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Thursday 28 November 2019

0 Gauge Class 33 Scratch Build - Part 8

There is more than one way to add accessory control to a model locomotive. I am not intending to use DCC as the track plan and range of locomotives will be very limited. It has been suggested that a small Raspberry Pi  computer is a good way of providing remote control of the loco accessories. I might consider that in future but for now I purged my existing stock of components.

This is my second implementation. The first had a pulse width modulator electronics circuit for adjustment of LED brightness (Search 'led dimmer circuit' for examples). This was driven from 4 x button cells with a separate AA cylinder battery to drive the fan motor. The dimmer circuit was not really required as the LEDS gave best light on full illumination so, to simplify matters it was removed. LEDS are now driven from 2 x AAA batteries with the fan power drawn off of 1 of the batteries.

Below is a view of the controls through the hole in the roof with the translucent access panel removed. You would not believe I spent nearly 25 years in electronics design and manufacture when you look at this birds nest of wiring. I'm not proud of it but it does work!

The switch bank is for power, leds and fan. The bluetooth speaker has an internal rechargeable battery and is controlled remotely from an iPad.

When it comes to operation, the fan and appropriate LEDS are activated/deactivated manually from the switch bank before/after the journey and the sound controlled during the journey.

I am not concerned that 'the hand of God' is evident because it mimics the prototype where the roof panel was removed for some maintenance jobs on the engine.

To Part 9.

To Part 1 of this series

Saturday 16 November 2019

0 Gauge Class 33 Scratch Build - Part 7

Well that was satisfying - my idea for head code display and cab interior lit by one clear LED works. But first, about window glass.

There are two concerns about fitting DIY flush glazing. Firstly, obtaining an accurate fit and second keeping the glass clear of scratches, debris and glue.

Accuracy was surprisingly easily achieved. The width and height of the window frame was measured and drawn onto a sheet of paper. The transparent acetate was laid over and the lines on the paper scribed onto acetate with a scalpel blade. The 'glass' was then cut from the acetate with scissors following the scribes. A little trimming was necessary to give a perfect fit.

The cab side windows on the prototype are held within the metal frame. On the model a thin layer of Superglue was laid inside the window frame and the glass placed into the frame (1st photo). The process of fixing the glass was troublesome with evidence of debris, glue overspill and scratches causing most to be reworked several times to get a reasonable finish. Even so close inspection still reveals some imperfections here and there.

On the prototype the cab front windows are held in place with a black rubber grommet. For the model a black plastic frame slightly large than the window aperture was 3D printed and glued to the glass before gluing the assembly in place (2nd photo). Needless to say with two gluing processes involved, instead of one, overspill was even more problematical causing several reworks.

And so to the head code display unit. The front of the display unit is transposable to facilitate either red bars, white bars or, alphanumeric characters.

The frame was 3D printed with an open base, top and front. (In the cab a clear LED located in the base of the display housing illuminates the display panel and throws light onto the ceiling of the cab illuminating the cab too).

The front panel was 'drawn' in my graphic editing application. Two with blanks and one with alphanumeric head code. These were printed onto sticky back paper, The parts cut out and stuck to thin black card. The bars and characters were then cut out and the panels stuck to their respective 3D printed frame.

Red transparent acetate was stuck to the rear of one front panel.

Clear actetate was cutout and stuck to the front for the appearance of glass and over this a black 'grommit' was glued, as for the front windows.

I now have three removable panels. Each can be placed into and removed from the middle window of the cabs.

The next photo shows the lighting effect  The glare from the display panel  upset the camera. The bars are much sharper than shown and the red more intense. Strangely, the blue light is not as intense as shown. I think it is reflecting pigments in the 'grey' painted interior.

The alphanumeric characters (not pictured here) indicate the freight train route within the region. Choosing which code to use posed a dilemma since the layout I shall build later will be fictitious, albeit following Southern practise. The layout will be a shunting yard alongside a waterway. On perusing the list of actual codes (linked to in Part 6) I noted that SW destinations with a wharf or harbour carried the letter E. But, this is no means exclusive and the whole code could be replicated across different routes n practise. Therefore, I had no issue choosing the number one to give a head code of 1E, which was also used for Lymington Pier and Southampton E. docks among others.

To Part 8.

To Part 1 of this series.

Sunday 10 November 2019

0 Gauge Class 33 Scratch Build - Part 6

The reference source for the cab detail came from YouTube videos. There is even one where the driver explained the function of the controls.

The wiring is for the LED headlamps and head code display board. The head code can be two white bars indicating the front of the train, or alphanumeric characters indicating a freight train route* within the BR(S) region, or two red bars indicating the rear. The usual method of lighting a model display unit is with switchable red/clear bi-colour LEDS for a bar configuration only.

* The loco is destined for freight working on a shunting type layout.

I am trying a different approach because I want the option of all configurations. The display unit is fitted with one clear LED giving upward light from the base of the unit. The top of the unit is open to let light into the ceiling of the cab, thus serving to light up the cab as well as the display unit. The illumination is a bit fierce so a dimmer circuit may be needed.

The 'glass' front of the unit is a removable panel with fitted transparent coloured bars or characters. Hence there is a number of panels that can be manually swapped for different displays. I know the lighting will be effective but have not yet designed the glass panel so, am hedging my bets that the system will work.

With regard to driver my plan was to place one driver in each cab for either direction of travel but I learnt that in my period (1960s) and right through the 1980s the policy was two crew who normally sat in the same cab. One was the driver and the other named Second Man who never drove the engine but took on ancillary duties.

I placed two crew in one cab to match the policy and none in the other. (Not ideal for one direction of travel where the cab will be void of crew.)

I wanted 3D printed uniformed figures for high definition and realism. The layered plastic method of my 3D printer is not suitable. I looked at Modelu and Hardy's Hobbies offerings. Only Hardy's had a uniformed seated driver of the period (and is a little cheaper than Modelu with fast delivery). The quality of the model is good and acceptable for inside the loco but, not quite as 'crisp' as I expected.

The way I designed the loco overall means that once the cab is in place it cannot be removed. I just hope the crew do not 'leave their seats' as it may be impossible to reseat them!

To Part 7.

To Part 1 of this series.

Sunday 3 November 2019

0 Gauge Class 33 Scratch Build - Part 5

The roof is made in five sections.The first photo is of No.1 end and shows the roof fan grill.

A couple of methods were tried to 3D print the grill. The problem is the ribs are very fine and to print this in situ requires supports to stop droop. The ribs were just too delicate and came away when the supports were removed.

Another consideration is that the grill centre sits proud of the roof and each rib is at a different angle to fit the roof curvature.

The solution was to print the grill as a separate flat component and to print a central column in situ with the roof. The grill was placed on top of the column and each rib gently bent to locate in a slot in the rim of the fan hole. The column was then cut away when the glue had set.

Second photo is of No. 2 end. The brown marks are sanded Wickes wood filler used to fill imperfections.

The printer threw a wobbly and failed to print the last few layers so, plastic padding had to be applied and sanded to complete the roof curvature.

The body and roof sections were sanded with coarse sandpaper to remove most of the layered plastic stratification. Then a coat of acrylic matte medium was applied and this sanded with fine emery paper to completely smooth the plastic.

Finally, details like door handles and ribbing were applied. This part is now ready for the paint shop.

What about the gap between roof ends?

The centre of the roof on the prototype is a removable fibre glass translucent panel finished in a beige colour that serves two purposes. First, to gain access to the top parts of the engine for service and second, to flood the engine room with natural light.

On the model it is the same except used to allow access to a control panel for lights, fan and sound. (no DCC here.)

The panel was printed in transparent plastic and then coloured with brown, fawn and black pastel scrapes; finishing with a coat of hairspray used as a fixative. Unfortunately, the diamond grid of inner plastic fill* has showed (I should have configured the print for solid infill). I have convinced myself it is fibre glass reinforcement.

* 3D printing thick sections normally results in the core being printed as a grid to save on plastic use.

The other part in the photo is one of two panels that fit to the sides of the roof. Not sure what it is, either coolant radiators or vents? What it does have is an array of vanes in each square covered with mesh.

This could be tricky to make. However, the first method I thought of worked first time. The core is one piece comprising square holes with printed in vanes (vanes just discernible in the photo). This is covered with mesh (described in Part 4). An overlaid frame is glued over the mesh. This frame was printed flat and then moulded to shape over a metal rod of required diameter under heat from a hairdryer to soften the plastic.

Interestingly, I can now feel the body & roof assembly has weight (100 gms) with more to come, which shuld help with track adhesion.

To Part 6.

To Part 1 of this series.

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