More ATM Projects

15"  9-point Mirror Cell Mount

  I briefly covered the mirrorcell in my construction article, I'll try to give you a little more detail here.  I started with an 18"x 18"x 1/4 piece of plate aluminium.  I cut down the corners and bored a 6" hole to reduce weight.  Next I drilled three holes to mount the triangles at.  I derived the locations for the triangles and pads using a formula from an article in Sky and Tel several years ago.  The triangles are located to the base using 3/8x 1" shoulder bolts. A 1/8" rubber washer seperates the two pieces to allow the triangles to align themselves, and a spring on the back keeps a constant pressure on them.  A 1/4" hole in the triangles sits over a 3/16" dowel to keep them from rotating out of alignment.  Next three holes were bored to take a polyethylene bushings that bolt to the base plate. The bushings are tapped 1/2-20 to take the collimating bolts that are mounted in the mirror box.  The plastic grips the adjuster screws snuggly so they will not move by themselves.  The triangles are made of 1/2" aluminium plate and was machined to leave three 1" circular pads to which I glued three pieces of  1/16 thick poltethylene, the mirror sits on these.
the mirror is kept in place by four aluminium posts bolted to the base plate.  I used 1/4" nylon bolts snugged up against the mirror to keep it from moving around, and on tor is a nylon block that extends out over the mirror to keep it from fallin out if the telescope is tipped over.  The collamination bolts were made from titanium (it was available :-) but stainless steel would do as well. I mounted them in the mirror box with bushings on the inside and the outside, the out side part was aluminium and nylon on the inside. A brass shim was used to take up any slop in the assembly and act as a bearing material between the titanium and aluminium.  A 7/16 hex was cut on the end sticking out of the mirror box  to take a wrench or socket for the adjustments.

mirror cell

retaining brackets

A Waineo Type Mirror Grinding Machine

  As a machinist I am accustom to letting the machines do the work with a little guiding influence from me.  So the thought of having to push glass led me to build this machine.  I came across several sites across the net with variations of Tom Waneo's machine.  I bought a couple of gearmotors from a local surplus store, and scrounged some materials from the scrap bin at work and went to work. 
  I made the platter 12" in diameter which should handle anything I can thick of for now.  I used 1" i.d. trailer axle bearings to support the platter spindle, since these are taper bearings you need to be able to tighten them.  I threaded the spindle below the bearings and made an ajuster nut to keep them at the proper tension. 
I'm still playing with pulleys to get the proper speed for the platter and I still have to build the drive for the overarm. 
There is still a lot of work to do, and I probably could have ground several mirrors in the time I have spent on this, but that wouldn't have been any fun.
Stay tuned for more.

return to previous page   go to the next page     return to front page