Point motors returning to original position

[Pedro48]

Hi everyone, it is a while since I have posted on the forum.

I have 4 sets of 2 points working together, 2 sets are working fine, but with the other 2 sets when I switch to the turnout one point resets itself to the original position. I am using Hornby surface mounted point motors (R8243 and Hornby Accessory controller R8247). All points are wired the same ( 2 red together and 2 green together. I am at a loss, any advice would be appreciated.

Thanks Peter from Australia.

[P-Henny]

It is common knowledge that the internal CDU in the R8247 is weak due to the relatively low internal capacitor charging voltage.

When two point motors are wired in parallel, the manufacturing electrical tolerances of the motors and/or physical point motor alignment can result in one motor of the pair being more dominent in terms of absorbing the limited amount of R8247 CDU current available.

My deduction is not that the R8243 is somehow being fired back to the other position, but more likely that the low power output of the R8247 is not enough to robustly fully operate the less dominent of the pair past the toggle action switching position and it is the point spring that is returning the motor back.

Another issue with the R8243 point motor is that it can physically flex and cause the internal solenoid slug to become sticky if the mounting screws are done up too tightly.

I suggest slackening off the screws of the two offending point motors such that you can detect slight movement of the motor with your fingers and then test the operation again.

With the R8243 removed, does the point move across by hand in both directions with a positive click. If not, then there is an issue with the point moving rail and/or point spring.

If after checking the point motor alignments and manual operation and performing any fixing screw adjustment fails to clear the problem, then you can use TWO R8247 decoders configured with the SAME DCC Addresses and wire one motor of the pair to one R8247 and the other motor of the pair to the other R8247. In this scenario, sending a single DCC Address operate command will cause both R8247 (ports with the same DCC Address) to respond and operate the two connected R8243 point motors together.

[96RAF]

I’m not sure I understand the question.

You fire a paired point and one returns to the original position, maybe you have them cross wired.

[P-Henny]

The OPs description seemed to be quite straight forward to me.

Two motors in parallel. One point drives successfully through and locks on the other side whilst the other point starts to move across but does not complete and lock but returns back to the pre-operated position.

If the OP comes back and says this understanding is not correct, then I will delete all my posts so far in this thread as that is the understanding for which they are written.

[Flashbang]

I read your inital post as that two solenoid motors are wired to one PAD port (Output group) One motor moves over correctly but the other one only just moves and the points over centre spring returns that point back to the starting place. If so, then.....

1) Try disconnecting one motor and then test the remaining one. Does it work OK? If so, then reconnect the other one and disconnect the one that just worked OK. Now does the second motor work OK. If each work on their own OK, then...

2) Is the wiring from the PAD to each motor and the returns in ideally in 16/0.2mm wire (0.5mm2 or 20AWG)? Using a smaller gauge of wire can easily lead to a fail to throw. You can use a three way piece of terminal block located near the motor to terminate the factory wires in one side and the new wires from the PAD in the other side.

3) As previously stated, the Hornby PAD only has one CDU (Capacitor Discharge Unit) for all four outputs and is a little under powered, plus you need to pause point movements for a couple of seconds to allow the internal CDU to reach a fully recharged condition after each operation. Can you move one motor to another port on that or another PAD? Or obtain a non-Hornby pulse output Accessory decoder that has a dedicated CDU per output.

Edit: Typos corrected.

[Rog RJ]

Possible obstruction in the point blades (piece of ballast for instance) causing the point not to fully operate and "bounce" back?

[Pedro48]

Thank you Paul,

I have rearranged the decoders to be closer to each set of points, they are now all working perfectly, simple solution.

Thank you once again

Peter

[P-Henny]

That solution suggests that the wiring is too thin as per item 2) in Flashbang's reply.

[Pedro48]

I am using DC Concepts decoder wire and I have not had this problem before.

Thank you all for your input.

[P-Henny]

No wonder that you had point operating issues. Decoder wire is ultra thin and not really designed for Solenoid point wiring. It is meant to be used when hard wiring a decoder into a non DCC Ready locomotive. Just because the R8247 is called a decoder, this does not mean that it is the same type of decoder that DCC Concepts decoder wire is used for.

Solenoid point motors have coil DC resistances that are typically less than 12 Ohms. The R8243 is closer to 4 Ohms. This means that they will try to draw peak pulse currents in excess of 3 Amps when being operated. The wire that is factory terminated on the R8243 is far thicker than decoder wire and should be treated as the minimum wire size to use when extending the Solenoid point motor wires. Many layout builders use wire that is 16/0.2mm or thicker to operate a Solenoid point motor (16 strands of 0.2mm diameter wires).

You say that you moved the R8247 decoder closer to the points, this I assume meant that you then terminated the R8243 factory fitted wires directly onto the R8247 thereby eliminating any decoder wire extensions from being in the circuit or at least minimising any length that was used.

[Pedro48]

I have soldered the decoder wire to the point motor wire. Previously I had tried telephone cable but I think it was too heavy.

[Flashbang]

Telephone wire is to thin! hushed

Moving the PAD closer to the point motors has overcome your small wire gauge size.

As I stated in my post above, the very smallest wire I recommend for reliable solenoid point motors is 16/0.2mm (0.5mm2 or 20AWG) This is my recommended minimum wire size, thicker wire can of course be used.

[Pedro48]

Thank you Flashbang.

I have searched some hobby shops for point motor wire here in Australia.

Some refer to Peco PL-38 series as suitable for Peco point motors. Would this be suitable for the Hornby point motors?

[P-Henny]

Peco PL-38 is 16/0.2mm so would be suitable. A cheaper option would be to purchase Domestic 5 Amp Electrical Flex and strip the wires out from within the outer sheath, use the wires and discard the sheath. Wire is wire, it doesn't have to be purchased from Model/Hobby shops.

For information (don't know about Australia but) here in the UK, wherever possible, one doesn't buy this kind of wire in Model and/or Hobby shops. That is unless you want to pay extortionate prices. In the UK, this kind of wire is purchased from either 'online' electronics component sellers or over the counter in 'Electrical Wholesalers'. The kind of outlet where electricians go to purchase their materials. In the UK, many 'Electrical Wholesalers' sell to the public as well as the trade as they want to maximise their annual turnover. They do expect however, the public to know exactly what they want though, as unlike retailers they are not geared up to guide public customers through the selection process of the available products. This is done, usually by selecting what they want from the traders paper or online catalogue and arriving at the counter with a list of stock code numbers & quantities they want to purchase.

The 'Electrical Wholesalers' I frequent, are more like a warehouse setup with a front end staffed counter where the products are ordered and delivered to, that is to say not a shop. The main advantage is getting the cheaper 'wholesale' price. I have to be cautious though, as some UK Wholesalers have a two tier pricing structure. One for trade and another for public. Thus I research my potential suppliers carefully.

[Pedro48]

Hi Guys

I was able to obtain some data cable at no cost to try out. All points are now working fine.

Thank you all for your advice.

Peter

[Flashbang]

Cat 5 Cat 6 etc data cable is still too small a wire gauge. The best option here would be to double up cores assuming the cable is at least 6 core, making it a three core cable.

Rule of Thumb..... MINIMUM wire size is 16/0.2mm - 0.5mm2 or 20AWG. But thicker wire is also fine. Thiner wire equals volt drop and that can result in poor operation of solenoid motors especially if two are operating together as is a cross over pair.