More Carriages in TT120.

[JimG]

After a small sortie into building a TT120 coach here I thought I might have a go at something a bit more adventurous. So I dug out my S scale drawings of a 48ft Caledonian 7 compartment First and did the necessary re-scaling and generaton of files. The major consideration was the CNC GCode file which cut the bolections. For my S scale builds and also the 1:32 scale builds, I had to hand code the CNC file to do the contour profiling of the bolections. That was about ten years ago and I had to get my brain round what I had written then. Fortunately I had written the program to take input of key dimensions so on the face of it should have been easy, but there was still room for finger trouble.
The first attempts didn't look right so there was a good few attempts on small test pieces to get it right.



This is an 0.3mm ball end cutter parts way through the rounds on the top left bolection...



...and a fraction of the test pieces as a result. But I got there in the end. Apart from finding out my dodgy garbage in/garbage out situations, I was having to deal with bolections which were about 0.1mm x 0.1mm (0.004" x 0.004") in section, so a thou one way or the other could make a noticeable difference.



I then went ahead with the main body construction, similar to the four wheel coach previously, in the Jenkinson "box" style with a 1mm floor, partitions and ends.







They were all put together to give the box...



...and the shaping of the inner sides provides the base for then outer sides to support the tumblehome.



The outer sides were machined and I had a bit if a fight getting them off the double sided tape which holds them flat on the CNC table - the top one looks decidedly crumpled. I managed to find an old roll of Letraset low tack tape and used that for the panelled ends, but the left hand end shows that it hadn't worked too well with the spiral flutes of the cutter tending to pull the styrene up in places and giving a deeper cut than intended. The ends were re-done.



The outers were glued to the box then I applied solvent to the bottom edges and pushed them in using the rules and weights to form the tumblehomes. I started using D-Limonene which had just arrived from Ebay. The D-Limonene is in the left hand glass bottle - also off Ebay (ten for £2.50). It's got a soft rubber stopper which I can get off easily with one hand which makes working with it a lot easier. The left hand bottle hold the MekPak and that's about fifty years old - it first held Haliborange capsules for my daughter in her infancy. This method didn't work too well since I must have overdone even the D-Limonene and the rules left impressions on the styrene.



So I went through the whole process again, taking more care when gluing the tumblehomes, and that work well.



Here's a closer shot showing the bolection detail, which might be a tad heavy. I remember a discussion with Cynric and Steve Cook at Larkrail's predecessor maybe ten years ago, trying to decide how heavy bolection detail should be. I had brought some S scale sides with three varieties of bolection dimensions and the general feeling was that the finest dimensions were best, giving more of a suggestion of the bolections. I think they might have thought that these ones are a tad on the heavy side.



The sides project the required amount to represent the panelling on the ends. They look quite good now and will benefit from some light sanding once the atyrene has hardened off.



One problem I find is that the tops of the sides between the partitions tend to wave about in the breeze - particularly the two closest on the left, so I'm looking at incorporating a partial "ceiling" on top of the partitions to locate the tops of the sides to hold them in line.

All good fun and it feels almost archaic in today's 3D printing world.

Jim.

 

[JimG]

I did a bit of adjustment and got a "ceiling" onto the partitions to hold the tops of the windows and doors in line.



The latest version is on the left with what is a 3mm wide border/ceiling of 1mm styrene round the inner top of the body and it works well.

I'm now having a fight with the double-sided tape. It's holding the styrene to the work surface but it's the very devil to get off with the glue and carrier separating meaning a lot of messing around with tweezers, meths and swabs. This tape has worked quite well in the past so I'm wondering if it's the heatwave that might be causing the problem. I've just got a new (to me) 3M low tack tape which arrived this morning so I'll try some of that and see how that works.

I'll now move onto the windows and roof. I find I have to cut the 10 thou Plastiglaze on the CNC mill since using a craft knife to cut the material causes crazing along the cut which, unfortunately, shows in the sizes I'm working with. I'll try using formers and a thin sheet styrene sandwich for the roofs which I've used in the past for larger scales. These coaches have arc roofs, so getting a former to mould them is not too difficult, if I can find something at the correct radius.



Just a quick shot with the TT coach's very big brother in 1:32 scale. Same source files for everything, just re-scaling and modifying the GCode files to work with different material thicknesses and cutter diameters.

Jim.

 

[MarkR]

Hi Jim,
Lovely modelling, I think hand sanitizer can be used to remove adhesive residue.
Having worked for many years with a variety of 3ms industrial adhesives (£100's per roll!) the bond to the substrate will increase with time.
Mark

 

[michael mott]

Hi Jim amazing work at the smaller scale The wonders of being able to scale with the CNC files unfortunately not a route I took and am a bit set in my hand work ways now to invest the time and money.

The comparison between the 1/32 and the 3mm is remakable.

Michael

 

[JimG]

The wonders of being able to scale with the CNC files unfortunately not a route I took and am a bit set in my hand work ways now to invest the time and money.

Michael,

I bought my CNC mill with money left over from closing down my business and retiring in 2010 - I had good trading in my last year. And it has proved a great acquisition for my advancing years when the machine can work to much finer and more accurate levels than my hands and eyes now can. All I have to do is push and click a mouse. But I think the cost would put me off now although I note that Giles is getting equivalent results out of his small router which is a fraction of the cost.

The comparison between the 1/32 and the 3mm is remarkable.

2.54mm to the foot - 1:120 scale. Peco, who have instigated this interest with their new products, have opted to use the much more accurate scale to gauge ratio of European and American TT. I believe that the States used a tenth of an inch to the foot as the imperial version, which is spot on.

How far I go with this scale is debatable. My activity was triggered by the wishlisting on RMWEB and started me wondering about scratchbuilding in the scale - if you can call CNC work scratchbuilding.

Jim.

 

[Mikemill]

I praise of CNC

Ability to build any loco carriage or wagon you want in any scale, at a fraction of the cost of bought items

Cut wheels from acrylic or metal

Built designs not commercially available

Total control of your project

Great satisfaction when your model is complete



Mike

 

[michael mott]

I note that Giles is getting equivalent results out of his small router which is a fraction of the cost.

Jim. If I were to try this type of working, this is likely the way I would go.

How far I go with this scale is debatable.

Yes the whole issue of where to go with the scale gauge thoughts is a bit of a conundrum for me. The thing is I don't have another 30 or 40 years to to even finish all the current projects that I have started over the last 30 years. The key for me is simply enjoying the flow and the moment and learning new stuff along the journey.

Ability to build any loco carriage or wagon you want in any scale, at a fraction of the cost of bought items

Mike, I agree with you on this, and the problem for me is, settling down to one scale and as I advance in years the larger scales get more easy to deal with which is of course inversely proportional to the space we have to play with.
Being able with the click of a mouse on the drawing screen to change scales is something I do like with my 2D cad. What I am looking for is a magic wand that I can wave over the 12 feet x 2 feet model layout space I have to change it to to seem like 48 feet x 8 feet. but then I would have difficulty seeing the detail.

Michael

 

[JimG]

I've now got on with doing some windows.



Here's the first attempt at a cut on the machine using some 10thou Plastiglaze (actually 11thou ) I'm using a 0.5mm cutter to keep cutting forces low and I'm using a bit of Seklema Multimat to hold the material to avoid having problems with cleaning double sided tape adhesive off. The Seklema product is an excellent product with a very smooth and slightly tacky surface which holds material firmly enough for light machining. The only reason I don't use it more is that its thickness is not consistent and would give me problems with larger pieces of material. It's really designed for 3D engraving where the tool sets its height from the material surface. However I can use it for smaller pieces such as the 45 x 65mm piece for the glazing.



...and the finished piece with forty quarterlight pieces. They are held by 0.1mm tabs top and bottom to prevent them disappearing off into the wilderness. The parts are quite cleanly cut and the swarf around them seems to be mostly dust which is probably attracted by static.



...and a test at placing them in the coach sides. The slots are nominally 0.3mm/0.012" and there's 0.1mm/0.004" clearance around the glazing so they fit quite easily. The fourth quarterlight from the right has the glazing partially inserted and the other three have them fully inserted, although the third from the right doesn't benefit from a bit of reflection.

The next job is to do the drop lights. The droplight slot in the body is 0.4mm/0.016" deep to allow for a bit of 5 thou Plastikard for the droplight frame (actually Evergreen 5 thou since the Plastikard 5 thou was rubbish to work with). This will allow me to model the occasional partially or fully open droplight.

Jim.

 

[JimG]

I got a bit diverted after an email exchange with a friend. He had also seen the TT120 announcements by Peco and his reaction was to start scratchbuilding a diesel in 3mm scale (101.6:1). And he sort of convinced me that a venture into TT120 wasn't wise, especially for the scratchbuilder. I did a bit of research and soon found that a lot of basics, like rolling stock wheels, were not available, at least not in reasonably fine standards. Whereas the 3mm Society has a lot of product.

So I had a look at 3mm scale.






...with the 3mm version behind and its TT120 version in front. I used the same methods with everything upscaled , by approximately 20%, and all went pretty well. I still need to fine tune the bolection machining. The test I did looked good, but the results on the full coach body were nowhere near as good. I suspect that my cutter height may have been a thou or two off. The bolection is 0.125mm/0.005" high so a couple of thou makes a big difference.

So where for the future -, that's if I want to venture into these smaller scales? 3mm scale does have attractions with a ready made, close to scale set of track and wheel standards. The thought of having to machine eight wheels for every coach in TT120 is a bit of a show stopper.

Jim.