Hi all
Quite some time ago I saw a model press article on a one way turning triangle the catch was you could only traverse it in one way.
I now cannot find the article
It was done I believe using diodes with no switching has any one got any idea how this was or could be achieved.
The layout I wish to set this up on is a standard DC job
The traverse one way round is NOT an issue as I just want to turn loco's on the triangle.
and if I can avoid switching the track the way a triangle would normally be done.
regards John
John,
I'll have to admit,,I never saw, or heard of what you are talking about,,,,I've only seen a wye turn around,with three wye turnouts,,that can have three entrance's and three exits...and that is a triangle..
Cheers,
Frank
Like Frank, the wye is the common way to accomplish this.
I am not familiar with the article you referred to, but I did find the following discussion of triangles, reverse loops, and diodes.
http://rail.felgall.com/rlt.htm
Rich
Alton Junction
It is far simpler than that. You need no fancy work to work this without special electronics. When the west switch is aligned for the turning spur, the spur only gets its power from the turnout contacts on the west. When alligned for the east switch the spur only gets its power from the east contacts. If both are aligned for the mane lion, there is no power to the tail.
Or is the LION missing something? Him would hate to miss his lunch.
ROAR
The Route of the Broadway Lion The Largest Subway Layout in North Dakota.
Here there be cats. LIONS with CAMERAS
I'm trying to think how you would do it with diodes, and can;t visualize that immediately. Using switch machine contacts, it would be pretty easy. Using 3 Tortoise machines you could put the whole thing into operation with one toggle switch which would line all 3 turnouts at once as well as switcht he polarity in the rails.
If it can be done with diodes, then you could use spring switches for all 3, and never do anything other than change the direction of the train to back into the wye and then head out in the opposite direction, but indeed it would be restricted to turning just one way, through trains going say clockwise would go through but a train running counter-clockwise would enter the wye.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Is the original question about how to do this without manually dealing with electrical switching, or with track switching? My immediate thought was to do this using slip swtiches, so the operator can ignore the positions of the turnouts.
For power control, use a DPDT latching relay. At the end of each of the stubs, install a dead section of rail, and wire it to throw the relay when powered. The engine will get to that section, the relay reverses power, and the engine leaves in the opposite direction. Because it got there using a slip-switch, it will take the opposite path when it goes back through the turnout.
It takes an iron man to play with a toy iron horse.
Hi Mister Beasley
The desire is to get rid of most if not all of the electrical switching as stated I have seen an article on using diodes to do it.
Which according to the article I now can't find (far to many mag's kept for that) means that you can only traverse the triangle to turn anything one way, it literally won't work in the other direction.
You have to go left side right side base every time you turn a loco.
biro springs can take care of the point setting area.
Bi directional running around the wye / triangle is not required as its sole function is to turn loco's around
I have one that is too big for any turntable that I can easily obtain in Aus.
Also three switches and a couple of extra lengths of flex track is cheaper than any turn table that is worth having.
For once the real estate taken by a turning triangle is not a problem.
John Busby Quite some time ago I saw a model press article on a one way turning triangle the catch was you could only traverse it in one way. It was done I believe using diodes with no switching has any one got any idea how this was or could be achieved. The layout I wish to set this up on is a standard DC job
DC Power is obviously applied to the straight track running along the bottom. The black rectangles are insulated rail joiners or gaps. This assumes insulated frog turnouts. If you trace it out carefully you will see a deadhead circuit, but I think the electricity will prefer taking the diode back to the opposite polarity.
It won;t short, but it won;t reverse the train, either. If you come in from the left side, let's say the top rail of the bottom section is +, and the bottom rail is - (by NMRA standards that means the loco should head to the left off the drawing, but we'll go with that because of the way you have the diodes). So the left rail is +, the right rail is -, all the way intot he tail at the top. OK, clear the turnout, throw it, or assume it's a spring switch. You need to reverse the polarity on the rails, so now the bottom rail is +, the top rail of the straight across part is -. Again it won;t short, the diodes block the short, BUT the left rail of the tail is still +, and the right rail is -, to the loco keeps going off the top rather then coming down into the right hand leg.
You're on the right track though. You can do it on a reverse loop using a bridge rectifier. A wye is a bit more complicated.
rrinker It won;t short, but it won;t reverse the train, either.
John Busby Quite some time ago I saw a model press article on a one way turning triangle the catch was you could only traverse it in one way.
One of the legs of the wye is set up to be a one-way track. No matter which way the direction of the powerpack is set, the track will always move the locomotive toward the exit. So the trick is while the locomotive is on the one way section of track, the direction switch has to be changed to align the poliarity of the "main" with the new direction of the loco/train.
From "start" the train enters the wye into the first stub to position 1. Change direction and reverse through the 2nd leg to the 2nd stub (position 2). Change direction and head through the 3rd leg now in the opposite direction. When the loco is in position #3 change the direction switch one more time, so when it gets to position #4 the mainline polarity is reversed taking the train back down the main.
TA DA!
I don't understand all of the complexity here with diodes and stuff.
Is this any different than a simple wye wired as a reversing section?
This is how I used to wire my DC wye sections. Works equally as well with DCC ! All you need is a set of DPDT contacts attached to the turnout. You have to throw the turnout anyway. You don't even have to touch the direction switch on your throttle - by throwing the turnout, you are changing the polarity, and hence the direction ....
It's also bi-directional. Just align the switch on the tail track to match your inbound move.
Mark.
¡ uʍop ǝpısdn sı ǝɹnʇɐuƃıs ʎɯ 'dlǝɥ
I also used this on my original DC layout (this one won't work for DCC). The bridge rectifier maintains the same voltage orientation within the loop no matter which way the direction switch on the throttle is thrown.
As you head towards the loop align the turnout for the proper route of travel - this is a uni-lateral set-up, meaning you can only go through the loop in one direction. Once you are in the loop, throw your direction switch on your throttle. This changes the polarity on the main, but your engine continues to move in the same direction. Polarity now matches so you can exit ....
Maybe this will trigger some thoughts as to how to use this in a wye set-up. (?) A bridge rectifier is nothing more than four diodes in an array.
richhotrain I don't understand all of the complexity here with diodes and stuff. Is this any different than a simple wye wired as a reversing section?
Texas Zepher richhotrain I don't understand all of the complexity here with diodes and stuff. Is this any different than a simple wye wired as a reversing section? It is what the original poster asked for. Everyone knows the normal way to use a DPDT switch.
Yeah, that's true.
TZ, I wasn't knocking your solution. I just began to wonder what, if anything, was wrong with the more conventional method.
Hi Richotrain
The problem is the normal conventional switching, I am trying to do away with as much switching as possible replacing it with simple electronics cct's or simple mechanical means
I will be starting construction very shortly on a very large layout (the one you only get to build once in a life time) in fact it will more than probably be my last one.
Because of its size I need to do away with as many switches as possible without going digital.
Oh and I can get diodes that in model rail use barring direct hit lightning strike will out live me at $0.00
I don't see putting a few diodes across IRJ's as being complicated.
What I need to know is what the pattern I need to use is and where the track feeds need to be, so the only switch's needed to turn the loco are found on the train controller.
That is four switches that don't need to be purchased, with three being replaced with springs and one with diodes
I need to do it all with out going down the "outlandishly expensive and incomprehensible to me"(my opinion that won't change) DCC path.
Note I have 48 years worth of multi national Analogue trains (a lot) so change is not a financially viable proposition at this late stage in life.
Mark R.Maybe this will trigger some thoughts as to how to use this in a wye set-up. (?) A bridge rectifier is nothing more than four diodes in an array.
I think if you take TZ's first diagram, with the 4 diodes, adn replaced it with a bridge rectifier, with the DC side connected to the lower part and the AC connection to the top track (or whichever one is the tail track), and the power is fed into the trail track side (the AC terminals of the rectifier) it would work, flipping the direction switch would change the direction, assuming the train comes in from the right, goes up to the top, reverses back through the left side, the across to the right back out the same track it came in on.
Interfacing this to the rest of the layout might be more difficult. But all three turnouts could have spring points so no point motors would be required, just flip the direction switch on the power pack at each point of the wye.
Randy - I've drawn out what you are describing several times and cannot see that it would work.
If the horizontal section at the bottom was wired through the rectifier, you would permanently have positive on the bottom rail and negative on the top to permit the engine to leave to the right.
For the engine to approach from the left, the top rail would be + and the bottom -. The engine proceeds up to the top tail track and the direction changes giving the initial approach top rail - and bottom rail +. Upon reaching the left tail track, the direction is again changed giving the original approach track top rail + and bottom rail -.
The polarity where the engine is on the left tail track now does match the polarity of the bottom track wired through the rectifier, but it does not match that of the original entrance track to be used now as the exit.
You would have to stop the engine in the section controlled by the rectifier and throw the reverse switch one more time, then proceed to leave. If that bottom section were long enough - you COULD throw your reverse switch while the train continued to move as long as the engine itself was fully within that controlled section as it would be unaffected at that moment you change the direction switch.
So close, but not quite. I believe the OP doesn't want the added monitoring of having to manually control within a specific section of track. (?)
Yup, missed that last change of direction, not going to work. It would need two direction switches.
I'm beginning to think a Wye is not going to work without some sort of relay or switch. Relays are cheap, with a DC coil and a diode to activate it only when the power pack is at one polarity, and DPDT contacts, it could provide the track polarity reversal without an extra DPDT toggle. If the OP wants it more automatic than driving the train to the bumper and flipping the reverse switch on the power pack, he's out of luck. There has to be SOME intervention - or a whole lot of complicated beam break sensors on each leg to reverse the train when it clears each turnout, at the very least. Even in DCC, making a train reverse itself with no operator interaction requires a lot of extra 'stuff' besides the polarity reverser.
Even the loop with a spring switch and rectifier isn't hands off - you still have to change the direction switch on the power pack in order to exit the loop. Unless you put in a sensor to operate a relay.