Mamod Steam Wagon Conversion

Conversion of a rusty rolling chassis from a Mamod SW1 into a flatbed lorry or dray

The aim of this project is to transform this ...:

The SW1 in original condition

... into this:

... based (very roughly) on this:

The starting point was advertised on ebay as a "steam roller", but it took all of half a second to see that it was, in fact, a Mamod SW1 steam wagon, with the body missing. What was there was in cosmetically poor condition but, apart from the body, essentially complete. The steel parts had some surface rust and some of the brass parts were somewhat tarnished.

However, after dismantling, cleaning up and stripping the old paint off, all was found to be in workable condition.

The first decision to be made was, what to do with it. I could try to obtain a replacement body and restore it to pristine condition. That idea had it's attractions and bodies have appeared on ebay occasionally. The downside to that route was that the end result would be just yet another restored SW1. It's not exactly the rarest of models. Therefore, I decided I would make something different out of it. I wanted to keep as much as possible of what I had bought intact, so it had to be a wagon of some sort. Several ideas were put forward by some forum friends which I added to a couple of my own for consideration. These included:
Tanker wagon
Breakdown wagon
Articulated wagon
Timber tractor
Three way tipper
Flatbed wagon

I eventually decided on the flatbed and, to retain as much of the original as possible and to add as little as possible in the way of major bodywork, I decided on an early cabless style. I looked through my collection of photos and a couple of books and found the nearest to what I had in mind was the 1906 Bretherton Steam Lorry pictured at the top of this page.

Having determined what I wanted to end up with, I set about comparing that with what I had already. The Bretherton lorry had a horizontal boiler, firebox and front axle, basically similar to the Mamod. It was a very basic design with little in the way of frills or cosmetics. It had no cab (considered a luxury in those days) and no mudguards (it didn't go fast enough to need them!). The chassis I had still had the mudguards attached, but they were easily enough removed, given that I was removing all the rivets, anyway, for ease of painting. One of the few non-essentials that the Bretherton had was a simple fairing around the works and the rear end of the boiler. I saw that the removed mudguards, suitably reformed, could form the basis of this fairing.

I bent the mudguards further into a right angle, keeping the existing radius, and made up some brackets to fix them to the chassis. One of the brackets next to the flywheel had to be shaped with a cutout to miss the drive belt. I'm glad I partially assembled the engine at this stage to check!

The fairing didn't look quite right, and it needed something underneath to form what I assume was a coal bunker in the original. I extended the depth of the fairing and formed some flooring with aluminium sheet. I extended the flooring on the driver's side backwards and down to form a crude foot well.

The flat bed itself I built from scratch with steel plate. To give it some visible thickness, I attached some brass U section around the edge. The original idea was to solder the brass to the steel. I cut the U section to size with suitable bevels at the corners. I brushed flux on to all pieces and placed them in position resting on ceramic tiles. I then tried to solder them together with a small blow torch. This was a total failure because, as soon as I heated one section of the plate, it distorted so much that it was impossible to get more than a couple of inches soldered.

After completely ruining both plate and brass strips, I gave up on that idea and decided to use araldite instead. This was much more successful.

Either due to bad measurement or (more likely) caused by over enthusiastic filing to get the 45 degree angle, there was a small gap at each corner. To cover this, I soldered a small square of brass over each corner. I suspect it may have needed this, anyway. Soldering was no problem on such small items using a 50w soldering iron.

Another problem with the large steel plate was that it rapidly started to show signs of rust after I removed it from the plastic wrapping. This meant that I had to paint it with primer ASAP - before I had time to photograph it. This means that the photos aren't as clear as they could have been.

The next step was to work out how to attach the bed to the chassis. It had to be easy to remove, to access the burner, After much trial and error (lots of the latter) I worked out and implemented a system of rails and brackets using angle section brass. Two lengthwise strips are arranged to sit on the main chassis members and two small brackets were arranged to locate either side of the square cross piece over the rear wheels, to locate the bed fore /aft. I left the longitudinal rails a few mm longer than the bed, protruding at the forward end. These locate the vertical supports of the name board. All this metalwork was attached with Araldite. If it proves not strong enough, I might have to use solder or nuts and bolts.

A rather complicated clamping system was required to hold the supports while the Araldite set. Even so, one of them shifted slightly off-vertical. It's not obvious at first sight so I've left it.

Finally, the name board was cut out and araldited in place.

For a livery, I decided on dark green for the bodywork, chassis and wheels, lined with yellow. The boiler, firebox and smokebox are black. I painted the flat bed brown to look like wood and, as an added touch, I gave the chimney top a copper coloured rim. I also swapped the red revering lever for a black one.

The dark green paint gave me a bit of trouble. The aerosol started making a puffing noise like a steam engine! Very appropriate but it didn't do much for the finish. It later started spluttering the paint out in large drops instead of fine droplets. I binned that can and tried to spray over with a different shade of green but a different manufacturer. Unfortunately, the two were obviously not compatible and only made things worse. I had to re-strip that bit. I bought another can identical to the first and it was ok to start with. I just about finished the job when it started the puffing noise like the first one. I've now binned both cans and won't use that manufacturer again (at least not in aerosols). The most surprising thing was that it is a highly reputable brand - Hammerite.

I've no idea what to put on the name board. It'll have to be something noncommittal so I can have a variety of loads. I might even use my own name :-)

Finally, the steam test. Thankfully, apart from a few leaks requiring new washers and tightening of the boiler fixing screws. it went ok. It was reluctant to run with the drive bands attached and I decided this was because they were too tight. I borrowed the pair from my other SW1 and it worked fine.

All done - it was a very satisfying project and I'm happy with the end result. I only hope the Mamod purists don't know where I live :-)

Since these photos were taken, I have added rubber tyres and brass hub caps.

Lots more photos of the progress of this project can be found here