Variation on MTH Loco Speed Control?

Age-no
Weight/size of engine-no
Load differences different engines are pulling-yes
Do all PS2 locos run at exactly the same speed, when set the same?-no

Cab,
Speed does vary just slightly on some engines, I proved this to myself by running engines on the same track at equal distance at the exact same speed.
My 263E Tin Plate ran slower than my 0-8-0 Steam Engine, at the exact same speed. I needed to know this to run two trains on the exact same level of my layout, and program routes correctly so the trains never wrecked. Some engines
I could not run together on the same level because of the speed difference unless I figured out the actual difference and set the speed differently on the hand held remote control.
PCRR/Dave

Being able to run two DCS controlled trains on the same track is way cool.

Pine, Read my fourth line again--it states "no," they don't all run at the same speed.

Cab,
I did miss the "no", we are difinitely in agreement!
PCRR/Dave

I have 2 of the SAME engine and they don't run the same speed using DCS. For one sample, when I run one at 42 SMPH I have to run the other at 38 SMPH. I bought them with the intention of lashing them up but there's no way.

I tried a bunch of stuff involving the timing tape, all to no avail.

- walt

Walt, Have you tried the 'All' command and see if that helps?

Most of my engines are more or less spot on with each other. Of course, there are exceptions such as my ABA set that has a lot of drag in the A & B dummy units to slow it down enough to get it out of synch with the other train. My other F3 (single A unit although I do run a dummy GP9 with it regularly) is quite off and runs much faster than the others.

quote:

Walt, Have you tried the 'All' command and see if that helps?

Yeah, I tried that too.

I've been fighting this for 4 or 5 years holding out hope against hope that something synchs them up. Nothing has yet.

I've pretty much convinced myself to give up on it. Notice the "pretty much"

I'm going to pick up 2 new tach strips at York in April and try one more time.

- walt

Getting back to Rhaichen's original question, he is not talking about operating with DCS. You've run off in a different direction with the thread.

He is asking if they all run at the same speed given the same number of volts which is conventional operation. The answer to that is "no". There will be variations among different engines. To keep one engine from catching up when operated on the same loop, you will have to try different engines and different voltages to see which match up the best.

If you have two engines you want to couple together in "multiple unit" operation in conventional, these variations in speed will cause the speed control in the two engines to fight each other - not good. Turn off the speed controls. If the engines seem to run about the same speed, they can be MUed, but keep the speed control off.

Again, all of this is in answer to the original question - not DCS operation.


(...and yes, you can answer questions such as this without using the word "lashup"!!!)

Jim

Just a thought or two:

These are mechanical devices obeying the laws of physics regardless of the electronics and software aboard.

The drivers on a locomotive are part of the drive train, therefore part of the gear ratio;
if the gearboxes has the same ratio in two different locos, but the drivers are greatly different sizes,
and everything else is equal (which never occurs, really), the two locos will run at different speeds.
Weight is not a factor, except regarding adhesion. A same-generation 0-8-0 and 4-6-4, for example.
But are the worm/spur gear ratios the same? I don't know. Since diesel drivers (yes) are all
pretty much the same size - as inthe real world - internal gearing is primarily what matters mechanically.

In my (admittedly light) experience, unless one of your locos is obviously complaining when double-headed,
or you plan to run them together for hours at a train show or the like, these differences are typically
not an issue. Casual home running is pretty light duty, even with mixed brands.

I would avoid a cruise/non-cruise combination.

quote:

Originally posted by walt rapp:
I have 2 of the SAME engine and they don't run the same speed using DCS. For one sample, when I run one at 42 SMPH I have to run the other at 38 SMPH. I bought them with the intention of lashing them up but there's no way.

I tried a bunch of stuff involving the timing tape, all to no avail.

- walt

Have you ever actually tried rotating the motor a set number of revolutions on each of them and seeing if they go the same distance? I'm wondering if maybe the gear ratios changed for some reason during the manufacturing run? Given the tach strip, I can't think of any reason they'd run at different speeds otherwise, it's supposed to be digital.

quote:

Originally posted by Rhaichen:

Using the MTH loco speed control at the default low and constant speed, do all (PS2) engines go at the same speed given the same amount of volts? Or, for example, will an 8-pound engine and tender go slower than a 5-pound one?

By "low and constant speed" I assume you mean the default mode toggled by Whistle-Bell-Bell. Ideally yes, different PS2 engines (even at different loads) set to the default speed mode should run at the same speed for the same track voltage. In practice they don't for a wide variety of reasons. For example, if you add load to an engine it needs to draw more current to run at a given speed. The transformer output voltage itself drops a bit. There is additional drop between the transformer, track, and the PS2 board itself where the voltage is finally measured. Bottom line is the engine sees a lower track voltage and can only assume the user lowered the track voltage and wants to slow down.

There are other esoteric factors such as how a smaller wheeled RS-1 "takes" or slips on tight curves vs. a larger wheeled 0-6-0. Or how a pure-sine transformer set to the same voltage as a chopped-sine transformer can result in different engine speeds. Blah blah blah.

IMO, the bottom line is to observe that even the DCS command guys, with digital speed control, don't get perfect tracking between engines. I suggest you benchmark your engines by running each on the same loop at a couple test voltages (say, 12V and 16V) and time how long each takes to run N times around. Put some load on each and do it again. Store the results. As a wag, if any engine is running more than 10% faster than the other or what it did last time, then you ought to look for some hardware issue like a dirty flywheel, broken gear tooth, whatever.

As for independent confirmation, if you don't have access to a club/friend with a DCS TIU setup, probably the cheapest way is to get a DCS Remote Commander (about $30?) and carefully step up the speed in 1 sMPH increments to, say, 10 sMPH and use a ruler and stopwatch to confirm the engine speed.

As for un-attended operation over long periods, I believe the most common method is to break the loop into sections, sense when trains are converging, and stop or slow the faster engine by adjusting its track voltage using diodes, relays, or the like. Dale H describes one method below.

Multiple trains on one loop