Building a Fairlie chassis (2001)

Jan van Mourik

Many years ago, I built a double Fairlie chassis using two 0-4-0 Fleischmann N gauge steam locomotives. The idea was based on the Ffestiniog double Fairlies, but obviously a very freelance interpretation.

M.A.Polet, 1980

After taking off the loco bodies, the motors were removed. The bodies would be needed later, so I put them aside for a while. The next job was taking the mechanisms apart completely, and cutting off the motor mount and rear coupler pocket in one piece, from both chassis blocks. One of these would also be needed later. The worms were removed from the motor shafts and put in a safe place as they are easily lost.

Thus, we were left with two sawn-off chassis blocks each with a pinion, axles, motion, cylinders and front coupler. From the loco bodies a great deal had to be removed: the cab, the boiler fittings etc., and after further cutting down we had an arrow-shaped metal block with the threaded hole needed to bolt the chassis to it. Part of the tanks of the original loco body was left in place

The cut down tanks were needed for strength and to protect the chokes and capacitor fitted to the current collectors. From above we can now see the pinion.

Using two pieces of pertinax PC board and one of the sawn-off motor mounts I assembled a frame which is a tight fit around the motor. The electric feed to the sprung carbon brush housings on the motor is also carried by the PC board. The photo clearly shows the inner motor frame. The motor has been fitted with extended shafts.

This has been realised as follows. After removing the worm I put the motor with its rear bearing on a vice, the jaws of which were set slightly open to accommodate the motor shaft. Using a hammer I gave a sharp tap on the other end of the shaft, moving this through the collector and armature. This is a risky operation as the motor may be damaged, but it survived all right. If it won't work, we always can use the other motor! The shaft extenders were fitted to the shaft ends using plastic bushes or sleeves that, together with the flywheel, came from the junk box. This proved to contain old insulated wheels from an H0 gauge locomotive which were ideal for the job. From one wheel I removed the flange, using a file, from the other I pressed out the plastic bush and used this as a connecting sleeve. It is impossible to fit a flywheel to the rear of the motor as this would obscure the fixing screws.

The extender shafts are two nails of correct diameter which have a corrugation about 3 to 5mm from the head used to grip the worms. In the pictures the shafts and worms still have to be aligned correctly below the pivot holes.

The carrying frame was made of 1mm steel sheet and consists of two identical parts that were bent to shape and soldered to the inner (motor) frame made of pertinax. In order to fit this assembly to the bogies, two small frames had to be made as shown to the left in the top diagram. These were fitted to the bogie top using an M2 bolt in a specially drilled and threaded hole.

The top diagram shows a flat layout sketch of half a steel frame on the right. The middle diagram shows a half-frame after having been bent, with the bearing hole to the left and the pivot hole to the top.

The lower diagram shows assembly of the half-frame, which sinks through the elongated hole in the auxiliary frame which goes to the bogie top. The large screw is M3 size, the smaller is M2. The diagram also shows the worm and the extended shaft (the extension bush has been omitted).

The screw marked M2 is used to fit the auxiliary frame to the bogie top. The worm needs to be exactly in line with the pivot which consists of an M3 screw passed through the holes in the half-frame and the auxiliary frame, being locked up with a nut fixed with superglue.

Some freedom of movement is needed at the pivot as the bogies will have to adapt to the track. The worm wheel is driven by the worm on the extender shafts, but despite this the bogies can swing to a considerable degree without locking the transmission. The chassis can pass through 19cm radius curves without problem.

Finally, a photo of all components built together, resulting in a smooth-running double Fairlie chassis. In 2013/2014, I finally built the locomotive shown in the last picture.

More photos