Bath Spa - High tech modelling: Bringing 1947 into the 21st century. 3d printed scenery, cnc milled track, laser cut baseboards and computer control

[Rabs]

I have to say I fully agree with much of your response, my post certainly wasn't meant as a criticism and I hope it wasn't taken that way. You are absolutely correct when you say that my fettling bits with comparatively basic tools and raw materials may not be seen by many as simple, the main reason being your skills with machine tools are way beyond my ability.

As for the cast crossings, they look clumpy to my eye although that may well be because they are simply rested in place so I will reserve judgement until they are painted and ballasted. That said I stand by the much greater flexibility of crossings assembled from individual, soldered components.

 

By the way, I love your workshop, particularly the way it has been put together.

 

Jerry, desperately trying to dig himself out of the whole dug by his earlier slightly clumsy post:-)

 

That's ok - no offence taken  We all need that sort of feedback to improve.  I wasn't being touchy, I was genuinely asking for your feedback on the frogs as you are a lot more experienced than I am.  I thought you were picking up on details that I had missed.  As you say, the proof will be in the pudding.

[kiwinewt]

I may have missed it, but what printer are you using? Have you thought about printing the points/etc rather than milling them?

[Rabs]

I have considered it, yes.  The only issue is that my printer isn't large enough to take a whole point base lying flat.  This means that I'd have to print it vertically and hence it would take a very long time.  The mill is quicker and more accurate for this sort of shape.  For example, the holes for chairs need to be a very precise size (0.95mm), and 3d printing tends to make small holes a bit variably so I'd only have to drill them out anyway.

 

My printer is a B9 creator.  I've got a thread of my printing work here: http://www.rmweb.co.uk/community/index.php?/topic/66521-and-who-says-that-home-3d-printing-cant-do-detail/

[kiwinewt]

I have considered it, yes.  The only issue is that my printer isn't large enough to take a whole point base lying flat.  This means that I'd have to print it vertically and hence it would take a very long time.  The mill is quicker and more accurate for this sort of shape.  For example, the holes for chairs need to be a very precise size (0.95mm), and 3d printing tends to make small holes a bit variably so I'd only have to drill them out anyway.

 

My printer is a B9 creator.  I've got a thread of my printing work here: http://www.rmweb.co.uk/community/index.php?/topic/66521-and-who-says-that-home-3d-printing-cant-do-detail/

 

I just read all through that. Wow. I hope I can get the same sort of quality with my RepRap and PLA... I guess I will find out when I have finished building it!

[Rabs]

I just read all through that. Wow. I hope I can get the same sort of quality with my RepRap and PLA... I guess I will find out when I have finished building it!

 

Have a look here, should give you an idea what to expect: http://reprapbcn.wordpress.com/2012/05/24/reprap-mendel-prusa-vs-3dsystems-sla-7000-stereolithography/

The output of the 3dsystems SLA-7000 isn't quite as good as the B9, but it's similar.

[kiwinewt]

Have a look here, should give you an idea what to expect: http://reprapbcn.wordpress.com/2012/05/24/reprap-mendel-prusa-vs-3dsystems-sla-7000-stereolithography/

The output of the 3dsystems SLA-7000 isn't quite as good as the B9, but it's similar.

 

Interesting. I have seen a lot better quality prints than that coming off the printer they are using there (Prusa Mendel i2) - which is the same as I am building. I have also seen *VERY* high quality by comparison off some of the more recent printer models...

 

This will be fun!

 

Now where did I put those Z-axis springs...

[richbrummitt]

If you blacken the frog and polish the rail head I think it will not be too obvious, like soldering rail directly to copper clad sleepers only reveals a lack of detail and chairplates on much closer inspection.

[Rabs]

The CAD for the laser cut baseboards is getting very close. The finalised track plan is:

 

And here is a snapshot of the woodwork design:

 

Everything in that image is 6mm ply parts which are the skeleton of the layout.  It's all been designed with tabs and slots to make assembly easier.  At the far end is a 1600x300 traverser with 5 running lines.  The module nearest is the most complex, with the bridge and the goods area.

 

I previously mentioned that I wanted to model the wagon shunting and my plan for this is to have an electromagnet on a robotic arm under the baseboard.  Here is the section from above:

 

The track in this area will be laid on sheet brass and the wood will be cut away below (as can be seen in the second picture above) so that I can get the magnet as close as possible to the underside of the track.  I don't need any electrical power to these areas because no locos were permitted in the goods yard.  Having a thin base below the track is necessary because I need to use a very small magnet.  In turn, this is because it needs to slide out under a pier over the river which is only about 15mm thick (you can see it to the upper right running about 2 o'clock in the picture above) and I don't want the magnet to be visible underneath this.

 

The design for the robot arm is quite simple:

 

Two stepper motors, one fixed to the base the second on at the end of the first arm section.  The magnet is then mounted on the end of the second arm section.  The lengths of the arms have been chosen so that it can reach everywhere without hitting anything.  It was quite a faff to get this right.  Working out a way to get a third stepper motor to drive the wagon turntable without that mechanism preventing the magnet from getting under the very centre of the turntable 2mm below the track was also quite hard.  I'm going to prototype these parts on the bench to see if they work before building up the main module.

 

There is another similar but simpler mechanism for the other goods area at the other end of the station.

 

So, that brings me to the home straight before getting to start building.  I'm adding final details now like holes for point motors and signals. Unfortunately I can't find a signalling diagram for Bath Spa at the period, so I'm trying to scrounge photos together to work out where all the ground signals are but I'm not confident that I'll get them all right.  If anyone can point me at a reference for a signalling diagram I'd be very grateful.

I was also surprised to see that there was no catch/trap point on the down goods yard (south side).  I had expected for there to be one on each of the goods areas.  Does anyone know if there was one on the north (Up) side goods yard?  I would expect this to be somewhere just in front of the shunting horse's stable if it existed.

Edited September 11, 2013 by Rabs

[bmthtrains - David]

A superb level of detail in your designs and preparation - you've go to be an engineer of some kind!

 

David

[Rabs]

guilty

 

I was taught that for most projects about 10% the time should be spent planning.  5 months so far, should be about right for a build that I expect to take about 5 years!

Edited September 11, 2013 by Rabs

[Tim V]

This one any good?

http://www.s-r-s.org.uk/html/gwb/S574.htm

[Southernboy]

Hello Rabs,

 

The degree of forethought, planning and attention to detail on your thread has caused me to become a compulsive viewer ... I'm really looking forward to seeing this project build over the next five years.

Edited September 11, 2013 by Southernboy

[artizen]

You deserve to be on Buntbahn.de!

 

Here is some inspiration - http://www.buntbahn.de/modellbau/viewtopic.php?t=6691&postdays=0&postorder=asc&start=120

[Rabs]

I've been busy in the evenings this week with the laser cutter producing the next 8 sheets of parts.  These are enough to complete 3 of the 8 modules, including their storage boxes.  I've also been able to sneak on some of the awkwardly shaped parts of the other modules, which will save some space later.

 

Here are the parts laid out ready to export to the laser cutter:

There are about 300 parts in all here.

 

Here is a typical sheet off the cutter.  I set the cut depth to go almost all the way through.  This means that the sheet stays in one piece but that the parts can easily be snapped out when I need them.

 

A couple of shots of perparation and gluing in progress:

 

I'm limited by space in my workshop and the number of clamps I have so it's going to take a few days to finish this assembly.  I've also got to wait for all the metal parts to arrive (nuts, bolts, alignment dowels, hinges and screws).  With luck I should have them finished by the middle of next week and can look at laying some track.  Only then will I see if my board-to-board alignment is accurate and repeatable enough.  If not I will need to reconsider and possibly make some more precise dowels on my lathe.

Edited October 16, 2013 by Rabs

[D1059]

This is going to be an amazing layout when complete - can't wait to see more

[Rabs]

Glueing continues:

The curved trackbed makes this tricky because it's right on the limit of the ability of the ply to bend.  I've already had to stick some bits back together after being too enthusiastic when making them conform to the curve.

 

The three boxes in this batch are finished gluing, just waiting for carrying handles and more feet to arrive:

Edited October 12, 2013 by Rabs

[Will J]

Hi Rabs, just tuned in to this thread. Looks fascinating in that you are actually doing a lot of the stuff I have been idly pondering but not actually acting on for a while, fascinating stuff! Having seen lasercut wood parts really revolutionise putting together model aeroplanes, the logical step seems to be to make a baseboard with carefully planned contours.

 

Watching with interest...

[Rabs]

@ Will J Thanks - it's always nice to have encouragement.  I'm pretty pleased with how it's all going together at the moment.

 

 

Almost all of Bath's turnouts are in the sections of track on the  arches or on one of the bridges.  This presents a slight challenge of how to conceal the point motors and how to run the actuation of the points when there's only about 3mm of clear height underneath the baseboards before things would start poking out under the arches.

 

As part of this batch of laser cutting I made a little test piece for a point mechanism to address this.  Here is the kit of parts before assembly:

 

• A small section of baseboard matching one of the turnout positions on the layout.
• A 9g R/C servo (about £2.50 on ebay) which will be driven by MERG CBus modules.
• Brass rod in brass tube crank where the lengths are measured from the CAD
• A fiNetrax turnout

The height of the motor mount has been chosen so that the lengths of the two ends of the crank, together with the throw of the motor, give the correct throw of the tie bar of the turnout and keep the horizontal component above the level of the arch:

 

When the motor rotates it swings the lower crank:

 

From the outside the mechanism is completely hidden:

 

The nice thing about this mechanism is that I can make the horizontal section as long as I like, so even for the points which are right in the middle of skew bridge I should be able to get it to work without having to compromise the appearance.

 

I was waiting to see if this worked before finalising the designs of the other modules so now I can get on with them.  

Edited October 12, 2013 by Rabs

[Rabs]

A more detailed view of the traverser design that I am testing on this set of cutting.

This module is one of a pair, the other is a mirror image to the right of this.  It has a series of slots for 600mm cassettes like this one:

These are long enough for 4 carriages or 20 wagons, so I can probably fit local trains on a single cassette but longer mainline trains will need two or even three.  To accomodate this I've made the track lengths to either side (rough curved pencil lines on the module) more than 600mm long.  This way I can put one cassette in place, slide the stock forwards or backwards to empty the cassette and bring in another to complete the train without anything poking out onto the scenic area.

 

The cassettes have carrying handles which, when you lift the cassette, close end doors to stop things rolling off the ends.  These doors are held open by little magnets when trains are running.  I'm undecided if I need side walls or not and will do some testing before finalising the design of the cassettes.  I've also designed them to allow a transparent acrylic cover to clip over the top for display and storage.

 

There are 3 full length slots for storage and 6 half slots (the other half is on the adjacent module).  Only 4 of the half slots can fit running lines with reasonable radius curves around the end, so the furthest two in these images will also be storage.

The whole top surface of the module slides to allow me to select which of the running lines connect to the rest of the layout.

 

The lower (fixed) and upper (sliding) parts are joined using ball bearing drawer runners, which you can just see here:

 

The whole lot will be driven by a stepper motor and a leadscrew, the mountings for which are included in the laser cut designs.

Home straight on the glueing of the track beds for the scenic modules now, I should have pictures of the finished modules all bolted together tomorrow

Edited October 14, 2013 by Rabs

[Rabs]

And here are the finished baseboards.  Time to get laying track!  Hopefully the alignment will be good enough.

 

[CaptainBiggles]

Been following this topic with great interest for several reasons.

A) it's awesome

B) I'm also a (young) engineer with dreams of a high-tech layout for the "next generation" of modellers

C) I was at school in Bath for 10 years near the station and know it well.

 

I am in awe of your work so far & there are so many questions, but one in particular is relevant to my current work. Can you tell me more about your intention to use MERG CBUS & servos as point motors? I'm a member & am using CBUS modules for my points & magnetic decouplers etc, but I'm not convinced there is a working CBUS servo driver without significant modification to the CAN_ACC module.

 

Keep up the inspirational work!

 

Joel

[Rabs]

Thanks very much!

Both the CAN-SERVO1 and CAN-SERVO8 are CBus modules which drive r/c servos.  The Servo8 (which I am using and is basically an ACC8 where the modifications have already been done for you - item 987 on the kitlist) can do up to 8 from one board and has a neat little wizard in the setup software so that you can choose the range of motion.  I've not used the Servo1, it may well have the same software feature.  The advantage of this one is that the PCB also includes the motor mount and a little hole for a pivot arm - meaning that when you add the motor you have a complete slow action point motor.  As I'm mounting my motors on the baseboards I don't need that feature, and having a separate board for each motor is more expensive than one board driving 8 motors.

[artizen]

I have been looking at buying my own laser cutter. This project just doesn't help at all!!!! I need one right away!!!!!! 

 

I particularly like the automatic closing doors on the cassettes and the fact the fiddle yard is a traverser at right angles. Lots of serious thinking going into this design. Always good to see an update.

 

I think you do need sides on the cassettes as the length can end up twisting slightly when handling although 600mm is surprisingly short for stock storage?

[Rabs]

I have been looking at buying my own laser cutter. This project just doesn't help at all!!!! I need one right away!!!!!!  

 

I particularly like the automatic closing doors on the cassettes and the fact the fiddle yard is a traverser at right angles. Lots of serious thinking going into this design. Always good to see an update.

 

I think you do need sides on the cassettes as the length can end up twisting slightly when handling although 600mm is surprisingly short for stock storage?

 

And a big one too for baseboards!  I've been looking at making a small one (A4 size) for making buildings and so on but there's no way I could afford one big and powerful enough for woodwork.  The workshop where I'm going to do this has one of these: http://hpclaser.co.uk/index.php?main_page=product_info&products_id=11.

 

As I said in the post above: I'm expecting trains up to 1800mm long, which will be split onto multiple cassettes for storage.  The platform at 800ft Bath is about 1700mm in N so this should be long enough.  The eagle eyed may have noticed that I've also put slots in the traverser module facing away from the rest of the layout.  These are in case I decide to extend the storage area or the layout in the future - so there's a backup plan if I do need more space.

 

 

In the meantime tracklaying begins:

 

I won't know for certain until I get some rails down to roll over and take it apart and back together a few times but it looks like the alignment dowels that I've chosen will be fine -  there's only about 0.2mm of alignment variation, so with a slight bevel on the rail ends it should be ok.

[artizen]

OK - the linked laser isn't as big as I thought. I have been looking at 600x900mm lasers in the 40W to 80W range and I seem to be able to get one from China for around $5000 (including exchange rate differences, 10% GST, customs duties, etc) landed here in Australia. Provided I have the workload to justify the cost, it is a feasible business plan at this moment (spending some of my inheritance money). Good to see that you are getting very high standard results from your machine which is all good news for my plans for the future!