Electromagnet uncouplers -modifying old Peco point solenoids (v2)

[Robin2]

Don't know why the OP wanted the original thread locked.

Quote from DCDave

As several have mentioned above anything beyond a very brief pulse of juice will burn the solenoid's out. Please don't anyone else try this as it won't work and may well start a fire.

A little bit of common sense will prevent a Peco or any other electromagnet coil from going on fire - add a suitable resistor to limit the current to a safe level. Of course the magnetic force won't be as great with a lower current, but with a suitable core (such as a nail) it may be sufficient.

There was an article about it in MRJ volume 79 in the context of Alex Jackson couplings. The author used two Peco coils on a single 2.5inch nail. Perhaps with the two coils wired in series there is sufficient resistance. The author also used 16v and 24v AC to power his coils so the inductance of the coils would also help to limit the current compared with using DC.

...R

[DCCDave]

Apologies if I've alarmed anyone with my response, but with reports of 'smoking coils' there's obviously some risk, perhaps overstated.

Cheers

Dave

[martink]

It is actually quite easy to build these beasties from scratch.  I use a four inch nail, a couple of plastic discs (poker chips, buttons, washers, etc), a 25g spool of 0.25mm coil winding wire and a small piece of circuit board to act as a baseplate.   I use the whole coil of wire, giving a resistance of about 20 ohms and hence an operating current of about 0.75A at 16V.  I can happily keep them turned on for ten seconds or so at a time.  FWIW, I use B&B couplings, but the electromagnets would work fine with MBM or DG, and should be OK with the Peco or Seep lift arms as well.

Drill a hole in each disc so that the nail is a tight fit, then push the nail through leaving one disc at head and the other about half-way down.  Put the pointy end of the nail in a hand drill, wind on a few turns of wire to hold it in place (maybe use a bit of sticky tape).  Put the spool of wire on a convenient bolt or something to serve as an axle, then use the hand drill to wind on all of the wire.  I wear a heavy work glove and run the wire through my fingers to maintain tension.  When it is done, I seal it all with a coat of PVA glue.  Use a saw to ensure that the copper clad board is divided into three sections electrically, and drill a (tight) hole for the nail through the middle section and screw mounting holes in the end sections.  When the coil is dry, push the nail through the hole in the circuit board, and solder the wire tails to the end sections. 

To mount the uncoupler, drill a hole between the sleepers, test the unit's fit and cut the nail to length.  You can even file it down to the same profile as a sleeper.  My early versions were long and narrow (due to the small plastic washers I used); later ones were more short and stumpy.  Some of the long ones were built with the baseplate at a 30 degree angle so that the uncoupler clears tracks beneath.

[Izzy]

I'm afraid to say that having tried the approach of using single coils from both Peco and Seep solenoids, and finding neither satisfactory,  being weak and getting too hot far too quickly, I have now adopted the use of rare earth cylindrical magnets.

These are fairly cheap to buy, are quite strong enough to work couplings at the right size, ( I use 6mmx6mm), and don't need any current feed.

The trick is working out how to move them in/out of position. You can either raise/lower or slide them to taste. I've used both servos and mechanical methods with both.

Izzy

[RST]

I thought this was going to degenerate so asked for the original thread to be locked as it proved my suspicions re Peco coils and the thread served its purpose.

When I was a kid I used to play with electronics and made up lots of solenoids pretty much exactly like martink.  That was back in the days when my old man used to bring home electronic bits from work, if I had any varnished copper wire now I'd definitely just make them myself again.

Maplins stock a small range of magnets now -going to nip in and have a look at their "Mega Super Magnets" to see what they're like before looking at mail-ordering any.  There seems to be more success stories using permanent ones of some type or another anyway.  Thinking about it for me it would be quite easy to have them swing in / out mechanically.

[Robin2]

Although I restarted this topic I am unsure myself as between permanent magnets and electromagnets. I also built an on-board infra-red controlled uncoupler which works but just introduces other issues - mainly which vehicles to put them in and, if you have a lot of them how does the operator remember which is which.

Making your own reasonably powerful electromagnet is a pain even if you have something to rotate the coil for winding. Buying Peco point motors to cannibalize for electromagnets is probably no more economical than buying small servos to lift and lower permanent magnets.

...R

[elmo]

I use the peco magnet both as sold and my own from cutting point motors on two and using them on a 16v ac gaugemaster supply have never had a problem with pecos own uncoupling system or with DG's although I no longer use DG's.

I have the top of the steel rod level with the sleeper top painted the same colour as the ballast. My switch system on my older layout is pecos now out of production 'flat' passing contact switches. I hold the switch down for the desired uncoupling time (generally less that one second) My new under construction layout is using stud and probe for the uncoupling.
I have never had any smoke nor have I burned any out, my oldest uncoupler being in use since 1988.

The only problem with 'lack of magnetism' with the peco magnet was with some DG couplings, but this turned to be a problem with the coupling. My mistake was following the DG instructions to the letter, I folded the steel dropper straight down. My magnets are placed in the centre of the track. After bending the steel dropper so it hovered over the centre of the track solved my problems.

I have read on this and other forums that the peco magnets are not strong enough but in my experience they can certainly do the job and i have never had a lack of magnetism problem with them.

Elmo