe that it's from some problem on the board or tach that makes it weaker? I adjusted the spacing and they have run well ever since. One was a brand new PS3 Dash 8 engine. Another was a brand new PS2 version of the same.

 It would be nice if I could tell you exactly what is wrong with yours. If it's that one engine is too fast, I'd suggest moving the tach closer like I did. If one is too slow, I'd be looking for binding, gear meshing (and lube), and/or similar issues. I have a 1 gauge engine that I believe is wrong because of some drive issue that actually made something weak. I'd blame the motor, but I suspect it's actually in the motor drive electronics. Because the engine was purchased used and looks well worn, I don't know what caused it. I considered a new board set but don't wish to experiment with losing more in the process. It runs and it stays on it's own. It draws more current than others and lags behind even more with the smoke on. I just monitor it closely to wait for something to change. It has been a few years now!

Thanks John and Joe!  John, I do have a rather extensive chart for ALL of my DCS-controlled engines showing times over and pre-measured distance.  I chose a relatively long distance since to me it allowed for more accuracy.  From my observations, the fast engine is running too fast. 

One of the other things that I did was run each engine with OTHER DCS-controlled engines starting off 2 or 3 inches apart and then running them at the same SPMH.  The faster one is definitely 'fast'.

Joe: when I get stuff out to start on my Christmas layout I'll try your suggestion.

As always, thanks = walt

Search for old post what to do was discussed before.   Make sure both engines full cleaned and lightly lubricated.  No binding.  Find which engine is out of spec?  Probably the faster one, but make sure you know which one is not running scale miles.  Make sure correct Sound File, make sure correct tach gap, clean non slipping flywheel, clean tach reader sensor.  Try again.  Also can clean motors.  Usually one is missing reading a stripe and winds up much faster.  G

Well, since he replaced the tach tape, one would hope he put on a clean tape.  The correct sound file and sensor spacing is certainly a concern.  I do have to agree, if they're stock MTH PS/2 locomotives, I can't imagine why they don't run at the right speed if all of that is correct.

gunrunnerjohn posted:

Here's a link to a set of custom tape images: Custom Tach Tape Image Post In DCS Documentation Thread.  The easy way to do this is to print these on 1/2 page gummed shipping labels using the "label" print paper type, that's how I do it. 

In order to pick the correct one, just take the exact image of a stock tape for your size flywheel and print the images on plain paper at first at full size.  Match the exact length of the 24 stripes from the stock tape to a 19 stripe image in the custom tape files.  Get as close as you can, you should be able to get pretty close.

John

Is there custom tach tape images for Proto 3 engines or are custom tach images the same as Proto 2 engines?  

I have Proto 3 engine that runs much faster than my other Proto 3 engines.  

Thanks

Same tape.  I'd do all the things George listed first, for PS/3, I'd make sure the chain fine and sound files are proper for your locomotive.

gunrunnerjohn posted:

Same tape.  I'd do all the things George listed first, for PS/3, I'd make sure the chain fine and sound files are proper for your locomotive.

John

My steam engine is upgrade from Proto 1 to Proto 3.  I am using RailKing Hudson, 4-6-4, sound file.  Where as my engine is Pacfic, 4-6-2.  I like the whistle on this sound file better which is the reason for using it vs the sound file for a 4-6-2 engine.  The engine is faster than 2 Premier diesels in a lashup which have 2 motors in each engine which I thought was strange.  The engine runs about 10 SMPH faster than my diesels.  I assume that a standard tach tape comes with each upgrade kit which may have been used with my engine or are there diffrent tach tapes that are supplied based upon the size of the flywheel?

I assuming I will need to use custom tach tape to slow it down.  

kjstrains posted:

gunrunnerjohn posted:

Same tape.  I'd do all the things George listed first, for PS/3, I'd make sure the chain fine and sound files are proper for your locomotive.

John

My steam engine is upgrade from Proto 1 to Proto 3.  I am using RailKing Hudson, 4-6-4, sound file.  Where as my engine is Pacfic, 4-6-2.  I like the whistle on this sound file better which is the reason for using it vs the sound file for a 4-6-2 engine.  The engine is faster than 2 Premier diesels in a lashup which have 2 motors in each engine which I thought was strange.  The engine runs about 10 SMPH faster than my diesels.  I assume that a standard tach tape comes with each upgrade kit which may have been used with my engine or are there diffrent tach tapes that are supplied based upon the size of the flywheel?

I assuming I will need to use custom tach tape to slow it down.  

As long as the tach is working correctly, then swapping out the tape is next. More stripes will slow it down. If you add several more and the engine seems to stay too fast, the tach maybe skipping stripes. It may take a few tries to get it dialed in perfect. You can use math to get the percent increase in stripes you need to get the desired slow down.

 I usually count the stripes on there now and make sure I am adding correct numbers of them on the finished applied tape.

wouldn't a resister on the faster motor solve the problem?  It would take some experimenting

I am surprised at how many have replied to this thread about speed variations which suggests that this is not an uncommon issue.  I believe that there is a solution that MTH could chose to implement.  If operators were allowed to enter a "scale factor" through the smart device app (or remote) which the DCS program would use to multiply with the operator selected speed (e.g.; enter a scale factor of .933 which would be multiplied by the  commanded speed of 30 MPH to realize a desired speed of 28) this would effectively allow operators to make the necessary adjustment without the need to perform surgery on the engine.   Just a thought.

Tom

Tom, to someone who knows nothing about the firmware, your idea sounds plausible.  There is probably something you and I don’t see.  I have had the same issue as you, a very slight difference in speed!  I tested running the two engines just a few inches apart and decided it was so close I would do as our panel of experts suggested, go ahead with it.  I was amazed I actually got something right with DCS.  Thank you for posting the question I should have asked to be sure.

Tom Jasper posted:

I am surprised at how many have replied to this thread about speed variations which suggests that this is not an uncommon issue.  I believe that there is a solution that MTH could chose to implement.  If operators were allowed to enter a "scale factor" through the smart device app (or remote) which the DCS program would use to multiply with the operator selected speed (e.g.; enter a scale factor of .933 which would be multiplied by the  commanded speed of 30 MPH to realize a desired speed of 28) this would effectively allow operators to make the necessary adjustment without the need to perform surgery on the engine.   Just a thought.

Tom

Once I have adjusted the speed on an upgraded or problem engine, it stays that way. I have not had to go back in. I like your idea. I'm just saying that it isn't a must have for me. After acquiring around 100 MTH engines, the most problem MTH ones for me were in 1 gauge ( 4 to date?). Most others that I post about are upgrades of other brands to PS control.

 I can't think of a single stock MTH O scale engine of mine, that was a problem with speed.

astarr posted:

wouldn't a resister on the faster motor solve the problem?  It would take some experimenting

No, it would only create new problems.  The speed control would still try to maintain the speed by cranking up the voltage.  In addition, adding a resistor in series with a motor just adds a heater inside the shell, not a good idea!

Tom Jasper posted:

I am surprised at how many have replied to this thread about speed variations which suggests that this is not an uncommon issue.  I believe that there is a solution that MTH could chose to implement.  If operators were allowed to enter a "scale factor" through the smart device app (or remote) which the DCS program would use to multiply with the operator selected speed (e.g.; enter a scale factor of .933 which would be multiplied by the  commanded speed of 30 MPH to realize a desired speed of 28) this would effectively allow operators to make the necessary adjustment without the need to perform surgery on the engine.   Just a thought.

Could is the operative word here.  There are tons of neat features that the manufacturers "could" implement, but cost and time are prohibiting factors.

Rubber tires, self-locking worm gears, and speed control, oh my! 

walt rapp posted:

I have 2 IDENTICAL RS-3 Erie Lackawanna PS-2 engines and couldn't get them to run the same speed!  5 SPMH difference.  

 

Walt are these the ones I landed up with ?

“PIRATES” and “KENNYWOOD” ???

taycotrains posted:

walt rapp posted:

I have 2 IDENTICAL RS-3 Erie Lackawanna PS-2 engines and couldn't get them to run the same speed!  5 SPMH difference.  

 

Walt are these the ones I landed up with ?

“PIRATES” and “KENNYWOOD” ???

YEP!  I was only trying to add to the conversation and unfortunately I wasn't careful enough to make it clear that I was talking about my past experience with those 2 engines.  I'll email a comment to you.  

- walt

So Walt, how did you fix it?

Shouldn't make any difference which loco is in the lead, since once coupled, they are locked together and will run at the same speed.

Running mismatched locos together is risky, as the speed control in one will pour on the power to make it run faster (heating its motors and possibly causing eventual failure), while the other will cut down the power to try to slow down, increasing the load on the other loco.

I must be lucky   Click on the triangle, Photobucket video. 

I've found that MTH locomotive are pretty consistent, but not identical. I will place the faster one(s) in the lead which tends to reduce derailing (I use scale-wheels on the club layout and some spots are a little flaky). The slippage takes care of the inconsistencies. I use the same technique with hi-rail locomotives and haven't experienced any ill effects.

If the differences are only a couple of percent, normally there's no issue in the MU configuration.  For DCS or Legacy, typically they're very well behaved.  TMCC locomotives are hit-or-miss as far as the MU configuration, many will run fine, others are very ill behaved.

I will always go back to this video to show how well behaved MTH consists are. I put my hands on individual cars and engines while this train was running. I wanted to see if any part of the train was under stress. I could slightly pull back on any part of the train and the whole would compensate. There wasn't anything out of sync and the pressure was slight and even throughout the train. There are cars that have very fine wheel profiles that would have jumped the rails if anything prompted them to. Yet the train ran perfectly. No lobster claw 3 rail couplers or pizza flanged wheels here to help.

here's a G scale train with distributed power that also runs fine. They've just crested the hill and start their descent.

here they start the nearly 2% grade on their climb around the yard.