Another scaletrax switch machine burns up

tick ... tick ... tick ...

George can you affix the dz 1000 to scale Trax switch? I've been using them for several years without incident (knock on wood).

The problem lies with their toggle switch, it can stick and you get burning switch motors.

 

So, one can go with real momentary toggles or be really careful using the stock toggle. I just flick mine manually.

In three years with two dozen switches we only had one burn and for the reason RonH mentioned. The toggle got stuck when a broom handle fell against it and held it on for a few seconds before falling to the floor. A freak accident but otherwise they worked flawlessly....

I agree Sam, In past I have used 054 and they worked flawlessly. Since then I went to larger #4 # 6 switches which were purchased recently in the last year or so. These are the ones not working.  

 

The toggle switches are another concern. I don't use them at all as I had issues with them burning too.  I prefer to wire everything through the TIU. I believe MTH addressed the issue you and Ron are talking about. 

 

Anyway there is nothing I could do about it now. I'll just be purchasing my switches and switch machines elsewhere.  #ROSS   

Have been using MTH switches for years. Have worked great. 

Layout controlled by DCS w/ switches controlled through the AIU, no toggles. Even have them on double crossovers, one AIU contact,two switches w/ no problems. The AIU uses momentary actuation, so no sticking toggles. Tom

 

 

 

GEF,

  

  The switch machines are definitely not fail safe.  If power gets stuck on, they will heat up and melt.  The real problem is not the switch machine but that power gets stuck on.  We know the toggle button gets stuck, but I believe it is possible for the relay in the AIU to also get stuck.  I don't use the toggles and use AIU or manual switch control only.  I have only had one switch machine melt years ago that was hooked directly to the AIU.  I checked the wiring and replaced and retested the switch machine and I could not get it to happen again. 

 

I can only surmise the switch relay in the AIU got stuck on.  These are the switch relays that are on the AIU not the Accessory relays.  The switch relays are supposed to turn on for one second then turn off, and if wired correctly it should turn the power on to your switch machine for one second then off.  The timing is not done electrically but rather through commands from the TIU through the serial cable.  The TIU sends a command to turn it on, then a second later another command to turn it off.  I'm guessing the second command did not make it and my relay stayed on.  This is very unlikely because the point to point serial communication should be very reliable, but possible and may explain why it has only happened once in ten years.  It is also possible that the relay arm inside the relay got stuck for some mechanical reason. 

 

Disclaimer..I'm basing all this on the fact that I opened an AIU and reverse engineered to try to fix one.  I found that the AIU switch circuits and the Accessory circuits where identical and each were controlled from the serial interface.  So I'm pretty sure the switches are control by software in the TIU through the serial cable.  If the comms don't work the relay stays on.

 

So first make sure you are not using the accessory inputs on the AIU to control your switches.  If your wiring is good and wired to the switch input and your power keeps getting stuck on to the switch machine, then you may have a bad AIU relay or bad AIU in general for the reason I described above.  Again, the switch machines are not the real problem but that power is not momentary and remains on for some reason.  You need to find out why power gets stuck on.

 

Rich

I went to MTH scale track switches because of Atlas machines burning up, and I had one of the scale track motors burn. I don't use toggle switches I use AIU throws and it still happened,and of course in a tunnel, Vic.

Rich,  Thanks for the help. I didn't think to look at the AIU. I am going to double check the AIU switch circuits. It is unfortunate that MTH doesn't offer these switch machines for sale being that switches are so expensive.  

 

Do you know if its possible to hook up a tortoise switch machine to scaletrax switches?  

 

George

GEF,

 

   I have not used tortoise switch machines so I don't know how they are wired.  You may be able to use the accessory controls with them since I think the tortoise will cut power automatically when the switch if fully thrown.  Also, if you have seen my part II video, I have used the Atlas Under the table mount switch machine.  If mounted correctly, they work great with the MTH AIU switch controls. The MTH switch machines as well most other types aren't very prototypical looking so you can hide them by using the Atlas.

 

B.T.W. I would imagine that the Atlas switch machines would heat up too if the power is constantly applied to its internal solenoid. 

 

Rich.

YEs you could use the Tortoise with Scaletrax. It's just a matter of having the room to mount it underneath and wiring it up to the AIU. If you can't mount it directly underneath the turnout, you can use a remote mount with the cable linkage and move the Tortoise to another location. No different than an Atlas motor, it's just a lot deeper, and the Tortoise does kill power once it's thrown so it won't burn up.

 

Then if you want a switch machine up top for your mainline tracks, you can use a static detail piece like these from Keil-Line.

 

Yes, they certainly will. It is not just MTH or Atlas, any twin coil switch machine is subject to these problems when power is left on too long. As you have already stated, these switch machines are fine as long as the power is prevented from either being stuck on by the switch controls or left on in some other way. It does not take long to burn them up if the power remains on.

Laidoffsick,  Thanks for that info. I will be contacting you about some more details of the install on the tortoise switches. 

 

Rich, I checked the AIU and it seems to be working fine as I tested all the circuits on a good switch machine. When I looked more closely at the inside of the motors of the switch machine I noticed some of the new ones did not have the slide bars connected to the plastic part of the throw bar. I was able to fix one. 

 

Thanks 

George 

No one mentioned the non-derailing feature. As an engine approaches an open switch the switch motor positions the switch to the correct position. It works by the wheels of the engine acting as a conductor to the short isolated section of the switch track just before the frog of the switch. If that piece of insulated track erroneously touches the section of track leading to the switch then the switch motor is continuously energized. The AIU switch relays actions are momentary and the non-derailment feature is supposed to be too. The switch motor is not rated for continuously applied voltage and will burn out. This probably is the case here as the motor did not burn out on application of power but burned up out of the blue which indicates the motor is being energized continuously by the shorting of the non-derailment isolated tract section or in either the AIU or the switch controller button.

 

How do I know this can happen? Every one of my  MTH RealTrax switches suffered this. I had to increase the gap for every one of my seven switches on my layout.

 

The AIU supposedly uses relays contact that are rated for at least 10 amps (I am told???). The AIU accessory section relays operate continuously and the switch relays are momentary. I don't know if the momentary function is done in the control electronics or the relays themselves (there are momentary relay available in the market place or at least their have been in the past). The switch button controller is meant to be momentary by your control so don't lean on the button for more than a couple seconds. And don't allow the control button or the button mechanism to stick on.

 

Note that once the switch changes to accommodate the coming train, internally there are electrical switches that deactivate the connection to the non-derailment feature for the direction tripped by the engine. So even if you park a train on the switch the switch motor is de-enrgized.

 

LDBennett

Have you considered using a PTC in series with the switch power?  Perhaps you could limit the damage when, for whatever reason, the switch is continuously energized.

 

 

 The AIU is rated at 4A, and the two that I have disassembled have relays rated at 5 amps.

 

 

It's odd that two of my AIU's are equipped with what sure looks like 5A relays.  Assuming that they are equipped with 10A relays is a mistake.  Also, since the AIU is rated at 4A, I suspect the PCB traces are not up to the task of handling 10 amps either.

 

 

 

Rich Battista

 

Sorry but I am not totally familiar with this track system as I have RealTrax. But I think my assumption that something is keeping the switch motor on is still valid while the mechanism I mentioned is not. The switch outputs from the AIU are momentary as also should be the manual control system. If either is not momentary then the switch motor will be powered continuously and the motor will burn out without any human intervention to change the switch.

 

That should be investigated. It may be inside the switch or from the AIU or from the manual controller. But the fact remains that the switch motor is on continuously or for a very long time which will eventually over heat the motor and maybe burn it up.

 

LDBennett

gunrunnerjohn:

 

I see from your pictures that the relays shown are all the same and indeed 5A contacts. Is this all the relays in the AIU?

 

If all relays are the same then the momentary action of the AIU Switch control relays is accomplished in the AIU control circuitry for switch control. For this problem it is possible that the AIU control circuitry is not doing it momentary but applying power continuously. or the manual control switch is erroneously applying continuous power to the switch machine motor or maybe the user has been using the accessory relay outputs for the switch motors (??).

 

Anyway something has continuous power on the switch motor is my guess.

 

LDBennett

All the relays were the same type in both of them.  I had more pictures of the others, but since they're all the same, I figured these would do the trick.

 

I'm not sure what the issue here is, that's why I suggested the PTC as a stopgap to keep from destroying switches until the real issue is found and addressed.

Seems surprise that MTH and others have not devised fail-safe turnout motors given that O gauge is larger so little more room for a micro-switch or some other motor/coil safety cutoff, especially if a train stopped over a derail rail thus keeping coil energized.  Atlas has a timer board that cuts power after short interval, but that can get expensive fast if lots of turnouts to control.

 

I know cost cost cost.  But the aggravation especially when motor is located in hard to reach areas should be vendor motivation to innovate.  I use the ZStuff motors they have a cutoff feature.  Why can't Atlas/Scaltrak/etc coil motors be electrically patterned after the old postwar Lionel O-22 motors which used coils to push pull the points?

I haven't smoked one yet, but that is an interesting idea. I may have to order some of those and try them out on my Atlas switch machines.

 

Still thinking about converting all to DC too, I don't suppose that would have any affect on the PTC would it?

DC doesn't affect the operation of the PTC, it's strictly current.

 

Another option is to use a CD discharge system for the switches, eliminates any possibility of leaving current on and cooking them.

 

Think I'll get some PTC's to fiddle with. So far no problems here though.

 

I've saved some of Dale H's drawings and one was a CD circuit I believe. May take another look at those too. I was thinking there was some drawback to the CD circuits, but don't recall what it was right now?

Something to consider is that DC tends to burn contacts while AC generally does not. When contacts break there is a spark/arc if current high enough.  DC tends to keep that arc going until the gap is large enough or other factors cause arc extinction. AC by its positive then negative sinewave nature, passes through zero which extinguishes arcs.  Thats why large DC switches use magnets to blow out the arcs (of course I realize toy train currents are no where near those huge currents like used in GG1 and subway substations!! Just point of information.)

 

A CD by nature is a DC current, thus I would wonder if an MTH AIU relays could handle the high instantaneous discharge current before the relay is commanded to open and the current has dwindled enough from operating the solenoid to fall within contact current range.  Basically an LC circuit with coil inductance and capacitance and all that goody mathamatics that go with it

Just EE esoteric speculation.  Sorry if I am OT here.

I appreciate the info. I have been fooling around with some old Atlas switch machines on the bench with DC just using the Atlas #56 switch controller. The switch machines were weak and barely operated the switch on the layout. I replaced them with new ones and all is well at the switches now. Was originally thinking about using an AIU for switches, but I think I really prefer using the switch controllers mounted right at the switches. AIU is on the back burner now, may not even use one?

 

The weak ones seem to have much more oomph with DC on the bench, but I have not tried them on a switch on the layout yet. These came with some used switches I got and they just did not perform well. Never had a problem with a new one. Not sure what is up with the weak ones, there is nothing visibly wrong with them that I can see?

 

I also found a Lionel crossing gate from my daughters old Lionel set from 1981-1982. Still worked but made a terrible buzzing noise on AC power at any voltage that was enough to operate it. Tried that thing on DC and it was completely silent! That's what got me to thinking about converting to DC for accessories. Well just the ones that will work on DC anyway.