The Bridges at Saltash

[jesse6669]

You might want to check that Silver Conductive Paint that Uwe is using for locomotives and turnouts (points) on the frogs to improve conductivity on points. I just ordered some (what I could find here in the USA anyway) and will be experimenting with it for locomotive wiring, lighting, track, etc. I can see it being used on rail joints to ensure good continuity as well.

[dkightley]

I've got some of the silver paint somewhere in one of my boxes of bits.....and I have to admit I'm not that much of a fan of it. Well, not for original build, that is!

I may try it one day when I'm in a repair situation and there's no alternative way of doing a conductive repair, etc.

The points on Saltash don't have any non-conductive areas.....so there's nowhere to try the conductive paint. I think I'm "on the fence" on this one!!

In the meantime......I've been laying a couple more sections of track that have either a power feed, an optical sensor....or both! It looks as if all the preparations and plans I made last year are slowly coming together. But there a long way to go yet!

[dkightley]

In my normal "jump around from one thing to another" way of working, I've been doing some CAD work on the Royal Albert Bridge. Here's the latest view of one of the spans:

RAB1.JPG (65.61 KiB) Viewed 3782 times

I still have to add the internal crossmembers that span from one side of the bridge frame to the other.

I've already got the end and centre piers printed....and a first cut of one half of one side of the girderwork is currently growing on my printer. around four hours worth of printing....which will be followed by a long session carefully prising support material off!

[dkightley]

And now with the internal crossmembers:

RAB2.JPG (78.52 KiB) Viewed 3783 times

[barneyadi]

Looking great Doug.

[dkightley]

What have I committed myself to do????

I've just finished printing what has been the most complex and fiddly pieces of 3D printing I've ever done. I thought some of the girders on the Forth Bridge were complex....but the side of the Royal Albert Bridge takes the biscuit!

IMG_3658_red.JPG (98.65 KiB) Viewed 3760 times

This is one piece! And the picture doesn't clearly show the complexity of it! It took almost 4 hours to print...and around an hour so far prising it off the printer bed and removing the support material....which I had to tease off with a scalpel and set of micro-pliers!

And I have 7 more of these to go! And a set of 22 crossmembers pieces....

[dkightley]

And then there were two:

IMG_3661_red.JPG (64.41 KiB) Viewed 3723 times

These two don't actually fit together like this...they're left and right sides of the same quarter of the bridge. But separating the second part from its support material was a darn sight easier than doing the first....which gives me a bit of confidence of being able to do all eight sections!

The only snag is that I'm having to fit printing in between printing orders from the TTG shop at the moment...but I'm not going to complain!

[gbtrains]

Good work Doug

keep up good great work , it is looking brill.

Regards
Graham

[dkightley]

And finally there were eight!

IMG_3664_red.JPG (115.36 KiB) Viewed 3655 times

I do, however, still have to prise two off their support structure. And you'll notice a couple of other prints....half a tube now printed in fine detail, and one of the road deck sections....well, two, superglued together!

And an extra shot.....here's a couple of the smallest size internal crossmembers. Hopefully, I won't lose them!!

IMG_3666_red.JPG (51.13 KiB) Viewed 3655 times

PS That is an SD card they're sitting on. I could only fit one on a micro SD card!

[dkightley]

Whilst printers print, I have to keep busy! Track laying....Portsmouth side benind the layout:

IMG_3669_red.JPG (100.69 KiB) Viewed 3631 times

….and Saltash side behind the layout:

IMG_3670_red.JPG (126.94 KiB) Viewed 3631 times

Sorry for all the junk laying around all over the layout. Its my filing system! And the hammer is there purely for its weight....I've not had to hit anything with it - yet!

Track laying now 80% complete....and I've found my track alignment pieces absolutely essential for getting twin track aligned and looking neat.

IMG_3668_red.JPG (111.64 KiB) Viewed 3631 times

One of the best tools I ever designed for T....even lines up platform edges spot-on! Which will be just the job for when I get to Saltash station...its twin track on a curve, and will be a doddle to line up and glue down.

[dkightley]

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 (56.77 KiB) Viewed 3436 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 (42.44 KiB) Viewed 3436 times

IMG_3675_red.JPG (49.42 KiB) Viewed 3436 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!

[dkightley]

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 (72.45 KiB) Viewed 3413 times

The single track end showing the joint onto the flexitrack in the viaduct section:

P1020094_red.JPG (46.14 KiB) Viewed 3413 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 (56.42 KiB) Viewed 3413 times

[rail450]

Hi Doug,

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

BR,

Siegfried

[rail450]

Hi Doug,

how did you isolate the tracks

New_Point.jpg (20.82 KiB) Viewed 3350 times

in the middel of your point?

Do you have fotos of this detail?

BR,

Siegfried

[dkightley]

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!

[rail450]

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

[dkightley]

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 (52.68 KiB) Viewed 3312 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 (54.02 KiB) Viewed 3312 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!

[rail450]

Hi Doug,

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

BR,

Siegfried

[dkightley]

The electronics does indeed utilise a latching relay:

IMG_3688_red.JPG (61.48 KiB) Viewed 3245 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!

[dkightley]

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 (91.87 KiB) Viewed 3246 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.