Hi Curtis, Ravi already has shown some ideas for a rail system at our last collaboration meeting which has many of the design criteria you are looking for. We should not try to re-invent this wheel by every group that takes a look at it. Cheers, Elton. On Fri, 12 Mar 2004, Curtis A. Meyer wrote:Dear Eric, Dan and Elton - Gary, Zeb and I started talking about infrastructure for positioning and installing the GlueX chambers yesterday. One of he things that came out of this is that Gary (our technician building the chamber) is very reluctant to have anything like the forward chamber packages "attached" to the front end of the strawtube chambers. He was also very reluctant to have the cable bundles passing over the length of the strawtube chamber. We then started to look discuss that we had thought that this would be the best way to accurately know where the chambers are with respect to each other. We then got to the rail system, and realized that if we had precisely located "stops" on the rails, we could accurately reproduce the chamber positions at least as well as we could do with the packages being attached, and possibly better. Even if we had the forward chamber come out the down stream end of the chamber, and the CDC come out the upstream end. At the moment, we are looking into a rail/positioning system that would allow for this, and allow us to accurately and reproducibly position the chambers inside the magnet. We asre also contacting the Regina group about being able to attach precision rails to the calorimeter. What is coming out of this early discussion is that the current 5cm of space between the chambers and the caloriemters may not be quite enough for the rail system. We may need to look into increasing this to about 7cm or so. Once we get a reasonable estimate on the numbers, we will need to decide with the calorimeter group where this space comes from. Equally spilt, all from DC's or all from calorimeter. curtis