Difference between MRC Tech 4 260 and MRC Tech 4 220?

Model Railroader General Discussion (Model Railroader)
1

Setting up for an expansion here, had a pair of 220’s, and needed one more.

Hundred mile trip to the L:HS, all they had was one 260. Now I have it.

There’s going to be times when a train moves from a block controlled by a 220 to a block controlled by a 260.

The only difference I can see between the 220 and 260 is the power rating. The question is:

Will a 260 set at say 30% throttle, move a train at or close to the speed that a 220 will, when its throttle is set to 30%?

I expect to find minor variations even between 220’s but I’d like to get the power packs as close as possible to make block transitions smooth.

Keep the 260 and wire it up, or wait till the LHS gets another 220 in and exchange them, what say you?

2

exchange

Tech 4 220 w/16VA & Momentum $50.59 Combines the momentum feature of the model 1500 and has the power of the model 2400. (MOME) Momemtum or flywheel action switch contains a delay circuit that mimics the lag time of speeding up or braking of real trains. Pressure brake

Tech 4 260 w/20VA & Momentum $57.79 Has 25% more power than the model 2500 Tech 2 series. Momemtum or flywheel action switch with LED indicator contains a delay circuit that mimics the lag time of speeding up or braking of. real trains. Pressure brake provides gradual

3

You should be close but may have to set the 260 to 25-27% VS 30% on the 220.

An option would be to “tune” the 260 with an additional load. A lighting circuit for structures would work.

You probably know this but bears mentioning. When a engine bridges 2 blocks which are powered by different sources you will notice a momentary speed increase as the engine will be getting power from both power packs. If running a single short switcher it maybe hardly noticed. If running a longer engine or multiple units, it is annoying, at least to me. Also the more power (VA) the packs have, the more noticeable this event will be.

Good luck with the expansion.

Jim

4

I think you are going to have to implement some mind juggling to get the speeds exactly matched anyway. I have 3 of the 2400s and they are not exactly the same at the same knob setting. But they are close and I remember which is which when doing a block crossover and it is good enough.

5

Budliner, the features are pretty much similar, just the power difference. Heh, and the price.

Soo Line fan, I’d forgotten about the two source “surge”, thanks for reminding me.

Virginian, I wondered about that too, slight differences in components, even on same make and model packs, making them mismatched by the dial settings.

Putting it all together, I’ll just save myself a drive, five gallons of gas wipes out the ten dollar savings anyway, keep the 260, and try to set up my routing so that I don’t cross power division lines while in motion. It’ll be wired up so that any one power pack can run all power divisions, or one power pack per division or any other combination, so I can say, dedicate a power pack to run the staging division and mainlines one and two, run the train from staging, down main one, cross over to main two, then pull staging and main one over to another pack. That way the running train will never cross a power division while running, but I can have seperate power packs running different divisions too. Let the power packs follow the trains.

Thanks for the help, it’s appreciated, and I really, really HATE that long drive anyway.

:slight_smile:

6

A much better solution is to implement block control, where one power pack powers a train where ever it goes on the layout. As you stated, let the power pack follow the train.

Power district control in DC (or AC) on shared trackage is asking for problems. Aside from the speed matching issue that the posts have pointed out, there is also a fault current every time a metal wheelset or truck bridges the gap between power districts. This fault current is proportional to the difference between the output voltage settings of the 2 power packs. When (NOT IF) the direction switches are set opposite (Murphy’s law in action) to each other, the locomotive will try to instananeously try to reverse direction as it continues to try to cross the boundary gaps in both directions, with a short circuit occuring as the wheels actually bridge the gap.

The more powerful the power pack, the greater the fault current until the overload protection/circuit breaker kicks in (assuming the affected leg of the power pack is protected).

With the MRC Tech series power packs, speed matching is theoretically possible. With rheostat control it is not. At each power district boundary, there will be a surge of the train as the rheostat resistance is halved (in addition to the fault current if there are two separate power packs).

All these reasons are why block (sometimes called cab) control was invented. Having the same power pack control the same locomotive throughout the layout eliminates these power district boundary issues. The commonly used dual cab control wiring has a built-in interlock that prevents the 2 power packs from assigning power to the same block at the same time. The final advantage of block control is that you only need ONE power pack for each train being run simultaneously.

Any of the basic and/or advanced wiring books cover how to wire for block control. I strongly recommend one.

my thoughts, your choices</

7

Thanks, Frank, both for your information, and for resurrecting this thread at the right time.

I finished laying the mains yesterday and wired them up temp style, one lead from a dedicated power pack to each main. When I woke up this morning, I wanted to update this thread, but was worried how deep in the stack it might be and whether I could find it.

I’ve tested three consists so far,

  1. A pair of Blue Box GPs, 38 and 50, pulling 4 boxcars and a caboose

  2. A pair of Atlas GP-7’s pulling 15 tank cars and caboose

  3. A Spectrum 2-8-0 pulling 8 Athearn heavyweights

  4. Not a consist just a BLI 2-10-4, first time I’ve gotten to run it since I got it 6 months to a year ago.

The results outdid my highest expectations.

Simplified, there are 3 mainlines, concentric ovals, with access between mainlines being #4 and #6 crossovers, insulated joiners between each set. The MRC 260 runs the outer main, a 220 runs the inner main, and the original 220 runs the layout as it existed before the expansion.

With all three MRCs set to 30% throttle, all of the consists and the BLI cross the division boundaries smoothly and with no change in speed, either at the crossover or afterwards. I’m sure part of that is due to the multiple locomotives and weight of the trains. The BLI has yet to cross a boundary under power, because it almost certainly won’t like the #4 crossovers, and the #6 crossovers are on the far side of the layout.

The lone, non-MUed 2-8-0 crossed the division boundaries with no surge or change in speed afterwards, but 8 heavyweights is a lot of momentum and probably masked some effects you’d see with just the locomotive travelling without the train.

The only overload I had was with the BLI, very early on. In the first month I had it, one of the tender wheelsets fell off, and I was lucky to locate it and realize what it was. Months later I found time to look hard at the truck assembly and found a metal

8

Well, I fixed the BLI.

It was making a horrid noise, like metal grinding on metal, almost like when you sharpen a knife on a grinding wheel.

I lubed the valve gear, checked it forwards and backwards, if anything the noise was getting worse. I ran it in, several laps each way at slow, them medium speed, and then packed it in, the noise wasn’t going away.

I opened it up, and the worm gear looked pretty dry, so I greased it through the little hole in the tower and that didn’t do any good either.

There was a little play, forward and back, in the motor mounts, so I ground some wooden shims out of toothpicks and tightened that up but it didn’t deal with the noise.

I pulled the gear tower cover, cut some flash off the universal shaft, made sure the worm and worm gear were well packed with grease, and then plugged the tender back in and ran it without the universal, to try and isolate the noise to the gear housing, valve gear, or motor itself. The motor ran nice and quiet, and the gear train, when disconnected from the motor, ran smoothly, no binding in either direction.

And then I spotted it. A band of color around the flywheel. It turns out the bearing surface between the flywheel and the flashing on the lead locomotive weight was running with no grease at all.

Out came the handy Dremel tool, and I polished that bearing surface so smooth it will never need grease again.

Noise problem solved.

I also fixed the bell, which was loose on one side and kept falling out, and reshaped the metal plate in the tender truck so it engaged the keeper pin, superglued it back into place, reseated the smokebox cover, which had worked loose and was showing headlight through the crack, and now she runs smooth and quiet, just like new.

Well, actually, better than new.

:wink:

9

Getting back to your ‘Original’ Question:

Kalmback has an inexpensive book out concerning ‘Common rail Wiring’ for two DC powersupplies - creating Cab A and Cab B.

It seems to work better when running blocks powered by separate cabs. Entually you’ll calibrate your ‘painted-on’ settings to closer match actual voltage outputs.

Most things electrical are within +/- 10% tolerances - your amplifiers, for instance.

IF it becomes that important to you, a pair of Volt meters will be in order (going rate $25 ea.) or you can ‘muddle’ through.

10

Thanks Don. I like the control panel voltmeter idea. Not one for each cab, not enough room, but one extra rotary cab switch will let one meter service all three packs.

The existing layout is wired two rail and working well, so the expansion will probably match.

While a VOM would answer the original question, the idea was to see if anyone here knew, before opening the box. MY LHS is already touchy about returning electrical items, actually returns are expressly forbidden and exchanges, wellllllll…

If someone in thisthread said, “No doubt, the 260 is more powerful, it will drive trains much faster at any given throttle setting”, I would have exchanged it, unopened, for another 220.

Instead they said, “It doesn’t matter, two packs at the splices will surge a loco anyway.”

So I kept it, opened it, and wired it up.

It works perfectly.

Well, almost perfectly.

Perfectly at 30% throttle.

At 60% throttle, the 260 is throwing a little more power. Just a fuzz.

That fuzz is important though.

None of my locomotives besides the BLI ever run at 60% throttle.

Like I tell my son. “Them ain’t slot cars.”

But the QSI sound decoder in the BLI is a voltage black hole. It doesn’t even move till 50% throttle.

At 55%, the BLI pokes along.

At 60%, it goes lickety split.

I probably need to adjust Vmax and maybe Vstart.

For now though, even a slight difference between the 260 and 220 at 60% throttle has large speed implications.

No matter, we’ll have “wandering cabs” after the wiring is done right. We’re just testing now.

If any questions come up then, and I can see the need to be able to cross divisions between power packs in addition to using cab following loco techniques, the voltmeter will give me what i need to make it happen smooth.

Good idea, I appreciate it, thanks.