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Re: The Bridges at Saltash

Postby dkightley » Wed Apr 03, 2019 10:16 pm

I've finally got the point to somewhere close to actually testing how trains run over it! I had to re-hash the pivot plate somewhat by increasing its size a little and changing the location of the pivot point....and change the curve of the rail slightly:
IMG_3673_red.JPG
IMG_3673_red.JPG (56.77 KiB) Viewed 1924 times

I've had to create a complete new set of rails to replace the original set....which were getting a bit scratched and bent with all the assembly and dis-assembly. The point looks and feels level and smooth....so it should take trains:
IMG_3674_red.JPG
IMG_3674_red.JPG (42.44 KiB) Viewed 1924 times
IMG_3675_red.JPG
IMG_3675_red.JPG (49.42 KiB) Viewed 1924 times

The two red wires are for powering the moving rails from a relay that switches polarity as the points are changed.

My only worry is that I may need to reprint all the parts in dark brown. I'll have to see how the white takes paint!
Doug Kightley
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Re: The Bridges at Saltash

Postby dkightley » Sun Apr 07, 2019 12:36 am

Having realised that some of the white parts will be visible in the finished point, I decided to reprint the trackbed and moving plate for the point. I also had to reprint the viaduct section as well...as one of the locating pins snapped off when I was doing a dry assembly.

Here's a few close-ups of the finished point in the viaduct. Firstly, a dry assembly of the reprinted parts...with the rest of the viaduct plugged in:
P1020092_red.JPG
P1020092_red.JPG (72.45 KiB) Viewed 1901 times

The single track end showing the joint onto the flexitrack in the viaduct section:
P1020094_red.JPG
P1020094_red.JPG (46.14 KiB) Viewed 1901 times
The flexitrack in the viaduct is a spare piece...the real bit of track will have less missing sleepers!!

And the business end of the point. The micro servo for the point sits inside the support for the trackbed for Saltash station. Its too dark, but under the ends of the track sections is the arm that operates the point, which has a socket tha sits over the servo arm..which simply pushes it side to side:
P1020093_red.JPG
P1020093_red.JPG (56.42 KiB) Viewed 1901 times
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Re: The Bridges at Saltash

Postby rail450 » Sun Apr 07, 2019 6:51 pm

Hi Doug,

the actual points have a lenght of 42 railway sleepers - will your perfect point also fit into that frame?

BR,

Siegfried
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Re: The Bridges at Saltash

Postby rail450 » Mon Apr 08, 2019 8:00 pm

Hi Doug,

how did you isolate the tracks

New_Point.jpg
New_Point.jpg (20.82 KiB) Viewed 1838 times



in the middel of your point?

Do you have fotos of this detail?

BR,

Siegfried
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Re: The Bridges at Saltash

Postby dkightley » Mon Apr 08, 2019 9:56 pm

There's a bit of a cheat involved in the isolation for these points...

Because the layout is designed to have automation using the MERG CBUS system with the locos all DCC operated, I have broken the layout up into a number of individually powered blocks so that I can use TOTI (train on track indicator) sensing to identify where trains are. The single track side of the point is the block incorporating the bridge, and the twin track side of the points consist of the eastbound and westbound Saltash station track blocks. I've placed the break between the blocks right at the end of the platforms...and thus the inboard rails that run up to the "vee" in the point are isolated from the three blocks....and this isolated section will be switched, along with the two rails on the moving plate, by the point servo to connect to the appropriate rail on the bridge track block.

This arrangement means that I don't have to put any break in the track pieces within the point itself....which would be needed in other circumstances. The power feed to this section is also off the pointwork...but the two short rails on the plate are fed from below.

Told you it was a bit of a cheat.....and I'll be taking some photos of these details when I get things wired up. At the moment its a pile of pieces!! Also...working on the track involves a lot of bending over to look at details close up …...and I'm doing this sort of work in short sessions to stop it killing my back! :?
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Re: The Bridges at Saltash

Postby rail450 » Wed Apr 10, 2019 7:13 pm

Hi Dough,

the tracks in the middle of your point look like soldered and shorted - is it a machanical sample only without electrical functionality ?

BR,

Siegfried
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Re: The Bridges at Saltash

Postby dkightley » Wed Apr 10, 2019 10:42 pm

Siegfried

Firstly, I'm not uncooked bread! ;) ...there's no H in Doug.

And to explain how the points will work...a couple of quick diagrams.

Red is the positive rail and Blue the negative rail....at least representative - DCC has an AC feed. Green is the switched sections of rail, which are connected to either the positive supply or the negative supply by an electronic switch triggered by the point servo control signal...and the track blocks are labelled in black. Note the rails have gaps to isolate the three track blocks from each other.

The first diagram shows the point set for eastbound traffic...and the switched rail sections are connected to the negative rail ----which is why they're shown with blue dashes.
IMG_3681_red.JPG
IMG_3681_red.JPG (52.68 KiB) Viewed 1800 times



The second diagram shows the point set for westbound traffic...and the switched rail sections are connected to the positive rail ----which is why they're shown with red dashes.
IMG_3680_red.JPG
IMG_3680_red.JPG (54.02 KiB) Viewed 1800 times


If I can get the wiring right I might even connect the two short rails on the moving plate by individual wires so the unused rail is not powered. I need to check the relay can cope!
Doug Kightley
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Re: The Bridges at Saltash

Postby rail450 » Fri Apr 12, 2019 12:33 pm

Hi Doug,

will you use bistable relays to store the polarity in the middle track part until you change the direction?

BR,

Siegfried
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Re: The Bridges at Saltash

Postby dkightley » Sat Apr 13, 2019 10:07 pm

The electronics does indeed utilise a latching relay:
IMG_3688_red.JPG
IMG_3688_red.JPG (61.48 KiB) Viewed 1733 times

This is a MERG pcb/kit designed to utilise a servo control of the point to switch live frogs. The latching relay is purely to accommodate the fact that the servo power is only switched on for the duration of the servo move...and then powers down to reduce overall power consumption. If the relay was not latching, it would cause issues!
Doug Kightley
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Re: The Bridges at Saltash

Postby dkightley » Sat Apr 13, 2019 10:14 pm

Whilst running around Saltash on Google Earth looking at the buildings I'm going to be designing soon, I stumbled across a situation that the Google Earth car captured that will help me put together a stock list for the layout. The old and the new passenger stock!:
RollingStockPeek.JPG
RollingStockPeek.JPG (91.87 KiB) Viewed 1734 times

This was in July 2018..but I'm not sure if the Class 800 was in service or on trials/driver training at the time.
Doug Kightley
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