[bobfett]

Hello All,

I have finally been able to work on the hidden uncoupling tracks from GRJ's excellent 2017 post (https://www.modeltrainforum.com/showthread.php?t=120914) and need some help.

At train shows over the past few months I've bought several old uncoupling tracks, taken them apart, put in .25 inch steel rod cut to come to rail height, made temporary electrical connections (with a push button), but cannot uncouple any cars. The coils all energize, there is a magnetic field (verified very unscientifically by holding a screwdriver blade over the steel rod) but no uncoupling action. I've tried with both postwar and modern freight cars.

Does anyone have any ideas on what I should try next? I've tried 4 different coils; could it be that all 4 coils are weak? Is there any way to test them that might point out their weakness or some other problem?

Thanks for any and all suggestions.

Bob

 

[gunrunnerjohn]

How are you powering the coils? The ones we did we used old bolts cut to length, and they're powered with 12-14VAC and have no problem uncoupling cars.

 

[bobfett]

How are you powering the coils? The ones we did we used old bolts cut to length, and they're powered with 12-14VAC and have no problem uncoupling cars.

Hi John,

I'm powering the coil with a KW set at 16 V. However, I know that only 11.5 V were getting to the coil after passing through the push button. Why I put the multi-meter on both sides of the push button this afternoon I don't know but I did wonder why the voltage dropped when it went through the button. I'll bypass the button tomorrow, run momentary power to the coil from the KW, and let you know the results.

Thanks.

Bob

 

[gunrunnerjohn]

Odd, but it sounds like a high resistance joint at your control. If they're at rail height, they should have plenty of OOMPH to decouple at 16VAC.

 

[bobfett]

Well, no joy in coupler land.

I by-passed the push buttons and jumpered from the KW to the 4 coils (individually). Powered up to 16 V, confirmed by multimeter connected to the coil wires. No uncoupling with a car/coupler button sitting right over the steel rod from the coil (at track height). Used my unscientific screwdriver blade test to confirm there was a magnetic field present. Didn't leave the power on for any length of time so as not to overheat the coils.

The only thing I think I'm doing differently from John's tutorial is using .25 inch steel rod (because I had it on hand) rather than a bolt in the coil. Tomorrow I'll check the "extra screws" can to see if I have any likely candidates to try that.

John, thanks for your suggestions so far. I'm open to any other ideas you or others may have.

Bob

 

[gunrunnerjohn]

I suppose the type of steel could have an effect, but it's hard to believe that's a major issue. There isn't anything else that was done special, it was pretty much as that thread shows.

 

[Pingman]

Have you tested the coils prior to installation? Can a coil hand held over an inverted car cause the coupler to open when energized?

 

[B&O Forever]

Send a picture. Someone might see something.

 

[Millstonemike]

I suppose the type of steel could have an effect, but it's hard to believe that's a major issue. There isn't anything else that was done special, it was pretty much as that thread shows.

True stainless steel is not ferromagnetic even though it's composed of ferromagnetic metal (iron, cobalt, & nickel).

 

[bobfett]

Still no uncoupling today.

I tried using a bolt in the coil rather than the steel rod. None of the bolts I had available were an exact fit for the coils. I used one that was slightly smaller (probably 3/16" rather than 1/4"). Had a magnetic field but not enough to open the coupler.

I reviewed GRJ's tutorial and the only difference I can see (other than using the steel rod) is that the gap I cut in my Gargraves center rail is slightly larger than the rod; in the tutorial pictures it is hard to tell but almost looks like the center rail touches the bolt/rod. Could that make a difference? I have approx. 1/16" or maybe less on each side of the rod. Also, the track has not been powered when I've tested.

GRJ and Mike: I don't think the steel rod I have is stainless. It was the left-over from some non-train project I did several years ago. When in the coil it does produce enough magnetism to pull the screwdriver to it but not open the coupler.

Carl: yes, I tested the coils prior to installation; actually, they're all on my work bench at this point. No, whether the car is inverted or upright the hand held coil/rod combination will only open the coupler when the rod is almost touching the coupler button.

B&O: good idea for a picture; I don't know if I will be able to get to it tomorrow - Saturday might be a better bet.

Thanks to everyone for trying to help.

Bob

 

[gunrunnerjohn]

Very odd, I'm not sure what is going on at this point.

 

[Millstonemike]

When you say "rod", do you mean "threaded rod"?

Threaded rod has significantly less mass (per inch) than plain rod of the same nominal diameter. And your bolt test used an undersized bolt.

IIRC, GRJ used a bolt with hex head still attached. I assume the bolt's stem was not threaded near the head. That's a lot more metal mass than 3/16" threaded rod..

 

[bobfett]

Mike,

No, it's a solid rod. I'm not in my train room now but it's 1/4" dia. by approx. an inch long, give or take; whatever length was needed to go from the bottom of the coil to rail height.

If I get a chance over the next couple days I'll get a 1/4" bolt with enough length to have the hex head below the coil and a solid shank to reach rail height.

Thanks.

Bob

 

[gunrunnerjohn]

Note that the bolt head is not left on the steel rod, it's just the unthreaded section of the bolt.

 

[B&O Forever]

I'm betting the rod is too long. Those coils can only energize so much mass.

I'm sitting by.....

 

[gunrunnerjohn]

Actually, the device in that picture above works perfectly. We have a bunch of them in the yard tracks, and they uncouple the cars no sweat.

 

[Millstonemike]

Did you happen to test any of the uncoupling tracks prior to disassembly?

 

[bobfett]

Success, sort of.

I was finally able to be able to uncouple a car with the coil, but with a modification from GRJ's tutorial.

First I tried using a length of 1/4" bolt (the solid shaft) with the head cut off, but it wouldn't uncouple. Next I tried a length of bolt with the hex head still on, coming through the coil with the head under the coil; when powered with 18 V from the KW it would activate the uncoupling mechanism. Leaving the head attached obviously increased the mass of the metal; would that give a corresponding increase to the magnetic field?

So, now a new question. Can anyone see a problem with leaving the head on the bolt? It would be going through pink Styrofoam insulation under my track. I'll activate it with a momentary push button. I believe someone in the original thread recommended using an inline fuse in case the button sticks; sounds like a good idea to me.

Thanks to everyone for your suggestions to make this work.

Bob

 

[bobfett]

Did you happen to test any of the uncoupling tracks prior to disassembly?

Mike,

No, I didn't try them before disassembly. There were no controls with them and the wiring on the under side of the tracks was in really bad shape.

Bob

 

[gunrunnerjohn]

The top of the core should be slightly above the level of the rail-head, perhaps around 1/16", that's what the standard uncoupling track does. The bolt head is going to be fairly obvious I would imagine sitting at rail-top height.