Inconsistent Loco Stalling

[The Captain90]

Pending construction of my layout I have built a small test track with a Peco electrofrog point and a straight track section off each branch. I have run a BUS under the board with dropper wires onto each track section and wired up a Gaugemaster PM1 point motor. To my surprise it all worked perfectly the first time.

I have a Hornby Majestic Set which will form the basis of my layout. As I said, all worked well but this only lasted 2 days. I have been using the two locos supplied with the Majestic - 4-6-2 'Bon Accord' Peppercorn and Co Co Class 47 Res. Even using the shunting speed both locos travelled faultlessley over the points in all directions.

Today has been a different matter. The diesel loco is still performing as it should but the steam loco has decided not to play the game. When the steam loco is travelling along the straight track secton and the wheels leave the main line and get onto the "prong" (don't know correct name)" it stalls but if points are set that it turns to the right hand fork it goes fine in this direction at any speed.

I have checked the track voltage at various points on the test layout with a multimeter which shown a constant 9.9 volts at all points. Even the point where the loco stalls is showing 9.9 volts. I have cleaned the track plus the loco wheels but to no avail.

Any thoughts as to what could be causing this stalling and is the voltage right for my DCC layout - I thought it would have been at least 12 volts. Also do all three large wheels on the steam loco pick up the power.

Merry Christmas to all. Santa arrives downunder in 3 hours so I better get off to bed.

[2e0dtoeric]

Nine volts? That is slightly more than half of what it should be, at 16 volts, with a DCC system. Are you measuring it as dc or ac? It should be ac, and even then it is not a true reading, because there is a digital signal overlaid on the voltage.

Regarding the stalling, it is either a dirty spot on the wheels, or one of the pick-ups that rubs on the BACK of one of the wheels is breaking contact if/when the axle and wheels shift slightly sideways on the curve.

Do all the wheels pick up - that depends - you will have to look underneath, and see! Usually the bogie wheels do not, and the front and rear pairs of drivers do. The middle drivers is 50/50.

[Chrissaf]

Captain, as you are using Peco elctrofrogs with Seep PM1 point motors. Are you, by chance, using the changeover switch in the Seep to power the Peco frog. If you are, I would be looking at the Seep point motor alignment and switch operation. The Seep switching can be a tad temperamental. It is not unknown for the alignment to go out over time due to the forceful jolt solenoid point motors generate.

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Check the voltage on the frog rails with the point in both positions.

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I appreciate that this suggestion does not fit in with the observation that only the steam loco seems to be affected, but maybe the Diesel is moving the switch rails slightly to make more reliable point motor switch contact. The more possible issues that are eliminated as being the cause, the easier it is to home in on the true cause of the problem.

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As 2e0 says, use the AC setting on your meter. It won't be accurate and you will get different readings with meters of differing measurement quality. My own meter (Fluke) give readings nearer 14.5 volts on Hornby Elite DCC.

[walkingthedog]

My bet is the moving blade isn't making good contact with the main rail. The diesel having a powered bogie at each end, I imagine, wiill push the loco through the points. Make sure the moving blade is hard up against the rail. 

[Chrissaf]

A very good point WTD has made regarding Diesel having pickups spread wider apart. That theory also fits in with a frog switching reliability issue (assuming frog switching is deployed).

[The Captain90]

 Thanks for your prompt replies guys. Yes Chris frog switching is deployed - I was a bit concerned with the wiring but got the points to fire first time.

Christmas morning here now so I will leave checking using your suggestions until later. Now off to see the grandkids (who the layout is being built for, yeah sure).

[Chrissaf]

Yes Chris frog switching is deployed

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In that case Captain, my money is on the Seep frog switch not making contact when thrown in the faulty direction.

[The Captain90]

By George Chris I believe you may be right again. When the point is thrown and I look under the board I can move the point motor a little bit more. Haven't had the chance to test this theory with the power connected and will do so in the next day or so (still busy with family Christmas activities).

If this proves correct does anyone know how I can get the frog switch to throw over further?

[96RAF]

Sounds to me like the motor isn't mounted exactly central Captn, such that the point will throw enough to route trains but not enough to throw the switch (electrical not mechanical).

it doesn't take much offset for this to happen. Adjust by loosening the motor mounting screws, tweak it a bit and tighten again. Repeat until mech and elect Operation in satis.

[Rog RJ]

If necessary you can enlarge the mounting holes slightly to get a little bit more movement of the Seep.

[Chrissaf]

Captain, the tolerances on the Seep motor switch function are very tight. It works by a mechanical slider fixed to the solenoid action moving across some PCB contacts. If the Seep motor is not mounted ABSOLUTELY IN THE CENTRE then the switch may not work in one or other of the directions, if off centre by just one or two millimetres.

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As I eluded to in my first reply regarding my solenoid jolt comment. You stated it all worked OK for a few days, then became faulty. The jolt of the solenoid is enough to make the Seep creep sideways. Initially, the Seep was probably just on the edge of its operation limit. The solenoid jolts only have to move the Seep a millimetre for one side of the switch contact to fail if not absolutely centred when first installed.

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Review this You-Tube video for an engineer who made a jig for getting the Seep centering spot on. A very useful tool to make if you have many Seeps to fit. As you will find out trying to modify the mounting hole positions after the event will not be easy.

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You may have to resort to drilling out the existing mounting holes in the baseboard, gluing in round dowels, then drilling fresh correctly aligned screw pilot holes. You could file out the holes in the Seep to provide some positioning adjustment, but this is likely to compound the problem as it will make it even easier for the Seep to creep after further solenoid jolts in use.

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Additional unasked information: The Peco PL10E motors with the optional PL13 switches attached have the same tight alignment issue. But the PL10E motors with Peco PL15 switches do not, as the PL15 switch operation is adjustable.

[The Captain90]

 Thanks for all the replies and guidance. Firstly I was measuring voltage in DC. When I changed my meter to AC I am getting 15.75V.

Thankls Chris for the link to the Seep Jig. I found this some time ago and have one. I used it to install the point on my test layout. It certainly made for an easy job.

I have looked at the point motor and I cannot see that it has moved - when the point is switched the contacts on each side appear to be clear (but only just). It is strange that now the loco is stalling on both forks of the point - at least its being consistant.

Did some voltage readings - Track (I have feeders on each peice of track) 15.75V. The Frog with no loco on it 12.0V. The Frog with a stalled loco on it 1.2V. I have checked all the wiring and it appears sound. Not sure if this makes a difference but I am using as the test point a Peco Streamline Electrofrog Small Radius Right Hand Point (SL-E91). Will however be using larger points on the main layout.

Obviously the voltage drop is the reason for stalling but I am at a loss to know what is causing this and how I can fix it. Any guidance will be appreciated.

[walkingthedog]

Your lucky to get a 4-6-2 to cross small radius points. 

[Chrissaf]

Frog with no loco on it 12.0V. The Frog with a stalled loco on it 1.2V.

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Just taking your comments at face value, This would seem to indicate that the Seep switch contacts are introducing a small resistance that is causing the volt drop. The following is a bit rough and ready as Ohms Law is only truly accurate in a pure DC environment. But a drop from 12 volts to 1.2 volts is 10.8 volts (the 12 volts should be 15.75 volts anyway , according to your measurements, so that alone is indicating some underlying issue with the frog circuit). Assuming the loco is drawing about 150mA. Then Ohms Law R = V/A or 10.8/0.15 = 72 ohms.

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Try giving the Seep contacts a clean and make sure contact spring pressure is there.

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Just to be belt 'n' braces, make sure your Seep is wired as per this diagram, but with the following comments in mind.

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• The R8216 Accessory Decoder shown in the diagram can be the R8247 decoder, or any other third party brand Accessory Decoder.
• The Accessory & Track Busses shown separately on the diagram can be one and the same. They don't have to be separate.

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The main focus of including the diagram is to confirm how you should wire the Seep changeover contacts to your track Bus and frog. That is the D, E & F Seep tags.

[The Captain90]

Thanks again guys (& ladies??) for your helpful comments. Chris I have my point motor wired as per your diagram, except A & B are switched around on the R8247.

Have cleaned the contacts, checked wiring. Now I am getting no problems when switching to the right track but the left is still giving problems but only about 25% of he time. When it does stall I have thrown the points back and forth a few times and it fixes the problem for a while. Think I will remove the point & motor and drill a bigger hole (currently 10mm, expand to 13mm) to ensure enough throw room. 

Again many thanks.

[Fishmanoz]

Sounding a bit like the old mechanic's adage - don't use force, get a bigger hammer. 

[The Captain90]

Your patience is appreciated. Hopefully I can solve my problem without pulling out any more hair. I have removed the point motor and checked the movement clearance. With my 10mm hole it is plenty big enough and looking underneath my board as the points are thrown the contacts are cleared no problems. Fortunately my test board is only 1m long so I can easily turn it upside down to watch the movement.

When I check the frog without a loco on it the voltage is 15.75v. If I check again after the loco has stalled the voltage is between 0.5 & 3.0v. Obviously the loco hitting the frog is causing the voltage drop, thus the stall, and I am at a loss to understand why.

Any thoughts?

[The Captain90]

 Sorry I should have added. Once the loco has stalled, if I get a peice of wire and touch one end to the track and the other to the frog the loco will proceed on its merry way.

[The Captain90]

if you are having a stalled motor/ loco ,the motor does not know it has stalled and will continue to try to drive , hence the current will increase, now obviously this current draw is not large enough to trip out any protective device, but is demanding more current than can be supplied causing the voltage to drop to your read voltage.

Thanks for this. What I don't understand is why is the voltage correct before the loco gets to the frog but it stalls upon hitting it.

[Chrissaf]

 Sorry I should have added. Once the loco has stalled, if I get a peice of wire and touch one end to the track and the other to the frog the loco will proceed on its merry way.

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Captain, to my mind I would treat that statement as proof that there is still an underlying issue with the frog switching circuit yet to resolve.

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Since you have stated that you have a multi-meter, then try this:

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With the TRACK POWER SWITCHED OFF.

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Put the meter in its measure lowest resistance setting, or if it has a continuity buzzer option then use that instead. remove your loco from the test track. Place one meter probe on the frog and the other meter probe on the point moving switch rail that is in-contact with the fixed rail. This should give a 'short circuit' low resistance reading or sound the continuity buzzer. Ideally the resistance should read zero.

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Now move the meter probe on the moving switch rail that is in-contact with the fixed rail to the other switch rail that is not touching the fixed rail. This should give an infinity 'open circuit' meter reading or not sound the continuity buzzer.

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Now switch the point to the other position and repeat the test above again. Only the moving switch rail that is in-contact with the fixed rail should give the 'short circuit' reading and the 'short' reading should move to the other touching switch rail with the switching of the point.

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If you don't get a 'dead short' reading in the tests described above, where I have indicated that you should get a short circuit condition. i.e you get a contact condition but it has a resistance value to it (i.e not a short). Then you will need to investigate where this resistance is coming from. A dry soldering joint perhaps. or a faulty Seep switch contact.

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Although this (what follows) is probably unlikely, if during the documented tests above the 'short circuit' condition occurs between the frog and the moving switch rail that is NOT in-contact with the fixed rail and the reading between the frog and the in-contact switch rail is 'open circuit' instead, then the D & E tags of the Seep motor are mis-wired and reversed.

[The Captain90]

Thanks for your prompt response Chris. I appreciate the time you have spent on this.

Have done as you suggested and on the left hand fork which hasn't been too troublesome the continuity meter is showing all is ok.

The right hand fork (or really straight ahead) which is my problem does not make the meter buzz where it should. At least this has confirmed my problem - now to try and fix it.

My soldering is not the best yet so a dry joint could exist. Is there any way of identifying this easily. What I will do, is take the point off and see if the fine wire Peco put on the frog is joined in all the right places. Perhaps when I installed it I upset one of the joints. I did solder a wire to this that I attached to the Frog Switch Feed on the PM1. If this doesn't work I will need to get another point motor in case the one I am using is faulty. The fact that everything worked perfectly for the first couple of days makes me think a loose connection could be the problem.

Thanks again.

[2e0dtoeric]

Solder dry joints are easy to see. They look gritty or crystallized, while a good joint is smooth and shiny. Also if you can see a little dimple in the solder, where the wire goes in, that might be a dry joint, too.

Dry, in this description, means a poor joint where the solder has not flowed onto both surfaces, usually because of dirt, or the surface wasn't hot enough.

When soldering, you are holding the wire and the connection together in some way, then putting the tip of the iron onto that, before adding the multicore solder, aren't you?

If you put solder onto the iron, then take it to the joint you are making - all the flux, which helps the solder to flow, will have burned off before you get there.

Also - if you are using the 'new' lead-free solder, it is horrible stuff to work with, as it needs to be hotter than lead/tin mix, and is much more prone to giving dry joints, or burned components.

[2e0dtoeric]

Another thought - you say the loco is 'stalling'.

To an engineer, stalled means jammed, still taking power, but can't move.

Do you mean the motor has jammed (could be making angry buzzing noises), or do you mean that the motor is getting no volts, so has stopped as though it has been turned off?

[The Captain90]

Another thought - you say the loco is 'stalling'.

 so has stopped as though it has been turned off?

Yes the loco is just stopping as if it has been turned off.

[Chrissaf]

Captain, as you are probably aware from previous answers I have given to your posts, that I too use Peco electrofrog points. On one occasion I found that where the Peco manufactured frog wire is fixed to the frog rails. One of the wire joints (there are two in close proximity) had broken away. This meant that only half the frog rails were getting power, affecting one direction of travel only.

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The manufactured wire fixing by Peco uses some form of spot weld rather than soldering. They can look good visibly, but proding with a fine screwdriver point will show up any weak wire welds that might have broken away.

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This of course requires the point to be removed from the board to inspect the point underside. If this is the fault, then the results of your tests to date are consistent with it being the issue.

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If it is the fault, then the broken wire joint needs to be repaired by soldering. The wire connection position is deeply recessed in surrounding plastic and needs an extremely fine tipped soldering bit to reach it.

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If the Peco manufactured wire joints on the point frog are sound and secure, then I fall back to my original diagnosis of the Seep motor not being centrally aligned or the Seep switch not fully functioning as normal. You would probably need to remove the motor to perform more exhaustive testing of the motor switch.

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PS - 2e0's description of a 'dry joint' is spot on.

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EDIT: A comment for the benefit of flyby readers of this post thread. This is a prime example of the usefulness of having a 'multi-meter' in the tool box. Even the cheap 'sub £5' meters on e-bay (imported direct from China) are worthwhile having. They make fault diagnosis so much simpler to perform.