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Friction mount

The well-known amateur-astrophotographer Jan Koet found an incomplete, but very heavy mount.


The total assembly had a weight of about 80 kg. and was fully made from stainless steel. The previous owner obviously had heavy machinery. The only problem was that the mount was not fitted with any drive system, but Jan still had an incomplete friction wheel.


So Jan came to me with the question: "can you make this into a working system​?"

These cases are always not very simple. When you start from scratch you can make everything like you think they should be. Now you must constantly adapt yourself to the existing situation.

Right ascension axis drive:

The friction wheel is 420 mm and the pinion 30 mm. This give a reduction ratio of only 14 x.

With an extra precision worm the desired reduction was realised.

The pinion is pushed against the friction wheel with great force. Both wheels are hardened.

​Great attention has been given to the parallelism of the wheel and the pinion.

The whole drive system is built inside a housing.

To prevent the forming of rust on the wheels Jan fitted heaters to the inside of the housing.


Declination axis:

The declination axis is driven by a large bronze wormwheel.


Great attention has been spent on the precision of the drive system, without any play or backlash.

The worm is pushed with ​constant spring-force into the wormwheel. For this the worm can pivot around a so-called flexible hinge. With this construction 5 of the 6 degrees of motion are eliminated.

The only remaining degree of motion allows only the movement of the worm inside/outside the wormwheel.


This drive has also been fully built inside a housing.

Jan fitted the mount to a sturdy pier and applied a dab of paint to it.









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