Posted By paul plutae on 4/17/2008 at 7:17 PM
In my quest for a stable prism bubble design, I believe I have found one that fits the bill.
The design enhancement, in my opinion, is the use of a single ball bearing for the pivot point of the bubble vial. That, along with a top screw adjustment feature will make this type of assembly easier to adjust in the field than the compression types.
Some assemblies use springs, other ones use a rubber gasket. Both of these designs have three pivot points as well as more areas that will develop loss in tension or compression memory. The ball bearing design has just one pivot point and zero compression memory or loss of tension problems.
The picture below is the design, but for a bottom screw adjustment, but it shows the simplicity of the whole design. Seco does have another product with the same ball bearing design, but with a top screw design.
I ordered two 8 minute vials of the top screw design. Once they are calibrated, the adjusting screws will be set with some super glue. These rods will only be used for control and kept in thier own cases. The cost for each assembly is $ 45.

Modified By paul plutae on 4/17/2008 at 7:19 PM