Disaster at Battledown #3

Managing Nova3D Washable Mecha Resin

This stuff has a mind of its own.

Lattice and handrails warped.
The whole part also twisted.

This is what it does to models designed with mostly thin plate sections and how to manage it.

1. Within minutes off the build plate it will steadily warp significantly. It does not matter if supports and rafts are removed or not.

2. Whilst wet from the wash cure it slowly in day/sun/light on a windowsill for a day, occasionally rotating for all surfaces to cure. Within a few hours it will regain its designed form.

After a few hours curing 
it regains its desired shape.

3. After cure there may still be minor warping evident in places. Heat the warp using a hair dryer for 5 to 10 seconds. Bend to the required form and hold in place until set.

Can't say I would use this resin again for models with mostly thin plate sections. I'd prefer a washable resin that has some pliability but with less warping. 

Nova3D Washable Mecha Resin used here is best for maximum pliability, from reviews I have seen.

To Part 1.

Disaster at Battledown #2

 More experiences using Nova3D Washable Mecha Resin.

I do like the fact that resin particles washed off settle at the bottom of the water tank rather than remaining suspended in the water.

I do not like the excessive warping that occurs in thin plate sections, which is what this bridge is mostly composed of. But, the situation seems to be recoverable.

Within minutes of being out of the print chamber and with supports still in place warping occurs that is quite worrying to see. (It's like those tinsel fish that curl up from the heat of  your palm). The material is also floppy like rubber. Even after curing in a UV light chamber for a few minutes the steady march of warping continues. I since read that warping is due to uneven shrinkage during the curing process.

What I had to do was carefully tie down components where areas have warped and then cure on a shelf in sunlight. Once fully cured the parts become hard with some flexibility that resists breakage.

These larger pieces were less problematical. Where warping was present I found heating with a hair dryer then moving and holding the warped part to the correct position until cooled eliminated the fault.

Before I started I wondered if the new imbedded handrails would print correctly. Well, they did! The two bent pieces at the end will reform when joined up to the next bridge part handrails.

The jury is out on the suitability of this resin. The next part to print could exhibit insurmountable warping due to its style requirements.

To Part 3.

To Part 1.

A Card Kit for June

Swanage Signal Box (pre heritage)

View the Card Kit here.

Disaster at Battledown - again

'Again', because previously I clumsily destroyed the signal at Battledown. This time there is a bigger disaster.

When I built the flyover bridge I used wire for the handrails (visible in the photograph). These were cyanoacrylate glued to the struts here and there (it looked great). Over time the wire between fixing points had become distorted and the plastic cracked at some fixing points.

Clearly the temperature coefficients of plastic and wire being different lead to stress during changes in ambient temperature between summer and winter.

I decided to replace the wire handrails with 3d printed versions using the same plastic resin. It was difficult gluing the new handrails in place, due to access restrictions and the use of cheap cyanoacrylate glue that did not want to stick. Nevertheless, I did get them fixed on one side of the bridge.

The nearside was even more difficult as I had to lean over the bridge to view the inside face. Positioning myself precariously I slipped and fell onto the bridge which caused the side to break away.

What to do about it?

I had never been happy with my choice of 3d printing resin (Anycubic Water Wash Resin +) as it produces very brittle models and tends to warp. It may be ok for 'blocky' models but not for those with a lot of thin plate sections. This, together with the replacement handrails that still drooped between fixings (see photo), I decided to remake the bridge using a better suited resin.

First though, I changed the design to integrate the handrails such that they are fixed to every strut. Also, I thickened some girder plates to reduce (in theory) warping.

With regard to resin choice I would like to keep the water washable aspect. I came across a review comparing several water washable resins. The one that gave the best toughness combined with good pliability was Nova3D Washable Mecha Resin.

First thing I noticed was the greater viscosity compared to Anycubic. Also, the resin does not run off the prints so well resulting in a little more waste to wash off. 

I first printed a batch of small bridge components (cross bracings) that were quick to print so that I can check the results before printing more complex components.

They printed perfectly and after curing in the sun for an hour the supports were cut away. Improved pliability was evident but I still managed to break leg(s) off quite a few whilst removing the supports. This might be because the the parts are very thin (0.33mm).

To Part 2.

 

Basingstoke MRS Expo 2025

Three layouts sparked my interest.

Tellindalloch in Autumn (00)

An unusual Scottish autumnal scene of a small branch line terminus where the trees steal the show. The layout was set in a 'box' framed in black with an off stage fiddle yard. 

This reminded me of my own Swanage loco yard model as it is about the same size, set in a black framed box and is an autumnal scene. There are issues with mine though in so far as the box has warped and operating potential is limited, since train movements focus on the single track shed and turntable. Tellindalloch inspires me to revisit mine to see if improvement can be made.

Market Bosworth (P4)

I am always excited to see finely detailed and authentic looking model railways. 'P4' is the clue here as to what can be expected.

Set in the early 1900's this layout is based on a real place. It is not a period that is often modelled. The locomotives, rolling stock and road vehicles spark interest due to their 'old world' character.

Of course, being P4 the modelling is to a very high standard. The building interiors even have lighting and finely detailed furniture.

Old Elm Park (0)

Simply, a locomotive yard but beyond the shed façade in the photo is the interior of a large roundhouse with turntable. A lot of details in both areas adds atmosphere to the scene, further enhanced by the deep depth of the layout.

There is a multitude of BR period locomotives on display. I thought they were all RTR manufacture and totted up the potential value to be around £20,000. I subsequently read that the owner is a locomotive builder so, if he had built the lot then a skilled modeller indeed.

This layout was my personal Best in Show.

Once Bitten Twice Shy

This is the distant signal at the west end of my Battledown Flyover Model Railway. The signal is made from a Ratio LNER upper quadrant signal pack UQ/80 with a customised platform. The lattice pole style and upper quadrant signal arm of the LNER signal is reasonably close in style to a Southern signal. 

On the other side of the embankment is the Basingstoke to Salisbury main line and two storage sidings. When needing access to that area my arm passes over the signal. (you know what is coming).

Unbeknown to me my woolly cardigan sleeve caught and locked onto the finial and signal arm. It was carried across the room where it dropped off onto the floor, closely followed by my foot which crushed it beyond repair!

I  gathered up the bits that I could see but nowhere could I find the signal arm. Now, I do have spare parts from the kit but not another lattice post. Time to design a post and fire up my resin 3D printer to make it. 

I'll recover detailed parts from the crushed signal and use a spare signal arm from the kit.

I use FreeCad for design and Lychee Slicer to create the 3D print file using its auto support creation feature. My printer is a Creality Halot Mage with Anycubic water washable resin.

The lattice network came out well but both ends were distorted and there was a bit of warping. The latter can be corrected during the UV curing process but the end distortions were considered too bad. 

The simple solution was to manually add extra supports to the ends and print again. By the way, print time for this model is 1 hour 12 minutes.

If I need to make another one in the future I think I can get away with the lattice spars being 0.5 mm wide instead of 0.7 mm that I had designed as this will give improved definition, especially at the top of the pole.

For me, semaphore signal assembly is the most difficult job on the model railway. It is so fiddly to achieve an operational signal arm.

Here is the new signal (photo right). In future, when leaning over it to reach the other side of the embankment, I must remember to remove it first - once bitten twice shy!

Postscript

Lost signal arm found. Well, only half of it. Weirdly, in the front passenger floor well of my car! Can only assume it was stuck in my sleeve and dropped off when I changed gear. But where is the other half?

A Real Gem for Denny Fans

From 1983 and recently published on YouTube. This grainy video starts off with a visit to a Great Central Heritage Railway. Stick with it because most of the video is Peter Deny explaining his modelling motivation, philosophy and techniques, interspersed with images of his model railways.

Also see Peter and pals operating his layout here.