I am running conventional trains. I would like to create a block on the down slope and insert a resister to lower voltage. What value resister & wattage?
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Resistors are a bad choice, the voltage drop varies based on the current demands. Also, they'll get pretty hot. Depending on how much you want to drop the voltage, I suggest 6A diode pairs, wired back to back. Each diode pair in series with the track power for the block will drop the voltage around .7 volts. Figure the amount of voltage drop desired and divide by .7, that's the number of diode pairs you need.
I'd probably put a a bunch of them in series on a dual-row barrier strip and then just move a tap to select the optimum voltage.
Buy a older ZW and do it the old fashioned way. They are reasonably priced now.
Rod Miller
romiller49 posted:Buy a older ZW and do it the old fashioned way. They are reasonably priced now.
Rod Miller
You mean by moving the handle? I think he is trying to create something a little more automated.
Rod is correct, this adjusts to the speed of the train, if you're running faster up the grade, you'll have a speedier descent.
One way to achieve this with a ZW or two separate transformers with variable output would be to make a separately powered block out of the down grade. Then adjust the "other" transformer to get the desired speed.
Make it simple: A transformer with 2 or more outputs, use a common ground and have the down grade a separate block and lower the voltage accordingly-based on engine, size of train and what speed you want.
gunrunnerjohn posted:Resistors are a bad choice, the voltage drop varies based on the current demands. Also, they'll get pretty hot. Depending on how much you want to drop the voltage, I suggest 6A diode pairs, wired back to back. Each diode pair in series with the track power for the block will drop the voltage around .7 volts. Figure the amount of voltage drop desired and divide by .7, that's the number of diode pairs you need.
I'd probably put a a bunch of them in series on a dual-row barrier strip and then just move a tap to select the optimum voltage.
John's recommendation is a tried and true method to drop voltage. For higher current rating, you can also use high-current full wave bridge rectifiers with the plus (+) and minus (-) leads tied together which will give you a 1.4 volt drop in each direction. I used four of them (25-Amp) to drop the maximum voltage on a home-built 20-amp transformer I was experimenting with.
So, using the single transformer method, like a ZW, the section of track on the down grade would be insulated from the rest of the layout. Let's say that binding post A is used for the majority of the track and binding post D for the down grade.
Does that sound like I am on the right track ?
Yes, just use a common ground. This way you can vary the voltage in the down hill block if you want to. All you have to do is insulate the middle rail.
Back in the day, I used the old ZW two controls idea. I had a long insulated outside rail section at the top of the grade (upper level) attached to a relay that switched the grade ahead to the lower voltage on the downhill trip. It took just a little trial and error with train length and insulated rail length and worked perfectly. When the leading end (engine) of the train arrived at the top of the grade on the downhill trip the voltage was already lowered by the relay. When it hit the bottom of the grade, the end of the train would have already released the relay but by then the engine was on the higher voltage section (on the flat). It was a fun project.
Earl
I think I understand. I am a little slow.
One handle for the uphill and the other handle for the downhill on a separate block. Why don't you guys just say what you mean?
Don't want to kake it tooo easy.
romiller49 posted:Buy a older ZW and do it the old fashioned way. They are reasonably priced now.
Rod Miller
Scotie posted:One way to achieve this with a ZW or two separate transformers with variable output would be to make a separately powered block out of the down grade. Then adjust the "other" transformer to get the desired speed.
jim pastorius posted:Make it simple: A transformer with 2 or more outputs, use a common ground and have the down grade a separate block and lower the voltage accordingly-based on engine, size of train and what speed you want.
George S posted:I think I understand. I am a little slow.
Dan Padova posted:So, using the single transformer method, like a ZW, the section of track on the down grade would be insulated from the rest of the layout. Let's say that binding post A is used for the majority of the track and binding post D for the down grade.
Does that sound like I am on the right track ?
These methods, used for decades+, cause large (30+ amps at 6-7 volts difference on a ZW) fault currents - direct short circuits - across the transformer windings with absolutely no internal circuit protection when the blocks are bridged by center rail rollers of locomotives & rolling stock.
The use of the diode array or a big Lionel type rheostat eliminates this problem.
Or you could make it really easy by just running modern trains that have cruise control. 
Rod
Yes, when they run, IF they run and are not out for repair.
Similar thread...starting with resistor migrating to diode method:
https://ogrforum.ogaugerr.com/t...ter-for-downhill-run
Diode/bridge-rectifier method $2-3 in parts. More hookup connections than a single resistor but worth the effort for reasons given earlier.
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ADCX Rob posted:These methods, used for decades+, cause large (30+ amps at 6-7 volts difference on a ZW) fault currents - direct short circuits - across the transformer windings with absolutely no internal circuit protection when the blocks are bridged by center rail rollers of locomotives & rolling stock.The use of the diode array or a big Lionel type rheostat eliminates this problem.
This deserved to be repeated! This is a VERY BAD IDEA!
Put retarders on the track like in a hump yard.
gunrunnerjohn posted:This deserved to be repeated! This is a VERY BAD IDEA!
I've done so, to mostly deaf ears. This is even more important with modern electronics on the track as they are susceptible to the resulting spikes. I always knew this was a problem but never realized the magnitude until I actually tested the fault with an ammeter last Spring.
IF YOU USE 2 TRANSFORMERS MAKE SURE THEY CAN NOT BE PUT IN PARALLEL TO EACH OTHER. THE BEST WAY TO DO THIS IS TO USE A RELAY
DALE H
"30+ amps" ???
Just look at the instructions that came with an old ZW.
Rod Miller
gunrunnerjohn posted:ADCX Rob posted:These methods, used for decades+, cause large (30+ amps at 6-7 volts difference on a ZW) fault currents - direct short circuits - across the transformer windings with absolutely no internal circuit protection when the blocks are bridged by center rail rollers of locomotives & rolling stock.The use of the diode array or a big Lionel type rheostat eliminates this problem.
This deserved to be repeated! This is a VERY BAD IDEA!
I believe you, but how is it that people have gotten away with it for decades?
Arthur P. Bloom posted:"30+ amps" ???
Take a big copper wire and short it across the windings of the ZW, what kind of currents do you think you'd pull? 30A is probably very easy to do, there's no current limiting, and the circuit breaker is NOT in the circuit. The limiting factor is probably the carbon rollers, I can imagine they'd take a beating if you did this often.
nickaix posted:I believe you, but how is it that people have gotten away with it for decades?
People have gotten away with drunk driving for decades as well, but sooner or later it catches up with you. 
I gave the problem (of using the ZW's two outputs A & D) a little idle thought sometime in the last few years. Shorting any one turn, any two turns, etc, will always produce, in the shorted turns only, approximately at most, the bolted-short circuit current of the ZW, as measured by the standard method. The resistances in the circuit and the wiring out and back to and through the two blocks, thence through the shorting locomotive roller pair, will reduce this somewhat, as will the operating temp reached in normal ops.
A general agreement seems to be this is 45 amps or so, counting only the carbon rollers and the inductive impedance caused by the reduction in power factor with overcurrent. This last is deliberate in that the contact coil is not wound over the primary coil excepting the fixed six volts @0-6v. That coil is wound with round #14, while the contact coil is wound with square #14 (=#13 in area). So there are a bunch of small uncertainties which favor measurement over calculation. Normal output is 6-20v.
It is worth considering that in normal ops, the carbon roller will alternately sit on top of one turn, or bridge one turn. Since the square wire has rounded corners, bridging is more likely. So, most (2/3's?) of the time, 45 amps (maybe 60 amps as the leakage reactance--I made it 0.414 per unit at a 45-degree lagging phase shift for the full 42-turn contact coil--for one turn would only be [41.4%/42 turns] one percent impedance added to the wire resistance. This would be versus 1.414 for the bolted-short, or [1.4 x 45amp bolted-short, =45+18amps] or 63 amps... more or less 60 amps, driven by [42 turns/14v on then-115v supply] 1/3 volt for the one turn.
So, the bridging watts for each active and bridging roller may be as much as [60A x 1/3 v] 20 watts. Well, so that is why this transformer tended to run hot, I had never considered the carbon roller issue so easily calculated... 
The roller resistance is about twice that of a single turn when bridging [no calculation, just obvious by inspection, as we say when we get tired of calculating]. Of course, if the handles are moderately active, this heating may only be 5w at the shorted loop, and 10w at the carbon roller, 2/3 duty cycle assumed.
You'll probably notice a lot of round numbers in the figuring above. These ZW's were designed in the age of the slide rule. "1.414" is also a round number for electrical work, as it is the square root of 2 and the ratio of peak to RMS average voltage of the AC sine wave. So the designer pushes his work in the direction of round numbers, to make his heating study easier. So, to reverse engineer the old stuff, you look for round numbers.
So I'd say if you don't stop the engine rollers across the voltage change points, you should not have too much trouble with the double rollers in one steel frame; with separated rollers you'll want to add some more wire to connect them to each other. Take your ZW, and connect it to the track with two lockons on each output with #18 wire-- take each of the two wires per post and break the insulation at the center, push it back a little so each wire can looped over its post, ends stripped (#18 stranded is about the biggest that can be clipped into a lockon).
With some added terminal strips and spade crimp-on wire terminations, these feeds can be divided two ways, one to run thru magnetic breakers (7A, perhaps) to the two blocks themselves. The other can be run through say 10-amp (or even 15 if needed) thermal breakers, and connected to a single isolated section of 3d rail at one side of the voltage change insulating pin, and similarly on the other side with the other voltage. If you are running electronic locomotives, this will minimize their exposure to slow breakers. Run a common return with each hot feeder to avoid the added inductance of large, open wiring paths delaying the breakers.
This arrangement gives flexibility to 0.33v for different trains, but not the simplicity of the diode strings. Note that the UL697 does not forbid the paralleling of outputs, only that such should be automatically tripped after not longer than 60 seconds. Although that now goes back a while, since I looked at it. I'd recommend staying well below that figure. I've assumed avoiding accessory loads on a ZW used in this fashion. You might also want only manual reset on the thermal breakers.
--Frank
nickaix posted:gunrunnerjohn posted:ADCX Rob posted:These methods, used for decades+, cause large (30+ amps at 6-7 volts difference on a ZW) fault currents - direct short circuits - across the transformer windings with absolutely no internal circuit protection when the blocks are bridged by center rail rollers of locomotives & rolling stock.The use of the diode array or a big Lionel type rheostat eliminates this problem.
This deserved to be repeated! This is a VERY BAD IDEA!
I believe you, but how is it that people have gotten away with it for decades?PEOPLE PUT PENNIES IN FUSE BOXES FOR DECADES IT WORKED WELL A LOT OF TIMES, A ONE CENT FUSE
DALE H
USING 3 TANSFORMERS SET AT 3 DIFFERENT VOLTAGES . T1 IS SET AT FLAT SURFACE VOLTAGE T2 IS SET AT UPHILL VOLTAGE. HOOK A SPDT RELAY USING TH INSULatTED RAIL COIL ACTIVATED BY DOWNHILL LOCATION. SEPARATE TRANSFORMERS USING3 T2 TO NC RELAY CON TACT. T 1 TO COMMON T3 TO NO CONTACT contact goes to track. center rail. No MATTER WHAT STATE THE RELAY IS IN THE POLES ARE NOT CONNECTED. A train occupying the downhill block will energize the coil connecting T3 to trackhttp://www.jcstudiosinc.com/RunningMultipleTrainsOnSameTrack
Wow, my brain is starting to hurt. Would controlling two or more trains via insulated track sections cause the same issues as have been discussed in this thread so far ?
I once set up a layout where two trains were running on the same track. The outside rails were insulated in a short section of track so that the train would stop there. When the second train hit another section of track that had a jumper to the insulated section, it energized the "stop" section. Very simple and foolproof, to me anyway.
Dan Padova posted:Wow, my brain is starting to hurt. Would controlling two or more trains via insulated track sections cause the same issues as have been discussed in this thread so far ?
I once set up a layout where two trains were running on the same track. The outside rails were insulated in a short section of track so that the train would stop there. When the second train hit another section of track that had a jumper to the insulated section, it energized the "stop" section. Very simple and foolproof, to me anyway.
Dan Padova posted:Wow, my brain is starting to hurt. Would controlling two or more trains via insulated track sections cause the same issues as have been discussed in this thread so far ?
I once set up a layout where two trains were running on the same track. The outside rails were insulated in a short section of track so that the train would stop there. When the second train hit another section of track that had a jumper to the insulated section, it energized the "stop" section. Very simple and foolproof, to me anyway.
Dan there is no insulated center rail thus no roller jumping
All the outside rails do is work the relay coils to provide train position logic. I"I made one up for a guy with a Helix and it worked OK for him
Two or more trains can be done easily with relays
Dale H
Here is a diagram a fellow member sent me a few years back. I like the "compactness" of bridge rectifiers over separate diodes.
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If I read this schematic correctly, the outputs of the bridge rectifiers are shorted !??
Gary Liebisch posted:If I read this schematic correctly, the outputs of the bridge rectifiers are shorted !??
They're only "shorted" if you are trying to rectify AC to DC. In this scenario, they are being "reconfigured" to provide controlled voltage drops.
Running up to seven motors at once in SF A-B-B-As and 12-16 lighted passenger cars as a norm, there was two ZWs per block, and I wonder what Gramps old layout would have read? Lol. No wonder he had those rules to be closely followed.
I just carried on following them on my own.
I never stop at the block junctions, and apparently luckily never ran my dual roller lighted passenger cars across them. Especially the plastic ones.
The following is my ceiling layout, I only run freight on it now, but that's been luck, now a rule.
I use a prewar Z, and one side of a KW. 2 loops, with a shared ground level mainline. 14 and 16 gauge wire, with 16g soldered to the track most spot, a few 18s to lock ons for crummy pin connection repairs, common feed bus is side by side and equal weight. The Z trips it's "newer" ZW type breaker in about 3 seconds or better, the KW about 4. I test once a year in Jan.
Ground level, the kw loop, is two blocks; the KW #1 and Z block #1. The Z block #1 is the shared track, kw loop with the graded loop. Both Z#1 & kw#1 set to about 10-11v average.
Yep, phased.
Z loop is 4 blocks; #1 shared level main, the rise on #2, hi-level #3, & drop grade is #4. The engine is dedicated to that graded line, a tmcc E-33 Virginan rectifier, normally a coal drag; naturally.
I don't have heat issues on track nor either transformer, etc. Z block #1 volt level is 11-12v,#2 the rise at 14-16v, #3 on top, up high, is 12-13v, the downhill 7v.
The downhill block and a section of the KW block are are relay & pressure switch controlled with diode voltage drops to slow trains to a near stop, but not enough for the tmcc or e-unit cycle to drop out. The drop is active if the shared main is not clear.
So you turn on the power strip with 8a breaker and it almost runs itself*, all Z voltages are preset. If I run anything different, it's on ground level loop and I can vary that speed on 3/4 of the loop with the KW if I want or need to.
* The KW block needs a 100% voltage drop section to be totally hands free. As is, only the KW ever needs adjusting, and usually only slight, about every 10 loops. Well matched speed, it can go about an hour then needs a quick boost, or throttle back to reposition the timing of the gap between trains.
My isolated lighting on kw handle #2, along with the luggage station. My auto turnouts on Z constant voltage with the center rail of the deviation taped off so there is no bridge on long arm rollers. It takes a bit of speed, no super slow creeping into the turnouts for the kw loop. You really can't creep into the 0-27 turnouts anyhow , so a blink of hesitation is no big deal.
My whole point in this is just to show on the down hill side your voltage is going to be very low. Likely as low as you can get without the e unit or boards dropping out. Stalling on the downgrade is tough. At ground level you need normal voltage, the rise needs plenty, and the hi-level more than the ground level, because cars are still on the grade. Finding exactly where to add block junctions will take some finagling too. So unless your laying track with a definite acme/apex and a valley, you will likely need all 4 ZW channels for smooth running and yelling "look ma, no hands" .
On the center rail tape: some locos would stop dead when they bridged, others didn't care. It didn't matter PW or tmcc, long roller arm or short, pulmor or can motor. But with tape, the all make it.
A bridge rectifier encases 4 diodes. By connecting the +DC and -DC leads (right side of diagram) , you get a 1.2 (maybe 1.4) voltage drop when you connect the AC leads in series to the load (left side of diagram). One of my PW transformers is too powerful for one of my engines, so I use a BR between the transformer and the track. The BR is rated at 6 amps.
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I also used these in series with the motor on my Lionel 2055 and an AF 312 engine. That way the smoke unit produces more smoke without having to run the engine at high speeds.
I insulated the downward section of the grade and use either 1 or 2 one ohm 5W power resistors to feed the center rail. This does hinder the action of the horn and/or smoke units a but but it does create a graceful decline speed.
Back in the really old days when they used wet cell batteries to run trains they told you to put light bulbs in the circuit. Would that work today ??
Hm, I'd be curious to know that also.
I'd also like to know about phasing transformers.
