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REW Red Devil


This engine was made for "The Chantry Challenge Cup", to be held at the STL 2014 event, which is for the toy mobile steam engine which can pull the greatest weight over a certain distance. I was going to just call it the 4WD but the name Red Devil was proposed and so I've adopted it.

The Red Devil is based on a Mamod TE1A traction engine, fitted with four wheel drive, gearing and extra ballast to provide the pulling power. The boiler and engine are standard Mamod parts. I have provided for two burner options (the rules are yet to be clarified). The first option is a standard Mamod vapourising meths burner. The other option is a Bix butane burner (with the piping rerouted to clear the gear shafts). Both have had the attachment reinforced and towing brackets fitted. There is also a towing bracket at the front which can be used for double heading (or pulling in reverse). There is no steering, with both axles fixed. This has simplified the 4WD implimentation.

The boiler is a standard Mamod TE1A boiler, 1 3/4" diameter x about 4 1/2" length internally (it looks longer on the outside). It has a standard Mamod 1/4" safety valve. The whistle and overflow plug holes have been blanked off. Steam is fed to the standard TE1A engine port face, which has a new improved Mamod cylinder and piston. These are the same dimensions as the original; 5/16" bore x 3/4" stroke, but the piston has oil retention rings cut into it. The engine is reversible in the usual Mamod fashion. The piston is coupled to the standard crankshaft and flywheel, but with brass bearings.

Instead of the original belt drive from the flywheel pulley, the crankshaft has been fitted with a modified Meccano 19 tooth pinion, which meshes with an unmodified 57 tooth gear wheel for the first stage of the gearing. The rest of the gearing is done using standard Meccano gears, fitted between Meccano plates bolted to the firebox sides. One stage has a dog clutch fitted to allow the engine to be run while the wheels are stationary.

The final shaft in the gear train is fitted with an 18 tooth Meccano sprocket, which drives a 36 tooth one on the rear axle by a short length of Meccano chain. The total reduction ratio is approx 1280:1. The front and rear axles are connected by chain over 36 tooth sprockets.

The rear axle has been fitted with improved bearing surface in the form of a stainless steel tube passing all the way through the firebox. The front axle is similar and fixed to the smokebox with meccano parts. All four wheels are fixed to their axles with screws into tapped holes in the axles. The sprockets (and gears in the later, high torque, stages of the gear train) have flats filed onto the shafts to prevent slipping. The wheels have been fitted with rubber tires for improved grip.

To improve traction, lead weights have been fitted in a tray slung under the boiler and also inside the rims of the road wheels. The weight inside the wheels adds weight on the wheel rims but not onto the axle bearings, thus reducing friction. The total weight of the whole vehicle is about 3.75 kg, with empty boiler and burner. It is probably approaching 4 kg in working order. The ultimate pulling power has yet to be determined but it easily pulls a 30kg transformer sitting on a Mamod trailer, slowing down the engine as expected but not by much.

The engine has been painted in red and black (hence the name) but very little else has been done to improve the aesthetics!

In the event, Red Devil pulled two trailors loaded with three 28 lb weights and an unknown weight of lead ingots up a slight incline! This version no longer exists and a Mk2 version has been created for next years event.

Make REW
Model Red Devil
Made 2014
Description 4WD traction engine
Cylinders 1
Cylinder Type single acting reversible
Piston Diam mm 8
Stroke mm 19
Valve Type Oscillating cylinder
Boiler Type Horizontal
Fuel Meths or butane
Mechanical Condition Good
Cosmetic Condition Fair
Paintwork New
Purchased 12/5/2014
Purchase cost
Additional cost