Saturday, 24 August 2013

Drive Sprockets - A method of Construction

As part of the build of 6 Pzkpfw IIs I'm currently working on, I needed to make 12 drive sprockets.   This method I'm about to describe will not work for every type of tank, but it may prove useful for many.
Firstly, the Panzer IIs sprockets are basically a disk with a raised rim and a domed central hub and drive teeth around the circumference.   The raised rim has bolt holes around the perimeter and the central hub has bolt heads around its perimeter.
I roughly cut the basic disks from 40 and 20 thou and laminated them for a thickness of 60 thou.   A hole was drilled in the centre of each and they were then turned on a mandrel in a Dremel to the required diameter.   The raised rim was then cut using a circle cutter and positioned and glued to the disk.   The central hole was enlarged to 1/8th diam. (the axle size I use).

To make the teeth, I made up a simple jig using an MDF base and two pieces of 5mm square hardwood strip glued just slightly apart from each other.   This allowed me to place a strip of 60 thou square styrene on the diagonal in the slot thus formed.   A Stanley knife was then used to scrape the upper edge down so a triangular section was formed.   These were then cut to the required width on a NWSL "Chopper".

Another two simple jigs were made up.   Both from a piece of pine for the base and a 1/8th piece of plastic rod to form an axle.   One was marked to give the correct spacing for the teeth and the other for the bolt holes on the raised rim.   This jig was used with the Dremel in a drill stand to do the bolt holes.

The teeth were then glued to the rim of the sprocket.

To finish the sprockets, circular pieces of 10 thou were made up in the same manner as the sprocket disks and glued to the centre of the sprockets.   A slightly domed hub was turned up from a suitably sized knitting needle and attached to the centre of the disk.   Finally a row of bolt heads, cut from 30 thou rod, was glued around the outside of the hub.

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