The Carson Precursor
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Arguably the finest miniature live steam locomotives of Edwardian times were made by James Carson & Co. of Cricklewood, North London. Here they are at the 1911 Model Engineer Exhibition. We don't know if the gentleman on the stand is Carson himself, but the large scale 'Great Bear' at the back of the stand is quite possibly the one made for Sir Berkeley Sheffield and now preserved by the Scunthorpe Society of Model Engineers.

Today, the best known Carson survivors are the Gauge 1 and Gauge 3 'Experiment' 4-6-0's. Here's a clutch of Carsons with a Jubb Interloper:

L to R: Gauge 1 'Experiment', Smithies boiler : Gauge 1 'Experiment', Flash Steam : Gauge 2 'Precedent' : Jubb Gauge 2 Atlantic

Gauge 2 Carsons are very rare. One example that does exist is the Gauge 2 Precursor seen in the above picture (painted green!) and described in this page from the 1911 Bassett Lowke catalogue. (Bassett Lowke was always reticent about mentioning Carson. Maybe the two didn't get on, because it's said that when Carson went bust in 1913, Bassett Lowke was waiting outside the building to buy up the assets).

This little engine came to me in a poor state from a trader at the Warley Model Railway show, where it was held together with rubber bands! The crank axle was buckled, the boiler covered in soft solder, much of the tinwork missing and the boiler painted bright green. However, it did come with a page from Carson's catalogue of 1911:

The note that the model "is now built with two cylinders" which seems to date it between 1911 when the catalogue was published and 1913, when Carson went out of business.

The loco is perhaps unusal amongst Carsons in still having its original Smithies boiler (described at the time as 'internally fired'). Our modern fire tube boilers, pioneered in Gauge 1 by John Van Riemsdijk, were still far, far in the future. This boiler had been heavily tampered with, having the backhead fittings held in place by a flood of soft solder. However the specification (below) says 'Brazed throughout' and that gave us a chance of restoring it to original condition.

Virtually all surviving Carsons have been re-boilered with modern boilers, but I wanted to know how well model locomotives in 1911 actually worked (if at all!).

It's often said that once a boiler has been patched with soft solder, it cannot be returned to hard solder. I can say that this is incorrect, because after painstakingly removing every trace of soft solder by scraping and burnishing with glass fibre pencils, my Son Paul was able to reflow modern silver solder around the replica backhead fittings that we had made. Once repaired the boiler was tested to modern model engineering standards and easily withstood the 200 psi mentioned in 1911.

The model as acquired. Note the little known LNWR experimental green livery!

The Carson Precursor boiler as cleaned up. Note the very high standard of construction, cast bronze backhead and brazed througout.

The Carson backhead as restored, cleaned of soft solder and regulator bush silver soldered in place.

The burner was a different matter, because there was no existing design to copy. I settled on a 6 wick layout with 1/4" wick tubes, all made from thin wall brass tubes. Although Carson said the model was supplied with tender tanks, none were present and obviously the tender had been flooded with about a pint of meths to feed the drip feed burner. The danger of this arrangement can only be imagined! A modern fuel tank with 'chicken feed' regulation was made to connect to the burner by flexible pipe. However, this arrangement far from eliminated the danger of 'flare ups' to which models in this period must have been prone.

Initially the burner was tried with ceramic wicks, which proved to be too floppy in this large size, aggravating the flaring problem. Ultimately these were replaced with rolled stainless mesh, which remains in shape and gives an adequately strong fire.

The crankshaft was straightened, the missing platework replaced and the chassis run on air. Initially, testing with a very small amount of meths in a temporary reservoir revealed a very lacklustre performance. But the model did move under it's own steam. The first Gauge 2 steam model to do so for a very long time! Much fettling, including repacking the pistons, which rely on graphited string, slowly improved matters. It became obvious that with early models like this, there is no reserve of performance to make up for shortcomings. Everything has to be 'just right'.

During this time, the lockdown of 2020, an oval of Gauge 2 track was assembled using vintage Bond's rail very similar in section to modern code 332. All 2000 sleepers were bandsawed from hardwood battens and indvidually secured to the track with stainless crews acting as spikes. The Carson was tested, fettled, and tested again on this track until it could run a full lap without stopping. But there was still no sign of the sparkling performance that Carson allluded to. Slowly things inproved and with the superstructure added back along with the restored tender, complete with compartments for meths and water. The water tank contains a suitably antique hand pump and in a concession to modern times, an Enots valve.

New baffling was added to the firebox to restrain the flaring problem and a handheld electric blower with onboard Lipo battery made for the event that the loco stopped with the blower closed. (Because of the relatively poor steaming of the Smithies boiler, the blower consumes more steam than it can produce). Now the little engine could make several laps of the track and even tow a tinplate carriage. Then, one day and for no particular reason, the Carson took off like a scalded cat and ran, with several carriages for minute after minute without stopping, and at breakneck speed. That was a real red letter day because at last the little engine was doing what James Carson had said it would do, 110 years ago.