lowering voltage on a down slope

Jim, The bulbs will sort of work, but for the price and better function, the diode is the best choice. The resistors next on function, the higher watt ceramic block type can get a bit pricey.

Dan, go to YouTube and search" Lionel + phasing, +transformers" Mike R. did a very good video on phasing years ago. It is entertaining for a tutorial, and it's very informative for a "beginner", including sine wave diagrams drawn and explained. It applies to new and old units alike, and I was doing it as a kid. It's really easy to do and pretty easy to understand. Great info to spread some very important saftey with. The kind of thing only one in a million would debate over.

Robs warning shouldn't be taken lightly really. Despite my actions, my eyes are peeled like a race car driver exceeding 100mph.

Is the electrical problem created when two pickup rollers are in contact with two separate voltage blocks ??

This thread got me thinking about this subject again.  I'm now confused as to why you wouldn't create a large current flow between two blocks when bridged by a pickup or pickups, even if both are fed from the same transformer output with one being at a lower potential via diodes, resistors, or the like.  If you have two places at different potentials, current will flow from the higher potential to the lower one, constrained by the resistance between the two points and proportional in power to the difference in voltages.  Given that the resistance of the pickup is essentially zero, it would seem that current would flow freely via the pickup between the two blocks.  Wouldn't this be a "bad thing" for the pickup (or the wiring between two separate pickups)?

In a fairly extreme example of up and down grade speed control, there is the 2014 Henning's Trains Christmas Tree.  Bill used two transformers, one for going up and the other for coming down.

F Maguire posted:

 

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.

 

Interesting analysis - as I'd considered this before but wasn't thinking it all the way through.  Maybe I'm learning something about variable transformers here: is the bridging of adjacent windings by a roller the cause of significant heat and power capacity loss via this type of localized short condition?

With the E unit turned off, why wouldn't a dead section between blocks so the pick ups wouldn't bridge  it work ??   The dead spot wouldn't have to be long and it  could coast down hill through the dead spot ??

I have done the bridge rectifiers technique that Dearborn Dave recommended on another forum with a dial to increase and decrease the number of bridge rectifiers to different blocks and it works like a champ. 

Jim, it would work for some. I forgot to consider or mention I mostly just lockout my e units anymore. Thats what the tape I mentioned does.

Ive also zip tied a roller up using only a single. The small flange on an isolation pin lifts the roller up for a split second and no bridge occurs. But you still need the speed for turnouts, and moving an engine to another layout you have to snip it.  Some locos you cant tie one up.  Tape covers the issue for anything run on that line.

(coasting downhill.. Lol. I have something to add to your "X" thread soon)

jim pastorius posted:

Is the electrical problem created when two pickup rollers are in contact with two separate voltage blocks ??

exactly the proper question to ask - Matthew B. had this problem on a double spiral layout with a long Polar Express train. It took some relay controls in combination with the diode droppers to prevent electrical problems. The controls were designed and created by the venerable Dale H. for Matthew. Wtach behind the tree at 00:48. You'll see the train climbing at a fast rate to make the spiral up. Then behind the tree, you can observe the engine slow while the passenger cars are still on the climb voltage.

Another way to skin this cat would be to put a DC motor as a generator in a box car, hook the wheels to the generator  with a resistor grid to burn off the electricity. A dynamic brake car !!

All those guys who insist on getting as close as possible to "prototypical" operation need to understand that keeping one's hand on the throttle, and regulating the train's speed, UP AND DOWN HILL, in real time is the ultimate prototypical method. And walk (with your itty bitty fingers) between the cars at any point along the ROW to uncouple, not press an orange button miles away. The dispatcher/tower man can choose the routes and set the signals by remote control...that's acceptable on my RR.