The North British Type 2s: Classes 21, 22 & 29

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Strathclyder

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To compliment the Class 28 Metro-Vick (Loaf) thread, this thread is dedicated to perhaps the most maligned of the 1955 Pilot Scheme diesels: the North British (NBL) Type 2 trio, consisting of the Class 21 diesel-electrics, the Class 22 diesel-hydraulics (aka Baby Warships) & the Class 29s (rebuilt/re-engineered 21s).

Much has been said and written about these machines (in print and online), and I thought it was high-time this forum had such a place for them. Between the issues that plauged them (the 21s in particular), their less than 15 years in service and the demise of their manufacturer, this should make for a fascinating thread (attached images copyright of Michael Mensing, Peter Lovell, Rail Photoprints & Bill Jamieson respectively).

Over to the rest of you. :)

2998099_1000.jpg 6348exeter70.jpg 56539a1777f5508850126a97cc3b9d6a.jpg Perth - RAILSCOT.jpeg
 
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I travelled behind class 21/29 at least three times - that is to say I can pinpoint the three occasions but there may have been more, one as class 21 and two as class 29.
All I can add is that none of these three trains suffered from a locomotive failure which is perhaps a better than average success rate! Perhaps I should add the longest of these trips was just over 30 miles which may have contributed to this 100% reliability.

The NBL of course also built the type 4 class 41, 5 in number, and the more numerous class 43 Warships. According to Wikipedia class 41 were withdrawn as non standard rather than as unreliable, although no doubt opinions may vary, after less than ten years in service, whereas the class 43 are quoted as less reliable than their Swindon built class 42 brothers, and lasted only slightly longer than the class 41.

The NBL type 1 - class 16 - was equally short lived and quoted as non standard and unreliable. NBL also built some 0-4-0 shunters with a similar lifespan to the others, with only the class 29 lasting more than about ten years and that with the benefit of being re-engined.

Obviously the expertise which supplied hundreds or possibly thousands of steam locomotives around the world did not translate into their diesel products!
 
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Strathclyder

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22s were quite a bit shorter. In converting the Hornby 29 into a 22 you had to cut a slice out of the body (and chassis, which made it wobbly!)
Didn't the bogie/wheelset design on the 22s differ from those on the 21s/29s? I can see differences between them in the OP images, but I (obviously lol) don't know enough to confirm the details one way or the other.
 

D6130

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I travelled behind class 21/29 at least three times - that is to say I can pinpoint the three occasions but there may have been more, one as class 21 and two as class 29.
All I can add is that none of these three trains suffered from a locomotive failure which is perhaps a better than average success rate! Perhaps I should add the longest of these trips was just over 30 miles which may have contributed to this 100% reliability.

The NBL of course also built the type 4 class 41, 5 in number, and the more numerous class 43 Warships. According to Wikipedia class 41 were withdrawn as non standard rather than as unreliable, although no doubt opinions may vary, after less than ten years in service, whereas the class 43 are quoted as less reliable than their Swindon built class 42 brothers, and lasted only slightly longer than the class 41.

The NBL type 1 - class 16 - was equally short lived and quoted as non standard and unreliable. NBL also built some 0-4-0 shunters with a similar lifespan to the others, with only the class 29 lasting more than about ten years and that with the benefit of being re-engined.

Obviously the expertise which supplied hundreds or possibly thousands of steam locomotives around the world did not translate into their diesel products!
It is said that the main reason why the MAN engines built under licence by NBL Co. for these classes of locomotive were so unreliable was that the drawings were sent over from Germany with metric measurements. Unfortunately NBL's workshop tools and jigs were all calibrated in imperial measures and apparently somebody in their drawing office didn't make a fantastically good job of the conversions.

Didn't the bogie/wheelset design on the 22s differ from those on the 21s/29s? I can see differences between them in the OP images, but I (obviously lol) don't know enough to confirm the details one way or the other.
Yes indeed. The 21s (and the converted 29s) had Commonwealth bogies, which made them extremely smooth-riding machines, despite their other shortcomings. The 22s had a different type of fabricated bogie with predominently leaf-sprung suspension. Both types had steam loco style spoked wheels.
 

Strathclyder

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Yes indeed. The 21s (and the converted 29s) had Commonwealth bogies, which made them extremely smooth-riding machines, despite their other shortcomings. The 22s had a different type of fabricated bogie with predominently leaf-sprung suspension. Both types had steam loco style spoked wheels.
I suspected as much, A relief to know I wasn't mad when looking between the above pics for bogie/wheelset differences lol At least the 21s/29s had smooth riding characteristics in their corner!

I knew the 22s had steam loco-style spoked wheels, but not the 21s/29s. May be due to the bogies partially obscuring the wheels that I've never noticed it before. Every day is a school day. And if nothing else, it's a oh-so subtle nod to their builder's history lol
 
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Cowley

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I suspected as much, A relief to know I wasn't mad when looking between the above pics for bogie/wheelset differences lol At least the 21s/29s had smooth riding characteristics in their corner!

I knew the 22s had steam loco-style spoked wheels, but not the 21s/29s. May be due to the bogies partially obscuring the wheels that I've never noticed it before. Every day is a school day. And if nothing else, it's a oh-so subtle nod to their builder's history lol

I believe all of their stuff had spoked wheels even the 84s, which seemed strange too.
 

randyrippley

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I believe all of their stuff had spoked wheels even the 84s, which seemed strange too.
The spoked wheels were just another example of how NBL were trying to build modern diesel locomotives using steam age techniques and Victorian engineering and tooling. Much, if not most, of their machining equipment was pre-WWI and badly worn, so not only were they trying to build metric designs using imperial tooling, but the wear in the tooling was greater than the degree of precision needed.
Spoked wheels were used because that's all they knew how to cast using wooden formers and sand moulds, rather than forging a wheel disc

I've linked to this page before, the detail it gives of faults with the class 22 indicates just how poor NBL's engineering was


MAN and the North British Locomotive Co.


Of all the firms supplying diesel locomotive engines to BR, MAN should have been a shining example. From producing Dr. Diesel's original engine in 1893, their subsequent production and reputation was steadily built up and advanced, mostly due to their 450 mm bore air-injection engine which ran at 450 rev/min and so successfully used in U-boats from 1917. Two of these submarine engines were installed in Southend power station after being taken out of U-boats exhibited there in 1919. These engines remained in service until 1955 and established a good reputation for reliability and longevity. MAN had also been a regular supplier of engines for railcars and locomotives, for which their 22/30 range engines gave up to 1900 hp. This engine was not suitable for the V200 locomotive envisaged by the West German State Railway (Deutsche Bundesbahn), and for this purpose MAN designed, rather hastily, their L12V 18/21 engine, intended originally to give 1000 hp at 1500 rev/min. One pair of these engines were tried out in one of the first five pre-production V200s, but subsequent locomotives only used the Maybach and Daimler-Benz engines.

The North British Locomotive Company (NBL) had three works at Glasgow, namely Atlas, Hyde Park and Queens Park, as well as a large and imposing design and administration office at Springburn. They could quickly turn out the goods when necessary, as for instance, in 1927 when they produced 50 LMS Royal Scot 4-6-0 locomotives in under 12 months. In common with the other steam locomotive builders in the UK, they had never had a reliable home market due to each railway company designing and building their own locomotives, and had to rely heavily on overseas business. When this market started to reduce through the weakening of Imperial ties and increasing pressure by American builders to sell their diesel locomotives, often backed by attractive loan facilities, North British looked increasingly to the potential for diesel and electric locomotives.

From 1948, NBL began to supply shunting diesel locomotives, usually with a Paxman engine, but their output potential was limited to 827 hp, which in turn limited NBLs ability to quote for higher powered units. To counter this, NBL contemplated going into engine production.

The building of a diesel locomotive involves the incorporation of three major items: the engine, the transmission and the mechanics, and it is more financially attractive if all three of these items are made or controlled within one organisation. At this stage only the Brush Group and English Electric were in this position in the UK. NBL could not obtain this status in respect of diesel-electric locomotives, but they could set about achieving this by imitating the Germans by supplying hydraulic transmissions.

Encouraged by the DB, the three German diesel engine manufacturers of Maybach, MAN and Daimler-Benz had all developed high-speed, high-output engines, and it seemed an obvious step for NBL to obtain the building rights for one of these. They had originally intended to obtain the licence for the Ganz engines, but owing to difficulties in negotiating behind the Iron Curtain this fell through. Maybach had already granted a franchise to the Brush Group for their MD range, but was found that MAN were seeking an engine builder in the UK and an arrangement was made for NBL to build the L12V 18/21 range of MAN engines. As far as the transmission side was concerned, the Maybach Mekydro range had been licensed to J. Stone & Co. of Deptford, but the Voith, better known and easier to understand, was still available, so NBL secured the manufacturing rights for that transmission, thus giving them all three major components of the diesel-hydraulic locomotive. Unfortunately, diesel engine production is a very specialised work, calling for a high degree of precision not usually found in steam locomotive manufacture. This was not helped either by the language problem and that of working in metric dimensions, all of which produced faults which showed up soon after the locomotives entered service.

With NBL's long tradition of supplying locomotives to the various railway systems including overseas markets, they were obviously well placed to obtain orders for diesel traction and, in fact, did very well in the U.K. initially, receiving thirty-one locomotive orders from the Pilot Order in 1955, comprising of five D600 and six D6300 diesel-hydraulics plus ten D6100 diesel-electrics, all using the same MAN L12V 18/21 engine. Further orders included twenty-eight D6100 1100 hp diesel-electrics in 1956, eighty-five D6300 and D800 diesel-hydraulics in 1957 and twenty more D6100 diesel-electrics in 1958.

The Western Region received their first NBL product in January 1958. 'Warship' class, number D600' Active', one of the five 2000 hp of NBL design with A1A bogies and two 1000 hp MAN engines. The engines for this and the following 'Warship', number D601 'Ark Royal', were built in Germany, however, one engine seized up on its first demonstration run out of Paddington. The Western received their first six D6300 1000 hp hydraulics in 1959, a further fifty-two between 1960 and 1962 and thirty-three NBL built D800 'Warships', also between 1960 and 1962.

One major advantage in the Krauss-Maffei V200 locomotive, was that it enabled 2000 hp to be available in a much lighter power unit than that obtained when using electric transmission. The first 'Warships' came out at 78 tons 12 cwt, whereas the English Electric D200 (Class 40) weighed 133 tons and the BR 'Peak' Class 44, with the Sulzer 2300 hp engines, weighed 136 tons. On being told of these weights, Herr Puls of Maybach remarked "mein gott"; so the Class 44 became known as the 'Mein Gotts'. But of course there were drawbacks in this saving of locomotive weight. The 'Warships' were not heavy enough to be able to brake an unfitted freight train, and their specific running resistance with hydraulic transmission was considerably greater than that of an equivalent electric transmission counterpart.

The first ten 1000 hp diesel-electrics went into service on the Eastern Region in 1958 and 1959, however by August 1959 availability was down to 51 per cent. Troubles varied from hydraulic leaks from the Behr fan, fuel leaks, to piston seizures caused largely by the burner insert in the cylinder heads falling onto the pistons. As a precaution these locomotives, D6110-6119, were de-rated to 950 hp and all returned to NBL, one at a time, for rectification. Other problems found were oil leaks into the battery box due to bad design, inadequacy of emergency fuel tank pipework, weakness of the oil pumps resulting in the shutdown pressure being reduced to 20-25 lb/in2, together with head injuries to the maintenance staff due to the bad layout of the turbocharger ducting which also caused inaccessibility of lubricating oil filters. After some measure of rectification the availability improved to 74 per cent by February 1960, but the Eastern Region had had enough of the D6100s and cunningly arranged for their fleet of thirty-eight NBL diesel-electrics to be transferred to the unfortunate Scottish Region, who already had the other twenty of them. The Western Region had in service by 1960 35 D6300 (Class 22) and 44 D600 and D800 (Classes 41, 42 and 43), and were beginning to learn the problems associated with high-speed engines and hydraulic transmissions. Not the least of these problems were electrical for control and protection devices and each diesel-hydraulic locomotive needed some 2½ miles of electrical wiring. German service engineers had been sent over to assist in the commissioning of the engines in the locomotives and were horrified at the rate at which the drivers accelerated away from a standing start and urged the drivers to be more forgiving in their rates of acceleration. The V.200 locomotives in Germany had not, at that time, been used for the sort of train weight and schedules that the engines were asked to cope with on the Western Region. In addition, the German locomotives received different working conditions in their running sheds on the DB similar to a pit garage for a formula one car, with meticulously worked out servicing arrangements for the various components of the locomotive. The sort of treatment given by BR was rather different to this, and the locomotives fitted with high-speed engines were expected to work under the same conditions of duty and maintenance as steam locomotives. Weaknesses soon began to show up on the Western Region with heads and pistons on the MAN engines, which meant that steam haulage often had to be resorted to. This was used both to supplement failed diesel locomotives, and to deputise for train heating when train-heating boilers also failed. All the problems that BR were finding was not helped by the attitude of the German engine manufacturers, who at first said that they had no problems at all in their own locomotives but later admitted to having had these same problems when BR complained bitterly. Often they did not agree with the remedies that finally proved to be effective in this country and blame was put on BR's track and its more intensive operation, but the whole process of trying to make foreign designs, built under licence by manufacturers not experienced in precision engineering was an expensive and wasteful process.

In April 1962, NBL went into liquidation and in November of that year produced their last locomotive, number D6357, for the Western Region. This meant that BR had over 300 MAN engines in service and entirely dependent on Germany for its supplies of spares. NBL's downfall was due to an overwhelming combination of the efforts to produce new-style locomotives and to manufacture and service both engines and transmissions under licence. The three parts of the organisation producing engines, transmissions and locomotives, did not pull well together, and the costs of rectification of MAN engines were just too much. They might have kept going if there had been any possibility of future orders, but NBL had no shares in the high powered engine market and it was obvious that BR were going to build the bulk of their electric locomotives in their own works.

A report of the principal problems with NBL built locomotives had been prepared by Swindon in September 1962 and read as follows:

(1) In early NBL built MAN engines, great difficulty is experienced in fitting replacement parts, due to non-standard building. Also many failures have been due to poor workmanship e.g. badly fitted taper seats for gears and flanges, additional drilled holes in castings causing oil leaks, balance weights slack on the crankshaft, split pins and locking devices missing, piston rings butting together, and general pipework of poor quality.

(2) Cracked or porous cylinder heads and/or cores plugs leaking.

(3) Exhaust manifold system complicated and unsatisfactory, expansion joints seized, stud threads stripped on cylinder head and manifold joint. Pieces of baffle plate become detached damaging turbo-blower blades. Experiment being introduced with stainless steel bellows to take up expansion and vibration.

(4) Cam followers wear, seize, and cause damage to the camshaft. Occasionally worn followers free themselves, and rotate, and if the tappet clearance has been taken up by adjustment, the push rods are bent by the action of the cams.

(5) Broken top chrome piston rings, thought to be caused either by lack of lubrication due to the severity of the new ring pack introduced to reduce oil consumption, or by ring butting due to build-up of carbon in the ring gap and behind the ring. The ring gap has been increased, but no evidence is yet available of any improvements noticed.

(6) Faulty CAV injectors, with a fractured collar on the spindle, lead to overheating of the burner insert which melts into the cylinder causing damage to pistons, liners and valves.

(7) Big-end bolt breakages mostly attributed to fatigue failures caused by inadequate tightening of the bolts when assembled.

(8) Big-end bearings damaged by the copper blanking plugs working loose in the crankshaft journal oil-ways; modification introduced with thicker collar and hole to facilitate riveting.

(9) Heavy oil leakage from white-metal oil seal at front of crankcase; repair entails re-metalling and reboring.

(10) Failure of ball races on fuel pump drive shaft and cradle.

(11) Insufficient drainage on the combustion air delivery box in the vee of the engine, combined with poor welding causing fuel leaks, leads to accumulation of fuel oil in the air box.

(12) End cover tapered locating dowels work out of the cylinder block causing oil leaks. A dowel retaining clip is now fitted to overcome this defect.

(13) Pistons suffer from thermal cracking of the crown and have to be scrapped .

(14) Excessive wear of piston top ring groove is thought to be caused by hard carbon building up in the wear-groove in the liner, and plain liners are now used whenever possible.

(15) Overspeed device is unreliable due to design weaknesses which are being discussed with the supplier.

(16) Scoring of the lower liner register during assembly has led to water leaks.

(17) Premature flaking of the lead flashing on the 'Glacier' big-end bearing is at present being investigated.

These same remarks also applied to the 58 engines in the Scottish Region in the Class 21 diesel-electrics as they were also fitted with the MAN L12V 18/21 engine, but in addition, they suffered from unnecessary delays in service due to the overheating trip shutting down the engine, which could not then be restarted until the whole system cooled sufficiently. This was altered to allow the engine to idle so that the fan could still operate. They also found that fractures in the connecting rods originated from the serrations on the mating faces due to insufficient radius at the base of the serrations. New rods were fitted, with serrations having a fuller radius, and proved satisfactory.

One root cause of a lot of the troubles with all of the MAN engines was the coupling in the drive to the fuel pumps. Due to the hardening of the rubber inserts, misalignment altered the pump timing which in turn caused overheating in the cylinder heads leading to piston seizures.

Many big-end bearing failures occurred due to the bearing turning in the housing. It was found that it was possible to have as little as one thousandth of an inch nip between bearing and journal. Larger shells with a higher tightening torque were introduced, but there was really insufficient depth of thread in the caps to take this increased torque.

The piston problems were never properly solved and attempts to get UK piston suppliers to supply pistons with Alfin bonded ring inserts did not materialise. They probably felt that it was a thankless task to undertake for such a small market, so the problem was left to Mahle, who were the original supplier. A suggestion was made in 1967, to test pistons made from silicone-aluminium, but this was never started as these engines were soon to be phased out.

Exhaust manifolds were a constant source of trouble having a partition designed to provide a two-part entry into the turbo-charger. This partition fractured, as did the entry pipe itself, but Glasgow works eventually made their own manifolds in mild steel, which were an improvement on the original and a lot cheaper.

In March 1963, the engine in D6123 in the Scottish Region was replaced by a Paxman 'Ventura' engine rated at 1350 hp. This 'Ventura' was similar to the two fitted in D830 (produced at Swindon in 1961) but at the higher rating, which the electrical equipment on the D6100 Class could accommodate. This was followed by nineteen more 'Ventura' replacements in 1965 but the remaining thirty-eight in that Region were allowed to run on until withdrawal in 1968/9. Those in the Scottish Region had suffered more from crankcase cavitation erosion due to water problems. In this Region the water treatment had at first been sodium dichromate, then sodium benzoate nitrate and finally borax/sodium metasilicate, whereas the Western had used the German recommended soluble oil treatment. Reclamation schemes were tried out using shot blasting and spraying with molybdenum and ceramic, but these were not in action long enough to be conclusive.

Some mention should also be made of the similar engines used in the 'Blue Pullman' railcars although these were German built and only rated at 1000 hp. Their performance was generally admitted to have been superior to the NBL built engines, though railcar duties are reckoned to be easier than those on a locomotive installed engine. These ten engines went into service in July 1960 on the LMR transferring to the Western Region in September of that year. They remained in service until 1973 when all the 'Blue Pullman' trains were withdrawn.

During the last few years of their reduced operation these engines had settled to an acceptable life cycle of 4000 hours between overhauls in the 'Warship' locomotives (D833-865). Problems were still occurring in the high-pressure fuel pipes due to cavitation erosion and fracturing of end nipples. Fuel injectors were changed every 3000 hours and all flexible hoses at 4500-6000 hours, according to overhaul procedures. The one feature of these engines that performed very satisfactory was the Napier turbo-charger, which had not previously been tried on MAN engines, and which amazingly worked better on these engines than on many of their own English Electric engines.

The MAN engine was basically a very simple unit, and with a little more initial development, limitation to 1000 hp and with good assembly procedures, could, and should, have been a perfectly satisfactory engine.​
 

Snow1964

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So is the view that they were poorly designed locos, or simply that they were so imprecisely built that would never work properly.

If they had been built exactly to tolerance would they have worked well, and survived decades. Or was the design flawed.

I get the impression that MAN engines (built properly and accurately) were good, and worked well.
 

randyrippley

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So is the view that they were poorly designed locos, or simply that they were so imprecisely built that would never work properly.

If they had been built exactly to tolerance would they have worked well, and survived decades. Or was the design flawed.

I get the impression that MAN engines (built properly and accurately) were good, and worked well.
Both design and manufacture really
On one of the type 2s - I think it it was the 21, clearances were so tight that the engine apparently had to be lifted to get at the oil filter

Its also worth remembering that DB fitted MAN engines to just one V200, preferring the other designs
 

Strathclyder

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I believe all of their stuff had spoked wheels even the 84s, which seemed strange too.
Huh, that I didn't know either. Though, given @randyrippley's post above, not surprising given the outdated, worn out and just plain unsuitable machinery/tooling NBL was using. The end results were entirely and sadly predictable.

So is the view that they were poorly designed locos, or simply that they were so imprecisely built that would never work properly.

If they had been built exactly to tolerance would they have worked well, and survived decades. Or was the design flawed.

I get the impression that MAN engines (built properly and accurately) were good, and worked well.
I'm with @randyrippley and say they were both as well. Mechanically, they were lemons as built (though by some accounts the last batch of 21s, D6138-D6157, fitted with 'Blue Star' multiple working equipment, were far better put together than the rest of the class. Answers on a postcard please if there's any truth to that or if I'm just spouting utter nonsense), but their (the 21s) crews reported extremely smooth riding qualites thanks to their Commonwealth bogies; the same of course applied to the rebuilt 29s. And it looks as if that those po-faced cab windows afforded more than adequate visibilty of the road ahead. Of course, none of the above really makes up for the classes' multitude of shortcomings in the long run.

And yet, despite all that, I just can't bring myself to outright hate them. They're something of a enigma in that regard to me. Yes, I can't deny they were duds in most key aspects, but it's that very same 'dud' status that endears them to me when by all rights it shouldn't. The Claytons & Metro-Vicks are the same. Dunno if I'm just a student of classic diesels or just plain mad. Probably a mix of the two lol
 

Cowley

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Not just you @Strathclyder, I love all the quirky old diesel dinosaur stuff and I’d love to have seen or heard some of them when they were still working (well sort of working anyway).
 

Strathclyder

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Not just you @Strathclyder, I love all the quirky old diesel dinosaur stuff and I’d love to have seen or heard some of them when they were still working (well sort of working anyway).
Am with you there. The Ivatt/Bulleid prototypes, DP1/DP2, Kestrel/Falcon/Lion, the NBLs, the Baby Deltics, the Metro-Vicks and of course the Claytons. The NBLs are a particular standout for me though, I think mainly because they were all built/assembled fairly locally and the 21s/29s called Scotland home for most of their short lives. Oh, and of course to hear them when they were 'sort-of-working'. ;)

The latter part also applies to the Claytons (and is partly why I hope D8568 visits Bo'ness one day lol).
 

Journeyman

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Apparently the MAN engines used were a rather outdated design, and were not ideally suited to modern diesel locos at all. Also, they seem to have worked better in the 22s than the 21s, suggesting the electric power train in the latter was a bigger problem than the engines.
 

Pinza-C55

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Not just you @Strathclyder, I love all the quirky old diesel dinosaur stuff and I’d love to have seen or heard some of them when they were still working (well sort of working anyway).

IIRC the DVD "From The fells to the Highlands" has a couple of decent clips of class 29s in Scotland. Very unusual sound.
 

hexagon789

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Not just you @Strathclyder, I love all the quirky old diesel dinosaur stuff and I’d love to have seen or heard some of them when they were still working (well sort of working anyway).
Same here, the quirky stuff is always more interesting. I'd expect a similar sound to the Blue Pullmans, same engines afaik for the 21s and 22s (uprated in the second batch of 22s iirc).

IIRC the DVD "From The fells to the Highlands" has a couple of decent clips of class 29s in Scotland. Very unusual sound.
Anything like the an HST?
 

D6130

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IIRC the DVD "From The fells to the Highlands" has a couple of decent clips of class 29s in Scotland. Very unusual sound.
Unfortunately that video is not available on YouTube. Any idea if it can be viewed on any other channel/site/platform?

Same here, the quirky stuff is always more interesting. I'd expect a similar sound to the Blue Pullmans, same engines afaik for the 21s and 22s (uprated in the second batch of 22s iirc).


Anything like the an HST?
The Paxman Ventura engines in the re-engined class 29s sounded very different from the NBL/MAN engines in the 21s and 22s. It's fifty years since I last heard one, but IIRC, they sounded a bit like a faster-revving, more high-pitched English Electric engine, with a pronounced declining whistle as power was shut off. There are several shots of 29s in action on at least three volumes of the 12 volume "Railways of Scotland" DVD series but, as far as I can remember, they were sound-free cine shots with background music dubbed over.
 
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D6130

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One of the many quirks of the re-engined class 29s concerned the livery and detail differences, which depended on whether the conversion was undertaken at Inverurie or St Rollox (Glasgow) works. This applied to both the two-tone green and blue liveried examples. And then there is the enigma of whether or not D6121 and D6122 exchanged identities sometime in the mid-sixties and if so, why? D6100-D6121 were built with 'eyebrows' (small rainstrips above the centre of the windscreens), whereas D6122-D6157 did not have them. However, all photos of D6121 taken after its conversion to a 29 in 1966 clearly show the rainstrips, whereas photos of D6122 (the last survivor and a sadly-missed preservation opportunity) taken in Woodham's Barry Island scrapyard up till its demise in 1980, clearly show the rainstrips and - as time and corrosion advanced - the last digit of the number on the secondman's side of one of its cabs clearly changed from a '2' to a '1'! One theory is that the two locos were in works together and that '22 was slated for conversion, but that they found some mechanical reason why it could not receive a Paxman engine so, a last minute decision was made to re-engine '21 instead and - to keep the paperwork straight - their numbers were swapped over. As I mentioned on a different thread, I cannot recommend highly enough Anthony Sayer's incredibly detailed book on the 21s and 29s, published by Pen & Sword in Barnsley at £40. (£5 discount available for subscribers to any of Platform 5's magazines).
 

hexagon789

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Yep. D6300-6305 were rated at 1,000 bhp, while D6306-D6357 were uprated to 1,100 bhp.
Any particular reason? Did they feel the performance lacking?


Unfortunately that video is not available on YouTube. Any idea if it can be viewed on any other channel/site/platform?


The Paxman Ventura engines in the re-engined class 29s sounded very different from the NBL/MAN engines in the 21s and 22s. It's fifty years since I last heard one, but IIRC, they sounded a bit like a faster-revving, more high-pitched English Electric engine, with a pronounced declining whistle as power was shut off. There are several shots of 29s in action on at least three volumes of the 12 volume "Railways of Scotland" DVD series but, as far as I can remember, they were sound-free cine shots with background music dubbed over.
So not quite like a Valenta or VP185
 

43096

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What engine do they have?
Paxman Ventura V6. Basically the V6 version (also used in Class 74) of the V12 Ventura fitted to the 29s and D830.

Ah, well I always think a 56 has a similar 'scream' to a Valenta at full power
That's because of the Napier SA-085 turbochargers that the 56s have. The Valenta had the SA-084 as built, both customised versions of the Napier NA-250.
 

Merle Haggard

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And then there is the enigma of whether or not D6121 and D6122 exchanged identities sometime in the mid-sixties and if so, why?

I've read about this too, and I'm not convinced it was subterfuge - it may simply have been a cab swap. I think that the NBL cabs were aluminium castings and possibly time consuming to repair. A loco with a damaged cab/cabs but no other damage could be repaired by 'borrowing' a cab off another loco under long term repair.

I don't have any evidence for the NBL Type 2s, but at one stage in the late 60's I visited Derby Works quite frequently, and this practice certainly applied to Derby Type 2s. For instance, I recollect that D5089 received the cabs of D5088 (might have been the other way round - notes in loft!) between my visits, with the donor loco sitting cab-less outside; I only noticed this by remembering the original number carried and its position in the workshop.
 

Strathclyder

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Any particular reason? Did they feel the performance lacking?
I'd presume so. Most likely the biggest power increase the MAN-NBL lump could handle without further compromising it's already shaky reliabilty.

Presumably more like a Class 14?
What engine do they have?
The 6YJXL, basically a 6-cylinder version of the 12-cylinder Ventura fitted to the 29s and Warship D830. The Class 74s (rebuilt from 71s) also had this smaller lump.

E: Never mind, @43096 beat me to it.
 

Inversnecky

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I've been quite interested to see photos of these in Scotland and the north east - they were gone long before my time, and as I'd no idea they were there, the photos are like a fossil record of extinct dinosaurs.
 

Cowley

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I've been quite interested to see photos of these in Scotland and the north east - they were gone long before my time, and as I'd no idea they were there, the photos are like a fossil record of extinct dinosaurs.

That’s a bit unfair on dinosaurs. They were far more successful. :lol:
 

Strathclyder

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One of the many quirks of the re-engined class 29s concerned the livery and detail differences, which depended on whether the conversion was undertaken at Inverurie or St Rollox (Glasgow) works. This applied to both the two-tone green and blue liveried examples. And then there is the enigma of whether or not D6121 and D6122 exchanged identities sometime in the mid-sixties and if so, why? D6100-D6121 were built with 'eyebrows' (small rainstrips above the centre of the windscreens), whereas D6122-D6157 did not have them. However, all photos of D6121 taken after its conversion to a 29 in 1966 clearly show the rainstrips, whereas photos of D6122 (the last survivor and a sadly-missed preservation opportunity) taken in Woodham's Barry Island scrapyard up till its demise in 1980, clearly show the rainstrips and - as time and corrosion advanced - the last digit of the number on the secondman's side of one of its cabs clearly changed from a '2' to a '1'! One theory is that the two locos were in works together and that '22 was slated for conversion, but that they found some mechanical reason why it could not receive a Paxman engine so, a last minute decision was made to re-engine '21 instead and - to keep the paperwork straight - their numbers were swapped over. As I mentioned on a different thread, I cannot recommend highly enough Anthony Sayer's incredibly detailed book on the 21s and 29s, published by Pen & Sword in Barnsley at £40. (£5 discount available for subscribers to any of Platform 5's magazines).
The whole D6121/D6122 identity swap thing (doesn't have quite the same ring to it as the Titanic/Olympic swap theory tbh lol) could very well be case of cabs being exchanged as @Merle Haggard suggests.

This RCTS page details this 'diesel dilemma' quite throughly for those interested in delving deeper into this. All rather intriguing no matter what the truth of the matter ends up being!

And lastly, you've convinced me to recommend that book (along with his one on the Co-Bos and the upcoming one on the Claytons) to my folks as a 25th birthday present for moi. ;)
 
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