Point operation using solenoids/stainless rod over distance

[Torr Giffard LSWR 1951-71]

Aft'noon all,

 

I'm currently designing the point activation mechanism for 3 sets of points on a steel viaduct for TG. I'm planning to use a spring return arrangement on each so that any failure of the point activation mechanism or linkage maintains the points in the 'normal' position and allows operation of the layout to continue. The stainless activation linkage will need to be up to 3ft in length if the solenoid or motor is to be housed at the end of the frame. The other option is to pass the activation linkages up through the brass caissons of he bridge and locate the motors or solenoids beneath the river level/under the frame.

 

Any experiences of remotely situated point activation esp. using solenoids would help.

 

Cheers

 

Dave  

[Gruffalo]

Can I suggest that you look into how aero-modellers operate control surfaces on their aircraft? They tend to use a "wire-in-tube" arrangement comprising multi-strand wire running in plastic tubes and also use a lot of fulcrums (fulcra???) to alter the direction of movement. The typical fulcrum has a series of holes so you can increase or decrease the movement from the solenoid throw according to your needs.

Where your layout includes hidden operating rods, this would be ideal for covering significant distances but in the most viewed areas, the actuation from the fulcrum could easily change to brass rod.

[ColinK]

Hi, on the OO layout I am building, I am using piano wire to control the points.  I got the wire from Arcadia Models in Shaw.  It is very stiff and I would expect it to work over the 3 feet you require. 

I've simply bent the wire through 90 degrees at one end and fed it through the hole in the Peco tie bar. The other end is also bent through 90 degrees and has a bead (from Hobbycraft) glued onto the control end.  The wire is installed in a groove cut into the baseboard top and covered with thin card.

It works fine and is very cheap.

The only downside is that piano wire is very hard to cut, so you will need very strong pliers/cutters.

[34theletterbetweenB&D]

Don't attempt drive rod or bowden cable style operation  with a solenoid. Slow motion motors are much the better choice, look at the Fulgurex or Lemaco pattern as these generate the linear movement you are looking for. (I use Fulgurex with drive rods as standard, one motor underneath the crossings operates a pair of points in crossover formation; this motor offers drive both ends which is what made it the choice for this application.)

[Torr Giffard LSWR 1951-71]

Thanks guys,

 

....a bit of investigating to do now.

 

Cheers

 

Dave

[Grovenor]

I'm planning to use a spring return arrangement on each so that any failure of the point activation mechanism or linkage maintains the points in the 'normal' position and allows operation of the layout to continue.

If using spring return then the linkage only has to pull and can therefore be very thin wire, I would endorse the comment above to avoid solenoids, go for some form of motorised drive such as tortoise or servo.

Keith

[Torr Giffard LSWR 1951-71]

Hi Keith,

 

I have a pack of 6 Tortoise motors for using directly beneath points but wasn't sure about remote operation esp. at approx. 3ft distance. Checking others experiences was the intention with this post.

 

Cheers

 

Dave

[Suzie]

A servo should be ideal for such a tricky situation because you can make use of the radio control bits you can buy in the model shop to make the linkages which are usually screw adjustable and clip on to the servo horn.

[Martin]

But if you want the point to return automatically to the normal position in any fault condition, then a solenoid that is powered to change the point, and a spring to return the point when power is removed from the solenoid, will give the required result. A servo type drive will require an active return system. The motion can be transferred using a thin wire, as mentioned by Grovenor.

 

regards

Martin

[Torr Giffard LSWR 1951-71]

....this was why I mentioned solenoids Martin...a point failure in a mid-way position on either of the bridges will disable a large portion of the layout for a good chunk of the  day.

 

Current experiments and investigations suggest that a long crank arrangement down the caisson tubes will be best, with point motors located beneath the river frame i.e. easily accessible and also with the option to disengage the motor (if it becomes defective) and lock the points in the 'normal' position. 

  

Dave