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Post by boxcarwilly on Oct 22, 2016 12:36:58 GMT -5
On the next phase of my layout I am going to have to install a counterbalance lift bridge to accommodate a walkway between phase 1 and phase 2. Since this new addition is going to be placed against a wall in my rec. room, there will be a 3 foot gap between it and the rest of the layout. This will be the walkway into the middle of my layout. Now I have the problem of passing power from my main control panel on phase 1 on the other side of the room, to phase 2. I have been over this several times and considered different aspects of this including running cables from the last module of my original layout, down and across the floor to the new layout. While this might seem like the easiest way to accomplish what I need to do, it isn't very practical solution. Here's the thing. On the new layout, much of it will be a yard, a station and the reverse loop. My vision is to have the main line which will be doubled through the station, the rip line and reverse loop powered from the main control panel across the room. The yard, and all the industrial sidings will be powered independently with it's own power source which will require a second operator. I'm throwing this out to everyone here, is there a more practical way to transfer the power across this gap through the bridge, without running cable across the floor between the layouts? Bare in mind, the bridge will be tilting up and back toward the new phase.
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Post by Rob Albritton on Oct 22, 2016 13:08:16 GMT -5
I'm throwing this out to everyone here, is there a more practical way to transfer the power across this gap through the bridge, without running cable across the floor between the layouts? Run it across the floor. That is by far the easiest, fastest, most practical and reliable solution. |
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Post by christoff on Oct 22, 2016 15:52:05 GMT -5
All tho I do agree with rob on the power through the floor the problem I have with it is that that leaves big room for error. If the power was on the bridge then power to phase 2 would be cut when the bridge is up. If the power goes through the floor and the bridge is up and Boxcarwilly or myself arnt paying attention we will have a major train derailment with a 3 foot drop
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Post by boxcarwilly on Oct 23, 2016 9:58:56 GMT -5
You're quire right Chris, and there would be power to the bridge, but it would be coming from the new layout and not the old. As we previously discussed, to prevent what you indicate, there would have to be some sort of power shut off when the bridge is up so derailments wouldn't occur. I don't know how we would accomplish that. I was considering just having the main power run to the end of the original layout and then install some contact points both there and on the bottom edge of the bridge so that when the bridge was down, the power would be continuous to the new layout, but when the bridge was up, the power would automatically be cut off. Since the yard would be powered independently, there would be no effect on power. It's the through and rip lines that would be affected as well as the signals and reverse loop.
Rob, I agree that running the power across the floor would be the most practical, the problem is protecting the cables from being kicked or stepped on since it will be a walkway and it falls right on a carpeted section of my rec. room.
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Post by markm on Oct 23, 2016 10:28:17 GMT -5
I have some thoughts and a couple of questions.
Both modules should have an absolute block for the bridge approach, at least as long as your longest consist (220mm?), that is controlled by the position of the bridge. This way a train can't go over the edge. One other feature of having the isolated track on #2 is that you could switch between the mainline and yard throttles: build a train in the yard with throttle 2, spot it on the mainline and hand off to throttle 1. You might want to consider occupancy detection on the span to lock out raising it.
I'm not sure I really understand your goals for this bridge, beyond getting to the other side. Is this a bench work bridge or a scale bridge? Is this going to be an operating part of the scenery or just a way to get back and forth? Do you want to operate the mainline from throttle 1 on #2 when the bridge is up? How do you want to control bridge operation?
A scale bridge would be really long and IMO a challenge to line up and maintain. Prototypes would probably use a lift bridge. Could that be work for you?
From what you've posted, I think I'd agree to run the power along the floor. Use a cable runner to hold the wiring.
Mark
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Post by Rob Albritton on Oct 23, 2016 14:11:54 GMT -5
As we previously discussed, to prevent what you indicate, there would have to be some sort of power shut off when the bridge is up so derailments wouldn't occur. I don't know how we would accomplish that. I was considering just having the main power run to the end of the original layout and then install some contact points both there and on the bottom edge of the bridge so that when the bridge was down, the power would be continuous to the new layout, but when the bridge was up, the power would automatically be cut off. Suggest a contact switch (micro switch) on the bridge, so when the bridge is down, the switch makes contact - that could then power some relays that would open and close as many power lines as you like. It just avoids having to perfectly match up power connectors on the bridge. Getting the track right is going to be hard enough. Best, -Rob(A) |
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Post by boxcarwilly on Oct 23, 2016 15:57:19 GMT -5
OK, let me answer these questions this way and I hope I don't confuse anyone in the process.
Mark:
The bridge will be an operating part of the entire layout as well as a walk through but whether or now the main line will be powered when the bridge is up, is still under discussion. Either way, the bridge track will be powered from a feeder from the new layout which will be fed from the main control panel. Just how it will be lifted is still a question that Chris and I are struggling with. I was originally thinking of fixing para cord to the free end of the bridge and with the aid of pulleys, operating it from the main control panel on the other side of the room which would mean the cord would have to go up to the ceiling, across the room and down again. A total distance of 31 ft. Chris, has suggested some kind of electric lifting device probably with a worm gear to lift the bridge and perhaps a remote control apparatus from the main panel. The bridge by the way will be hinged at the end of the new layout.
The main line which will be doubled to accommodate a double sided platform with the station on one side, The rip track, and the reverse loop which will now be located at the farthest end of the layout, will all be powered from the main control panel. The yard itself, and all industrial and other sidings will be powered independently as previous stated so they will be isolated from the main. I do however, see your point about making the rip track part of the yard power. Makes sense.
As for blocking the main before it crosses the bridge, I thought of that but I'm not sure how it would work and there is very little room for such a block to be placed. It's difficult to imagine without pictures I know and if I could do a Power Point presentation, I would.
The bridge itself will span a 3 ft. gap and is made up of 4x8" Rohukan steel bridges glued end to end. What I'm still trying to figure out is how to keep them rigid enough to withstand the strain of being lifted from one end and also how to secure the track inside so it doesn't shift side to side or front to back. There are holes in the beams of the bridge sections which line up with either Marklin or Rohukan track, but the problem is, if I do it that way, then the track will be below the walkways on both sides and I don't think it's supposed to be that way according to the prototypes I seen.
Rob,
Going across the bridge will only be one line, however, there are 4 signals, and two turnouts that will be controlled from the main control panel across the room. I like the idea of the micro switch and it could power those specific areas on the new layout. As to matching up track and so on, I think that if I build in some kind of double sided guide on the old layout right where the bridge will be meeting the track, with very fine tolerances, theoretically the bridge, and track should line up perfectly each time it's lowered. If I do it this way, then if I have contacts on the bottom of the bridge, they should line up with those on the module across the gap. The trick is going to be keeping the bridge rigid over the 3 ft. span and yet make it easy to lift from the hinged end and not bind on the trailing track.
The ideal solution would be to keep the power running on both layouts even when the bridge was up and that way, trains on the main line on the new layout could still be controlled from the main panel on the old layout.
I have been researching this for several months and have found lots of examples of tilt type bridges on model railroads of different scales, but none of them have gone into detail about power, bridge and track alignment and lifting devices. It was hard enough finding pictures of how the tracks at the hinged end line up without binding when the bridge is up.
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Post by markm on Oct 24, 2016 21:16:51 GMT -5
Willy, Now that I understand your project, I have so many ideas for you I don't know where to start. Mechanical: Won't you really need 5x8" bridges (36" for the span + 2" each for landing and takeoff)? I think ultimately you'll find that you need to mount the bridges to a piece of aluminum stock, say 1/4" x 1/8", to keep things rigid enough. Since you want to walkways to be at the same level as the rail, you could add an appropriate styrene strip to the roadbed to get it to the right height and to stiffen the assembly. A bit of a wild thought would be to also add a deck above the tracks. We have several such bridges here in CA: en.wikipedia.org/wiki/I_Street_BridgeDon't know if it would work with the Rokuhan bridges. On the landing side I think you'll need a slot for the bridge to sit in and an alignment pin: basically a pencil shaped pin that slips into a funnel shaped hole. To me the biggest alignment issue is the track spacing between the bridge and module 1. My thinking is to use the Märklin or Rokuhan adjustable track piece, one end fixed to the module and the other end attached to a block with the alignment socket that is allowed to move longitudinally. This way the bridge will pull/push the track into position. For lifting the bridge you could use a servo (requires a non-trivial controller) or a gear box and motor (requires limit switches). I think you'll find what you'd need at a robotics hardware supplier. Electrical: I've done this quick sketch of what we have talked about so far but for some reason the 100KB jpeg doesn't want to upload. I'll try again later. Some additional electrical thoughts until then. As I understand bridges and you signal comments, the bridge approaches should be stop and proceed on clearance. So it would seem that even if the bridge is down, you would want control at the master control. I think you might also want to add flashing red LEDs to the bridge: it's a hazard to navigation at scale and prototype. Something to think about, Mark |
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Post by boxcarwilly on Oct 25, 2016 13:24:49 GMT -5
Thanks so much Mark for this input. Much of what you talk about has already been considered. One problem that I face is the free end of the bridge will only have an approach track of less then 4 inches due to the proximity of a tunnel coming out of the mountain. As for the hinged end, I don't really want to put in a pit of any kind if I can avoid it. Any Prototype that I've seen doesn't show such a thing, but they do show the bridge track raising up and back over the approach track. As for the span length, I can shorten the gap to accommodate the 32" combined length of the bridge with an additional 1 inch on both ends. If need be, I have a couple of 6" girder mounted tracks that I can add to each end but I really don't want to if I can avoid it. As for lifting the bridge, I want to stick to the KISS principal. The less complicated the better. If that means cable and pulleys operated from across the room, so be it. I know it will spoil the aesthetics but it may be necessary especially where costs are involved.
In examining my original design for the new layout, I think I'm going to have to make a longer lead in track which will power the line through the station and the reverse loop at the far end powered from the master control panel and make the rip track part of the yard power. Then as you said, trains can be broken down and assembled on this track without interfering with the main line. I just need to move everything down about 2 feet and change the configuration of part of the yard. Adding flashing lights to the bridge was an option, but I'm looking at going with a scaled down version of the flashing lights that you'd find at a grade crossing if I can find such a thing. They'd be mounted to the wall above the bridge.
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Post by markm on Oct 26, 2016 7:49:34 GMT -5
I don't know if cables and pulleys are the simplest route but you know your layout and space much better than I. Have you considered something like the Viessman 4551 slow motion solenoid?
You might want to reconsider the lights on the bridge. With the addition of a relay and a couple of batteries they might come in real handy in if a power failure catches you on the wrong side of the bridge.
Hope you'll keep us informed of the progress and show us the final result. I don't recall hearing of a bridge project quite as ambitious as yours.
Mark
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Post by boxcarwilly on Oct 26, 2016 10:35:26 GMT -5
Mark:
Don't know anything about the solenoid but will investigate. In as far as a power failure, if that were too happen, this bridge will be far enough off the floor that one could easily crawl under it on all 4's with no difficulty at all.
Thanks for all the suggestions. Much to digest and consider.
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Post by BAZman on Oct 26, 2016 14:00:51 GMT -5
I use an Aluminum square box "tube" for one single track 3' span and 3" wide U-channel for the double track span (sides pointed down). I use a 'funnel' plate, like mark describes, so the side walls fall in place, self centering.
Lifting and lowering manually is easy. Motorizing it is more complicated. If a counter balance is extended from under the bridge to under the layout, the effort would be minimal. You can buy 12 volt gear motors surplus (www.mpja.com) to pull a cord up and down off of the end of the counterbalance. Microswitches stop the motor.
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Post by boxcarwilly on Oct 27, 2016 11:14:52 GMT -5
Thanks Jeff. Another great idea. The square aluminum tube was something I considered but I'm looking for something in a fibreglass so that it can be seen through something like a towel rod. Then I could drill holes in it to match the holes already in the bridge deck and screw the section right to the rod. Then I was thinking adding to horizontal Plastistrut I beams to build up the track to the level of the walkways. Maybe a third down the middle. Then using flex track with a power feed somewhere in the middle and either screwing or gluing it to the beams. I'm am considering doing away with the cord and pulleys and just lifting the bridge manually. It will still have to rigid enough so as not to be misaligned every time it is lifted and lowered. Guides at the free end should solve that problem.
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Post by boxcarwilly on Dec 6, 2016 12:10:53 GMT -5
Well I've completed my counterbalance lift bridge and although it didn't come out the way I had intended, it works! I had a lot of doubts in attacking this project, but to my surprise I managed to come up with a reasonable facsimile of the concept. I had a lot of problems with the placement of the hinges and what made it even more difficult is the bridge actually lifts on a 25 degree angle and this is because of the placement of the two phases of my layout. There was no other way to make it work. I had wanted to make it in such a way that the hinged portion of the track would come up and over the approach track, but after much experimentation, I found that I had to make a pit for the overhanging bridge track to go down into when the bridge was lifted. Keeping them perfectly alignment at both ends keeping the bridge rigid and supplying power to the bridge track where challenges on their own but I overcame them and the bloody thing actually works. I'm using string to manually lift and hold up the bridge now, and I'm still trying to decide how I'm going to accomplish this part when I'm running my trains alone and someone wants to pass through the walkway that the bridge spans. I'll add some pictures at some point. Now with that part done, I can work full speed at the new modules of which there will be 4. These will house my yard and some industrial sidings. Lots of work to do.
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