An Experimental Point

[Stuart Birks]

My next project is going to be a rebuild of the small station side of my layout, a few pictures can be found here

http://myweb.tiscali.co.uk/sbirks/railway/branchline.html

For the rebuild I have decided to make all the track so that I can get a nice curve on the entrance to the station. Having never built any point work before I thought I would do a trial point to see how it goes. Rather than just build it as a standard point I wanted to try a few experiments.

Hide the blade drive as much as possible
It’s GWR so the track should be “joggled”
Hide the cable connections for the frog and blades and also switch the frog polarity as required
Weathering the track and sleepers
Point rodding and a facing point lock

Since this was very experimental I haven’t shown it as a work in progress as it might have gone wrong and been abandoned at any stage so I will run this thread backwards.

This is the final result and if anybody is interested I will show what is underneath the board and how it was made..
 

 

 

 

 

And a couple of videos of it in action.

http://www.youtube.com/watch?v=uz_9Y5lk0JY


http://www.youtube.com/watch?v=gb3Lt7jhp_Q


And nobody tell me I have forgotten the detection bars. They might come in the Mk2 version although they will just be dummies.

So is it a success? I think so but any comments will be welcome. This must be viewed as a prototype, it will never go on a layout but hopefully I will incorporate what I have learnt into the layout when I do build it.

Stuart
 

 

[hayfield]

Stuart

 

Stunning piece of modelling. What parts have you used please

[shanks522]

Very impressive! 

 

Graham.

[Stuart Birks]

Stuart

 

Stunning piece of modelling. What parts have you used please

Thanks John

 

The main point is a kit from C&L. The tie bars, cranks and point rodding is from Ambis engineering and the rodding stools are from Brassmasters. Plus a few odd bits of brass wire and tube from stock.

 

Stuart

[Andy Y]

I haven’t shown it as a work in progress as it might have gone wrong and been abandoned at any stage so I will run this thread backwards.

 

 

 

Most definitely interested!

[Debs.]

Lovely work; show us what`s in the undercroft, please!

[truffy]

The main point is a kit from C&L. The tie bars, cranks and point rodding is from Ambis engineering and the rodding stools are from Brassmasters. Plus a few odd bits of brass wire and tube from stock.

You make it all sound so obvious!

[-missy-]

Top modelling skills!

 

Missy

[martin_wynne]

Brilliant -- except for one thing. It's not a point. It's a turnout, or on the GWR a "single lead".

 

In P.W. terminology a point is a single moving switch blade (so called because it is pointed). Two of them linked together by means of a stretcher bar make a "switch" or a "set of points". A set of points linked to a crossing makes a turnout.

 

Many modellers get this wrong, but when you have gone to so much trouble to build a superb turnout it does seem a shame to call it by the wrong name.

 

Martin.

[Geoff Cook]

Lovely work; show us what`s in the undercroft, please!

 

At a guess a from the sound a Cobalt point motor

[Stuart Birks]

Thanks for the comments. This is how I made it.
 
I started with a C&L point kit. Not having bought anything like this before I wasn't sure what I needed or what I was going to get. The kit comes with the C&L thin sleepers but thinking I wanted a bit more depth to get the tie bars in I glued some extra strip underneath them to make them the thickness of the thick sleepers. Otherwise the kit was built basically as standard.
 

 
I left out the sleeper where I wanted to hide the blade movement pins but the pins can be seen here. Just 0.5mm brass wire.
 

 
I recalled reading somewhere that it was a good idea to build the turnout (got told off by Martin for calling it a point ) on double sided tape. That worked fine but then I wanted to remove it to put in on the test board. Big disaster, although I had glued the slider chairs to the rail I must have done a poor job as when I removed it from the tape all the sleepers that just had slider chairs fell off. Luckily it was not too bad to print another template and use pva to stick it all back together. It was also mounted on 3mm cork.
 
Under the tie bar area I made a unit that contained a couple of sliding things, one for the blades and one for the facing point lock. This is the same thickness as the cork so fits nicely.
 

 

 
Now for the bit underneath. It is all based on a plate with some slots milled in it to give the required sequence of movement. The plate moves vertically as shown here so pins in the slots will move horizontally.
 

 
This is driven by a slightly modified Cobalt motor. There's another guarantee on the void pile.
 

 
Bolt a load of bits together and it ends up looking like this
 

 
And this
 

 
Probably over engineered but this is a prototype.
 
And here are a couple more videos of it in action

 

http://www.youtube.com/watch?v=gH2rPMGDT-c

 

http://www.youtube.com/watch?v=B_TBaQbXmIQ

 

On the drive I have used some threaded rod which give some adjustment for the movement. On the one for the blades I put a couple of springs to take up extra movement. The plate gives 2mm of movement where the blades only require about 1 to 1.5mm. In practice they don't work and are not needed. There is sufficient give in the mechanism to take up the extra movement.

 

Back on top with the point rodding, only the first section between the stools moves. It just slides under the rest of the rodding which is fixed.

 

I hope that is enough of an explanation.

 

Stuart.

 

p.s. No prizes for the first person to spot the massive design flaw. Still its only a prototype so I can correct it if I make one for real.

[hayfield]

Stuart

 

Stunning bit of model engineering, how many more are you going to make for your layout. Buy the way the point turnout looks top class as well

 

Regarding double sided tape, I cut strips about 2mm wide to lay the sleepers on, to get them off just flood the plan with white spirit which degrades the glue. I also stick the slide chairs to the rail first with superglue, but you can use Butanone to stick the chairs to the rail

[gordon s]

Some amazing work, probably the best I have seen in terms of turnout operation.  Can you make me 75 in the next few weeks?……:-)

[ThePurplePrimer]

I find that just fascinating - a little bit awe struck if I am honest

[-missy-]

I find that just fascinating - a little bit awe struck if I am honest

 

Make that two. I can see this is the sort of stuff you enjoy.

[Stuart Birks]

The bit I forgot to include was putting the joggle in the rail. I just made a simple jig like this

 

 

The top plate is fixed, the lower one is bolted with a couple of spring washers so it can move a bit. The step is 0.25mm resulting in s 0.2mm joggle. The rail springs a bit loosing the 0.05. This seems to work well. the tip of the blade supplied by C&L is 0.2mm. Its big enough to show but not too big to cause a problem.

 

Stuart

 

 

[Stuart Birks]

Can you make me 75 in the next few weeks?……:-)

 

Thanks for the comment. This one took 3 months. I think you can work that out yourself.

 

Stuart

[Stuart Birks]

Stuart

 

Stunning bit of model engineering, how many more are you going to make for your layout. Buy the way the point turnout looks top class as well

 

Regarding double sided tape, I cut strips about 2mm wide to lay the sleepers on, to get them off just flood the plan with white spirit which degrades the glue. I also stick the slide chairs to the rail first with superglue, but you can use Butanone to stick the chairs to the rail

 

Thanks. The tip on thin strips of tape is useful. I did flood it with white spirit to release it and that worked and I had stick the chairs with superglue, I just did a rubbish job of it. Perhaps I will try the Butanone another time. I have also thought of building it straight on the cork then I don't have to remove it.

 

My current track plan which is only on paper at the moment only requires 3 with the facing point lock but for the rest I don't have enough clearance between the board and the fiddle yard underneath to mount a cobalt in the normal vertical position so I will still need something simple to allow it to operate on its side.

 

Stuart.

[LNERGE]

Your superb point machine mimics this type perfectly. I wonder if the SGE HA mechanism could be miniaturised?

 

[iak]

VERY impressive and clever sir.

[Stuart Birks]

Your superb point machine mimics this type perfectly. I wonder if the SGE HA mechanism could be miniaturised?

 

Considering that my point turnout is driving the rodding not the other way round then at first sight all that would be required is to replace the rodding with a box with a couple of wiggly bits sticking out from it. It should be easy, possibly easier than having the rodding.

 

Stuart

[flexible_coupling]

Disadvantaged by my own geographical location (I'm in Australia!), I have what may be a terribly 'simpleton' question with regards to the way that the SGE mechanism operates... The bar running from the 2nd crank (parallel to the rails, centred between) that links somehow to the tie-bar.... is there some kind of rack-and-pinion transferring the force 90-degrees to the tie-bar to pull the blades from side-to-side? Or is there something else at play that my imagination can't process right now?

 

I'm building a small finescale 'O' layout with a single turnout in the display area, planning to use hardwood sleepers and C&L chairs etc., and to have super-detailed and 'dummy-operating' linkages with a "motor" such as the whole SGE product demonstrates would be a delightful touch. I'd most-likely draw up the motor body in 3D and have it rapid-prototyped for myself, I think.......

 

EDIT: I had another look at the diagram when I got home from work and realised how it all really operates... feeling a bit embarassed!

[Stuart Birks]

EDIT: I had another look at the diagram when I got home from work and realised how it all really operates

Understandable, there are lots of bits wiggling about all over the place. Glad you see it now.

 

I would be really interested to see the result of having parts made by rapid prototyping.

 

Stuart.

[johndon]

The operating mechanism is a great bit of engineering.  Now, when can I buy some

 

John

[Stuart Birks]

Now, when can I buy some

Sorry, no intention of selling any. All I can say is there is no patent or copyright.

 

Stu