The Tank Engine That Never Was.

An article by Nick Feast.

All photos by Nick.

A fellow member of Bournemouth Model Engineers had started to build a Q1 to my design several years ago.  However the project was offered to me, and although I had already completed 2 locomotives as detailed in the Model Engineer series in 2009, I thought I could make use of a third one!

                                                   
I had an idea in the back of my mind that I had seen a drawing of a proposed 0-6-4 tank engine in print somewhere but couldn't find it, so went ahead with my own interpretation of what a Q1 tank might have looked like.

                                                   
I believe this was the sort of engine that was proposed as a potential replacement for the many obsolete tank engines that were in use across the Southern Railway network after the war. 

In the end of course Bulleid had his own ideas, and much money and effort went in to producing the doomed Leader!

Nationalisation stopped all that and the result was that the BR Standards were the engines to replace the ageing M7s and the like.

                                                   
I decided that this imaginary design would have been produced in the Brighton drawing office, so the styling is very much Class 4 Standard tank, having curved tank and bunker sides. 

This matches the cab and tender radius of the Q1, probably the only goods/mixed traffic design to have a profile designed to match coaching stock.  There is also an element of W class tank at the back, with a short bunker overhang.

The cutaway cab and the sloping side tanks (like the Z) were to improve lookout as with the inset bunker at the rear. 

I assumed that the loco would be used bunker first on branch lines a lot of the time.

The 0-6-4 wheel arrangement is not as unusual as you think, there being examples on both the LMS and LNER, as well as several narrow gauge designs.  The Southern inherited a few from the SECR, as Wainwright had designed one for suburban passenger trains back in 1913, the J class.

                                                   
The chassis conversion to a tank engine was fairly straightforward, having decided on the type of bogie to use. 

The frame extensions are welded on with a small plate behind to strengthen the join.

The attached photo should show how the bogie is supported.  It is basically the same as a Bulleid pacific front bogie, with sprung axle boxes and the weight taken via pads each side on the frame members.  There is also side control on the bogie. 

If there is too much weight on the rear, I can grind down the mounting pads, or soften the bogie springs.

                                                   
I purchased another two pairs of tender wheels from Polly (which confused them), and laid out a bogie similar to the Schools/Bulleid pacific design.

Axle centres were 120mm and the distance from the rear drivers to the leading bogie axle is 116mm.

The full length of the locomotive over the buffers is 825mm.

                                                   
I decided to reduce the size of the firebox slightly and incorporate a taper into the rear of the boiler barrel, which is more to the prototype design.

The ashpan is therefore slightly smaller which fits better into the tank engine layout. 

                                                   
Having found that the perforated Rosebud grate worked well on another loco, I used one on the tank engine. 

Trial and error with the draughting also led to a multi jet blastpipe, and initially this loco had a 3 jet version.

I have used 5 jet versions on the other 2 Q1s, and as the steaming on this one wasn't as good, I have refitted it to also have a 5 nozzle blast pipe. 

                                                   
In 2019 I wrote a feature for the M.E. about hinged roofs, that showed both the Q1 tank and an SECR L class I have been working on for some years.  Shortly afterwards Cedric Johns sent the magazine a copy of a weight diagram of a proposed Q1 tank which appeared in 'Bulleid of the Southern' by HAV Bulleid.  This must have been the image that was lurking in my subconscious all the time!

The side tanks and bunker are dummies, all water and coal is carried separately on the driving trolley.  A dedicated 4 litre tank has two 90 degree plumbing valves for the supply to the injectors via the push on fittings.  One reason for not having water in the side tanks is that lead is a lot heavier! Much added weight has been incorporated using the dummy side tanks to improve traction, and compete with some of the 5" gauge locos on passenger hauling.  At the time of writing, owing to Covid lockdowns etc. it had very little use so far, I am hoping to get it onto the track a bit more this year.

I can produce the extra drawings for anyone interested in building one, it is 90% regular Q1!