A Safe Power Source For Z Scale

OK, now I'm confused (again!)

In reading some of the older posts here regarding which power packs are "safe" to use, I'm seeing a lot of mixed reviews concerning the Rokuhan RCO2 I purchased. It's my understanding that some of the earlier RCs had some production issues; I bought mine about 3 weeks ago, so I guess it's safe(?) to assume mine is not one of those. So far, it seems to be ok with my MT F7s, yet I've read several posts where the MRC #1300 is "better".

Can someone give me (us) a definitive answer? Also, I see that MRC offers some sort of diode/resistor "bank" (AT 8800) to reduce voltage: has anyone had any experience this this item?

Thanks.

Mark in Oregon

 

Hi Mark,

There are some VERY strong options out there on power packs, so lets talk basic.

First, everything I'm talking about here is normal, analog, Direct Current (DC) power - NOT DCC! and I'm going to over simplify a bit.

There are three power pack components:
1) Voltage
2) Amps
3) Frequency

Lets talk voltage.
That dial on the power pack? that regulates the voltage. You can use a power pack that goes up to 10,000 volts on Z scale, so long as you stop twisting the dial once you reach the maximum voltage designed for your locomotive. In Z scale that is somewhere between 9 and 12 volts. Here is a rough guide to maximum voltage:
Marklin Locomotives: 10 volts
New AZL Locomotives: 12 volts
I think the MTL F7 was rated at 9 volts, but I'm sure someone can help here
Same with the MTL GP35 and SD40-2 that used the Maxon motor. I think they used the 9 volt version.

MRC actually made an N scale power pack with a physical stop in it so it would only go 0-9 volts (the normal one went up to 12 volts, which is common in N scale)

Will you kill a 9 volt locomotive if you send it 12 volts? Eventually, yes. But for a few seconds? No real harm if it's running well and not under a heavy 40 car load. So there is nothing wrong with using an N scale power pack.

Newer locomotive design use highly effieicnt can motors that run at 12 volts. Older Marklin and MTL F7 units still use what I call "slot car" motors that use more power, and get hotter. Protect them by keeping them under 10 volts. How? Dont run them at full power if you use a 12 volt pack!

Lets talk Amps
Most Z newer scale locomotives draw less than 100 miliamps. Even the older slot car motors don't draw much more than 400 miliamps. Most power packs make 2 amps or more. Thats 20 newer locomotives worth of power! You don't need that much. In larger scales (HO) you do, but in Z scale it can actually cause problems. What happens when a loco jumps the tracks on a turn out and shorts out the track? With a big power pack, you get all of that energy slamming through your wires, track and loco. Ouch! With a smaller pack, you still get everything it can make, but since it has a smaller punch, it does less damage.

NOW a good short circuit fuse / detector is a good idea. The old "light bulb" trick works just fine for analog DC systems.

Lets talk frequency
Frequency is also known as pulse power. This is a pretty common design where the power pack will pulse, or send little spikes of higher voltage at a given frequency when the throttle is at low settings. This can help regulate the slow speed by changing the frequency of the pulses. Imagine a hammer moving a stone by hitting it over and over. The hammer hitting the stone is the pulse. The faster you hit it, the more faster will move.

Compare this to a power pack that does not have pulse power. It is more like a bulldozer moving a boulder. It will push harder and harder until eventually the boulder starts to move, but when it moves, the force of the friction letting go means it will probably jerk to life quickly, and keep going at a pretty good speed once it breaks free.

Again, most modern power packs use a combination of pulse power at low speeds to get things going smoothly, and then the pulses fade out as speed builds and it eventually goes to full smooth analog power. But remember that little MRC power pack that was a modified N scale unit? well, this is where the problem comes in. Lets say we use a N scale unit designed for a max of 12 volts, but we want to run our MTL F7 up to a max of 9 volts. No problem, just max out at 3/4 throttle and we will never go over 9 volts. Ah, but those pesky pulse power designs, that is an issue. Those pulses dont completely fade away until 1/2 thottle or more - sometimes max power. That means we are pulsing that MTL at a much higher voltage than we would like. The pulse power hammer is still banging away on it well after it is moving smoothly out of the yard. That is not good, and will shorten the life of the motor.

The solution? Some people (including me) use diodes to lower the track voltage. This is a little component that will pretty much just lower the entire voltage range by a few volts. Now you can use a common, inexpensive, quality, 12 volt N scale pack, and have it deliver the pulses in the way it was designed, but over a voltage range that maxes out at about 9 volts. Perfect for MTL and Marklin locomotives.

I think you are also now beginning to see why we came to the conclusion that 12 volt motors are a good idea for Z scale, and why all of our AZL locomotives now use 12 volt motors. It makes everything simpler: no modifications required.

We also like the rokuhan power packs because they work straight out of the box with good controlability and good short circuit protection. Thats the best simple solution.

Good luck!
-Rob(A)
AZL

 

So it sounds like I'll be ok if I continue to use the Rokuhan unit, since it is made for Z scale.

FWIW, I have tried it with some of my N scale, and it works well with them, too...

Thanks, Robert.

Mark in Oregon

 

Rob did a great job explaining it, so now I dont have to to.

The Rokuhan RC-02 is perfectly safe for all Z, as are all of the Rokuhan controllers. I'm not sure about any problems with their first controller, the RC-01, but all the bugs were worked bout by the time the RC-02 and RC-03 hit the market.

Looking at the current MRC website, why are the Tech 7s listed as Z controllers?

The following DC controllers are suitable for Z:
Rokuhan RC-01
Rokuhan RC-02
Rokuhan RC-03
Blue Line(Ex Zthek, Ex Stonebridge) Snail Speed Controller
Medvend AN-1-X Panel Mount Analog Speed Controller
MRC 1300, modified with that physical sop on the dial to prevent higher voltages.
Marklin Mini-Club power supply
Jorger power supply (Is this still sold anywhere?)
Any others?

The MTL F7 uses an older motor, and has some complicated gearing, so it draws a larger amount of current. If you try to run 2-3 of them on a RC-02, it may trip its overload protection. When you get get a AZL engine, you will see how much less current newer motors need. With my GP7s, 6V is 100 scale MPH, so I only use the lower 1/3 of the RC-02s controller dial for realistic operations. When my nephew comes over, I switch out the AC adapter to one with a 5V output so that he doesn't abuse my trains.

 

ZThek Snail controllers are superb, so are the Stonebridge Snailers (Zthek's too) - run on a 9v battery, or plug a wall wart into them. Either way, your lok will never experience damaging amperage (the iron fist inside the 9v operating glove) OOP i think, so may have to hunt one.

Marklin has made z controller power packs since 1972. still make one, but now it is a wall wart with a reostat controller box. Good German construction.

LGB makes one, looks identical to the Marklin white pack (only grey/red dial), but much cheaper used because it is a panty-waist in amps for a multi-engine lashup or sound boards in G scale locomotives. So G runners toss it for pennies and get a Bridgeworks trafo very soon after purchasing their G starter sets. Good German power, except it runs to 24 volts. Run it with care and you won't release the magic blue smoke. You may never need warp 10+; then again, you don't need a Dodge Hellcat with 700+ hp, but in the hands of experts, a useful tool.

 

Once Oli Passmann released one sample, Z-scale snail with pulse power (Real voltage ~9 V max) which is very efficient. But I don't see it anymore on Oli's website...

Dom

 

You can find the updated new BlueLine Snail Speed Controller here:

http://www.ztrackcenter.com/electronics/blue-snail-1

They are great!
Rob

 

Charlie,
Both? The Rokuhan unit will give you a little more power than the snail simply because of the difference in power source. I don't see much of a difference between the two running a single loco and 8-12 cars. After that the Rokuhan seems to win out.

Also, I use NiMh rechargeable batteries with good results. I get about 4 hrs/charge for the 9V and 6 hrs/charge for the AAA batteries in the Rokuhan.

To use the Rokuhan with the MTL feeder track, you'll have to buy a feeder cable, A0008, and cut off the track end. I'd also suggest keeping the track end and cutting it off with about 4-6" of wire, in case some day you want to power a Rokuhan track with a Snail.

Hope this helps,

Mark

 

AZL locos and MTL GP9 & GP35's (and maybe the SD40) will run much longer time than an MTL F7 or Marklin . The MTL F7 will give you the shortest life as they draw the most current. Current is the amount of drain on a battery.

 

For physical placement on the layout, the Rokuhan will be best. It gives you a large knob, easy direction control and better motor drive technology at lower speeds and can run batteries. The larger MRC unit listed is larger, an N scale with a screw to stop it at Z scale colts but no poor low speed running technology.
The SnailSpeed/Blue Line is great for portability and keeping the layout lighter but, requires batteries or a cord to a wall-wart for continuous running.
Did I mention the Rokuhan?


The BAZ BoyZ