This week I have another new replacement part to share with you, this time for an N Gauge Dapol Class 73.
The Dapol Class 73 (Pre DCC-ready version), as shown below (stock Dapol photo), has a central motor which powers both trucks or bogies. This is now common practice on all N gauge diesels. Because the motor is fixed to the chassis and the bogies rotate a linkage or drive shaft is needed to transfer the power.
The drive shafts connect the brass fly wheels on each end of the motor to worm gears on top of the gear towers in the trucks. The drive shafts have a ‘cross’ on each end which fit into slots in the fly wheels and worm gears. This arrangement allows the gear towers to rotate while still being driven. Below you can see one of the original drive shafts with the crosses on the ends. The particular model I’m working on came to me with a missing drive shaft.
The drive shaft was then drawn up for 3D printing and designed for Shapeways Smooth Detail material (formally known as FUD). I use this for its accuracy and strength as it’s a hard acrylic plastic. As there are two drive shafts in each model I made a set joined together by a figure 8 loop to keep them together while in production. The loop is not actually connected to the drive shafts but the holes are not big enough for the crosses to pass through. The loops can simply be cut off.
The test print came out very well with nice crisp detail. As the material is translucent its somewhat hard to photograph.
With the loops removed you can see the drive shafts are almost identical to the original injection molded part.
The new shafts can then be fitted into the locomotive. As their the same shape and size their a direct replacement and work perfectly. You can see the drive shaft replacement on the right is also sloping down. This shows how this method of connecting the drive shafts allows of a lot of flexibility in the alignment of the two ends.
A pair of drive shafts for the Dapol Class 73 are available here.
Normally drive shafts are different lengths for different locomotives even though they are made by the same manufacture. This is because when locomotives have a different wheel base its easier to change the length of the drive shaft than alter the motor design. If you have a locomotive which needs a replacement drive shaft and you can’t find one send me a message via the contacts page and I can probability help.