Bubble Muddle, Toil and Trouble

[Mol_PMB]

CIE cement bubbles are all the same, right? Nope, of course not!

They were the first wagons built on the 'CIE standard' 20 ton capacity, 20' long, 12' wheelbase 4-wheel underframe, and the design evolved through 7 batches between 1964 and 1972.

In this thread I'll look at some of the variations between the batches as-built, and those which were a consequence of later modifications.

Firstly, let's look at the stock books. Pender & Richards (1967) list the following:

• 25050-25069, built 1964, 21 ton capacity, 20'0" long, vacuum brake
• 25070-25094, built 1965, 21 ton capacity, 20'0" long, vacuum brake
• 25095-25099, built 1967, 20 ton capacity, 20'0" long, vacuum brake
• 25100-25104, built 1965, 21 ton capacity, 20'0" long, vacuum brake
• 25105-25119, built 1967, 21 ton capacity, 20'0" long, vacuum brake

'Bulk Cement Wagons. To cater for the increased output from the cement factories and Limerick and Drogheda, three series of bulk wagons have been turned out. These differ only in detail. The tanks, which are individually numbered, are loaded by gravity and emptied by pipeline'.

By the time the first edition of Doyle & Hirsch was published in 1979, production was complete. The full list of 150 wagons is given as:

• 25050-25069, built 1964, 10.2 ton tare, 20 ton capacity, 12'0" wheelbase, vacuum brake
• 25070-25094, built 1965, 10.0 ton tare, 20 ton capacity, 12'0" wheelbase, vacuum brake
• 25095-25099, built 1967, 10.5 ton tare, 20 ton capacity, 12'0" wheelbase, vacuum brake
• 25100-25104, built 1965, 10.0 ton tare, 20 ton capacity, 12'0" wheelbase, vacuum brake
• 25105-25119, built 1967, 10.5 ton tare, 20 ton capacity, 12'0" wheelbase, vacuum brake
• 25120-25139, built 1970 10.5 ton tare, 20 ton capacity, 12'0" wheelbase, vacuum brake
• 25140-25199, built 1972, 10.5 ton tare, 20 ton capacity, 12'0" wheelbase, vacuum brake

The mention of 'these differ in detail' and the differences in tare weights got me looking at my own photos, and those of others, to spot the differences. I was surprised how many differences there were!

Operationally though, they were all effectively the same, and the working timetables list them all together with 10 ton tare and 20 ton capacity.

[Mol_PMB]

I'm going to be discussing differences in the following areas:

1. W-irons
2. Solebar reinforcements
3. Solebar eyes
4. Bufferbeam ends
5. Vacuum pipes
6. Plain end treadplate
7. Other details at the plain end
8. Tank number
9. Handbrake
10. Tank support brackets

There may be other differences that I haven't spotted yet.

 

[islandbridgejct]

This looks interesting. I'll come back when you have some more done.

Alan

[Mol_PMB]

Let's start with the first batch, 25050-25069, built in 1964. Even within the batch there were some variations.

The National Library of Ireland has a nice photo by James O'Dea, at Derry in 1967:

https://catalogue.nli.ie/Record/vtls000307375

1. W-irons: These are the plain plate type, but the hornguides are festooned with bolts - 16 at each axlebox. This is a key feature of this first batch, which remained unchanged.
2. Solebar reinforcements: There aren't any - it's just a plain channel section about the W-irons. This was soon modified.
3. Solebar eyes: There aren't any.
4. Bufferbeam ends: These are short, the bufferbeams barely protrude beyond the solebars and are no wider than needed to hold the buffers.
5. Vacuum pipes: These are low, hanging below the bufferbeam.
6. Braked end treadplate: There isn't one. We can see the top of the vacuum cylinders.
7. Other details at the plain end: There is a bar across the end above the bufferbeam; this may be a vac brake load changeover valve?
8. Tank number: 25062 was the 13th cement bubble built (the series started at 25050), and its tank carries the number 13. Not 062!
9. Handbrake: this is perhaps the biggest difference to what we're used to. It's a handwheel not a lever. Similar handwheels were used on the previous type of wagon built by CIE, the 25201-25435 series flats https://irishrailwaymodeller.com/topic/17496-cie-ballast-wagons-late-1960s-to-1980s-not-hoppers-or-flats/#findComment-250654, and of course on the vac fitted H vans and cattle wagons.
10. Tank support brackets: without a handbrake vee hanger in the middle of the solebar, these are more obvious. They have chamfered ends.

This photo in the IRRS archive dated 1966 shows another bubble with this handwheel brake below the solebar, and other features the same as the wagon above:

https://www.flickr.com/photos/irishrailwayarchive/53508783939

Of course in the 1960s these wagons would have been grey.

Edit: here's a super photo from Ernie showing one of this first batch of bubbles in colour, dated 1967 and still in original condition with the brake handwheel below the solebar. I think it's 25068:

However, 1970s and 1980s photos of these first-batch wagons show some changes, as well as the livery changes to orange and later ivory. This photo by Jonathan Allen on Flickr dated 1978 shows the first wagon with the handwheel above the solebar rather than below. Additionally, the solebars have been reinforced with vertical ribs above the W irons:

Another Jonathan Allen photo from 1970 shows a short train with two early wagons having the handwheel above the solebar (the rest are later batch wagons with the familiar long brake lever):

I'll leave you the fun of looking at 1970s and 1980s photos of cement trains and spotting those with the handwheel brakes - they're quite obvious when you are looking for them...

This IRRS archive photo shows 25058 at Limerick, freshly overhauled and repainted in ivory in 1986. It retains its handwheel brake (above the solebar). The tank number has also been changed, it's now '058' whereas originally it would have been '9'.

https://www.flickr.com/photos/irishrailwayarchive/53508119127/

 

Moving now to the 2000s when I took most of my bubble photos, here's the class leader 25050:

Revisiting the list of characteristics we looked at for the wagon in original condition, with changes marked in bold:

1. W-irons: These are the plain plate type, but the hornguides are festooned with bolts - 16 at each axlebox. This is a key feature of this first batch, which remained unchanged.
2. Solebar reinforcements: 7 vertical ribs have been welded above each W-iron. The exact number and spacing of the ribs varied between wagons, as they were a later modification.
3. Solebar eyes: There aren't any.
4. Bufferbeam ends: These are short, the bufferbeams barely protrude beyond the solebars and are no wider than needed to hold the buffers.
5. Vacuum pipes: These are low, hanging below the bufferbeam.
6. Braked end treadplate: There isn't one. We can see the top of the vacuum cylinders.
7. Other details at the plain end: Nothing. The parts perhaps associated with the brakes seen in the 1960s photos have been removed.
8. Tank number: 25050's tank carries the number '050'; it would originally have been '1'.
9. Handbrake: this has been modified to the long lever type, the same as on the later wagons.
10. Tank support brackets: without a handbrake vee hanger in the middle of the solebar, these are more obvious. They have chamfered ends.

Here is 25067 seen from the other side, basically the same except the arrangement of solebar reinforcing ribs, and the installation of a raised treadplate over the vacuum cylinders.

Here's 25059, showing the raised treadplate at the braked end more clearly, as well as some sort of box or housing on top of it. That may have been associated with the brake handwheel arrangement when positioned above the solebar.

Here's another view of 25067 and we can see from this angle that it also has a similar boxy housing at the braked end:

Ernie's photo of 25065 on the left shows the raised treadplate over the brake cylinders, but not the boxy housing. Note the solebar reinforcing ribs are evenly spaced (like 25050 above) rather than the uneven arrangement seen on 25059 and 25067.

We'll finish the first batch with another of Ernie's photos showing 25067 and 25068 together. This shows the short bufferbeam ends particularly well. Note also that the raised treadplates are secured with 5 bolts each side (we'll see in due course that the later wagons have 6). These two seem to have lost their tank numbers.

Edited December 3, 2024 by Mol_PMB
marked in text

[Mol_PMB]

The first 20 bubbles built in 1964 were evidently reasonably successful, but the design could be improved. We've already seen how the brake arrangement was changed (twice) and the solebars were reinforced.

So when the second batch of 25 wagons 25070-25094 were built the following year, there were differences.

Once again we can thank the National Library of Ireland and James O'Dea for a nice photo of 25083 dating from 1967:

https://catalogue.nli.ie/Record/vtls000306704

We'll look again at the list of 10 items:

1. W-irons: Just about visible in the photo above, but we'll see more clearly later, these are W-shaped rather than triangular plates.
2. Solebar reinforcements: rectangular plates welded to the front of the channel section about the W-irons provide extra strength.
3. Solebar eyes: These are fitted to the front of the solebar reinforcement plates.
4. Bufferbeam ends: These are longer than the first batch, they protrude beyond the buffers.
5. Vacuum pipes: These are high, on an upstand above the bufferbeam.
6. Braked end treadplate: There isn't one. We can see the top of the frame channels.
7. Other details at the plain end: Difficult to see in this view, but it seems to be just the vacuum pipe.
8. Tank number: 25083 was the 34th cement bubble built (the series started at 25050), and its tank carries the number 34. Not 083!
9. Handbrake: this is now a hand lever. However, it's not the later standard type - it has a Morton clutch on the vee hanger, rather than reaching past the vee hanger to a link arrangement.
10. Tank support brackets: They have vertical ends rather than the chamfered ends of the first batch.

The IRRS photo from 1966 that I linked in the previous post also features one of these second-batch wagons 25074, viewed from the other end:

https://www.flickr.com/photos/irishrailwayarchive/53508783939

Also in the IRRS archive is this view of 25078, freshly overhauled at Limerick in 1986. Apart from the new ivory livery and the tank number (strangely 078B), its condition is unchanged from the 1960s photos:

https://www.flickr.com/photos/irishrailwayarchive/53508119122/

This IRRS view shows 25086 in 1985, again as-built except livery and tank number:

https://www.flickr.com/photos/irishrailwayarchive/53511538110

 

Moving to the early 2000s and my own photos, here's the first of the batch 25070, and in the second photo 25086:

We'll look again at the list of 10 items, again the modifications from original condition are shown in bold:

• W-irons: These are W-shaped rather than triangular plates.
• Solebar reinforcements: The rectangular plates have been replaced by plates with fishtail-shaped ends, on both wagons pictured
• Solebar eyes: These are fitted to the front of the solebar reinforcement plates on 25086, but absent on 25070.
• Bufferbeam ends: These are longer than the first batch, they protrude beyond the buffers.
• Vacuum pipes: These are high, on an upstand above the bufferbeam.
• Braked end treadplate: There isn't one. We can see the top of the frame channels on 25086. It's possible there is a flush plate on 25070 but it's hard to see.
• Other details at the plain end: Just the vacuum pipe.
• Tank number: 25070 carries '070', 25086 has no tank number.
• Handbrake: The hand lever arrangement has been modified to the standard type with a long lever reaching past the vee hanger to a link arrangement.
• Tank support brackets: They have vertical ends rather than the chamfered ends of the first batch.

So, fewer modifications to this batch but there were still some changes implemented over the years.

[Mol_PMB]

Also in 1965, there were 5 bubbles built numbered 25100-25104. I cannot explain why the numbers 25095-25099 were missed out, and this gap was filled in a couple of years later.

25100-25104 had the same tare weight as the other 1965-built wagons described in the previous post, and were probably similar originally. I have not yet found any older photos of these. However, here's my photo of 25100 in the early 2000s:

We'll look again at the list of 10 items, in this case the differences from the other 1965 wagons in 2000s condition are highlighted in bold:

• W-irons: These are W-shaped rather than triangular plates.
• Solebar reinforcements: Vertical ribs above the W-irons.
• Solebar eyes: These aren't any.
• Bufferbeam ends: These are longer than the first batch, they protrude beyond the buffers.
• Vacuum pipes: These are high, on an upstand above the bufferbeam.
• Braked end treadplate: There isn't one. We can see the top of the frame channels.
• Other details at the plain end: Just the vacuum pipe.
• Tank number: 25100 carries '100'.
• Handbrake: The hand lever arrangement is the standard type with a long lever reaching past the vee hanger to a link arrangement.
• Tank support brackets: They have vertical ends rather than the chamfered ends of the first batch.

The only difference from the other 1965 wagons is in the area of the solebar reinforcements and eyes, and in this respect the 25100 batch are more like the original 25050 batch. It is possible that the 1965 production started with 25100-104, and the 25070-25094 batch followed with the improved solebar design.

[Mol_PMB]

The next batch of bubbles was introduced in 1967, and this comprised 20 wagons numbered 25095-25099 and 25105-25119.

I think these were built new with the final version of the brake gear, a long lever reaching past the vee hanger to a link arrangement. They also had a raised treadplate at the braked end of the wagon.

I linked this wonderful 1970 photo from Jonathan Allen in an earlier post too, but I'll put it again here and talk through the different wagon types:

• Starting from the brake van end, the first bubble is a 1967 model, with the long brake lever reaching past the vee hanger, and you can also see the raised treadplate at the nearer end.
• The next two bubbles are the 1964 model, with handbrake wheels (above the solebar).
• Then there's a 1965 wagon, with the shorter, more angled brake lever.
• The clean one is another 1967 wagon, with the raised treadplate and long brake lever distinctive.

Finally, just behind the loco is another 1965 wagon, bringing up a total of 2 of each type that existed in 1970.

Here's an IRRS archive photo of 25098, newly overhauled at Limerick in ivory in 1986, which also shows the long brake lever and raised treadplate:

https://www.flickr.com/photos/irishrailwayarchive/53509328864/

 

Moving now to the more modern photos which are a bit clearer, here's 25114, 25098 and 25110. I think these remained basically unmodified from the as-built condition.

We'll look again at the list of 10 items:

• W-irons: These are W-shaped rather than triangular plates.
• Solebar reinforcements: rectangular or fish-tail ended plates welded to the front of the channel section about the W-irons provide extra strength.
• Solebar eyes: These are fitted to the front of the solebar reinforcement plates.
• Bufferbeam ends: These are longer than the first batch, they protrude beyond the buffers.
• Vacuum pipes: These are high, on an upstand above the bufferbeam.
• Braked end treadplate: A raised treadplate is provided. It has 6 fixing bolts each side (rather than the 5 bolts on the plates retro-fitted to the first batch).
• Other details at the plain end: Just the vacuum pipe.
• Tank number: matches the last 3 digits of the wagon number
• Handbrake: The hand lever arrangement is the standard type with a long lever reaching past the vee hanger to a link arrangement.
• Tank support brackets: They have vertical ends rather than the chamfered ends of the first batch.

 

[Mol_PMB]

The penultimate batch of bubbles was built in 1970, numbered 25120-25139.

The IRRS has a photo of one of these newly built and only partially painted; it has tank number 80 so it would be wagon 25129: 

https://www.flickr.com/photos/irishrailwayarchive/53570447106

Jonathan Allen comes up trumps again with this image on Flickr showing 25138 in 1976, by which time the number on the tank matched that on the wagon:

As far as I can tell, these wagons were identical to the 1967 batch apart from the W-irons, which were a plain plate type slightly different in shape to the previous W.

For completeness we'll look again at the list of 10 items:

• W-irons: Plain triangular plates.
• Solebar reinforcements: rectangular plates welded to the front of the channel section about the W-irons provide extra strength.
• Solebar eyes: These are fitted to the front of the solebar reinforcement plates.
• Bufferbeam ends: These are longer than the first batch, they protrude beyond the buffers.
• Vacuum pipes: These are high, on an upstand above the bufferbeam.
• Braked end treadplate: A raised treadplate is provided. It has 6 fixing bolts each side (rather than the 5 bolts on the plates retro-fitted to the first batch).
• Other details at the plain end: Just the vacuum pipe.
• Tank number: matches the last 3 digits of the wagon number
• Handbrake: The hand lever arrangement is the standard type with a long lever reaching past the vee hanger to a link arrangement.
• Tank support brackets: They have vertical ends rather than the chamfered ends of the first batch.

Frustratingly, this batch of wagons seems to have evaded my camera in the early 2000s!

 

 

[Mol_PMB]

Finally, there was a large batch of 60 wagons built in 1972, 25140-25199. By now the design had matured and these seem to have been identical to the 1970 batch, and they remained largely unmodified through their lives.

The photo in the Doyle&Hirsch stockbook shows one of these when new, here's 25156, and note that the tank number is 156 matching the running number, so the tank numbering policy must have changed by 1972:

For completeness we'll look again at the list of 10 items:

• W-irons: Plain triangular plates.
• Solebar reinforcements: rectangular plates welded to the front of the channel section about the W-irons provide extra strength.
• Solebar eyes: These are fitted to the front of the solebar reinforcement plates.
• Bufferbeam ends: These are longer than the first batch, they protrude beyond the buffers.
• Vacuum pipes: These are high, on an upstand above the bufferbeam.
• Braked end treadplate: A raised treadplate is provided. It has 6 fixing bolts each side (rather than the 5 bolts on the plates retro-fitted to the first batch).
• Other details at the plain end: Just the vacuum pipe.
• Tank number: matches the last 3 digits of the wagon number
• Handbrake: The hand lever arrangement is the standard type with a long lever reaching past the vee hanger to a link arrangement.
• Tank support brackets: They have vertical ends rather than the chamfered ends of the first batch.

I've got loads of photos of this batch so will just pick a few views showing different angles; here are 25151, 25154, 25177

And the very last one, 25199:

Note that many, but not all, of these have had their solebar reinforcement plates modified or replaced with the fishtail-ended variety. Otherwise they appear to be as-built except the livery.

 

[Mol_PMB]

I'll finish with a few more of Ernie's excellent photos showing whole trains of bubbles. Can you spot the difference from this distance?

1967:

1973:

1979:

1990:

1999:

In general, the modifications over time made the various batches more similar to each other. The differences are more obvious in the grey and early orange eras.

The IRM models represent the 1970 and 1972 batches accurately, and are very close for the 1967 batch

They're also pretty close for the 1964 and 1965 batches later in life, and passable for the 1965 batch in original condition too.

They're not great for the 1964 batch which had handwheel brakes from the 1960s into the 1980s, though to be fair most of the models numbered in that batch are offered in the later ivory livery.

Pack J must have been a Friday afternoon job - it contains two wagons numbered in the 1972-built batch, which were never painted grey - both the 1970 and 1972 batches entered service in orange. And the third wagon in Pack J is one of the 1964 batch, which ought to have handwheel brakes when in grey livery.

 

Edited December 3, 2024 by Mol_PMB
typo

[Mol_PMB]

I've just snapped up a set of 3 IRM bubbles on ebay for £99.50 which seems like a reasonable deal (at least after a few pints). Of course, having said in my previous post that Pack J was the 'Friday afternoon job' that's completely wrong, that was the set that came up for sale. So over Christmas I now have a nice challenge of regauging and modifying them with a variety of details and appropriate liveries for some of the different batches described above.

[Robert Shrives]

Hi 

Thanks for taking the time to create this data file - The idea of standard is much followed by the Tin car saga!  

Robert 

[Mol_PMB]

An eBay purchase a few weeks ago on this theme - a nice clear slide of 25075 in orange livery, green-carded at Limerick:

This wagon was in the second batch, and would have been delivered in grey livery in 1965. The photo dates from 1979 by which time it had been repainted with orange tank and grey frame, and then had a chance to get fairly grubby.

Reviewing the list of 10 items as I did up-thread:

1. W-irons: These are W-shaped rather than triangular plates.
2. Solebar reinforcements: rectangular plates welded to the front of the channel section about the W-irons provide extra strength.
3. Solebar eyes: These are fitted to the front of the solebar reinforcement plates.
4. Bufferbeam ends: These are longer than the first batch, they protrude beyond the buffers.
5. Vacuum pipes: These are high, on an upstand above the bufferbeam.
6. Braked end treadplate: There isn't one.
7. Other details at the braked end: Difficult to see in this view, but it seems to be just the vacuum pipe.
8. Tank number: 25075 carries tank number 075; it has been renumbered from the original.
9. Handbrake: this is a hand lever. However, it's not the later standard type - it has a Morton clutch on the vee hanger, rather than reaching past the vee hanger to a link arrangement.
10. Tank support brackets: They have vertical ends rather than the chamfered ends of the first batch.

What's particularly useful about this photo is that it clearly shows the as-built brake configuration of the second batch, which was different from the other batches and was later modified to match the last batch.

One day, when I get through my wagon backlog, I plan to modify an IRM bubble to represent this batch.

 

[Mol_PMB]

The HMRS collection has a clear view of one of the first batch of wagons retaining its wheel handbrake into the mid 1980s:

[ADP157] CIE 25050 cement wagon

 

 

[Flying Snail]

Just coming into this thread now following the announcement of the latest run of cement bubbles. I have to say the amount of research here is very impressive! Excellent work @Mol_PMB!

[Fowler4f]

1 hour ago, Flying Snail said:

Just coming into this thread now following the announcement of the latest run of cement bubbles. I have to say the amount of research here is very impressive! Excellent work @Mol_PMB!

I wholeheartedly agree !

[Mol_PMB]

Thanks to ebay and @Stoby of this parish, I now have a full set of IRM grey bubbles - only two packs were produced in this livery:

From left to right, we have 25069, 25083, 25084, 25109, 25159, 25187. All the IRM bubbles are the same moulding, which accurately represents the later batches (delivered in 1970-1972), but the early grey ones had some detail differences.

Of course there's nothing I like more than destroying the value of collectable models by modifying and weathering them, so I'll be working on these fairly soon to back-date their details. The brakes are the biggest difference but there are many other detail adjustments needed. And of course I need to re-gauge them which isn't so straightforward on these early IRM models.

In preparation for that I've been reviewing the available photos of grey bubbles and I thought I'd just summarise the findings here (some of it repeats links earlier in this thread, but I have found some more).

 

As correctly modelled by IRM, the 'BULK CEMENT' lettering is white on the grey bubbles, which helps to distinguish the grey livery in black and white photos. There's also the date as a clue, of course.

In the IRRS archive, a photo at Inchicore dated February 1964 with what must one of the first bubbles, still in primer I think:

https://www.flickr.com/photos/irishrailwayarchive/53505734117

From the NLI O'Dea collection, a bulk cement train (mix of 1964 and 1965 batches) at Straffan in 1965 https://catalogue.nli.ie/Record/vtls000306759

From the IRRS archive, two photos of a pair of bubbles at Boyne Road in 1966. The nearer one is 25074 of the 1965 batch, and the other is from the 1964 batch:

https://www.flickr.com/photos/irishrailwayarchive/53508783939

https://www.flickr.com/photos/irishrailwayarchive/53508466241/

From the IRRS archive, a bulk cement train at Hazelhatch in 1966. The wagons are a mix of the 1964 and 1965 batches:

https://www.flickr.com/photos/irishrailwayarchive/54327467196/

From the NLI O'Dea collection, a photo of 25062 (1964 batch) at Derry in 1967 https://catalogue.nli.ie/Record/vtls000307375

From the NLI O'Dea collection, a bulk cement train (the nearer four are all from the 1965 batch, including 25083) at KIldare in 1967 https://catalogue.nli.ie/Record/vtls000306704

From the NLI O'Dea collection, a bulk cement train (mix of 1964 and 1965 batches, possibly the two clean ones at the front might be 1967 batch?) at Hazelhatch in 1967 https://catalogue.nli.ie/Record/vtls000306218

Other NLI and IRRS photos with distant views of bulk cement trains in 1967, few details visible:

https://catalogue.nli.ie/Record/vtls000306208

https://catalogue.nli.ie/Record/vtls000306209

https://catalogue.nli.ie/Record/vtls000307373

https://catalogue.nli.ie/Record/vtls000306207

https://www.flickr.com/photos/irishrailwayarchive/53570455706/

https://www.flickr.com/photos/irishrailwayarchive/53447301180/

https://www.flickr.com/photos/irishrailwayarchive/54257011099

From Ernie on Flickr, a super pair of colour photos at Belfast GVS in April 1967. The wagon immediately behind the locos is 25068 (1964 batch) and the remainder are a mix of the 1964 and 1965 batches:

There's also a colour photo of a grey bubble at Derry in 1967 in the 'UTA in Colour' (Young) book, page 66

Another colour photo in the IRRS archive showing Cabra in February 1968. Only 3 bubbles are visible, all rather distant but all grey:

https://www.flickr.com/photos/irishrailwayarchive/53510447552/

A black and white photo of Cabra also in 1968:

https://www.flickr.com/photos/irishrailwayarchive/53511485009/

 

So then, we've got up to the year 1968, and very confident that the 1964 and 1965 batches carried the grey livery initially. Not so sure about the 1967 batch based on the evidence above, many of the photos pre-date their construction. Can anyone confirm?

 

I haven't found any bubble photos dated 1969, but there are lots of them in 1970, maybe because they changed colour.

In June 1970, here's 25129 of the 1970 batch being painted for the first time. Most of the tank is still in primer, with its delivery address stencilled on and even bearing the name of the ship it crossed the water on! But the tank is being painted orange and the underframe grey. So the 1970 batch never carried the original grey tank and black underframe livery:

https://www.flickr.com/photos/irishrailwayarchive/53570447106

But it wasn't just the new ones that were orange. Here are 25051 and 25053, from the 1964 batch, each with a coat of orange in May 1970:

https://www.flickr.com/photos/irishrailwayarchive/53510419397/

https://www.flickr.com/photos/irishrailwayarchive/53511314086/

From Jonathan Allen on Flickr, a whole train in orange in October 1970, and this includes wagons from the 1964 batch as well as newer types:

Again from Jonathan Allen, this rake contains 1964, 1965 and 1967 or 1970 wagons in orange, photo dated December 1970:

By the early 1970s everything was orange:

So, it seems that there was a major (and surprisingly rapid) repainting campaign in 1969-1970, the older wagons becoming orange, and the newly built wagons in 1970 and 1972 entering service in orange.

 

That sets my grey rake firmly in the 1960s, and requires me to back-date the details to the 1964 and 1965 batches, maybe also the 1967 batch as I haven't quite confirmed if they entered service in grey or orange.

[Mol_PMB]

I have spent some more time peering at this NLI photo dated June 1967. https://catalogue.nli.ie/Record/vtls000306218:

The first two wagons definitely have a long brake lever extending past the vee hanger, and so they are from the 1967 batch. That would explain why they're so clean - they are almost brand new. 

Now, look at the underframe - it's a pale colour, apparently matching the tank. Being new, the wagons are clean and the colour hasn't been influenced by weathering. It's definitely not black. 

I've had a look through more books and my back-issues of IRRS journals (not a complete set by any means) and found a couple more useful photos of grey bubbles.

The book '35 Years of NIR' (Allen) page 92 has a colour photo at Portadown dated June 1968, showing BUT railcars on the Enterprise with a long rake of grey bubbles adjacent. Although the photo is at an awkward angle looking along the train, parts of the underframe of the nearest wagon are clearly visible and sun-lit. They are grey, matching the tank colour. I can't quite tell whether that bubble is from the 1965 or 1967 batch (it's not a 1964).

The IRRS Journal October 2013 issue - vol 25 no.182 - has a colour photo on p384 showing A40 and B161 hauling a rake of grey bubbles (and brake van) off the Foynes loop at Limerick. The photo is undated but must pre-date A40's re-engining in 1969. Most of the bubbles have moderate weathering, but there's one towards the back of the train that stands out as having a clean grey underframe, and it appears to be a 1967 batch (again it's a bit indistinct).

 

So, I'm coming to the conclusion that the 1967 batch were indeed delivered in grey, but it was all-over grey - no black underframe. 

The IRM models of grey bubbles all have black underframes. Ernie's photo of 25068 looks like good evidence of black underframes on the 1964 batch of wagons:

I'm now undecided about the underframe colour for the 1965 batch!

It must be said that after a bit of weathering from cement dust and brake dirt, the original colour of the underframe is rather hard to distinguish in most photos, especially monochrome images. Perhaps a good dose of weathering on the models is the answer!

 

Here are two colour photos of a whole train of grey bubbles in the 1960s, which give no useful information on underframe paint colour!

https://www.flickr.com/photos/irishrailwayarchive/53449790845/

https://www.flickr.com/photos/irishrailwayarchive/54257011099/

Another whole-train photo from the IRRS archive, dated 'm1960s' but I think it's 1969/70 based on A31's livery. Not very useful for wagon livery details though:

https://www.flickr.com/photos/irishrailwayarchive/53447019558/

Another 'm1960s' photo. A 1965-batch bubble is in the background, already looking pretty grubby:

https://www.flickr.com/photos/irishrailwayarchive/53447018728/

 

So far, I haven't found a colour photo that clearly shows a mixture of original grey and orange liveries. Seems odd, it must have happened in the livery transition period. The liveries can be hard to distinguish in monochrome photos though.

I'd better get back to some modelling rather than just researching the next project. Hopefully someone else has some late 1960s bubble photos that would confirm the liveries of each batch?