DC for prewar crossing gates

Yes, the coil will run hotter on DC. Enough to damage it? Probably not. The item of issue is the plunger becoming magnetized operating on DC and eventually start sticking. Just put a tiny drop of white glue from a toothpick around the base of the bulb and socket and that will prevent the bulb from working loose.

@Chuck Sartor posted:

...The item of issue is the plunger becoming magnetized operating on DC and eventually start sticking...

A simple way to degauss the plunger if this happens is to run it on AC.

@Chuck Sartor, if Joe is only using a bridge with NO FILTER caps, then he should experience the same heat in the crossing gate coil, perhaps even a tiny bit less due to the loss in the diode bridge, right?

George

But if you "mute" that coil, it takes away the fun of the accessory buzzing, think gateman, oil derrick, and similar solenoids (especially when screwed to the plywood base).    Of course it goes without saying, the rotary beacon, crossing flasher with ringing bell and other accessories that use the "finger washer" vibrator motor won't operate.

Not sure if some like the red belt coal loader (also maybe log loader?) and similar using a universal motor would run more quietly on DC (or better yet, filtered DC)?

The noise of the gates never bothered me.  It was the fact that the vibration always causes the bulbs to unscrew.  The bridge clearly reduces the vibration and noise so the bulbs stay put.  I didn't think to add the cap because the bridge accomplished what I needed.  As long as the coils don't over heat while a train passes, its a simple fix.   Today, I power the gates with a PWC ZW with 135 watt bricks.  When I was a kid, my dad had an old Duncan 100 watt transformer he used to power it and other accessories.  Pure or chopped sign wave both yielded the same results.  The bulbs always loosened up.  A bayonet bulb would have also fixed the problem if they made such a socket to fit those gates.

With some specific few exceptions, DC is generally better for most operating accessories.

@ADCX Rob posted:

A simple way to degauss the plunger if this happens is to run it on AC.

How about a diode in reverse across the coil so the back emf demagnitizes the plunger?

@GeoPeg posted:

@Chuck Sartor, if Joe is only using a bridge with NO FILTER caps, then he should experience the same heat in the crossing gate coil, perhaps even a tiny bit less due to the loss in the diode bridge, right?

George

Sadly, no. I cannot remember my electronic theory as it has been so long. It has to do with coil saturation that does not happen with AC, but happens with DC. Just rectifying the AC voltage and feeding that to the solenoid/coil or whatever will cause increased heat. Best used for intermittent applications.

Can't totally agree with your statement Bob. Look at all the vibrator powered accessories. Everything from the lowly Banjo signal to the large Rocket launcher, Culvert loader/Unloader, 494 beacon, Sawmill, Lumber unloader, Barrel loader, etc. Of course, DC will not work. On modern accessories that use a small DC motor, a diode is already in the circuit. And solenoid operated accessories operate better on AC, but a bit noisier. 

You are correct. The list of accessories you cited are the exceptions I mentioned.

Not to be a smart a## Bob, but what accessories are you referring to that run better on DC?

Currently on my layout: lumber mill, barrel loader, culvert unloader, gantry crane, refueling depot, crossing gate, crossing signal light, track switches & trackside IR sensors.  Any accessory using a vibrating platform will need AC.

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How about a dab of Loctite® on the lamp?