Fixing the Decauville

The live steam community is a small one, but it’s incredibly supportive. When there’s a problem, members of the community come together to help each other fix it. This is a good example: a story about a product that didn’t live up to expectations – and what the community has been doing about it.

Decauville - delivery
(Maybe THIS year it’ll actually get to run?)

It’s been more than a year since Peter Foley and I picked up our 7/8″ Accucraft Decauville locomotives while attending a steam-up in western New York – yet due to a number of engineering issues with the models they still haven’t turned a wheel under steam.

That’s about to change, however: on Saturday, Peter and I took our beautiful – but mechanically unsound – steamers for a visit with Jeff Young.

Jeff and Peter
(Jeff and Peter in the workshop at the start of our day. Four hours later, those smiles were harder to coax out of hiding – but we had locomotives that might actually steam! Note the black rectangles in the lower left: those are the replacement gas tanks.)

Jeff has been working his connections in the live steam community since last year to secure upgraded parts to turn these shelf queens into track-worthy models. They had a number of problems as delivered from the factory, including a poor burner design and a gas jet that was too aggressive. Most challenging, the gas tank was located right next to the boiler, which meant when the boiler heated up (as they do), it would actually boil the butane in the tank. Not a good thing.

The fixes included:

– Installing a new burner. This was straightforward: a single screw holds the burner in place, so one simply removes that, swaps the burners, and replaces the screw.

– Installing a new gas jet. From the factory, the Decauville was fitted with a #5. Jeff picked up #3 and #4 jets for us. They’re a screw-in replacement.

– Removing and replacing the gas tank with a new one designed by Accucraft UK and built by Accucraft in China. This was the big project for the day.

Ex-works, the gas tank was located in the right-hand water tank. (This was not used for water, which goes directly into the boiler through a valve under the steam dome.) The new tank would go under the floor of the cab, between the frames.

While the old gas tank could’ve stayed in place, we needed to remove the body so that we could unscrew the connector on the feed line. This required finding and removing about a dozen small bolts… loosening the lubricator… disconnecting the steam pipe from both ends (throttle and cylinders, via the lubricator)… and removing the gas regulator (disguised as a brake stand). We also had to remove the throttle handle, which was in the way for drilling the floor to accept the new tank.

A variety of metric and BA tools were required. This set from Wiha came in handy, and I will pick up one at my local tool supplier:

Wiha Tool Set
(Tool collecting: the hobby within the hobby!)

With everything in pieces, we used a marking template supplied by David Mees at AbbyBach Engineering Services to locate the three holes for the new gas tank:

(We labelled the template with a marker before sending it on to the next Decauville owner – as explained below.)

This is cleverly designed with two pins that line up with two screws in the cab floor. These would be drilled larger to accept the mounting bolts for the tank – one of which is hollow, and designed to mate with the connector on the as-delivered gas line.

Decauville - cab interior
(The cab interior, as delivered: Note the two screws in the floor. The original gas tank is in the near side tank: the filler valve can be seen in the shadow across the top of the tank.)

The third hole – upper right in the photo above – is the location for the gas tank filler valve. With the holes marked, we put the Decauville under the drill press and carefully created the new holes – enlarging them in three or four steps to the size we needed.

Here’s the new butane tank in place between the frames:

Decauville - butane tank

We then annealed the gas delivery pipe so that we could bend it to connect with the new tank. It’s not pretty, but it’s out of the way of fingers, and it’ll work just fine.

Decauville - piping
(The tank has two threaded rods which pass through the footplate. Two nuts secure it in place. One of the threaded rods is hollow and designed to mate with the gas delivery pipe. The shorter pipe in this photo will connect to the gas jet in the burner. Note the gas tank filler valve on the floor to the left of the far bolt. Also note the hole to the right of the near bolt: we accidentally had the template turned 180 degrees, which resulted in an extra hole in the floor. We marked the template for the next user(s), and I’ll add a bucket or other detail to cover the hole.)

The procedure took the best part of four hours, and – frankly – put our already impressive vocabulary of swear words to the test. But it’s done, and we celebrated with a late lunch on the patio at Cuchulainn’s Irish Pub.

I know that in addition to those people mentioned here, many others in the live steam community – including other Decauville owners, but also those who have no skin in this particular game – have been working over the past year or so to address the shortcomings on this model. While I can’t give them a proper shout-out here, I’d like to thank them for their help: Much appreciated!

Thank you, Jeff and Peter, for turning a daunting project into a fun day out, and turning a frustrating locomotive into something I look forward to running!

(While visiting Jeff’s workshop, I couldn’t resist snapping a photo of his scratch-built “Windus”: If I’d only stuck to clockwork…)

Leave a Reply

Your email address will not be published. Required fields are marked *

Time limit is exhausted. Please reload CAPTCHA.

This site uses Akismet to reduce spam. Learn how your comment data is processed.