Poor Hornby point closure with R8243 motor

[nalaselig]

I have a number of Hornby points in my system that due to limited clearance below I have installed 6 surface mounted point motors (R8243) controlled by Expo Drills & Tools A28025 SPDT on-off-on sprung to centre switches from a regulated 12V supply from  Gaugemaster Model D Dual Track Controller. Everything is working as planned but although the motor 'fires'  in some cases the closure of the point is not complete. As suggested in the installation instructions when  there is an 'operating problem' I have tried loosening the mounting screws and when that did not improve the function, disconnecting the wire spring in the point but the problemn remains. I am new to model railway building so I asked my supplier (points & motors) whether I needed a CDU in the circuit but was told it was necessary. Was trhat bad advice and will fitting one improve their function?

Thanks 

[poliss]

The spring in the points should ensure it closes properly. It's possible that it's become loose or the spring has stretched.

The spings are removed only for certain types of slow acting point motors, such as those of the stall variety.

[Chrissaf]

Disconnecting or removing the point turnout spring was IMHO not a good move. As Poliss said in his reply, the removal of the spring is something you should only contemplate with 'slow action' point motors. Solenoid point motors in the main don't include 'end of travel' locks, thus the spring is IMHO essential to keep, to perform this 'end of travel' locking action.

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If the point did not lock (with the spring in situ) then the issue you were experiencing was either lack of spring tension or poor point motor alignment. It is also possible, but not proven, that the 12 volt supply you are using does not have enough oomphh. Either too low a voltage or too low  a current - see comment later about CDU. The spring tension can be checked by removing the point motor and seeing if the moving switch rails snap over when operated by hand. If they don't, then it is the point spring mechanism at fault. If they do, then it is the motor alignment at fault. Subject to the power supply comment above.

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If you are unable to re-fit the point spring and produce a 'snappy' manual operation prior to refitting the motor, then you will probably have to replace the point for a new one.

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I have come across old Hornby points where the spring is present, but the action was still not 'snappy'. On those occasions it was other delicate parts of the point mechanism that had become weak or out of alignment. Particularly the contact wipers that were positioned under the moving switch rails. Either that or the switch rails were just sloppy due to old age and wear & tear.

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As a 'rule of thumb' I would always recommend fitting a CDU (personal preference). The CDU will give a bigger current kick and overcome any stickiness in the point and point motor travel. Operating Solenoid points on 12 volts DC is IMHO just about OK, provided the power supply in question has a high current capability. Fitting a CDU will provide additional current to the point motor if the the power supply is lacking in power output. I find 15/16 volts or more for point motor firing gives far greater reliability. My non Hornby point motors needed 18 volts for reliable robust operation.

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The other big advantage of using a CDU, is that it becomes impossible due to the way the CDU circuit operates to hold the current passing through the Solenoid coil 'ON' i.e. if holding the non locking switch over against the return spring. Thus a Solenoid motor operated via a CDU will 'fail safe' to prevent coils overheating and becoming damaged.

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For that reason alone, they are worth the relatively small sum of money being asked for them.

[sparrow hawk]

Hi

I have used 3 of these on my layout. All of them had  the same issue ,to start with. I found ,that it was due to poor alignment, of the point motor.You need to make sure it is level ,fully aligned with the point ,and that the screws to secure them to your layout are not too tight.

For me it was just a  matter of trail and error before ,I got them to work,loosening the screws,slightly each time.

Even now sometimes they do not throw at all.

I would not use them again unless I had no choice especially on curved points.

Hope this is of help,

[96RAF]

I have seven of these on my layout, two sets of which are paired.

 

I use a GM CDU and have no problems throwing Hornby standard points.

 

the only problem I have found is if you put them on the inside of the point curve they can catch on certain locos, in particular the fuel tank of my Calss 56. A close encounter with a large file soon sorts that out.

[RDS]

... the removal of the spring is something you should only contemplate with 'slow action' point motors ...

 

Chris, My policy of 'if all else fails, read instructions' doesn't normally allow me to check but looking at the instructions for the R8243, appears to show the removal of the spring.  I say 'appears' because there are no words to support it but the diagram seems to show it being removed.  (These instructions are in the Download section of this website, if you don't have them)

[nalaselig]

Thanks everybody. As an absolute beginner I am going to have to take some time to digest all the information! However, an immediate reaction is why do Hornby: 

1. Recommend disconnecting the sporing for their solenois motor if it doesn't function properly? As RDS points out the instructions do show you how to do it! It is going to be very tricky to replace them but fortunately I have 10 others which I am installing with Cobalt slow action motors so I can use the spring-less ones with them! 

2. Why do they recommend in their installation instructions that it will work perfectly well with a 12V supply? I have a 16vAC supply on my Gaugemaster control but as my Cobalt motors will run on 12V I wired my system to run from the 12 V supply which Hornby said would be fine.

3. The Hornby points are brand new so should I expect the spring to be weak. I will check the 10 others I have as you (Chissaf) suggest. I am pretty sure the alignment of both the points and the motors to them are OK but I will check them out again.

Chrissaf, sorry to be dumb, but could you illuminate my darknes about what does the abreviation IMHO stand for?

Finally, I guess there is pretty much agreement that a CDU would be more than a good idea! However, I also suspect that Sparrow Hawk has really put his finger on it!

Thanks again guys for all this information and getting back to me so quickly. I am puttiung this all together for my grandson who spends his summers with us and he arrives in 4 weeks time so I don't have much time!

Alan

[poliss]

IMHO = In My Humble Opinion. 😆

[Chrissaf]

@RDS

Chris, My policy of 'if all else fails, read instructions' doesn't normally allow me to check but looking at the instructions for the R8243, appears to show the removal of the spring. 

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That is precisely the reason I included "IMHO" twice in my opening paragraph. I am aware of what the R8243 instructions say, but IMHO I disagree with them. In hindsight, I should have made myself clearer.

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IMHO = as per Poliss' post above.

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@Alan

Why do they recommend in their installation instructions that it will work perfectly well with a 12V supply?

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In my earlier reply I wrote:

"Operating Solenoid points on 12 volts DC is IMHO just about OK, provided the power supply in question has a high current capability. Fitting a CDU will provide additional current to the point motor if the the power supply is lacking in power output."

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Expanding the above statement with additional detail:

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It's not the voltage, it is the current that is the critical electrical factor for reliable Solenoid operation. For example, 12 volts provided by a 'lead-acid' battery can maintain 12 volts even when drawing 10's of Amps. Thus, the statement that the product works on 12 volts is technically correct. But if the 12 volt power supply in question cannot provide adequate current, then the voltage output of the power supply will fall far below 12 volts as more and more current is drawn from it.

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A Solenoid point motor would like to draw an instantaneous current at switch on of about 4 amps. This is probably far more than the 12 volt output of your Gaugemaster Model D can supply. Hence my comments inferring that perhaps your 12 volt supply does not have enough oomph for reliable Solenoid operation. A CDU charges up relatively slowly, thus a CDU does not need a high current supply input. It is the charge stored on the internal capacitors of the CDU that provide the high current kick required by the Solenoid. Once the capacitors have discharged to fire the Solenoid, they can then charge up again at their own pace via whatever current the input power supply can provide.

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This 'High Current' requirement of a Solenoid point motor is also the reason why the current should never be applied for more than a couple of seconds if you want to prevent the Solenoid coil from over-heating. Left connected for long enough to a high current power supply (without a CDU) it has the potential to burst into flame. The CDU provides just the briefest pulse of current and can't start the capacitor re-charge process until the Solenoid load is removed from the circuit. Thus only a small trickle current (about 50mA) is passing through the Solenoid coil if it is left connected. This is not enough to do any damage to it.

[nalaselig]

Thanks again for all the information and the update. I will switch the Hornby points to the 16vAC supply and install a CDU on that circuit and hope that fixes it. 

I have checked the quality of the spring action on the points where it remains in place. I should emphasise that they are all brand new straight out of their packages. I am afraid I am not impressed that almost every other one does not demonstrate the 'snap action' you (Chrissaf) describe. Consequently, I really hope the 16vAC/CDU solution is the answer and the slight scepticism I detect in Sparrow Hawk's response is not also at the bottom of it. If it is, I would be grateful if I might be better off with another surface mounter motor. Any suggestions? My cobalt slow action motors are working perfectly but I don't have enough space under the board in the positions where I have used the Hornby motors.

Thanks again gor the great advice. I really appreciate it.

Alan

[Chrissaf]

I am afraid I am not impressed that almost every other one does not demonstrate the 'snap action' you (Chrissaf) describe.

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That might be because all my current layout track is Peco with Peco points. The Peco points whose part numbers begin with ST (Set Track) allegedly have the same geometry as Hornby's. I have seen many comments on the forum that Peco points are preferred to Hornby's.

[Michael_A]

I have 16 Hornby points on my layout utilising this point 'motor' (it's a solenoid. not a motor...) The  only issue with operation is alignment and the tightness of the screws. (Solved by keeping them slightly loose)

 

So strongly suspect a CDU will solve the problem.

 

Oh, and I never even considered removing point springs..........

[Nick_]

I have used both Hornby points and Peco points. Peco points have stronger springs than Hornby point so they do have more of a 'snap'. Hornby points don't 'snap' as such, but the spring is strong enough to hold the point closed either way. I agree with others who have stated that point motor positioning is critical. Get it wrong and one way or the other the points won't close. I also agree with Chrissaf that it's the amps that matter and without enough power (i.e. volts x amps) the point motors sometimes won't properly switch.

[nalaselig]

Thanks for all this advice plus the extra contibutors input. I knew they were solenoids not motors but that is what Hornby call them! Similarly, it was also in the Hornby installations instructions to disconnect the spring if they did not function efficiently. I will know better next time including which brand to buy.

Acting on the advice received, I have replaced the spring-less points with points with springs intact - it was far too challenging to replace the spring and fortunately I can use them in the layout where they will be controlled by DCCconcepts Cobalt slow action motors (these are brilliant even in the hands of a novice); I have changed the supply to 16vAC from 12V with a provision to include a CDU when I get one  and I have checked the alignment of the motors (solenoids) to the points. The good news is that 5 out the 6 now seem to closing properly. I need to recheck the mounting/alignment of the exception but I supect that the CDU will hopefully put me in full business.

Thanks everybody. It has been a rewarding as well as a learning experience

Alan

[Chrissaf]

Thank you Alan for the detailed feedback.

Another IMHO moment. The other advantage that the CDU will bring to the solution is the elimination of the annoying buz that the 16 volts AC supply imparts on the point solenoid when operated (being an annoying buz is my personal opinion, some people prefer it as it gives positive feedback of solenoid operation). The CDU gives a 'Half Wave Rectified' DC pulse, thus the only noise is the loud click of the solenoid being thrown.

Chris