Midland double-framers and the Gronk...

I once heard a bit of idle chit-chat suggesting that the early LMS/EE Gronks were based on a steam bottom end, possibly a Kirtley well-tank? Is there any truth or substance to this, or is it so much Scotch Mist?

I did discover in my searchings earlier that one Johnson Half-Cab was converted into a diesel, unsuccessfully.

 

Interesting - That the early Gronks were built using steam bottom halves is considered antiquated, but the thought of a Kirtley curved double-framed Gronk would have been seen as the ultimate in parsimony! It might have looked nice though!

Richard.

 

So were the early Gronks steam-based then? Or did they just reuse wheelsets at most?

 

Evolution ?
I'm sure the tale about steam bottom halves only relates to the earliest experiment.

12003 (LMS 7080), 12065 and D3791 -- all at Walton Old Jct, Warrington.

12003 (7080) (sorry Kodak 127 Brownie) was the first of the 30 jackshaft driven shunters & D3791 became 08624 latterly still in action with Freightliner
Apparently LMS 7069 also survives but never carried a BR number





Street cred totally gone now

 

I don't know if this is where the theory comes from but the first LMS diesel shunter was No. 1831, built on the frames of an ex-Midland 0-6-0T. See
https://www.derbysulzers.com/derby1010.html

 

Thanks for the link LMS2968. That was a relly interesting looking locomotive!

Knut

 

Yes and it kept the same number because it was officially classed as a rebuild, although a bit of a drastic one! The wheelbase of a gronk is much shorter than of a midland 0-6-0 as they all had an 8 foot plus 8 foot 6 coupled wheelbase.

 

That loco looks as if it had a rigid coupling rod between two of the driving wheels with the jackshaft in the middle, but that would surely not be able to accommodate vertical movements of the axles. How did it work?

 

I did mention the Johnson half-cab that became a diesel, but I had understood that the 08 frames and wheelsets or designs for same were originally from a steam loco?

 

I don't know if someone was pulling my leg, but I was told that the frames of the Paxman D95XX diesel hydraulics were modified Dean Goods chassis.

 

I’m fairly certain that the crankshaft drove the rod through a floating bearing that allowed the rod to move vertically with regard to the crank pin.

 

Not quite; I was told by Chris Bailey (involved with D9531 / 37) that he had identified the bottom end as being based on the GWR 94xx chassis.

 

The Class 08 was an amalgam of 2 prototype designs; the Armstrong Whitworth design with Sulzer engines and jackshaft transmissions (7059-68) and the English Electric design with English Electric engines and transmissions (7069-78) which were combined in further LMS orders for 7069-79 based on the Armstrong Whitworth mechanical portion and the English Electric drive train. Despite this development further orders were placed for locomotives fitted with jackshaft drive (7080-7119) but English Electric engines; some subsequently entered wartime service with the War Department and returned to the LMS after the war ended hence the batch of 30 surviving locomotives becoming BR 12003-12032. The English Electric design was perpetuated by the LMS, initially for War service with the Ministry of Supply, and 13 were returned to the LMS to subsequently became 12033 - 12044 whilst the LMS / BR built 12045 - 12102 and Darlington built 12103 - 12138 to the same design for Eastern and North Eastern depots.

The English Electric design was then modified and the "standard" Class 08 entered service from 1953 although, initially, 3 variants were introduced using (i) standard English Electric engines (ii) D3117-3126 with Crossley engines and Crompton Parkinson traction motors that became the original Class 09 but were withdrawn before receiving the designation (iii) various batches built by Darlington and Doncaster Works with Blackstone engines and GEC traction motors for Eastern Region depots that became Class 10; a small batch (D3152-3166) was fitted with BTH traction motors but these were withdrawn in 1967/68 before the introduction of TOPS.

 

Yes, the jackshaft pin works in a vertical slot in the coupling rod to allow for vertical movement. The thrust from the jackshaft is therefore longitudinal only.

 

Do you really believe that? I'd say about the only thing they have in common is that they both have six wheels and plate frames, both totally different in design. They may have been designed to do the same jobs but I'd say that's where the similarity ends.

 

Without doing a detailed comparison, a 94xx has 4' 7.5" drivers; and a D95xx has 4' 0" drivers. If nothing else, that difference in size would require significant changes to the chassis. And that's before you get to the point that a steam loco has cylinders to brace the front, and a motion bracket half way along its length, whilst a diesel presumably needs completely different arrangement and position of stretchers because the mechanical layout (and how it all fits) will be completely different.

The 94xx / D95xx chassis "equivalence" seems to be one of those things that has acquired the status of latter-day enthusiast myth, which has become accepted by repetition, without anyone thinking about primary source.

Tom

 

The overall coupled wheelbase is the same, 15' 6", but that's it. Different wheel spacing, extra cut out for the drive crank, 18" longer frames on a D95xx, completely different size and shape. Wouldn't surprise me if the frames of the diesel were thicker too. Other than being made at Swindon, there's not a lot of similarity.

 

Thank you both. That makes sense and explains the shape of the coupling "rod" with a deep section in the middle. Presumably that seemed better than conventional jointed rods which would have been very short.