TMCC Signal Loss in Metal Bridges

On my 305 Hellgate, I put electrical tape on the bottom of the metal ties to isolate them from the bridge. This solved my loss of TMCC signal issues.

or ground the bridge.

bigdodgetrain posted:

or ground the bridge.

Steve, DO NOT follow bigdodgetrain's advice!  What you would effectively be doing is connecting the "U" post on your transformer to the ground wire in your house wiring.  The TMCC signal would be destroyed.

The metal ties on your track are in contact with the metal bridge bases, so the bridge superstructure has track common power and hence the TMCC track signal is radiating from them.  Your locomotives see track signal from below (the track) and also from above (the bridge) but can't see the other side of the signal that is radiating from your house wiring.  Insulating the ties from the bridge bases like Mike D suggests should work.  If you still have problems in the bridges after insulating the ties from the bridge bases, then you can connect an earth ground wire (from the house wiring) to the bridge superstructure and that will cure any remaining signal problems.

Bob, not sure how bigdodgetrain meant to ground the bridge, so you both may be trying to tell me the same thing, but I'm a bit thick headed on electrical issues. Insulating the ties should be no problem on the Hellsgate bridge, but the Ives bridge would be quite difficult. Are you saying to take a ground wire from a wall socket and attach it to the bridge? If so, cant it be like a 22awg wire?

thanks

Steve

I would NOT earth ground the bridge.  Bob's idea of isolating the metal ties from the bridge deck is sound advice.  He is correct by grounding the bridge (ala the ground plane solution) you are effectively connecting the track half of the signal to house ground signal.  Also if not already, power the bridge from an accessory transformer without the TMCC signal associated with it.

As others have suggested insulate the track from the metal bridge. If any part of the older tinplate track touches the bridge you lose TMCC signal. The insulating tape method works. I use that even on the newer repro Lionel Hellgate which has plastic insulators.

I found this could not be relied upon and had to cover the track ties with tape.

It's straight forward to test with a multimeter on the continuity setting. Any continuity between the track and the bridge is a bad thing. Also if you have lights in the bridge, power them from a separate transformer than the one that powers the track.

Nick

MartyE posted:

I would NOT earth ground the bridge.  Bob's idea of isolating the metal ties from the bridge deck is sound advice.  He is correct by grounding the bridge (ala the ground plane solution) you are effectively connecting the track half of the signal to house ground signal.  Also if not already, power the bridge from an accessory transformer without the TMCC signal associated with it.

I don't get it. I think we had to earth ground our Bascule bridge to prevent stalling.  Maybe I'm confusing earth ground(water pipe or green on a wall outlet) with  something else. We no longer have the bridge, a MTH big boy got stuck in the middle and tore off just about every traction tire. It didn't quite fit.

everyone has always said to ground an item when there is signal issues.

what has changed???

One technique I have tried that worked nicely with the Hellgate was running a insulated earth ground wire in between the girders on the top of the bridge roughly centred above the two tracks. In no way should any uninsulated earth ground wire touch the metal of the bridge. 

I was able to do away with this wire when I found that I had  continuity between one of the tracks and the bridge. That was killing the TMCC signal. Once that was fixed I have no signal issues with the bridge.

Nick

bigdodgetrain posted:

everyone has always said to ground an item when there is signal issues.

what has changed???

Nothing's changed, but the problem is that the track is in direct contact with the bridge here.  By grounding the bridge you are effectively placing ground to the U post on the TMCC/Legacy base, thus shorting out the signal.  You first have to insulate the bridge from the track so the bridge is not connected to the track side of the signal.  Others posting here have suggested that this alone is usually enough to fix signal issues, and grounding the bridge is then not necessary.  With the track touching the metal of the bridge, the bridge acts like a cage around the locomotive, blocking the ground-side of the signal from reaching the engine's antenna.  

JGL

JGL has it correct.  I guess I should clarify that if you first isolate the metal ties and in turn out side rails from the bridge then it would be less of an issue but I wouldn't recommend this if the bridge's metal chassis is used as the common for it's power.

Nick has it right. Using an earth ground wire will solve the problem but it should be insulated from the bridge.  The earth ground wire does not need to be bare or stripped of its insulation to function. I used a 12 gauge wire without stripping off the insulation on my post war bascule bridge to successfully restore the signal loss. I did not insulate the track ties from the bridge.

Papa Steve,,

   Black Electrical Tape the conventional ties or make custom FasTrack or RealTrax pieces for your 305 Hellgate Bridges, either way keeps the Legacy signal strong.  I plan to run the HG Bridge lights, from an old ZW, have not tested that yet.  You can run one single FasTrack line thru 305 HG Bridge and test the Legacy like I did, works perfectly.  You will need to cut custom FT pieces for running dual thru the 305 HG Bridge however.  For me a project for the next Christmas layout.

PCRR/Dave

bigdodgetrain posted:

everyone has always said to ground an item when there is signal issues.

 

what has changed???

What is changed is that folks are confusing the earth ground (the house safety ground wire that is carrying half the tmcc signal) with the common side of the track power (the outside rails which is carrying the other half of the tmcc signal). So obviously connecting them together will short out the tmcc signal.

Dealing with having the bridge connected with common can probably be solved as some have reported by stringing a (insulated from the bridge metal) "ground" wire thru the inside of the bridge over the track...or some such arrangement as that.

I solve TMCC signal loss in metal bridges problems by isolating the metal ties (a layer of carpet, cork, or other insulating material) and use plastic screws and nuts to fasten the track to the metal deck.  Search for Nylon 6/6 Pan Head Machine Screw, Black, M3-0.5 Thread Size, 42 mm Length, and matching nuts on the river site.  Running Earth ground wires as previously described is the second step.  Sometimes connecting the entire metal bridge to Earth ground is necessary but the bridges cannot be lighted or have any layout power connected.

I have a run of 9 #270 bridges on one of my modules.  The metal bridge sides do not extend above the level of the engine antennas.   I haven't insulated the ties and over the years of operating on this module in various show venues, I haven't seen a TMCC signal issue on this bridge.  I presume that the drop ceiling with Earth-grounded conduit above the module in commercial venues provides sufficient TMCC Earth ground signal reference.   However, let a metal bridge (even a signal bridge) go over the top of the locomotive and signal loss is certain.   I haven't tested how high the sides of an open top bridge can go without isolating the metal ties from the bridge but my guess is anything above the antenna (hand rails on steamers) will cause some signal loss.

Thanks to all for the input I don't have any TMCC loco's of my own to test with. I have it wired in for the other operators that come over. I will insulate the ties on the Hellgate and next time I have the gang over, we'll check it out. If it works there, I'll have to find a way to do the same to the Ives bridge, but that is going to be a challenge.

Steve

I run Gargraves with wooden ties through my hellgate with no problems. Since there is no metal contact of track touching the bridge base it would seem the recommendation of insulating the ties from the bridge base would be the solution.

Romiller