Sarum Bridge

Post details of your T gauge layouts and the progress you are making.
martink
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Sarum Bridge

Post by martink »

Hi, I am new to the forum and T gauge. I normally model in N but felt like trying something different, so a few weeks ago bought one of the HST starter sets with a few odds and ends and gave it a try. As a result, I decided to make a small (by N standards) automatic tail-chaser layout in T. After two weeks of hammering, sawing, gluing and swearing, tracklaying is complete and I can now run a train. No automation or scenery yet, and I'll be stuck working on some other projects for a while.

Sarum Bridge is a highly wrapped dogbone layout in a fictitious location somewhere in England. Overall dimensions are 1'8" x 4'8.5" (I like round numbers), with 15m of flexi track (about 4 scale miles). The main focal points are a 900' viaduct and a station with four platform faces. The track is divided into four sections eventually allowing three trains to follow each other around the layout. The automatic stop positions are the four platforms. It is currently wired as a simple oval - just an overgrown train set.

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hedge
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Re: Sarum Bridge

Post by hedge »

Really like the look of this! Will watch progress with much interest.

martink
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Re: Sarum Bridge

Post by martink »

A last spurt of progress before pausing for a couple of months. The only thing I expect to do in the next week or two is add more rolling stock - I have some 3D printed loco and wagon shells and suitable chassis on order (thanks, Ozrail). I'll see how they turn out.

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And a rough and ready video...

http://youtu.be/zuQ2-VBGIDY

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nscaler69
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Re: Sarum Bridge

Post by nscaler69 »

martink wrote:And a rough and ready video...
http://youtu.be/zuQ2-VBGIDY
Nice video there, I like the continuous single tack idea.

mattd10
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Re: Sarum Bridge

Post by mattd10 »

Absolutely superb! This is exactly the effect im going for, albeit on a smaller scale! How are you going to do your automation and detection?

Sent from mobile device

martink
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Re: Sarum Bridge

Post by martink »

Thanks guys - feedback is always appreciated (especially positive!).
nscaler69 wrote: Nice video there, I like the continuous single tack idea.
A video always brings it to life, and seeing the full HST running at scale speed over a nice long stretch of track is pretty much what encouraged me to build this one. The design was really a toss up between a dogbone or an equivalent length double oval. The main advantages I saw to each were that with the dogbone each train runs over the whole layout rather than just half of it, while with a double oval you get redundancy. However, even in T, those balloon loops still take up a lot of space!
mattd10 wrote: Absolutely superb! This is exactly the effect im going for, albeit on a smaller scale! How are you going to do your automation and detection?
I find I have a marked preference for the highly wrapped lots-of-track style of layout, and T allows a modeller to do things well nigh impossible in larger scales. I have to keep reminding myself that this one is the equivalent of 14' x 5' in N, but even there I try to squeeze in as much as possible. My main N gauge layout also crams as much into not much more space (6 platform terminus, MPD, 4-track main line set up as an out-and-back with auto queuing of up to 5 trains, fully signalled, door-sized layout, still under construction). This T gauge excursion is basically to give me a change of pace before getting back to N.

I've sketched out the rough automation design - it is a straightforward variant of what I am already using in N. Four sections, each with two ambient-light LDR sensors (stop and slow) with sensitivity determined by the relative intensity of all 8 sensors, and two speed control relays (stop, slow, medium and fast) per section. A PIC16F690 to handle the control logic. Three separate 555-timer-based PWM controllers to set the three speeds. Stop positions are the four platforms, so trains will be continually slowing, stopping, starting and accelerating from the station. I've also been fiddling with fibre optics, looking at some sort of working signals - basically R/Y/G searchlights with below-board LEDs, possibly disguised with dummy three aspect heads or even semaphore arms. That part may or may not eventuate, but I'll use a few shift registers on the control board to give me enough outputs to handle 8 relays and 16 LEDs as well as the 8 ADC inputs from a 20 pin chip.

jesse6669
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Re: Sarum Bridge

Post by jesse6669 »

That is just fantastic Martin. And all in 4x2 feet! Keep us posted after your hiatus.

martink
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Re: Sarum Bridge

Post by martink »

The first batch of rolling stock is complete and rolling (!) - a short rake of OzRail's 4-wheelers, hand-painted in bright primary colours (brown and grey). I am currently plucking up courage to tackle a couple of the loco body shells, and trying to decide between BR blue to match the HST, or my preferred BR early green.

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Ozrail
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Re: Sarum Bridge

Post by Ozrail »

Looking great Martink, Hope they run smoothly for you.
Just some advice, try and run the freight train with 2 motor units.
Check out my Shapeways store for T-gauge stuff.
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http://www.shapeways.com/shops/everythingtgauge?s=0

martink
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Re: Sarum Bridge

Post by martink »

Ozrail wrote:Just some advice, try and run the freight train with 2 motor units.
Yup, I've already figured that one out. When I get a longer train I'll double head it and maybe see about permanently wiring two locos together. Something similar for a future passenger train as well - either using a second HST extension set as a passenger rake or add a powered siphon.

The wagons run surprisingly well given their very light weight, at least after I realized that the coupler springs really weren't helping and decided to leave the couplers sitting loosely. Are there any known longevity issues with the wheel bearings, given the fragility of the 3D plastic?

Ozrail
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Re: Sarum Bridge

Post by Ozrail »

martink wrote:Are there any known longevity issues with the wheel bearings, given the fragility of the 3D plastic?
This one I'm still not sure of the answer, as I really haven't come to this issue yet.
Yes I do run my wagons, but not like everyday, and mine have been around a few years now. (Around 3 years+ now)

I do have a Flying Scotsman and a Thomas who runs more often (mainly Thomas) and they have the same setup as the trucks.
So yeah, you should hopefully get a fair amount of running with them.
Check out my Shapeways store for T-gauge stuff.
Image
http://www.shapeways.com/shops/everythingtgauge?s=0

martink
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Re: Sarum Bridge

Post by martink »

I've now painted my small collection of diseasels, 3D printed body shells from the usual suspects. All are done in BR blue to match the HST set. As usual with objects of this size, the photo is very, very cruel - they look a lot better at a normal viewing distance. I currently only have a chassis for the class 42 - the others will get their wheels during the next stage of layout construction a few months from now. I also need to see about getting some BR double arrow decals - I don't want to even think about trying to hand-paint those! Has anyone been down that road already?

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jesse6669
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Re: Sarum Bridge

Post by jesse6669 »

Looking really, really good!

martink
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Re: Sarum Bridge

Post by martink »

I hadn't intended to do any more work on the layout for a few months, but it was calling to me... looking at me reproachfully every time I walked past... :( So, here goes another week or two of effort.

Progress so far:
- scenery: basic substructure done with removable hilltops to allow access to the balloon loops, backscene cutouts for more access, started work on the stone facings for the viaduct, ordered a castle for the larger hill (Lilliput Lane's Conwy Castle just happens to be about 1:450, plus it looks more interesting than Old Sarum).
- rolling stock: added BR double-arrow decals to the locos (the smallest N gauge size is only a little over-scale), more chassis and 3d-printed stuff on order (enough to give me three runnable trains, even if a little short and under-powered)
- electronics: built and tested the three PWM controllers (the overload protection circuitry ended up as complex as the basic controllers!), automation computer design under way to fit on the same circuit board, basic panel design and location finalised.

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hedge
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Re: Sarum Bridge

Post by hedge »

The BR arrows look great as does the controller PCB. So glad you decided to progress the layout!

martink
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Re: Sarum Bridge

Post by martink »

I've been making slow and steady progress on the layout. There are about half a dozen separate sub-projects underway, most of which should come to fruition in a week or so (with pictures), but just a quick update for now...

Scenery - I've pretty much figured out a rough plan for what goes where, depending on how various structures & such work out as the various bits and pieces arrive at my door.
Rolling stock - I've motorized the class 55, added a short newspaper train and have a pile of new stock ready for painting. Longer term, I will definitely be going with two permanently-coupled & wired motor units per train.
Electronics - the automation is up and running in full speed / sudden stop mode, and I am currently working through some problems with the speed control relays. Sigh. The first-attempt signals are behaving themselves and proving very useful during development, reprogrammed as needed to display the state of the track sensors, the speed relay settings, etc.

As hoped for, one of the end-hills gets a slightly-underscale castle along with the requisite tourists and car park... Some resurfacing and painting will be required to blend it in, but the Lilliput Lane product is a very, very nice model. It actually looks better in reality than in the pictures - lots of interior detail, which you can see because there is no roof!

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martink
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Re: Sarum Bridge

Post by martink »

A few more sub-projects completed and closed out:
- the current round of rolling stock expansion is basically done - lots of wagons painted up ready for wheels, couplers and more motive power.
- the automation is up and running, and the signals are fully functional though still only the initial trial version (bent pieces of optic fibre) for now.

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tjejojyj
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Re: Sarum Bridge

Post by tjejojyj »

Hi Martlink,

I don't know about anyone else but I'm impressed. Can I ask what you are using for the automation? Some programmable chip?

I have a Pololu Baby Orangutan microprocessor board (http://www.pololu.com/product/1220/) and I'm going to have a stab at using this as the basis of my PWM controller. (I bought it last year out of curiosity to learn about them but hadn't done anything with it). It seems to me that this could also be used for automating features on basic layout.

Regards,
Tim J.

martink
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Re: Sarum Bridge

Post by martink »

I standardized on the PIC16F690 some time ago as a good general purpose device, and it is pretty much equivalent to the one on the CPU board you are using except that it only has one set of PWM outputs instead of the two available to you.

Dead easy to use - just connect 5V and ground, then do what I want with the 18 I/O pins. In this case, I have hooked up 8 LDRs as track sensors, a MAX7219 to drive 64 LEDs for signals and a future illuminated signal box diagram for the spectators, a couple of switches and LEDs on a small control panel, and a 74LS164 shift register to give me a few more outputs for driving the speed-control relays. There was enough room on a single piece of Veroboard for all that plus 8 relays plus 3 PWM controllers. The software is written using the free version of the Hitech C compiler. If you are interested, I'll be putting the circuit diagram, circuit description and code up on my website sometime in the next few days.

Basically, all of those mid-range chips are very similar, whether PIC, ARM or whatever. Unless you are doing something unusual or trying to squeeze every last cent out of a commercial design, it is generally a case of going with what are you comfortable with, what software you have available, etc.

So, what sort of automated features are you thinking about? Some are much easier to implement than others, and not always the obvious ones.

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tjejojyj
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Re: Sarum Bridge

Post by tjejojyj »

martink wrote: So, what sort of automated features are you thinking about? Some are much easier to implement than others, and not always the obvious ones.
I was initially thinking of having two trains running in opposite directions passing in the stations but the reported unreliability of the points means I will just aim for two trains chasing around a continuous loop stopping at each of the stations. Rather than switching blocks between fixed speed controllers as you have I was thinking of switching the blocks between two controllers that each follows each a train and automatically adjusts the speed. (It would be nice to program some inertial acceleration and braking but I'm under no illusions that t-gauge is not likely to be up to such refinements.)

Tim J.

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