A Ground Frame for a Plank!

[SHMD]

I have an 7ft Test Plank.

 

It has 3 points arranged as a passing loop with 2 points forming a crossover and uses Peco code75 track work witht the sleeper spacing widened.

I built it to practice many aspects of model railway building in readiness for my first permanent layout - Tenbione. Namely: Track laying, ballasting, painting, modifying, wiring, controlling, operating...

 

This, I am pleased to say, has been informative, useful and enjoyable.

 

It was/is controlled by my 2012 Innovation entries: Smart Driver Board (SDB) and its spin off the Throttled Cab Controller!

These drive the locos with PWM DC plus some nice added features/capabilities, such as PC control and Journey Record/Playback that create a very effective shuttle unit. Ideal for a Test Plank!

The points were controlled by me 5 way point driver board which is current programmable, Serial coms controlled and with live frogs. This is connected to 3 Seep point motors. The points are operated by toggle switches on my 8 way Toggle Lever Board (TLB).

 

The Toggle Lever Board was a great success but there are a couple of drawbacks.

One is that I can not butt two, or three, boards together to create a Signal Box Lever Frame.

Two is that I tried to save space and had the toggle switches on a pitch of 0.45" instead of a 0.5" pitch.

Thus I created yet some more PCBs. A board that can input Push Buttons OR display Bi-Colour LEDs - HIB1. A board that can input toggle switches - TIB. And finally, a general uController board with 3 ports, power and coms - ACB1.

 

 

It is the testing of the Accessory Control Board - ACB1 - and the I/O boards that I am building this Ground Frame to run switch the points on my Test Plank.

 

Here is the initial sketch of what I want to achieve:-

 

 

 

Kev.

 

[SHMD]

A little bit about the Plank...

 

The 7ft track plan.

 

The Test Plank's original Control scheme.

 

The under board wiring which is wired for DC (when I get around to 'adding' the isolated section wires!).

 

The finished Plank running trains.

 

 

Kev.

 

[SHMD]

OK, now to building the Ground Frame's wooden base.

 

The basic material is wood from B&Q.

This is "Stripwood" and is available in lots of widths, thicknesses and lengths.

They cost, on average, about £2 each for a 900mm length.

They're really good value but do inspect each piece - not just for warping/splits etc but also for the unsightly zig-zag glued joints of which there are many.

 

I've used wood glue and panel pins but, after a test or two, I found it necessary to pre-drill the 'nail' holes otherwise the pins split the ends of the 'planks'.

 

The base is complete except for the cut-out for the lever mechanism. The electrical cabinet uprights are positioned to assess the next stage of the build.

Also, in the pic, is the bare PCB TIB1. This can have up to 8 toggle switches to 1 10way IDC connector - to simplify the wiring.

(Next time I'll put more thought into lining up the nails!)

 

The Electrical Cabinet (is there another name for it?) begins to take shape. This time using wood glue, and hence, the miniature tools.

 

 

Kev.

 

[SHMD]

More assessing and planning...

 

Here I am sizing up the Cabinet for the Accessory Control Board - ACB1.

 

Plan view.

 

..and thinking about the Cabinet Doors.

 

 

Kev.

 

[SHMD]

The Accessory Control Board (ACB1) is a home designed PIC based general purpose I/O board.

Think of it as a very VERY simple Arduino or Raspberry Pi! (Can I stress the 'very simple' here!)

 

Its specs are:-

PIC18F4550 based so 32k of Flash program memory, 2k of RAM, 20MHz clock and 35 pins for I/O via many built in peripherals (Serial, SPI, USB, PWM, ADC, etc...)

Serial TTL coms.

Separate SPI coms.

7 to 24volts dc at 1amp. (or 7 to 18vac at 1A).

3 8bit I/O ports,

Port A = 8 off inputs (analogue(10bit) or digital 0-5v) or 8 digital outputs (0-5v at 25mA).

Port B = 8 off digital inputs (0-5v) or 8 digital outputs (0-5v at 25mA).

Port C = 8 off digital inputs (0-5v) or 8 digital outputs (0-5v at 25mA) A full H-Bridge PWM driver I/O is also available.

0.2" pitch screw terminals or 0.05" pitch IDC connectors.

ICSP = In Circuit Serial Programming means I don't have to dismantle it to re-program it.

 

 

 

 

Kev.

 

[SHMD]

Now for the Instrument Panel.

 

For this I will use my Human Interface Board - HIB1.

Basically this board has a 10way ribbon connection in and 8 positions for either tactile Push Buttons or Bi-Colour LEDs. These are freely interchangeable and even which side you mount them on.

The LEDs are Bi-Coloured meaning that each LED can give 3 different states: Off, Red or Green. (If you change between red and green quickly then you can make orange but that can tie up the processor.)

 

Here are two HIB1s. One fully populated with Push buttons and the other with B-Coloured LEDs.

The test program just turned the LED from red to green when its corresponding pushbutton was pressed - all via a ACB1.

 

For the Plank's ground frame, I will configure the HIB1 pcb with 5 LEDs, (one for each lever), and 3 pushputtons for I don't know what!!!

I will mount the pushbuttons and LEDs on the other side of the PCB and then mount the whole thing in a wooden box which will then be mounted on legs to become the 'Instrument Panel'. (Is that the right name for it?)

 

 

 

 

 

 

 

 

Kev.

 

[SHMD]

The Instrument Panel had a lid glued on (but is open underneath) and was plonked on temporary legs to assess things.

 

Things were moved around and ideas tried..

 

A lot happens in the next views.

The Instrument Panel has its legs decided on and glued into position.

The Electrical Cabinet gets its doors added (after much deliberation).

The ACB1 gets wired up - Just 2 ribbon cables. (4 more wires are needed: 0volts, 5volts, Rx and Tx.)

The toggle switches have some 'levers' added via some 'chocolate block' barrel connector. (Thanks Dad!)

I cut a piece of brass and add the holes to mount the toggle switches. (I'm still thinking about this.)

 

 

 

 

Kev.

 

[SHMD]

At work we have a machine shop.

This includes a full time sheet metal worker.

Sooooo.. I takes along a sheet of 16s gauge brass and a sketch to make the lever frame.

 

He knows his stuff and quickly points out the flaws and lack of critical dimensions with my sketch.

However, he soon has enough to quickly knock out my design over lunch but...

 

 

A rough idea of what I want.

 

But this is what happened.

The damned thing fell apart at the corners!

The "tin basher" said that the brass should have been able to take the folds.

 

Hmm.. So this weekend I had ago myself but instead of using 1.5mm thick Brass I used 0.8mm Copper sheet.

I bent this in a woodworkers vice using a bar of metal and a copper mallet.

It's not finished as the top still needs to be curved and the side 'angles decided upon.

 

 

Kev.

 

[SHMD]

More of what I am trying to achieve.

 

After 'forming' the top curve, (just visible in this view), I started marking out the lines for the 5 slots.

(Maybe I should have done this when it was flat!)

 

 

 

Kev.

 

[SHMD]

This is how the insides will work.

 

 

Now, for marking out the end pieces, I just plonked the formed copper frame onto a piece of (now) scrap brass.

I used a permanent marker pen and ran it around the copper both inside and out so as to gauge (groan) where to file down to. 

I did the same for the other side too but the2 pieces are not interchangeable - close but not quite.

Good enough for me.

 

Here's the finished end, in place, ready for soft soldering in place.

Note the gap between the Brass and the copper.

 

Soldering by blow torch - it's the way forward!

Note the copper wire I used to 'clamp' the copper frame to the brass end pieces.

This held things firmly in place whilst I attempted my first ever soldering of sheets.

I didn't use flux - I couldn't find it - and just used my normal 5 cored 'electronics' solder!

(The vice is what I used to bend form the copper sheet in.)

 

 

The result..

 

 

Amazingly, the permanent marker ink survived the blow torch!

 

 

Getting closer.

 

 

Kev.

 

[Rob Rossington]

Thats bloody brilliant!

[RailWest]

Actually, it looks so good that I'd be tempted to concentrate on the ground-frame as a model and forget about the 'plank' !

[Barnaby]

Some super modelling work being done there Kev.

I do like the slip over choc-block connecters to slave drive the switches.  Great tip and filed away for future reference as a way to operate my ground frame, I was going to spoke drive off the bottom of the lever arm to a slide switch but not any more.

 

Thanks, one more to add to my list of ONES TO FOLLOW.

[Donw]

Very interesting. The first attempt with folding up a brass sheet, did you make a groove at the rear of the fold line? Bending beyond 90deg does stress the material and stretch the outer edge. Even with etched kits where there is a half etched groove it can pay to deepen it. Once the fold is made a fillet of solder along the rear strengthens the fold. In practice the copper which is more ductile has done the job.

 

Don

[SHMD]

Thanks guys.

 

Feedback is always welcome.

(Especially when I don't know what I am doing!)

 

 

Kev.

[SHMD]

Some super modelling work being done there Kev.

I do like the slip over choc-block connecters to slave drive the switches.  Great tip and filed away for future reference as a way to operate my ground frame, I was going to spoke drive off the bottom of the lever arm to a slide switch but not any more.

 

Thanks, one more to add to my list of ONES TO FOLLOW.

 

Hi,

 

We use these 'choc-block connectors' a lot at work and, in quite a few different ways, on the Scientific Instruments we make.

But we call them 'barrel connectors'.

 

 

Kev.

[SHMD]

Very interesting. The first attempt with folding up a brass sheet, did you make a groove at the rear of the fold line? Bending beyond 90deg does stress the material and stretch the outer edge. Even with etched kits where there is a half etched groove it can pay to deepen it. Once the fold is made a fillet of solder along the rear strengthens the fold. In practice the copper which is more ductile has done the job.

 

Don

 

Hi Don,

 

The first attempt, at bending the 'brass' sheet, was done by our resident tin basher at work. So no, I didn't score the back of the fold first. (But a tip I have filed away for future use.)

I found that I couldn't even bend the 1.5mm thick sheet – so I thought I would let an expert do it for me.

 

This week I was curious about the failure and so I analysed a piece at work.

 

It turns out that it is not Brass at all! It is Phosphor Bronze instead!

 

Our 'tame' tin basher was not surprised at all and reeled off the properties, proportions and uses of the two materials even before looking at the printout of the analysis I had done. I measured mostly Zinc and Copper with about 10% tin plus 3% lead. (I didn't notice any phosphor peaks in the spectrum I obtained.)

 

The 'brass' sheet I had was bought by my father. When I heard he was off to a model engineering exhibition I asked him to pick up a piece of brass sheet for me.

Phosphor Bronze is far more durable than brass but can not be formed. (Casting and machining being the main ways of working it.) Phosphor Bronze is also far more resistant to tarnishing than Brass and thus all those 'brass' plaques, outside 'respected' businesses, are actually Phosphor Bronze.

 

 

Whereas working the copper sheet was easy.

The material is malleable, ductile and very very forgiving. (The first of the small folds, at the base of the frame's casing, I actually bent the wrong way by about 45 degrees before noticing my mistake and bending it ~110degrees the other way with no ill effects!)

 

 

Kev.

(Now I'm curious as to why the copper sheet, changed colour, to look like brass when I heated it up!...)

[Donw]

 

Hi Don,

 

The first attempt, at bending the 'brass' sheet, was done by our resident tin basher at work. So no, I didn't score the back of the fold first. (But a tip I have filed away for future use.)

I found that I couldn't even bend the 1.5mm thick sheet – so I thought I would let an expert do it for me.

 

This week I was curious about the failure and so I analysed a piece at work.

 

It turns out that it is not Brass at all! It is Phosphor Bronze instead!

 

Our 'tame' tin basher was not surprised at all and reeled off the properties, proportions and uses of the two materials even before looking at the printout of the analysis I had done. I measured mostly Zinc and Copper with about 10% tin plus 3% lead. (I didn't notice any phosphor peaks in the spectrum I obtained.)

 

The 'brass' sheet I had was bought by my father. When I heard he was off to a model engineering exhibition I asked him to pick up a piece of brass sheet for me.

Phosphor Bronze is far more durable than brass but can not be formed. (Casting and machining being the main ways of working it.) Phosphor Bronze is also far more resistant to tarnishing than Brass and thus all those 'brass' plaques, outside 'respected' businesses, are actually Phosphor Bronze.

 

 

Whereas working the copper sheet was easy.

The material is malleable, ductile and very very forgiving. (The first of the small folds, at the base of the frame's casing, I actually bent the wrong way by about 45 degrees before noticing my mistake and bending it ~110degrees the other way with no ill effects!)

 

 

Kev.

(Now I'm curious as to why the copper sheet, changed colour, to look like brass when I heated it up!...)

 

 

Ah that explains it. I had thought it to be hard brass with probably a low copper high zinc content. Brass can vary somewhat. I have seen copper pipe changing colour when overheated during soldering Usually trying to get the rear of a pipe joint up to temperature when the flame can only be applied from the front) perhaps it got a little hot.

Don

[SHMD]

Today I worked on the base plate.

I envisage that this will be mounted underneath the wooden platform.

 

Here it is already cut out of 'bronze' sheet and marked up ready for drilling the 5 holes for the toggle switches.

 

The holes line up pretty well with the toggle switch positions on the PCB!

 

Once completed the toggle switches were added.

 

 

Kev.

 

[SHMD]

These shots show the swing of the toggle switches.

 

The toggle switches, I chose, have three positions ON-OFF-ON and the ACB can detect all three states. ie, it will react only when pulled fully off or return fully to the home position. (Even a ON-ON toggle switch can be left on the 'invalid' mid knife-edge position!)

 

 

Kev.

[SHMD]

A quick glimpse of what I am aiming for...

 

...but before that can come to pass - some more metal work is required.

After marking out then comes the drilling to help remove material and guide the filing!

 

Needle files are good but they can be hard work.

If you have a lot of material to remove the think about mounting the needle file in a 3-jaw chuck. Much easier!

 

Once the 'slots' can accommodate a larger file, then the real progress can be made!

 

Without the frame casing the toggle switch extensions only vary by a small amount - close to the pivot - but further away the error gets multiplied!

 

The frame casing not only evens things up but also makes operating the levers much more positive and eliminates the possibility of damaging the toggle switches with all that extra leverage!

I am really pleased.

 

Kev.

 

[Donw]

A quick glimpse of what I am aiming for...

DSC_0389a.jpg

 

...but before that can come to pass - some more metal work is required.

After marking out then comes the drilling to help remove material and guide the filing!

DSC_0390a.jpg

 

Needle files are good but they can be hard work.

If you have a lot of material to remove the think about mounting the needle file in a 3-jaw chuck. Much easier!

DSC_0394a.jpg

 

Once the 'slots' can accommodate a larger file, then the real progress can be made!

DSC_0396a.jpg

 

Without the frame casing the toggle switch extensions only vary by a small amount - close to the pivot - but further away the error gets multiplied!

DSC_0397a.jpg

 

The frame casing not only evens things up but also makes operating the levers much more positive and eliminates the possibility of damaging the toggle switches with all that extra leverage!

DSC_0398a.jpg

I am really pleased.

 

Kev.

 

I am not surprised you are pleased it looks very good.

Don

[SHMD]

One of the main reasons for the frames casing is to line up the toggle switches.

As I have said previously the toggle switches are not all the same. The all have slightly different throw angles (+-7.5%), different springiness(!), different side 'play', etc etc.

Add to this the fact that the switch levers are tapered. ie small at the base and wider at the top means that when I add the barrel connectors then the extended brass lever is not central to the toggle levers axis.

Worse still is the fact that the toggle levers are free to rotate and then the offset can come out at any angle!

 

Adding the frames casing 'fixes' most of these problems, but I have choses 3 position ON-OFF-ON toggle switches.

So when the switches are in the mid OFF position then the differences between the base toggle switches becomes apparent. Luckily, I don't envisage more than one lever requiring a 'valid' mid position so the differences will not be seen in reality.

 

 

Kev.

 

[SHMD]

Actually, it looks so good that I'd be tempted to concentrate on the ground-frame as a model and forget about the 'plank' !

 

Thanks RailWest.

I have had this thought myself but the Test Plank is up and running and the Ground Frame is very generic as I have no drawings, no photos and no prototype that I can recall!!

 

The Test Plank is just that and my work on this Ground Frame is only possible because the Test Plank is there.

(Future tests to include Controller(s) development, signals, Automation, wheel (axle) counters, Current Monitors, painting, ballasting, insitu-modification, etc.... A test bed for all my future works!)

 

Besides, the Test Plank runs trains (by itself) whilst I get on with work on the Ground Frame.

 

 

Kev.

[SHMD]

Having aired the problems of the barrel connectors, and the toggle switches, I still think that the barrel connectors are very good.

 

I get them from BnQ.

(I've already used 24 but can only account for ~8 of them!)

 

There are two main types: solid brass or folded sheet metal.

I much prefer the solid brass ones.

I also think that replacing the course screws with grub screws is a good idea.

 

The barrel connectors in place.

(Don't forget to 'space' the barrel connector above the toggle switches to allow them the full +-7.5' travel.)

 

 

Kev.