Heljan Gresley O2 2-8-0 'Tango'

[Brush53Falcon]

Herewith four CAD/CAM images of the O2/4.

[Brush53Falcon]

.........and four more

[Woodcock29]

Thanks for these drawings Brush53Falcon they look fantastic. They will certainly show up the lack of detail in my NuCast examples!

I know they are only CAD drawings but I presume comments are welcome. I note that the lower corners on the cab spectacles appear to be too rounded. Interesting to see both lengths of side handrails are catered for in the stepped tenders.

Woodcock29

[strang steel]

Those are just wonderful drawings. I am trying not to get too excited.

Are the cab spectacles too rounded? Compared with this photo, I see no obvious error - http://www.flickr.com/photos/31514768@N ... t5N-9VurRU

[ROY@34F]

Thanks "Brush",looking good ,but I think the bottom of the front cab spectacles look too rounded,as Woodcock says.
Regards,Roy.

[strang steel]

Ok.

Let me try this photo then - http://www.flickr.com/photos/robdaniels ... 5N-9VurRU/

Is that not rounded at the bottom?

[45609]

No, definitely not. Look more closely. The dirt is rounded but the window frame has sharp corners.

O2 cab window.png (203.25 KiB) Viewed 5645 times

cheers....Morgan

[strang steel]

Oh yes, so it is.

Sorry. I must get new eyes.

[ROY@34F]

OK,John,I was almost ready to concede,but when you see Morgan's photo,(with thanks),they look to have virtually no rounding.
So I hope very much this will be addressed by "Brush"/Heljan.
I certainly did'nt think they looked right in the cad pictures.
Kind regards,Roy.

[strang steel]

That's ok Roy.

When I look at the ex-works loco, I can see just how filthy the examples I chose were. Presumably while the project is still at the design stage, these are the details that can be sorted out easily and without much extra cost.

I think this policy of two-way dialogue between Heljan and their customers, is an excellent way to proceed.

[45609]

Just to take this cab window shape a little further I looked through the Doncaster drawing lists this morning and found the following references.

Y1099, Cab for O-2 class engines with Side Windows, xx/09/1931, E.O. 326; 328; Engine number 3461 and 3477 to 3486; 359; 364, 365 O-2; 1931; 1932; 1940; 1940

Y1127, Cab Arrangement for O-2 Class engines L.H. Drive, xx/03/1932, E.O. 326 O-2; 1931

In addition to this there are over 580 other search hits for drawings containing the search terms O-2 or O2. All of these drawing records (in an Excel spreadsheet) can be downloaded from the NRM website.

http://www.nrm.org.uk/ResearchAndArchiv ... Works.aspx

Half way down the list enlititled "Works"

A request to view drawings and a visit to NRM search engine, something I've done quite a few times, can be very revealing.

Having said all of this the essential shape of the spectacle plate window should be two large radii joined by two vertical and one horizontal edge with sharp corners. The upper radius runs parallel to and is concentric with the cab roof radius the lower one does a similar thing with following the diameter of the round top firebox.

Cheers....Morgan

[Brush53Falcon]

Thank you Gentlemen and in particular Morgan for taking the trouble to bring attention to the cab spectacle window debate.

Whilst over in Denmark recently I had the opportunity to see the CAD/CAM up on the screen, "raw' as it were, and I was alerted to the shape of the spectacle windows followed by the question, which one shall I draw? It had become apparent to Heljan that there were two types on the side window cab and a decision needed to be made as to which window style we were going to adopt. This side window cab is initially going to be a one version component which suited both the O2/3 and O2/4. Of the two versions of spectacle window one is typically Gresley, more of a streamlined design whilst the other is very much akin to the Thompson B1, which it may even fit. I have spent the last few hours looking through and blowing in to all the O2 images I have. Allowing for the dirt builds up etc. I also plotted the various shapes in relation to the boiler and roof contours and yes there are two distinct types. I had previously flagged this up with Tony Wright, and surprisingly even he hadn't realised this, but does concede that there are differences.
I quickly conducted a survey before writing this and of the O2/3's and O2/4's numbered from 63947-63987 I have found 27 different engines with the rounded Gresley style of window and 14 engines with the Thompson square cornered style. In some cases I have found engines with both types and this indicated that some cab fronts were rebuilt when reboilered in the late 1950-1961 period. This of course has given us a slight dilema in which window style to use as the models chosen use a mix of both. I think it is also fair to say that it is easier to take material away than to try and add it so to go with the rounded design for the first two releases seems the most sensible. Modellers could then, if they so wished, file out the apertures to make them more angular. My research also confirmed the window styles in the images that Morgan submitted were indeed of the Thompson style, as he kindly pointed out.
In reply I have attached a few images from those I have permission to use.

Perhaps when the next versions are to be released of the O2/1 & O2/2 we will have the opportunity to maybe revise the tooling to change the spectacle window design to the later style. In these two batches within numbers 63922-63946 I can only find 2 engines with the rounded windows as opposed to 12 with the later angular cornered design.
Obviously all of this depends on cost but this would be the most opportune time to make the change. The cost of providing this option at this time is quite prohibitive and I hope you understand the reasons behind this compromise. As had been said before the O2 Tango project has been a 'minefield', but enjoyably so, and I'm sure Heljan wiill try their utmost to replicate this fine engine in miniature.

[strang steel]

Those close up cab photos seem to suggest even more detailed differences.

63987 appears to have a riveted spectacle plate with them spaced equally around the edge, plus equally spaced rivets down the cab front panel, whereas 63958 has none around the spectacle plate, but 5 very closely spaced towards the cab side window, then a gap, and more rivets lower down the cab front.

I think your decision is the right one, and we can then attempt to add or remove the details depending on the number of the loco(s) we wish to run on our layout, if we can find a decent close-up photo - or just ignore that level of accuracy and run them regardless.

[45609]

Indeed and a detail difference that is also new to me too! Apologies duly offered. In light of this info it seems that the course of action is the most intelligent and pragmatic solution. Well done Brush!

Morgan

[Woodcock29]

Hi Everyone

What a minefield indeed! This is terrific dialogue and we must thank Brush53Falcon for his dedicated work on this with Heljan.

Since my first post raising this matter, I have been pawing over Yeadon Vol 9 and 'Greenie' Part 6B which have the best selection of photos of O2s that I have that are easy to locate.

I agree now that in fact there is a rounding of the bottom corners of the spectacle plates on the majority of O2s with side window cabs and the 02/3s in particular. However, something still strikes me as not quite right on the CAD drawings. I think now that the bottom of the spectacle is too narrow and this is what accentuates the roundness of the bottom in the drawings and makes it less subtle than it was in reality. This means that the spectacles in the CAD drawings are a bit narrow overall. This could be because the spectacles are set out too far from the firebox in the CAD drawings?

It appears to me from what I have seen in photos is that the O2/4s rebuilt from O2/2s were also given a side window cab at rebuilding and as this was in the Thompson era they were given what might be called cabs with standard Thompson features and hence they have the sharp cornered spectacles as on other Thompson designs such as the B1. I may be proved wrong of course.

I offer these comments purely with the aim of refinement of the design on hand to give us the best possible model.

I hope I haven't led to more confusion. I know one thing we have all learnt a lot more about the O2 story - one of my long time favourite Gresley designs (I've had my Nucast 02/2 running for 31 years).

Thank you Heljan for being prepared to produce these models.

Woodcock29
(in sunny South Australia)