4mm Caprotti contrast

Dan Randall

Western Thunderer
I'm a dyed-in-the-wool Western Region man, but I love the LMS version with "gorilla" steam pipes and am biding my time, waiting for one of the high-end kit manufacturer's to produce a 7mm scale version.... ;)

(Any chance of some 3/4 front views please Dave?).


Regards

Dan
 

Dave Holt

Western Thunderer
Hi Dan.
Sorry if it's a disappointment, but my model is based on the configuration of the loco shown in a photo dated Sept 1952. By this time, the original "Gorilla" steam pipes you mention had been replaced by the later, straighter versions, so they are the type fitted to the loco. Despite this, here are a couple of front 3/4 views taken on the Leamington Clubs "Clarenden" layout. My Crab and Jubilee also appear.

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Dave.
 

Focalplane

Western Thunderer
I have a half built Comet Caprotti Black 5 and did a lot of research in choosing the particular variant. The first batch of Caprottis were the Gorillas, the second batch much less gorilla-like. The other main difference between LMS and Standard Caprottis was the moving of the rotary drive from inside the frames to outside the wheels as your models show so well. And 71000 also adopted the outside rotary drive for ease of maintenance.

Caprottis were used in many places, one even visited Snow Hill Station!

Paul
 

Dave Holt

Western Thunderer
Yes, Paul. As you say, there was a whole raft of variations and modifications over quite a small batch of locos. You definitely need to pick a specific loco and date. I found the Wild Swan Profile books absolutely invaluable for mine.
These two locos are among the few for which I have any detailed, in-build photos. I came fairly late to digital photography, so all my earlier efforts were done before I could take reams of pictures. Indeed, the following shots of the BR Standard version were actually taken on 35 mm film by Barry Norman in connection with a proposed article for MRJ, which never came to fruition. I hope he won't mind me posting some of his work here. These files are re-sized scans of enprint sized prints he kindly sent me some years ago - hence the quality of the files.
Both locos follow my now standard arrangement of fully floating compensation, with twin beams on the centre and rear coupled axles and a single beam linking the front coupled axle and the centre of the bogie. The latter is arranged so that the frames can only slide and pivot under rubbing blacks and the weight is transferred direct to the external bogie compensating beams and wheel sets by means of a pin inside a hollow pivot tube; the pin bearing on a cross shaft connecting these outside beams. All a bit complicated, but it allows a realistic appearance and operation of the bogie whilst giving an almost exactly prototypical weight distribution and maximum stability of the loco on the suspension. My first efforts, with a fixed, driven rear axle, single beam on the front two and a bogie just along for the ride, tended to lift the inside rear wheel on curves - a bit like a kidies' tricycle toppling over when cornering too fast.
The arrangement of the bogie and front compensation is shown in this sketch and the photo shows the bogie assembly, less wheel sets. The hollow tube pivot is soldered into the bogie mounting frame spacer below the cylinders. Side control is by the hair-pin springs sticking out to the rear and there are light spring wires bearing on top of the axles to push the bogie frame up onto the side bearing blocks.
InkedBogie_comp_sketch_001_LI.jpg
Std_5_Cap_Bogie.jpg

The bottom end of the pivot tube, with retaining wire can just be seen in this shot of the underside of the chassis. The wheel sets are held in by a keeper plate which carries the dummy springs, ash pan and hopper gear, sand pipes and support brackets, etc., and also the wire pick ups, which bear on the backs of the wheel rims, hidden behing the brake hangers and blocks.
Std_5_Cap_Chassis_Underside.jpg

Brakes clip onto mounting pins at the top and the rear assembly is fixed to the rear of the keeper.
Std_5_Cap_Brakes.jpg
One of the main purposes of the series of photos was to show how the outside drive gear was built up. The only parts of the DJH kit used were the cylinder castings, the centre axle drive gear boxes and the suspension links at the rear end of the main drive tubes. Everything else was scratch built from sheet, sections, tube and wire. I have to say that I'm rather proud of the universal joint representations. Till soldered up, they actually would rotate and drive the shafts! It was an interesting exercise to work out how to best split and build up the various parts of the gear. This is what I came up with.
Cylinder unit.
Std_5_Cap_Cyls.jpg
Main drive shafts and gear boxes. The bits of wire on top are parts of the exhaust steam to injector, steam heat and vacuum brake pipes located between the frames.
Std_5_Cap_Drive_shafts.jpg
Reversing shafts and gear boxes (shown the opposite way round, for some reason).
Std_5_Cap_Rev_rods.jpg

The whole lot is held together with 14 BA screws to give the complete assembly.
Std_5_Cap_Valve_gear_assembled.jpg Std_5_Cap_LHS_Loco.jpg

Another highly visible and distinctive feature of these locos is the arrangement of the the lubricators and drive and the arrangement of pipes under the RHS of the cab. The lubricators are mounted on a massive cast bracket and part of the steam supply pipe to the exhaust steam injector passes through the bracket, just below the lubricators. I was very lucky to have access to the preserved fully size loco at Butterly for photos and measurements. Quite by chance, the engineering drawing for the lubrication system was clipped to a board near the loco, so I took a photo of the drawing and was later able to scale off for the bracket details. The injectors, bracket and piping, and the lubricator arrangements are permanently attached to the frames. Castings for the injectors and water feed valves are from Alan Gibson.
Also visible is the rather crude but effective adjustable length coupling bar to the tender and the intermediate rubbing blocks - there are matching blocks on the tender drag box. The coupling bar is adjusted so that the blocks almost touch to avoid visible play between loco and tender.
Here are the results. I also try to include as much piping as possible, to help create an impression of the real thing. Here we see two water hoses, vacuum pipe, steam heat pipe, tender steam brake pipe and coal space spray pipe.
Std_5_Cap_Chassis_RHS_rear.jpg
Std_5_Cap_Chassis_rear_underside.jpg
Std_5_Cap_RHS_rear.jpg

Finally, a view of the fully assembled chassis, without the body. I've just noticed that, in this shot, the lubricator drive return crank has not been screwed into the correct position
Std_5_Cap_Chassis_RHS_complete.jpg

Dave.
 
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AJC

Western Thunderer
Thank you for the sketches and detail pictures, Dave - the compensation arrangement is especially interesting and food for thought with future projects in mind (not that I build many large locos).

Lovely stuff,

Adam
 

Dave Holt

Western Thunderer
Here are some photos showing the Ivatt/Stanier Caprotti Black 5 in various stages during construction and the finished model. The basis of the loco is a Comet kit. modified to render it suitable for P4 and to suit my preferences. The compensation arrangement is identical to the BR Standard version, previously described. In this case, the Comet tender had the inner chassis replaced by one of the lovely Lanakshire Models kits, which provides CSB type sprung suspension.
Starting with the chassis.
Cap_Blk5_001.JPG
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One of the major issues to be resolved was how to split the pipework, etc., between chassis and body, due to the open nature of the steps and high cab base. Because of the low footplate leaving a large gap under the boiler, I decided to include replicas of the frame spacers and internal pipes and inside Caprotti drive shaft. Again, these had to be split between footplate unit and chassis.
The Comet kit is designed to have the cam boxes mounted to the footplate and the cylinders on the chassis. On other models I had seen, the resulting joint line between cylinders and cam boxes was too visible in the finished model, so I decided to make the whole thing one assembly. As a result, unusually, the cylinders and slide bars are fixed to the footplate (now part of the body) rather than the usual mounting on the chassis. Seeing as there is no outside valve gear to trap the cross heads/con rods or to complicate the issue of final assembly, the arrangement works perfectly.

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Finished, fully detailed footplate and cab unit.
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Close-up of the brake lever with bits of the rear part of the pull rod, pipework and exhaust injector.
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A kit of chassis parts, primed ready for painting and assembly.
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Then assembled.
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Motor and DCC chip fitted. The tin of paint is holding the front end down by compressing the light wire springs in the bogie, to give the final ride attitude.
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More to follow.

Dave.
 

Dave Holt

Western Thunderer
Early stages of the body with the boiler/firebox being trial fitted. The boiler to firebox joint wasn't very good and required rather a lot of filling in with low melt solder. The dark blotches are where I splashed flux and didn't clean it off quickly enough.
Cap_Blk5_003.JPG Cap_Blk5_004.JPG

The main loco structural units prior to assembly. The painter asked for the boiler to be fixed to the footplate before painting and lining, so that was done later on.
Cap_Blk5_013.JPG
Assembled prior to painting showing pipework details and lubricator drive. This later suffered a major accident when the return crank unscrewed and jammed the mechanism up. When I tried a bit too hard to untangle it, the whole thing disintegrated. The replacement is both more substantial and a better replica of the prototype, so some good came of it.
Cap_Blk5_031.JPG
Cap_Blk5_011.jpg
Cap_Blk5_012.JPG
Of course, things don't always go smoothly. The etched tender sides were rather thin and without fully realising, I had managed to crease/ripple the RHS. However, this really showed up when painted gloss black (to take the lining transfers). Luckily, I managed to remove the damaged side and fit a replacement (having had to buy a whole tender body kit to get it).
Cap_Blk5_030.JPG Cap_Blk5_020.JPG
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Friend, David Clarke, painted, lined and weathered the loco, based on photos of actual locos in service.
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Finished loco with crew and coal.
Cap_Blk5_027.JPG

Dave.
 

Lancastrian

Western Thunderer
Hi,

Numbers 44748 - 44757 were built with the large radius steam pipes, likened to a gorilla's arms.
Numbers 44755 - 44757 were built with double chimneys.
Numbers 44738 - 44747 were built with longer straight steam pipes and the bend just above the cylinders.

All the above were single inside drive-line with Leyland Motors style universal joints.

Numbers 44686 - 44687 were built with outside drive-lines, double chimneys and raised running boards/platforms. Many drivers have stated they should have been Class 6 engines.

Ian
 
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