New Britannia Design for 5" Gauge

Because of our involvement with building Britannias for our customers I decided that  a complete new design was required so to that end I have begun completely re-designing this magnificent locomotive to the Works Drawings.  The new design does not use anything which has previously been used from other designs and all new drawings are being prepared.  A complete new set of patterns is being made which are very close to scale. 

Frames  

There are three different chassis for the Britannias so the details of all the different types have been included on the new drawings.  This is because 70000 to 70034 and 70050 to 54 have roller bearings on all axles so therefore have six large horn openings.  70035 to 39 only had roller bearings on the driving axle so they have two large horn openings and smaller ones for the leading and trailing coupled axles.  70040 to 49 had plain bearings on all axles, including the trailing truck so they have all small horn openings for all axles and did not have Timken covers on the trailing truck.  So as not to copy what has gone before the frames I have supplied laser cut are for 70040 to 49 with all plain bearings.

So far the frame plans and cross sections have been completed and the frames and all the stretchers are available as a laser cut set.  I will also be making new patterns for the motion brackets and slide bar brackets.  The drawings for those are also complete. 

Cylinders

New patterns have already been made for the cylinders and these follow similar design to my BR 2-6-4 Tank so have all passageways cored out and the back plate has been cast on.  Therefore the machining amounts to boring the cylinders, facing the ends and facing the back plate.   The only other work required is to tap the holes for the cylinder covers.  Castings for the steam operated cylinder drain cocks are already available.

Wheels

The Britannia wheels have a very distinct pattern on the face of the boss because the front of the wheel is flat and the more normal boss is on the back.   The new wheel patterns have faithfully reproduced this and they have the correct oval spokes and “V” rims.  The new wheels will be available shortly.  Suspension is by conventional leaf springs but from our experience these have been designed as all steel with no Tufnol.

Rods and Valve Gear

A complete set of rods and valve gear is available CNC machined.  The quality is such that they only require the bushes fitting, oil holes drilling and a final polish.   The expansion links are doweled together and come ready hardened and include hardened die blocks.  The set or any separate parts thereof are available now (to order).

Lubrication

As with the 2-6-4 Tank the lubrication system has atomized oil fed to the cylinders via an atomizer as per full size.  The left hand lubricator will be used for cylinder oil and the right hand one will lubricate the main axle boxes, slide bars and valve guides.

Boiler

The boiler has been completely re-designed to eliminate the troublesome combustion chamber.  The firebox has been designed exactly like the full size one with the tube plate set forwards but it is accessible from the inside so that if there is a leak it can easily be fixed.  The main features of the new design of boiler is that it is the correct shape externally and the correct length, and it now has eight superheater flues so that it takes the same superheater as my BR 2-6-4 Tank.  The boiler has been designed so that it also complies with the Australian Boiler code and has been approved by them.  The boiler drawing is complete.  The superheaters provide 270 sq. ins. of heating surface.

The smokebox barrel is already available as a laser cut set and again follows full size practice with a lift out section behind the chimney for access to the regulator and superheater header.  New patterns will be made for the front and rear rings and door so that the door has the correct curvature.

The ash pan has been designed as per full size with rocking grate, front dampers and bottom ash doors.

Cab and platforms

The cab and footplating is a faithful copy of the full size ones and the drawings and the laser cut cab kit is already available.  The side platforms including smoke deflectors will be available shortly as a laser cut kit.  The new design gives a loco of the correct finished width.

Brakes

The braking system is as per full size with steam brakes on the loco and tender and vacuum braking for the train.  The whole system is designed to work and all fittings are provided.

General Fittings

We already stock a full range of fittings for all the BR Standard Locomotives and these are all listed elsewhere on the web site.  The cab layout is exactly as per full size.

Tenders

Tender drawings are being prepared at present for the BR1/1A, 1H and the BR1D all of which were fitted to the Britannias.  A laser cut set of parts is already available for the tender chassis plus castings for wheels, horns etc. and the tank kit for the 1D tender will be available shortly.   The kit for the 1A and H will follow later.

PARTS/DRAWINGS AVAILABLE TO DATE

Drawings

Parts Available

Laser Cut Frames including rear trailing frames
Complete set of laser cut frame stretchers including smokebox saddle
Laser cut cab kit
Cylinder blocks & end covers (available very shortly)
Laser cut smokebox barrel including lift-out rear section

All of the BR Standard fittings in our current catalogue are suitable for this new design