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T A N K SC A R R I E R SG U N SA R M O U R E D   C A R S

 

"SdKfz 2 Kleines Kettenkraftrad".

Operating a Kettenkrad.

   (Ver 2)

 



That Gearbox!

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The Cletrac driveline. The taller handle is for the
gear change the shorter one for the 2 speed transfer box.


If you happen to see mostly anyone start up and then drive off in a Kettenkrad, or pull up and then have to maneouvre one, you will probably notice quite a bit of fiddling going on. NSU, being a motor bike manufacturer apparently didn't see any reason to alter their thinking when designing the gearbox and transfer box. The best way I can describe the gear mechanism is "dog engagement". The gears themselves are all straight cut - strong but no help. The mechanism to cause them to mesh is the "dog", it has 5 possible engagements (ie. slots) per revolution: there is no lead in, you either time it right or it doesn't mesh. This means that even up changes have to be made with an ear to engine revs as to road speed and gear ratio.
Up and down changes by necessity are double clutched.
Gear engagement won't be hurried, you either time it correctly or it won't engage.
I have pulled up and stopped, switched off the engine, knocked the gearbox out of gear and then been unable to re-engage the same gear. The slight movement of the drivetrain due to residual stress was enough to mis-align the dogs.
The above also explains all the fiddling, it is quite normal to pull up in a Kettenkrad and find it won't go into first gear. You have to "feather" the clutch until you can persuade the gearbox to go into 1st or reverse. Likewise the transfer box.
In its day, crash gearboxes were the norm and the Kettenkrad would have been nothing out of the ordinary, particularly to motor bike riders. In their case, if a bike didn't want to go into gear, you just rocked it with your feet - not an option with a Kettenkrad!


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Although not for an NSU product, this BMW drive train schematic
clearly despicts the sliding dogs. Items "O" and "N". You will note that
the gears actually remain in mesh all the time and are engaged and
disengaged by the sliding dogs.





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Item 31 points to one of the sliding dogs.


In the picture below you can see a clear view of the sliding dog and the integral dog engagement on the gear cogs of the transfer box.

From the top down:
A,B,C - integral dog on the low range input gear.
1,2,3 - low range dog on the sliding selector.
7,8,9 - high range dog on the sliding selector.
X,Y,Z - integral dog on the high range input gear.
The low range output gear is the large gear behind the low range input gear. The high range output gear is not visible from this angle.


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Transfer Box.


In this picture you have to look a bit harder to see the sliding dogs, you will note they are almost identical to those in the transfer box. Thus they are no easier to select.
As you can see, the mainshaft has the various input gears machined directly into it, thus they are fixed to it.
The reverse and 1st gear sliding dog is obscured in this picture.
2nd gear integral dog (X) is engaged by the sliding dog section labelled (5).
3rd gear (top gear) integral dog (W) is engaged by the sliding dog section labelled (4).
The output of the gearbox exits to the lower right in this picture direct into the differential.


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Gear Box.




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Ver 2.

 

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