anyone talking to Chief about GMTIIc?

[veja74]

seems the talk of getting the AR on the back of the crystal has vanished and was just wondering if anybody is working with Chief on a project for this or not. I haven't had rollies since I sold of my pepsi GMTII and my EL Explorer 2 but I will be receiving a CHS GMTIIc today and wanted to work out this mod. I have worked with Chief many Omegas and here are a couple of my thoughts:

1. the problem with taping off the crystal except for the cyclops area is that the vacuum chamber reaches temps in excess of 500 degrees F, that is why the cyclops must be removed first as the glue would melt and it would just fall of in the coating chamber. Tape would just burn up.

2. Chief used to have a single sided application that was not nearly as durable as the double sided AR. Nice thing about that is if the inside of the crystal were coated it would be super easy to polish off everything but the area under the cyclops

3. the alternative would be to create a mask with something like a thin ceramic or even glass disk. The area for the cyclops could be cut with a fine diamond bit and a dremel. Use a solid disk for the front side of the crystal and sandwich the crystal between the two disks. Since this would be a durable material it could be reused for subsequent AR runs.

4. lastly, do we know if it is only the area under the cyclops that is coated or does the cyclops itself still get a coating as well?

so... any thoughts? I get kind of obsessive about accuracy and have loaded my 3 Omegas with gen parts so I would love to have this degree of accuracy with my new GMTIIc as well.

On a final note, anybody know what the crystal reference is for a 116710? I couldn't find it in the crystal ref in this forum.

[freddy333]

I cannot see how you are going to mask off sections of a crystal without burning off the masking material.

The only scheme I can figure that might work would be to take a small, thin sheet of sapphire, sized/shaped to match the underside of the cyclops, AR & then glue it to the underside of the crystal. No idea where to get the sapphire or if a thin sheet can be AR'd though?

[veja74]

You are correct, that is the point I made in item #1. However, it should be possible, as stated in #3, to use either a glass or ceramic material with the correct area cut out for the cyclops. I don't know if everyone recalls the way AR used to be done where the crystal was held in place by two small clips? The area where the clips touched the crystal did not have any AR. We could achieve the same thing for the GMTIIc by using a material that would not melt at 500 degrees. It could even be metal, as long as it is in contact with the crystal it would keep the crystal from getting AR except for where the cut out is.