overheating solenoid

A guess might be a shorted turn in the coil, that will GREATLY increase the current and cause the symptoms you see.

Are you using the AC terminals on the power pack? the solenoid will draw more current on DC than on AC....

@50 years of fixin posted:

Are you using the AC terminals on the power pack? the solenoid will draw more current on DC than on AC....

Yes, I'm using a CW-80 which only puts out 15 VAC at full throttle.

@dkdkrd posted:

Talk about commiseration!....

Some time ago I sought help (OP of thread) on renovating an old Lionel No.80 semaphore I got in a purchase of....stuff.  Needed help on rewiring....got it....from my wife's perseverance in online searching.

The second item...rewinding the solenoid coil...I never found an answer to... How many coils of wire should be on the solenoid?  There were 30 coils (3/8" total length on a 1" armature) and lot of witness of additional coils on the underlying tape wrap.  One posting said that these old standard gauge accessories were very over-designed, so I surmised that a full wrap of the number 28awg wire for the 1" length (approx. 80 coils) would be a good try. 

I found a local electric motor repair shop that rewinds armatures.  He gave me 50' of 28awg enameled wire, no charge!  I wound the solenoid, taped it with high-temp 3M No.27 electrical glass tape with thermsetting adhesive.  Jury-rigged a set up with the core plunger suspended above on a rubber band.  Applied 12v to the coil, and BAM!!.....worked like spring-loaded mousetrap!  Sez I, 'I'm home free!'

Assembled it into  the semaphore, wired per the Lionel instructions my wife found, applied the same 12v from the same old MRC O27 Dual powerpack (80VA) I had used for all my workbench repairs and the test of the newly wrapped coil, and....immediately got an 'overload' on the powerpack! 

Applied power to the light bulb leads......OK.

Applied power to the solenoid leads, mounted in the semaphore base,....Overload!

Both solenoid coil leads are free.  VOM confirms the coil is not shorted to the coil armature.

The mechanical actuation of the semaphore arm is clean, aligned, and works smoothly/freely with finger pressure.  

I do not often give up on something electro-mechanically simple like this accessory, but I'm on the brink.

Any ideas?  I'm beyond embarrassment...so give me the 'Duh!'...if there is one.

KD

Any wire left? Measure resistance for about 10' of it.

Esitimate length on the coil.

Now measure the coil añd compare actual Ohm value to the test length measurement.

You might be able to find a large enough difference to detect a short in the coil as ohms will be too low if it is shorted. 

Lower the voltage until you find the least amount you can use too.

General purpose magnetic coils do get real hot. Lionels designs weren't a cobble; it was purpose refined. Some heat more than others but they ofen pull harder too. 

Heat vs work needed vs volts vs wraps vs lentgh vs wire gauge vs amps, back to heat.... and dont forget slug quality. It's design a balance.

Sometimes heat build up has to be dealt with by lowering voltage to a holding voltage after the grunt work is done. I.e. your windings may be too strong or less efficient (I think you need to dial down voltage or windings or change gauge.)

We see this build up addressed in old whistle relay controls on transfomers. In one fast handle sweep, it begins with a offset voltage boost, the relay closes, then the handle hits a new contact that lowers the offset voltage partially, so the coil isn't still grunting to pull still, but instead calmly 😎 "cooly"❄️ holding it up. They use the trick on pinball flippers too. Once flipped up, a switch drops the voltage to a minimum to stay up. When they act funny one of the voltages or switch position or sw. leafs is usually out of whack. 

I believe this book has information concerning rewinding various motors and coils, including the wire gauge and number of turns. Rewind these items to factory specs.

Larry

A lot of solenoids and coils will over heat and burn up without the plunger/iron being in the coil. When rewinding a coil it is a good idea to count the number of wraps as you cut the old ones off. Saving a couple of wraps is helpful in getting the right size wire.🤔

@TrainLarry posted:

I believe this book has information concerning rewinding various motors and coils, including the wire gauge and number of turns. Rewind these items to factory specs.

 

Larry

Thanks for the book recommendation.  I will likely purchase it, however my solenoid is wrapped with paper in between each layer of wire.  I do not know the first thing about rewrapping wire for any component.  

Also, it is getting a little confusing with the replies since KD is riding on my post with his problemed solenoid.  I believe some recommendations are trying to solve his problem but I can't run it a voltage that keeps the heat down because the "hot" is connected to track power and since the motor is a Prewar standard gauge engine, it needs the higher voltage to run decently.

Here are some observations I have noticed in testing/operating the solenoid:

1. The plunger seems to "flicker" rapidly up&down unless it is close to 15 VAC.  Again, that's were the heat really kicks in and burns my fingers while holding it.
2. There is never a short, but I notice the fan of my CW-80 slows down slightly when turning on the solenoid.
3. Before I noticed the overheating issue, I was testing the reverse and trying to tweak the pendulum as it wasn't always catching.  While doing this my alligator clips sometimes crossed themselves and had a brief short.  Could this have started my problem?

1 sounds like a bad coil, take an ohm reading and/or feel for dead or live portions (strength and eveness of the pull on the slug).   If not rewound, check against the coil spec. of Lionel.

2 It's not a "dead short", but a mild one and burried (likely) Ohms are likely low, but present. The amps draw went high, the transformer began working harder and the fan is also fed from the supply. (a layout lamp would dim too)

3 no gator issues to the coil, (direct short; ohms are near 0).  You basically gave the current an easier path to follow than the coil.

So, is it possible/recommended to "rewire" the solenoid?  If so, what equipment and knowledge would I need to do so?

Greg

Easier to replace a coil than "re wind" it.

If you are confident in your ability to count wraps and wrap tight; compact, and neatly you could try; lionel specs can be found or some shops like the TrainDoctor may offer a rewind service if that interests you vs replacement.

Although I've wound a number of coils in my life, doing it manually is pretty tricky.  I found the best way I could do them manually was to have the spool of magnet wire on a carrier where it could unspool freely.  I would then use a foot controlled slow spindle with the coil attached to wind each layer and then put the layer wrap and move on to the next layer.  It's possible to do it, but as previously mentioned, I buy them whenever I can. 

I did get a company commendation from my first employer right out of the service, IBM, for hand winding a IBM 2540 card reader/punch clutch coil to save a customer lots of money and a days lost processing.  It looked sloppy, but it worked, and they were back up in half an hour.