My SGL Reading Pacific Gets A Legacy Command Upgrade

Great job. I like hearing how you did it and learning. Thanks.

nice Job John really a beautiful job much would that have cost to upgrade! Alan

Beautiful work John

Electronic wizard at work eh? Look great John.

Ok, when you going to offer Legacy upgrades to the general public?????  Yes please.

The SGL Pacifics were originally planned to have TMCC, that is why the antenna is there on all of them. My understanding is that due to cost overruns in the project TMCC was replaced with less expensive QSI-3000 which was on its way to obsolescence. It was also originally planned to have fan driven smoke which was replaced with a seuthe. These were some of the factors hurt the original sales.

John, it’s a pleasure seeing your talent at work, even with no understanding of what you’re doing.

Gene

Looks like 3rd Rail's 'Quiet Drive' minus the flywheel. Same builder at the time?

Not sure how long they've been at it but I see that Lionel is posting RCMC diagrams on their support site:

https://www.lionelsupport.com/...s/71267SRCMCLP3.JPEG

Thanks, guys, I've been wanting to do something with this one for quite a spell.

@Alan Mancus posted:

nice Job John really a beautiful job much would that have cost to upgrade! Alan

Probably more than many folks would want to pay, it's all custom wiring for the Legacy upgrades.  It's the labor that's the killer, not the price of parts.  The parts are no more then a TMCC upgrade.

@superwarp1 posted:

Ok, when you going to offer Legacy upgrades to the general public?????  Yes please.

I'm not sure I'll be doing that, with the time they take, I can't see anyone wanting to pay for them.  I've done a few diesel Legacy upgrades, sometimes they're considerably quicker.  However, some of the diesels have issues at very slow speeds.  Of course, that's similar to MTH PS2/PS3 low speeds.  The reason that factory Legacy diesels are so smooth at low speeds is the RCMC speed control loop is actually tuned for each model.  I suspect that means anything that uses a different gear or motor combination gets a new set of tuning parameters.  Of the four diesels I've done, two run smoothly right down to dead slow, the other two aren't smooth until speed step 4-5, not unlike some of my MTH stuff.  I have to believe that the speed control tuning makes the difference.

@rdg_fan posted:

The SGL Pacifics were originally planned to have TMCC, that is why the antenna is there on all of them. My understanding is that due to cost overruns in the project TMCC was replaced with less expensive QSI-3000 which was on its way to obsolescence. It was also originally planned to have fan driven smoke which was replaced with a seuthe. These were some of the factors hurt the original sales.

Yep, I figured it must have been intended to have TMCC, there's no other reason for that insulation of the shell.  It was a pleasure not to have to fool around with Kapton tape and plastic screws.

@Norm Charbonneau posted:

Looks like 3rd Rail's 'Quiet Drive' minus the flywheel. Same builder at the time?

Not sure how long they've been at it but I see that Lionel is posting RCMC diagrams on their support site:

https://www.lionelsupport.com/...s/71267SRCMCLP3.JPEG

Norm, the drive certainly looks like 3rd Rail, right down to the drive shaft and gearbox design.

I've stumbled across the Legacy wiring diagrams previously, I wonder how to get a set of all of them?

@gunrunnerjohn posted:

Probably more than many folks would want to pay, it's all custom wiring for the Legacy upgrades.  It's the labor that's the killer, not the price of parts.  The parts are no more then a TMCC upgrade.

I'm not sure I'll be doing that, with the time they take, I can't see anyone wanting to pay for them.  I've done a few diesel Legacy upgrades, sometimes they're considerably quicker.  However, some of the diesels have issues at very slow speeds.  Of course, that's similar to MTH PS2/PS3 low speeds.  The reason that factory Legacy diesels are so smooth at low speeds is the RCMC speed control loop is actually tuned for each model.  I suspect that means anything that uses a different gear or motor combination gets a new set of tuning parameters.  Of the four diesels I've done, two run smoothly right down to dead slow, the other two aren't smooth until speed step 4-5, not unlike some of my MTH stuff.  I have to believe that the speed control tuning makes the difference.

If you are close to what Bruk charges you will have working coming out of you're ears and what Bruk charges plus the discount we get once a year at the 50% off sale, still cheaper than buying new. No diesels here for me to worry about.  LOL

Bruk has an edge with his 3D printing skills, that's a significant part of doing some of the conversions, especially if you want to add the extra smoke features.  Or maybe I'm just slower in general.

@gunrunnerjohn posted:

The reason that factory Legacy diesels are so smooth at low speeds is the RCMC speed control loop is actually tuned for each model.  I suspect that means anything that uses a different gear or motor combination gets a new set of tuning parameters.  Of the four diesels I've done, two run smoothly right down to dead slow, the other two aren't smooth until speed step 4-5, not unlike some of my MTH stuff.  I have to believe that the speed control tuning makes the difference.

Lionel's combination of double reduction gearboxes and an encoder with more resolution in combination with a better control loop is why Legacy stuff runs so well. The double reduction allows the motor to turn more for a given final gear ratio - more encoder pulses at higher motor velocities is better feedback into the loop. The 'tuning' is probably more like a turns ratio factor to correct the speed curve to match up different gear ration and wheel diameters.

I like Legacy for the fact that it has 100% usable and reliable speed steps. No hunting or hesitation, etc.

@Norm Charbonneau posted:

Lionel's combination of double reduction gearboxes and an encoder with more resolution in combination with a better control loop is why Legacy stuff runs so well. The double reduction allows the motor to turn more for a given final gear ratio - more encoder pulses at higher motor velocities is better feedback into the loop. The 'tuning' is probably more like a turns ratio factor to correct the speed curve to match up different gear ration and wheel diameters.

I like Legacy for the fact that it has 100% usable and reliable speed steps. No hunting or hesitation, etc.

Norm, I think the double gear reduction has more to do to get the motor past the cog state more than anything…….even as finite a control as Legacy is, there’s just no replacement for Pittman’s Lo-Cog armature design, ……I do think however, Lionel did a pretty good job overcoming this, where MTH still has issues with their vendor’s selections, ….we’ve proven this out by swapping out the overseas knockoffs in MTH engines with Pittmans, and drastically improving ( especially) the low speed smoothness….naturally, this is all just my POV, ……others might whine,…..😉

Pat

@Norm Charbonneau posted:

The 'tuning' is probably more like a turns ratio factor to correct the speed curve to match up different gear ration and wheel diameters.

Actually, according to the guy that actually coded it, the tuning is a lot more than gear ratios and/or wheel diameters.   I asked that very question.

After all, MTH does enough "tuning" to get the speed right based on gear ratios and wheel diameters.

I did enough servo loops for aircraft cockpit instruments in the 80's and 90's to know that there's more to smooth operation than gear ratio.

Tuning is tuning - speed curve correction is something else. Without going off the deep end too much, I work on closed loop systems of many types, some electromechanical. In my world PIDs are for optimizing loop response and things like turns ratio corrections are for adjusting displacements traveled, etc. In our electromechanical stuff, motor velocity is what's tuned. Displacement is what's corrected/calibrated. I admire Lionel's smooth controls but don't think it's too complicated.

Since I don't have access to the code, I defer to Jon Z. as to the complexity.

We initially used DC servos in the instruments, but then moved to stepper motors.  It was an interesting balancing act between response speed and pointer overshoot on the display.  Basically, we had to hit the slew speed specifications, but couldn't have any visible pointer overshoot.  It wasn't always that easy to get right.

@gunrunnerjohn posted:

Well, this has graced the shelves long enough, it's time to allow it on the layout.  Since I'm strictly command, first step is a command upgrade.  For this one, I decided on a Legacy upgrade.

I popped it open and right away a small problem arose, no flywheel!  That precludes the RCMC upgrade, no room for a flywheel!  So, to my secondary plan, use the Legacy BEMC back-EMF board instead.

This is the complete chassis, the two plugs go to the shell.

Another problem with no flywheel, the BEMC uses a hall effect sensor on an axle to generate the chuffs.  I have a custom coded Chuff-Generator I use for BEMC, but it also needs a flywheel.  But wait!!!  There's a 2-lobe cam on the axle in the big hole over the first drivers.  I fabricated an aluminum bracket for a chuff switch and mounted it.  In a wonderful twist of fate, the BEMC has an odd behavior of it's hall effect sensor.  It toggles from positive to negative for a chuff, then for the next chuff from negative for positive.   By using all the contacts of the chuff switch, I had that exact behavior and generated 4-chuffs/rev in the process, perfect!

I mounted the BEMC on an aluminum base with a tab folded up for a heatsink, and covered the base with Styrene to insulate the bottom of the PCB.

The board assembly slips inside the boiler tube and screws to the convenient screws that were holding the CV power supply for lighting and the Seuthe smoke unit.  Naturally, I also included a fan driven smoke unit and LED headlight.

Here's the shell complete with all the wiring done, the two connectors join to the chassis and the wires get tucked into the boiler tube.  I used a pair of LED's for the flickering firebox and another for the cab light.  Not shown is the aluminum duct tape covering the flickering firebox, I found that the LED's were leaking light down on the track.

In an odd layout, I put the TMCC RCDR in the tender and not with the BEMC board where it normally goes.  That was due to the fact that there is no easy way to do an antenna on the locomotive.  Nothing detaches so I could insulate it for an antenna, many times you can use the pilot, not today.

Here's the tender with all the parts mounted.  In another odd twist, I didn't have to do anything special to create a TMCC antenna for the tender.  Apparently, the SGL locomotives are "TMCC Ready", because the tender shell was already insulated with a wire soldered to it for an antenna.  It was obviously a factory job because it was way too need even for a craftsman to have done.  The insulating gasket was obviously punched out to shape, and the screws were all insulated from the chassis with special washers..

An oddity of having the RCDR in the tender is I had to send the serial data two ways!  I had to send it up to the BEMC in the locomotive, but since the chuff switch is in the locomotive and inputs directly into the BEMC, I had to send the composite serial data back to the tender, with out that link, I was missing the chuff!

Wiring finished, just have to dress it up a little and pop the shell on and it'll be ready.

And here's a drive-by with the completed upgrade!  The only thing left to do is to put a better sound board in it, I have one for the Pacific coming, but it's not here yet.

I take my hat off to you sir!