NSU cross frame safety bicycle

This NSU cross frame belongs to the collection of the Bad Bruckenau bicycle museum in Germany. It is really something special.
Look at the way the handlebars are constructed, with a brake button in the middle.
Then there's the wonderful meachanism to adjust the chain tension, probably using a left hand and right hand thread.
Really original constructions for this German maker, in years when most German/French/Dutch firms were happy copying the English designs.

By the way: this way of tensioning the chain doesn't work too well, although more producers, like ClĂ©ment, used the bar to adjust the chain. Problem is: if a rider of some weight (lets say 75 kilo) takes place on the saddle, the whole cross frame starts to 'work' a little. Other firms (like Rudge) used the bar between head and bracket to correct this torsion. In this NSU construction the torsion will only stretch the chain. So when a heavy man uses the bicycle, the chain gets overstretched. 

Click the picture to see more pictures of this wonderful bicycle.