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email dave@allmon.com

My QuickCam only site

one of the first lessons learned from the prototype is that 0.040 aluminum is not a structural material. It flexes like aluminum foil. I had anticipated this nearly a year ago, and bought 0.100" aluminum plate in the same order as the 0.040. My only concern was cutting the holes in it. The fly cutter worked so well with the 0.040 stock that I had to try it. It gets a bit noisy, but with WD-40 applied to the surface during cutting, it is OK. I cut all holes by going halfway from each side.

The back plate screws to the front of the camera using the holes provided for the T-adapter. All the workings of the filter wheel are on the back plate - the front plate has only the telescope mounting female T-thread.

To make the female T-thread, I cut a ring off the end of a male-female T-extender, and epoxied it into an appropriately sized hole in the front plate.  The extender is still functional, if a bit shorter than before.
 

Here are the basic parts. The back plate and wheel are in the rear, and the front plate is in the front. The black ring on the front plate is the female T-thread. The eight mounting holes in the back late are a product of dyslexia - not a design feature.

This picture demonstrates the difference in size between the 25mm and 50mm filters. The white rectangle at the top hold the 50mm IR blocker. For now, I have the 25mm filter mounted in a cell made from 2mm Foamie, and stuffed in the threaded recess in the front of the camera.

Here is the original motor. Notice the "400 S/R" on the side. Ooops. The controller will allow that to make 0.6 revolutions per second. It takes about 16 revolutions to go one complete revolution with the 15.88:1 reduction. That´s 4 revolutions, or 6.67 seconds per filter, assuming one is moving through the filters sequentially. With this ratio, I would like to get down at around 1.5 seconds per filter change. To do this, I need to use a motor which has only 100 steps per revolution. I found one I think works better at B.G. Micro.

This is the drive method. Friction wheel. The tire on the prototype was made by chucking the rear shaft in a drill and applying silicone to the front shaft. I used a flat-tipped tool to shape the silione. The new motor has no rear shaft, and so I used a drill bit as the form. I selected one which was about 75% of the shaft diameter. I used the drill press this time, but the hand drill would have worked fine. A touch of WD-40 acted as a parting agent.

The tire does not need to be perfect, because the drive ratio is not used in determining the position of a filter. It does need to contact the edge of the wheel through an entire rotation of the filter wheel.