Thursday, 8 October 2020

3D Printing in Winter

I had previously suffered some disillusion over a very low success rate with the 3D printer but I've had quite a run of success over the summer. Oddly, I had my first unsuccessful print the other day, completely out of the blue. The next print was fine but it got me wondering as to why.

Generally the 3D printer is fairly tolerant but I noted that the failed print happened right when the temperature dropped outside. The printer is upstairs in my den but it is next to the most northerly corner of the house and there is this point in the year when the temperature drops but it isn't cold enough to put the heating on.

Reading the label on the next bottle of resin I noted that it said that it works best between 25 and 30 degrees centigrade and we were definitely no longer that warm so what to be done? Reviewing the Facebook support group for my printer I noted that someone had used reptile heaters to heat the printer. You can get ones with thermostats built in but they appeared to have limited control.

In the end I elected to purchase a device that is basically a control box that has a thermometer on a cable and two mains sockets to turn the heaters on and off. I also purchased two small reptile heaters. I then had to drill some holes and into the printer to feed the cables without fouling the lid or any internal mechanisms. The reptile heaters were glued to the inside sides of the printer and the thermometer is glued to the back. All this is carried out with the Bosch cordless glue gun which is in itself a fantastic piece of kit.


Now I can set the temperature to be maintained between 26 and 28 degrees centigrade and if I put it on far enough in advance the resin will be at a suitable temperature for printing. It would benefit from more heat, these reptile pads are only 5W each but the next size up would not fit. It took a few hours the first day but the second day it hadn't cooled off that much and was up to temperature within 90 minutes. At 10W total it could be left on all day. That's less power than this computer uses and 0.3% of our kettle. 



Saturday, 3 October 2020

Welshpool No 85

The other project on the go is the Dundas Models Sierra Leone No 85 which runs on the Welshpool & Llanfair. Again, it's a quick build to provide extra locomotive power for the layout as and when exhibitions are back on.

Since being on the WLLR it has had some interesting liveries but after the lining of Triumph I have opted for the full black that was used on the WLLR just prior to it being withdrawn for overhaul. 

The model has gone together well. I would have to say it has been one of the crispest and simplest to put together. The only place that has needed filler is round the smokebox door, the side tank pieces being of slightly different length. Unfortunately you can't just trim a piece off the other end as that end fits tightly into the rear of the cab but really it is a minor inconvenience.

One aspect of modelling it in the year before overhaul is that it had the extra coal bunkers on the front of the water tanks. The bunkers supplied in whitemetal are, of necessity, quite thick. In real life the metal of the bunker would have been half an inch maximum but the thickness of the whitemetal was such that it translates to 3 inches in real life.

I found some brass offcut and bent it to shape but I made the mistake of not filing the groove at the bends with the result that the corners were curved rather than rectangular. Once I had corrected my error it still looked rather rounded. 

I knew I had to redo them but then I realised I could probably just print them. It was the work of a couple of minutes followed by a couple of hours of printing time but it gave me the opportunity to experiment with printing direct on the print bed which worked unexpectedly well, despite the fact that I made the wall thicknesses to be 0.4mm which comes out to just over 1 inch in real life.


The picture shows the three different forms, left to right. I am sure others can fabricate these parts quicker than I can print them but as it was literally 5 commands to design them and 1 extra command to produce the mirrored part, I am happy with what I can achieve.


Saturday, 26 September 2020

Axleboxes

If you look closely at what I have achieved so far with the 3D printer it has been very much a case of how to join circles and squares together and how to curve and chamfer edges. I've made plenty of progress and this summer seems to have been very successful in terms of how few failed prints I have had.

Over drinks one evening, my friend Simon was showing his progress on an early GWR horsebox. It has the most intriguing axlebox and spring arrangement where the ends of the springs are connected to J hangers rather than directly onto the solebar which is the more traditional way of doing it. Of course, I decided this was the next challenge I needed.

As always, there is a lack of good photographic evidence since most photos of wagons have the underframe in shadow. There were a couple of good pictures so dimensions were taken and the following was drawn up.

The axlebox itself is still a collection of squares and circles but the spring was the challenge and was built up from 3 point arcs. A circle was put on each end of the top leaves and then it was about trimming the shape to form the circle. It was a couple of hours work but I learnt so much about how to build up more complex shapes. It came out alright but when offered up to the vehicle my interpretation of dimensions was off.


Revisiting the dimensions led to a design that had more depth to it, the axlebox was chunkier and the width was narrower. I also needed to improve the printing supports. I am surprised it printed with what I did on the first pass.




In this form they have gone onto the model. I've learnt quite a bit more about printing and it is nice to give something back to my friends who have been so generous with their time and support for my modelling.

Sunday, 20 September 2020

Welshpool Coaches & 3D Prints

 Another huge break between posts. How does that happen? The last 3 months have been largely devoted to 3D printing. After the success with the side windows on Triumph I knew I had to get back to the Welshpool & Llanfair Pickering coaches. The big outstanding task was the roof. How to do it? How to roll it and then the fittings. What were the best fittings, the torpedo vents and the oil lamps. After a couple of purchases that really weren't what I was looking for, I decided I must surely be able to design and print suitable ones.

I've been following Vladimir Mariano on YouTube and he has some excellent courses that have been advancing my skills at 3D design. I had to learn a few more commands but eventually I came up with the following design. There are no drawings for these so they are an interpretation of all the photographs I could lay my hand on.

Having the design is one thing, working through the practicalities of printing took more effort. Essentially the printer prints upside down so you have to think about supporting edges that are in free air. There are also issues around where resin can collect and build up in unexpected places. The final design looked like this - you chop off all the unnecessary bits after printing.

There are nearly always supports required with 3D prints and if you let the printer software add them then they conspire against you and make these size prints take 3 times the time they should. I have developed my own technique for adding supports within the CAD program which is working so far for me. I also replicate items to create strips of 12 items, 5mm apart which nicely fits the printer build plate

Bearing in mind the body of these lamps is only a few mm high they are a tad challenging to photograph but here is the best I could achieve with my camera


The torpedo vent was done in much the same way. There are some drawings but their accuracy is not assured and the photographs are challenging simply because most are taken from ground level and the Pickering coaches had an enormous rain strip which consistently hides useful detail. the WLLR does have some replica coaches but with anything replica there are going to differences with the original and I have no way of knowing what is accurate.

Again, only a few mm high so hard to photograph but the end results do seem to have been worth it.

I have also done the guard's stove chimney for the composite coach along with a brake cylinder to go under the coaches. Who knows, the coaches may make an appearance soon!

Thursday, 25 June 2020

Hotel Chocolat Saves The Day

I needed a break from paid work so took a week off. There wasn't a clear plan for the week except to spend time modelling and possibly going to a non-essential shop! I have a few projects on the go and really wanted to complete Triumph and make progress on the Pickering coaches.

What happened was I had some inspiration about how to do something on the 3D printer and, despite the recent problems with printing (not sticking, test file not printing, build plate shifting), I just decided to get stuck in and see where I got to.

What I ended up doing was going on journey printing windows. All the Bowaters engines had sliding windows and stable type doors. It's not clear why but there are two reasonable possibilities

  1. the land is very flat and so the wind howls through
  2. the paper business is very dusty so maybe there is a lot of paper dust flying around
Do a Google search for Triumph then you will see what I am talking about. These windows vary between 1, 4 and 6 panes and I've manage to find examples in green, black or plain wood (presumably paint worn away). The time in question for Triumph they were a green, 6 pane affair.

I did a crude measure of the gap on the engine where the window should go and came up with the following:


The dimensions are roughly 11mm by 9mm. The dimension of the edge probably works for a house window but those on Triumph are much slimmer. I adjusted the dimensions and came up with this variant that was worth painting just to see how it fared:


Getting better, though really I have gone too thin. The core dimension is 0.5mm and, after curing, there is enough strength for the item but I felt it needed refining and so I came up with this:


That looks right. It may not be dimensionally accurate but it looks the part and has the strength to withstand some handling. Time to add the glazing. I have been meaning to try Kristal Klear for a while so I broke it out, read the instructions and achieved this:


It really does dry clear and provide a glazed look. Put the unglazed and the glazed next to each other you see a brewing issue:


The glazing has made the window panes smaller and the frame larger. It's unclear if it is a trick of the light or a leeching of the paint but suddenly it doesn't look so fine. If you put it on the locomotive then it starts to grate for not being as fine as some of the other parts:


If that was the best I could achieve then I would live with it but I wanted to do better.

I had an idea from how doll's house windows are done, typically full sized front but recessed at the back with an insert that holds in the glazing. Doll's house windows are often 10cm in length, not 10mm so would it work?

First I had to find a suitable glazing. That non-essential shopping led us to Hotel Chocolate from which purchases had to be made and said purchases were wrapped in clear cellophane which, according to the micrometer, was 0.05mm thick. 

Back to the CAD package (Fusion 360, free for personal use). If I made the outside depth and edge 0.7mm and put a 0.4mm recess into the frame and produced an insert that was 0.3mm thick then it should just go together with a tad ofspace. Here's what it looks like on the screen.


Those parts are thin but, painted up, glazed with Hotel Chocolat Cellophane, held in with Kristal Klear you get this:


The printing layers are showing at this magnification but the bars have retained their thickness and aren't distorted.

Here is the end result stuck onto the engine with a piece of blu-tak:



It's definitely a case of using the right material for the job. With much encouragement I have been working in brass and made the fire irons on the cab roof out of 5 thou brass and some nickel silver wire (every engine at Bowaters had fire irons on the cab roof).  The oil cans on the buffer beam were another 3D print (again, all engines at Bowaters had them, sometimes just 2, sometimes as many as 5). It took me probably 7 goes to get those right but they really have handles on them and now I have got it right I can print some more.






Sunday, 7 June 2020

A green, a green, my kingdom for a green

Finding the right green has been quite a saga through lockdown, requiring several deliveries, none of which were right. Of course, right is a matter of perception but I knew the look I wanted to achieve. Early in the process, Simon de Souza had suggested Humbrol grass green but I had ignored him, as you do. When he suggested it again and did a paint swatch it was, of course the green that most closely matched what I was looking for. A burst of British summer meant I could do the spraying. I elected to paint the black with a brush rather than mask it up as the black blends round the end of the tanks anyway. It would be faster this way.

Another suggestion from Simon was to not use pure black but to use a dark grey. I decided to listen this time. Not having a dark grey I took the quarter full pot of black and added a couple of dollops of white and one dollop of reddish brown - precision mixing.

Then came the lining. Suffice to say I almost threw the engine at the wall. Matt Kean produces beautifully lined models and he would have done this one for me but I wanted to learn. I have several locos tucked away and they all need similar lining so it seemed a skill I should learn.


This is all I have managed so far, one side, both water tank fronts and one cylinder. Some of the lining has had 4 or 5 attempts. It just would not lay flat. I've experimented with red and blue Micro Sol and still not got the technique right but I will get there!

It looks a little toy like without the roof (did I say I bent the one I made...) and would be much better with the correct chassis but that will have to wait until I learn how to make my own chassis. So many skills to learn...

Monday, 11 May 2020

How riveting

With several projects on the go it is inevitable that they go slowly. Lockdown hasn't changed the time available during the week for modelling but at least there are good solid modeling times at the weekend.

Here is the work of a labour of love, adding rivets. I lost track of the number of hours spent doing this and there is still the other 3/4 of the engine to do.


It's a job that can be very rewarding when they go on well but when they don't... It is also so fiddly that I lost track of which spacing of rivets to use. The difference is so small that I went "space blind" at one point and definitely used the wrong ones. Also, having started the other side tank I now realise I have missed 3 rivets off this side. I think I may have just labelled myself!

Ultimately I am still pleased with the first attempt at using these decals. I am hopeful it will add depth to the model when finished. I'm guessing another week until all the rivets are on and by then the next attempt at finding the correct green will have been delivered by the postman bearing gifts.

3D Printing in Winter

I had previously suffered some disillusion over a very low success rate with the 3D printer but I've had quite a run of success over the...