Almost all steam breakdown cranes were fitted with a Spencer-Hopwood vertical, water-tube, boiler as were very many other steam machines, but there seems a shortage of information on the invention of this very efficient boiler.

According to an obituary recorded in the Proceedings of the IMechE volume 164/1951, page 382, the inventor was Arthur Lincolne Hitchcock-Spencer (http://archive.pepublishing.com/content ... 1484k6qgq/). But did a Mr Hopwood also play a part?

I have a maker's plate from a S-H boiler built in 1947 and this carries seven patent numbers, however the UK Patent Office (as was) could not trace any of the patents! They assumed that the numbers must have been Registered Designs rather than patents, but I disagree.

If you see yourself as an amateur sleuth, there's a challenge for you!

When you talk about vertical water tube boilers, it could be implied that the tubes were vertical, when in UK anyway they are nominally horizontal and it is the cylindrical boiler that is vertical.

Peter Tatlow

Peter,

Agreed! It is confusing terminology particularly to the unitiated. A Hopwood boiler could of course correctly be described as "a vertical boiler", "a water-tube boiler", and/or "a cross-tube boiler".

For those who are unfamiliar with the Hopwood design, it consists of vertically-orientated cylinder with a concentric cylindrical firebox, and the firebox is surmounted by a vertical cylindrical flue. Within the combustion space in the firebox is a bank of near-horizontal water tubes connecting the water spaces on diametrically opposite sides of the box. The result is a robust and very free-steaming boiler capable of being forced to a degree impossible with locomotive-type boilers. It is arguably the best, and certainly the most successful, of the various designs of vertical boiler that the world has seen.

Other boilers used on British-built BDCs include simple vertical fire tube or VFT boilers, together with wierd and wonderful designs like the Turner patent boiler (which bore a closer resemblance to a very short loco boiler). However the "best" boiler, in terms of perfomance, cost and durability, was the Spencer-Hopwood.

I am not actually aware of any vertical boiler designed with vertical water tubes and rather doubt that it would be practicable to build such a thing.

This looked like the best thread to post these extracts of a drawing for a No.18 Spencer-Hopwood boiler in. It is ironic that this is one of the few drawings found so far for the 2 NSWGR 70T Craven cranes due to them being converted to diesel.
The drawing is New South Wales Government Railways drg 34682 dated 7/5/1930 & is noted as being traced from Craven Bros drg 30080.

Very interesting drawings, many thanks for posting them.

The boiler is essentially very similar (and seemingly of similar size) to the 1939 Cochran Hopwood boiler I am currently overhauling for GWR No 2, which is, I suppose, unsurprising.

Do you happen to know what the large port on the uptake liner (opposite the point of entry for the blower pipework) is for?

Glad they were of interest.

According to a partial & faded print of the NSWGR piping drawing for the 2 70T Cravens, the large opening opposite the blower pipework inlet was for the exhaust pipe from the cylinders.

Jeff, I wondered if that was perhaps the case, and it is extremely interesting since it is the only case I have yet come across where the exhaust is used to force the draught on either a Hopwood boiler or a crane boiler. Most UK cranes have the exhaust running up a separate pipe completely outside the boiler, and rely solely upon the blower ring if forced draughting is needed.

Given that on a typical UK boiler, with the aid of the blower, it is possible to have flames coming several feet out of the top of the uptake, the boiler in the drawings must have been a formidable steamer!

Hi Jeff

Drawings very interesting and a great help in understanding its composition. I am in the process of gathering information to build a 5 inch scale model, and the boiler looks an interesting(beastie!) article to make.

Have you any further details please?

Ian

The boiler drawing I posted is the only details of the boiler that I have for the 2 70T Cravens. I do have access to a selection detail drawings of the 2 cranes (sadly many are very poor prints). I also do have many detail photos of 1073 when it was being dismantled & reassembled for preservation. If you require further info PM me so I can email you particulars.

Jeff

Interesting to see a drawing of the Spencer Hopwood boiler - we are currently overhauling the boiler of our 50t Craven, 1015-50 which is the same basic design but a fair bit smaller. Fitting the [44] tubes is one of those exceptionally difficult tasks which BR presumably carried out with the firebox removed at heavy overhaul. Expanding the small end of the tubes from within the water space has to be done by hand with a range of short expander mandrels and is VERY hard work. The tubes are 2 1/4" nominal diameter 9swg thick.