Five Bad Layout Ideas

[Frank53]

so if I understand this correctly, the "feeder rail" is the center rail?

You isolate the center rail and feed power to that section through a resistor? The outer rail feed stays the same?

[lionelsoni]

That is the way it works.  But Daan's terminology is a little strange to me.  The term "feeder" usually refers to the wires used to connect the track to the transformer, particularly when connected to a part of the track far from the transformer.  I have never seen the word "variator".  I think he means "rheostat", which is just a variable resistor.  Lionel made 5-ohm rheostats, which are easy to find and cheap, but I would not describe them as triangular.

A modern alternative to the rheostat is a string of bridge-rectifier modules, which do not suffer from the voltage variation with load that Daan correctly described for resistors.  These have been discussed extensively recently:

http://www.trains.com/trccs/forums/1151451/ShowPost.aspx

Using a Variac or multiple transformer outputs for this purpose is a bad idea and can be a fire danger.

[Frank53]

Bob:

Your depth of knowledge in this area is most impressive, particularly to a wiring dork such as myself. If there is something I know nothing about (possible exceptions being brain surgery and nuclear fission) it is wiring.

I read the thread and it might as well be in Chinese. Any chance you have the "4 Dummies" version?  

I am thinking there is a device that gets hooked up in line between the power source and the third rail. Is that basically true? What about the feed to the outer rail?

What I want to do is be able to have the power to the track be high enough so the train will ascend without straining and after it turns around and comes back it will descend the grade slower without throttle jockeying.

[lionelsoni]

You're on the right track, so to speak, Frank.  It is just as you are imagining:  The outside rails are continuous around the layout.  Only the center rail is isolated where you want a lower speed.  The rectifier modules go in series between that center rail and the same transformer output that powers the rest of the track.  You use as many modules as you need to get the voltage reduction, and therefore the speed reduction, that you want.

[Odd-d]

In the halcyon days of my early Lionel days I learned that no matter how gentle I made my inclines I found that neither my 736 and 773 engines could be controlled running downhill.  Both engines would come blasting down Hell bent for leather no matter how slow I tried to run them.  If I turned it too low the train would just stop because the speed range starts at 5 or 6 volts.  So what lesson did I learn fom this?  Huh??  AVOID SLOPED TRACKS.  Perhaps nowadays with TMCC or DCS finer controls and cruise control slopes will work better downhill.  Uphill slopes of course will limit the length of the train just because your little engine will simply slip its drivers.  On my pike the lower level route does not connect to the upper level.  The lower level, the Stepford & Eastwick RY is a heavy electric commuter line running heavy MU cars, and the upper level is the busy double track oval mainline steam (no diesels allowed) railroad and a separate trolley line.  No hills wanted.  I am toying with the idea of a hilly logging line for my KLine shay.  I also have some On30 that seems to run on slopes without slipping or "cogging".  Odd-d

[Frank53]

Thanks for your advice Bob.

[daan]

Apart from the weird terminoligy I seem to use it's as you figured it out, frank. There is one problem with it. If you feed the center rail through a resistor, the train will descend slower, but also uphill it will get lower voltage. You could use a 2 position relais for it and wire it to your switchmachines, that way that the resistor is switched on when the train goes downhill and off when it goes uphill (combined by switch straight = no resistor, switch turned out = resistor on.)

The problem with postwar steamers not being regulatable downhill is something purely mechanical. An AC motor has a field and a rotor coil, no magnets. In any DC canmotor the magnets "stick" to the rotor when no power is supplied, reducing it's speed. (the reason why momentum flywheels are used; they avoid abrupt stops). On AC motors whithout power or with just a little power there is absolutely NO braking force apart from the friction in the gears. Steamers used straight gears, no wormwheel combination, and straight gears have very low friction. The low friction of the gears in combination with the lack of any braking force in the motor results in postwar steamers braking loose when going downhill.

The F3's, Alco's and even the turbine have wormgears which have a lot more friction when the wheels try to drive the gears the other way round. Those can be regulated (sort of) going downhill.

 

[lionelsoni]

I find it interesting that prototype locomotives have the same behavior as the models with universal motors that Daan describes.  Their series traction motors are larger versions of the traditional toy-train motors and, like them, provide no intrinsic braking.  Unless, of course, the locomotive is equipped for dynamic braking, which requires rewiring the motors on the fly to serve as generators.

Here's the most recent topic on the subject of controlling speed uphill and down:

http://www.trains.com/trccs/forums/1151451/ShowPost.aspx