"SdKfz 2 Kleines Kettenkraftrad".

Operating a Kettenkrad.

   (Ver 1)


Tracks and Suspension.

The ride of the vehicle is initially bumpier than those multiple road wheels would suggest, this may be more to do with the prominent track pads than link joint vibration. This soon smooths out as the vehicle picks up speed and becomes a background sensation, different but not unpleasant. In the case of the Kettenkrad, unlike most tracked vehicles I have NOT noticed a "sweet spot" in it's speed range, where vibration is at a minimum and in general the vehicle seems happiest.
Soon after moving off, the characteristic clatter of the Kettenkrad starts and is the prominent noise of the vehicle. It is generated not by the tracks, but by the roller sprockets.
Those rollers are another characteristic of German semi-tracked vehicles and are there to minimise track wear. The downside is they are the noisiest aspect of the vehicle. They are a "dry" design, with hardened rollers running on hardened pins, hence the clatter. If you look carefully at the sprockets you will see that the rollers are actually offset from the radial centre of the sprocket - thus there is a left and right sprocket and they are not to be used on the other side. This was so that the track weight is born by the rollers and does not slap against the rubber cushions on the sprocket.
I suspect that addressing the noise issue of the rollers at that time in history was just too difficult.
Like almost all tracked military vehicles, the track is directional. So it is to be installed with the open end of the link (the "fork tynes") being the first part to face the ground when moving forwards. Thus the pad is the last part of each individual link to approach ground.
The track is actually quite quiet.
Here in lies another oddity of the WW2 German semi-track design - the tracks are effectively with the vehicle for life. The design utilizes a lubricated needle roller bearing system. The "horn" of the track is actually hollow and is a grease reservoir. Providing the maintenance schedule is followed, not a problem. The reality is that most Kettenkrades had to work for a living post-WW2 and were neglected. The result is there is insufficient lubrication of the needles, dirt gets past the seals and everything gets chewed out.


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Track bearings, new and old.

Back in WW2, that meant a track bearing rebuild. 60 years later it still means a track rebuild except that the parts are the problem. NSU were very clever, they made all the dimensions non-standard, including even the seals. Which commercially meant that only they were tooled up to supply the needed spares. Interesting behaviour during a war, especially if your factory gets bombed and your ability to produce spares is affected!
The hardened outer and inner race that the needle bearings run in were a special item. Luckily, a Czech dealer has organised for the periodic production of new races - the downside is the price. They are used on nothing else, not even the next vehicle up in the German semi-track family.
There are 30 needles (fortunately, they are a standard size and still available) per bearing, 2 bearings per track link and 80 links per vehicle.


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80 links, cleaned (including inside the horn),
de-rusted and painted.

Which adds up to 4800 needles, 160 each of inner and outer races and seals, 80 track pads held on by 4 bolts each = 320 bolts.


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80 Track pads - cleaned and painted.

Next we come to the "track pins" (bolts) that join the links together. These again were a unique part, which fortunately somebody has had reproduced - the threaded portion is of smaller diameter than the bolt body. This was to enable a "Bullet" to be attached to the end of the bolt: when the bolt was hammered in to the last 2 links to be joined on a track, the bullet acted as a centering device (makes the job much easier) AND protected the bolt threads.


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The track pin/bolt. Note the necked down thread.

Not having a genuine "bullet" (or having heard of any in existence) I made one from an old mild steel bolt, centre drilled it and tapped a thread in it and it was good to go. A high tensile version would better withstand usage.


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Track pin/bolt with bullet not quite fully screwed on. When fully on, there is only the slightest joint.


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A typical track link. This picture only shows one bearing and only 5 needles.
Also visible is the bolt, seal and dust shield for the bearing.

So although the tracks are a problem, it is not a case of "when they are worn out, end of story" as you would encounter with traditional dry pin track.

Suspension is torsion bar, which was very innovative in its day, the operator's seat is also sprung, as was common on motor bikes of that era. Combine the 2 and the operator can experience a fair amount of movement over rough going. The effect is to greatly soften the ride, not to eliminate movement.
The torsion bars can be "set" so that the ride height can be adjusted or for sag in the bars. Likewise a heavy load at the back causing the back to sit too low can be remedied. Looking at the picture below you can see that the bars are in pairs and located vertically. This is most unusual as normally torsion bars are grouped horizontally to minimise vehicle height.


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Torsion bar suspension.

This brings us to the front suspension: which does its own thing without any apparent effect on the vehicle. It is most odd to watch the front fork jumping up and down, yet have full steering authority AND not feel anything being transmitted back through to the handle bars other than normal left or right deflection.


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The front wheel parrallelogram suspension.



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