Model Mechanics - 'Eagle' drawings

[stoomraider]

Hello all,

Well the Class V kit, Eagle or Merlin etc has arrived, and what a superb piece of work it is. I have never seen an etched brass/nickel silver kit before and am truly impressed with it.

I need some opinions regarding the conversion to G3 or N25GA scales.

The kit is in 4mm/ft, making the correct gauge 21 mm. This then needs enlarging threefold to 63mm, close to our gauge, but produces model to 12mm/ft. A convenient scale since 1mm = 1 inch! This again makes the model smaller than the 13.5mm/ft that is currently adopted. The 4mm kit shows that the frames were widened behind the motion brackets to cater for the wider Irish gauge, and probably the reason for the positioning of the con rod inside that of the coupling rod. I understand that the Class V relied heavily on Beyer-Peacocks experience with the Midland Compounds, and they do appear similar. Since the front section is narrower than the rear, I wonder if I can assume that the loco used 4' 8 1/2" wide frames and cylinders etc, from the Midland Compounds?

What do the forum members think, what would you like to see done - keep totally to scale or enlarge to fit in with other loco's?

Errol

[MikeWilliams]

Hi Errol,

If it were me, I'd stick totally to scale, which is of course 13.5mm/1ft.

Mike

[IanT]

Well Errol, I'd say it depends...

If you intend to builld a one-off 'Irish' engine - and your other stock will be to 4' 8.5" - then I think Mike is probably right. I'd build her to 13.5mm and squeeze the gauge by 7.5mm.

If however, you intend to build an 'Irish' railway - e.g. other 5' 3" locos and stock, then I think it would be much better to get it right. I'd still stick with 63.5mm gauge but build to 12.7mm (1/2") scale. Everthing will "look right" and you will have no niggly doubts about compromises (which we all have to make - big or small).

In fact there is quite a lot of 1/2" scale G3 stock still around (mainly pre-war) and it mainly 'notices' when you have a train of mixed scale carriages. Where the train is all to 1/2" scale it doesn't tend to stick out so much, even when run alongside trains of the larger 13.5mm stock.

So if this is just a single Irish engine - but everything else will be 'standard' gauge, then I'd manage the gauge down. If it's all to be Irish Broad Gauge - then I'd stick with 63.5mm track. It's a standard model gauge - whereas 71mm for instance is not (5' 3" at 13.5mm).

With 63.5mm track you can still run "guest" G3 locos and stock (provided there is clearance) and your 12.7mm scale Irish "trains" would not look too out of place over here in UK (if you ever visit).   

Sorry, I cannot help with the Midland query though!

Regards,

Ian T

[Ted Sadler]

One society member has already built an Irish 4-4-0 to run on 63.5mm track. I'll need to ask him which scale he chose.

Ted

[IanT]

That's Rogers 'Eagle' Ted and it looks & performs very well.

I've never bothered to check the 'scale' of this design before but I've just had a quick look at the original Martin Evans drawings.

The main drivers are specc'ed at 3.3/8" diameter - which is 85.725 mm

I will not bore you with the math - but if the original engine had 6' 7" drivers, then it appears Martin Evans designed the 'Eagle' to a scale of just over 13mm/ft (13.02 to be exact) -so not quite mid-way between 13.5 & 12.7mm. If you are going to compromise on scale Errol (albeit slightly) this might be a simple way to do so.

Rogers 'Eagle' certainly doesn't look out of place with other G3 locos at GTGs, I'd always assumed it was to 13.5mm in fact.

Regards,

Ian T

[stoomraider]

Quite a good response for a day!

Question - Did the Irish railways used a similar loading gauge to the UK.

I think that I will design to the standard 13.5 mm scale, at least for 2.5" gauge and I will adopt a true scale for the larger gauges. Narrowing the frames by 4 mm either side won't make much difference, I hope for 2.5". It might be possible to disguise the frame spacing above the running boards!

As for the 'Eagle', it seems to be far too long and out of proportion, cabs too high, rear axle under firebox and not behind boiler etc.... - a loco for the beginner.

I have seen photo's of Roger's loco - tender has been modified to look more correct and lovely paint job.

Thanks for the input
Cheers
Errol

There appears to have been a number of different blue's used in the life of these loco's!

[MikeWilliams]

Errol,

I can't answer your question about the Irish loading gauge, but on several occasions standard English rolling stock has been used, certainly from the 1870s right up to recent times with BR MK11s.

Mike

[IanT]

Hi Errol,

"Loading Gauge" is a topic that pops up from time to time and normally I think there is a very simple practical answer to it - that being that if the model is built to scale - then it should (by definition) fit within the loading gauge of the railway in question. My impression of Irish practice was that generally they used a 'British' approach rather than a 'Continental' one. Whilst that doesn't actually answer your query I do have a suggestion.

In practice the real question (to my mind) is really about 'clearance' - a related but different issue.

In the case of your GNR(I) if you are building 'overscale' as suggested earlier - then I would suggest that clearance is pretty important as clearance will be tighter than with a true scale model. The Society does have recommnedations in this area (to suit 13.5mm scale stock) and if used then I do not think there will be any problems in practice.

Regards,

Ian T

[stoomraider]

Hi Ian,
The Class V kit scales up to just under 9 feet fullsize, (34,5 mm at 4mm/ft) which is well within the normal loading gauge. I did find a reference to an Irish coach 'taking full advantage of the Irish loading gauge and being 10ft 2in wide'.

13.5 mm is it then.

Both the Class V's and the Midland Compound's used the same piston stroke and cylinder bores (Wikipaedia).
Maybe I must do both!

Cheers,
Errol

[croned]

The Irish loading gauge is a little wider than the UK Mainland but not that much. I do not have the exact figures but as a guide the widest lines where in the South of the country on the GSWR.  When Maebh was moved from Belfast to the museum in Cultra they had to take the whistles off to give clearance on the old BCDR track to Cultra. Merlin / Eagle ran on the GNR(I) which would have similar clearnaces to the BCDR. I measured the clearance between tracks on the Cork Cobh line (GSWR) earlier this year and found them to be 6ft ie the same as the UK. The difference in loading gauge must be taken up entirely in the difference in track gauge. I would suggest that the GWR loading gauge would not be any more than an inch Narrower than the GNR(I) one. I read an article in the latest Railway Archieve magazine where DSER engines where regauged to the narrow gauge and used in Richborough military port and on parts of the SER which is the only case I've heard of of broad gauge engines going the other way. The design was basically an LNWR one though.

The 10 ft 2 in coach mentioned was Park Royal bodied and I have seen the last revenue earning set running on the Waterford line. We have one in Downpatrick with seating arranged 3 on one side and 2 on the other.