Making rollerbearing lateral supports

Nederlandse versie klik hier

Above is a picture of my 'bearing edge supports', and here is a picture of the supports mounted inside the mirrorbox. Like piano wires, they can follow the (very small) axial movements of the mirror, when it sets on the pads when going from horizon to zenit and from zenit to horizon. Why not stick to piano wires? Two reasons:
1. I like to experiment with lateral supports, looking for the best way to support the mirrors edge without visible deformation of the mirror.
2. When I collimate the primary when collimation is relatively far off, the mirror tends to 'hang' a bit in the piano wires. Pointing the scope in vertical direction lets the wires 'jump' to neutral position again, after which the collimation can be finetuned, so it's not really a big deal. But after I motorized my telescope (Mel Bartels' stepper system), pointing the scope up was a bit more work then it used to be and I decided to look for another solution.

How did I make them?

In the 15 mm (outside) diameter tubing (so not 20 mm like the picture says), fits a 12 mm outside diameter and 10 mm inside diameter round piece of copper tubing. The copper is glued into the square aluminium and a 10 mm threaded rod is glued into the copper tubing. The rollerskate bearings are 22 mm outside diameter.
When the epoxy is cured and the assemblies are painted flat black, I just take the piano wire supports out of their holder (a connector nut) and put the bearing supports in place. A one minute job. The nut on the threaded rod functions as a locking nut.

Another design
Rob van Vreeden, one of the memebers of my local astronomy club, also uses bearing supports, though completely different disigned, in his 16 inch tri-dob. A picture of his mirror cell is here and a closup of one of the bearings is here.

Go to: main menu

Go to: the mirror cell Go to: secondary and spider Go to: the truss construction Go to: the double sling
Go to: piano wire supports Go to: roller bearing edge supports Go to: computerizing
Go to: A 20 inch f/3.6 computerized Dobsonian Go to: Building a trilateral computerized 20 inch f/5 Dobsonian
Go to: Project: five 12 inch lightweight Dobsonians Go to: Motorizing a 12 inch lightweight Dobsonian
Go to: 20 inch telescope Go to: Equatorial platform Go to: Scotch mount Go to: Binocular mount Go to: Dobsonian tips
Go to: Bending aluminium Go to: Collimating Go to: Making a Krupa collimator Go to: Dotting the primary
Go to: A ballhead type telrad/finder mount Go to: Mirror making log of 300 mm mirror Go to: Astronomy
Go to: Using digital finder charts at the eyepiece Go to: Astronomy links Go to: Building a spherometer
Go to: Building a Bath interferometer Go to: A Foucault-Ronchi-Lyot tester Go to: Building a mirror making machine
Go: Home

Email: Jan vanGastel