GWR N6 Loco Coal Wagon in 7mm, a 3D beginner's first attempt

[GWR57xx]

Having been encouraged by the solebar success I wondered if 8s might allow the body to be printed in one piece.

So another test - nothing ventured, nothing gained ...

 

 

Sadly, NOT.

 

It is certainly much better than the results at 5s with none of the big blowouts seen before, but there are still very bad layer lines for the lower third of the body (A).

 

 

There are also (B) some small pinholes. Not easy to tell from the photo, but they are tiny holes all the way through the side.

 

The opposite side wasn't quite so bad, just one pinhole:

 

 

So it looks like I'll be printing the body as two pieces to be glued together later. No big problem!

 

Also, I'll stick with the 8s exposure time for now as it seems to work well for strength and I can adjust the diameter of holes to cater for the expansion so that they end up being the correct size in the finished print. Thanks for suggesting that @beejack, I would never have tried it otherwise.

 

[Miss Prism]

Try to thin down the thickness of your solebar flanges.

 

[GWR57xx]

25 minutes ago, Miss Prism said:

Try to thin down the thickness of your solebar flanges.

 

Thanks. I also want to slim down the V hanger and W irons once I’ve got the basics sorted. Then it will be a case of experimenting with different thicknesses to get the best compromise between thinness, stiffness and brittleness for the resin.

[GWR57xx]

I've been doing a few changes to the design. 

The solebar flanges have been made thinner, as have the W irons and V hanger.

Supports have been added to the brake handle and ratchet and these both now print ok.

The door hinges have been moved down onto the solebars - I was originally working from a good quality photo of a P4 wagon, which nominally uses the same chassis as the N6 but on looking at fuzzy & grainy images of N6s (I can find any clear ones) they clearly have a totally different hinge system.

 

I am a little bit concerned that the details (straps, brackets, rivets etc) are not prominent enough. I've only been looking at the prints so far as plain grey resin, so I took some recent test prints and gave them the Halfords grey acrylic primer treatment:

 

 

 

The details show up much better with a bit of primer, compared to the plain resin on the right.

 

I've also been working on the main chassis. This is the first test version - still needs a few tweeks, such as profiling the back side of the buffer beam to give the drawhook and spring full movement.

 

 

 

 

It also rolls quite nicely.

 

I took a video, but unfortunately I don't seem to be able to login to my Youtube account in order to add it here - YT says it's sending me an email to verify my identity (to the correct email address), but the email doesn't arrive...

 

[GWR57xx]

As far as I can tell from internet searches no N6s made it into preservation. Does anyone know differently?

 

[GWR57xx]

BTW, I know I get null points for chassis veracity, but the resin is pretty light so this arrangement of beams gives me plenty of space to add extra weights.

I plan to have eight 5g weights, three over each axle and two midships.

 

The components currently weigh in at 62g, so an additional 40g brings it up to a respectable level.

 

Should I move the centre crossbeams slightly to squeeze in another two, which would bring the total weight to 112g?

 

I think the rule of thumb for 7mm is 1g per mm of length?

 

The N6 is 16' over headstocks, so 112mm in 7mm model form, so I think I just answered my own question...

 

[GWR57xx]

I managed to login to YT today, so here's the quick 12s clip of the rolling chassis:

 

 

Not too bad...?

 

[GWR57xx]

Those have all been development versions of the parts so far, but now I think I've finished making changes.

I've printed off a full set of parts, which have had a spray of primer and will be left to fully dry overnight before getting a coat of wagon grey.

I've also drawn up a jig to help with assembly and to ensure everything stays totally straight while being glued:

This is on the printer now and will be washed and left to dry overnight before final cure tomorrow.

I've also ordered some transfers from @railtec-models (hopefully I used the correct code).

 

[GWR57xx]

I've painted the wagon using the shade of grey that I had planned to use, but having seen the result I'm now not sure.

Here it is, sandwiched between Dapol and Minerva 5 plank opens for comparison:

 

 

So I dug around in my paint collection and came up with a few alternatives.

Using a spare reject body I hand painted patches of five different colours:

 

 

 

 

 

Against the original (1) again:

 

 

 

 

Would you say that any of the alternatives shown above are "better" than (1)?

 

In case the answer is "none of the above" then I've ordered another different grey (I hope I don't have to try 50 before finding the right shade!).

 

I checked with gwr.org: GWR standard goods stock livery where there's a photo of two ballast wagons at Didcot, one black and the other a very pale grey so maybe I'm worrying unnecessarily?

 

Or maybe, since I'll be making a few of these, I should have a couple of different examples?

 

[dpgibbons]

Nice work.

 

I think the Minerva is a fair reference colour for GWR freight grey, but RTR models, paint makers and preservation societies all have their own views. However, after the effects of fading, dirt and coal dust, any of your shades would be plausible.

[GWR57xx]

The postman delivered another shade of grey today:

 

 

The body on the right flew too close to the sun, hence why it's a reject.

 

Slightly annoying really as it had printed nicely and was just hanging at an angle on the printer to drain the excess resin back into the vat. The room it's in never normally gets direct sun but on this evening the low sun in a clear sky must have just angled in and been enough to cure the resin before I noticed what was happening. Not like we've seen much of the sun in August, so a bit unlucky but lesson learned...

 

The design of the hanging bracket I bought doesn't allow the printer cover to be fitted back on while it's in use, so maybe I'll try to find a better one as the cover should have prevented this if it was there.

 

[GWR57xx]

In the same package were a couple of different primers: dark grey and black.

 

I've primed up three reject floor pieces, one in each primer colour, which I'll leave overnight to fully set. Then I'll paint a strip of each contender on each of the primers to see what effect that has.

 

[GWR57xx]

Here's the three reject floors in primer, together with the Minerva wagon and original shade body:

 

 

The dark grey primer (B) might be a contender itself?

Would save having to do a topcoat...

We'll see how the colour patches look tomorrow.

 

[GWR57xx]

Here are the colour patches on the three different primer bases:

First up, taken in bright sunshine:

 

Indoors, but with lots of natural light:

 

I added two more colours to the list which at first I thought were definitely not contenders.

However, (9) dry brushed with (3) and a little bit of (8) looks like it might make a pretty good rendition of this faded 5 plank wagon from gwr.org.uk: GWR standard goods stock livery

 

So now I'm still not sure.

 

The colour of the Minerva wagon doesn't look a great deal like any of the wagons at Didcot to my eyes. The Didcot examples appear to have a lot more blue than either the Minerva or Dapol/Lionheart RTRs?

 

To my eyes the primer colour doesn't seem to make a huge difference to the final result - a testament to the pigments used in the paint I guess.

 

[dpgibbons]

That gwr.org.uk wagon livery article specifies standard GWR grey as a mix of black 7:1 white, and notes that Didcot uses a darker 14:1 mix to allow for the effects of ageing and weathering.

 

So - definitely no blue.

 

As Didcot's rationale for the darker shade indicates, the grey becomes faded and grubby in use and so could resemble almost any of the shades you have tested. I think all you can say with confidence is that outside of the wagon works, no two GWR wagons would be an identical grey, and they would have become a lighter shade with age.

 

 

 

Edited September 2, 2023 by dpgibbons

[GWR57xx]

The second wagon is now in black primer, although I should have fitted the buffer shanks before doing so!

I'll fit and prime those before doing the top coat - just need to decide which grey to go with. I'm leaning towards number (5) at the moment.

 

 

 

Also the @railtec-models transfers arrived in the post this morning, thanks Steve.

 

 

They are for these two, so now I need to decide how many of these wagons to build...

 

[GWR57xx]

When applying transfers I'm not sure whether it's necessary or best to gloss varnish the whole model rather than just the patches where the transfers will go.

 

As Railtec helpfully supply spares with their sets I decided I'd better do a test before committing them to the good wagons. I also wanted some practice in applying the transfers. So I applied gloss varnish patches by brush - the first ones (on the reverse) were awful because the varnish was too thick, so on the second wagon side I diluted it a little with water. After it was dry I then applied the transfers.

 

 

I think you can just about make out the varnished areas.

 

Following Railtec's advice I'll leave these for at least 24 hrs before giving them a coat of matt varnish.

 

I want to see whether the gloss varnish patch is still discernible after this so I can treat the good wagons accordingly.

 

[GWR57xx]

First wagon still in (1), second wagon now in (5) for this photo:

 

 

I was toying with the idea of keeping the first wagon in (1) but I think there's way too much difference between the shades of grey, so it has now also been painted in (5) to match.

 

[GWR57xx]

Transfers transferred. I've been doing a lot of waiting for paint and transfers to dry...

 

 

Had a slight issue with 9631. You can see there's a bit of silvering, especially obvious in the centre of the "G", where the transfer hasn't sunk into the surface contours.

 

Both bodies were sprayed with gloss varnish literally seconds apart and from the same batch of paint. 9449 came out fine, 9631 had bad orange peel.

 

I think it was my fault though. There was a bit of paint left in the cup after a couple of passes and stupidly I thought rather than waste it I might as well go over it again. Lesson learned.

 

Also it was a very hot day and I used the Vallejo recommended 3:1 varnish : thinners. I think it was possibly getting a bit dry by the time it landed, so next time I'll try a 2:1 mix.

 

I didn't want to try removing all the paint using IPA because that would probably also destroy the resin body. And I didn't want to throw the lot in the bin so I ploughed on with adding the transfers.

 

Railtec suggest Humbrol Decalfix (which I don't have) and to avoid MicroSol/Set (which I do have). So I left it. I've now given both a spray of matt varnish at 2:1 which appears to have gone on fine, but I think perhaps I should have tried a tiny bit of MicroSol first?

 

Hopefully a bit of weathering will mask it...

 

[brossard]

These wagons are coming along very well.  Interesting about Railtec, which I have no experience with (HMRS and Fox mainly).

 

I use spray gloss varnish first (used to use Glosscote but I think that has been discontinued).  I also use MicroSet to "prime" the surface and, after the decal is on use Microsol to make sure the decal is flat.  When dry, I use a coat of spray matte varnish.

 

I don't get on well with HMRS because there is very little wiggle room.  I prefer water slide (like Fox) so I can poke the decal into place.

 

A sterling job with these.  Given your learning curve, I don't think kit manufacturers have a lot to worry about....yet.

 

John

[GWR57xx]

The Railtec transfers went on very well on the whole, but I was very glad to have a spare of each because one “LOCO” somehow vanished (one minute it was on the work table, next minute nowhere to be found) and one of the numbers I failed to do the “tablecloth trick” well enough and it folded up on itself - my lack of practice more than anything else.

 

They only needed a few seconds submerged in water before they were ready to slide into place.

 

[GWR57xx]

Apart from a final bit of weathering these are now done.

Two rolling chassis with all the buffers, hooks, couplings, wheels & bearings fitted:

 

 

 

Floors added:

 

 

Bodies added (not glued down yet):

 

 

I'm really pleased with these. They're better than anything I thought I'd be able to produce when I started on the design work, and I think they hold up very well against the RTR wagons I've got. At least it's something a bit different...

 

[dpgibbons]

Congrats. Great work! Would you consider sharing the print files? 

[GWR57xx]

2 hours ago, dpgibbons said:

Would you consider sharing the print files? 

 

There are a few threads discussing this issue at the moment.

I wouldn't be comfortable giving away and losing control of something I've put so much effort into.

 

[GWR57xx]

I thought I'd posted this earlier but apparently not, or it's lost in the ether somewhere.

So just in case anyone's interested here's a list of the paint samples and a reminder of what they look like.

 

All are Vallejo except primer (A).

 

 

Primers:
A: Halfords Grey rattle can
B: 73.603 German Panzer Grey
C: 73.602 Black

 

 

Samples:
1: 70.836 London Grey
2: 70.868 Dark Sea Green
3: 70.900 French Mirage Blue
4: 70.995 German Grey
5: 70.862 Black Grey
6: 71.056 Panzer Dark Grey
7: 70.994 Dark Grey
8: 70.991 Dark Sea Grey
9: 70.816 Luftwaffe Uniform WWII

 

 

The winner (at least for me, this time) being (5) Black Grey.