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Author Topic: Barco DP2K-23B lamp change John Roddy Expert Film Handler Posts: 114 From: Spring, TX, United States Registered: Dec 2012 posted 06-05-2016 12:51 PM                        quote: Steve Guttag I'm still at a loss as to why Barco doesn't use a split washer on their Anode connection (or a wave washer). That alone would take a lot of the risk out of the torque specification on the ring lug. They actually did. And then they sent out an Info-T telling everyone to get rid of them ASAP and go back to flat washers. Again, this is a connection for electrical contact, not structure. This is why I had good results with filing the surfaces. The largest the surface area that's met up between the lug, washers, and nuts, the better. That's why the star washers are no good. Great for keeping them in place, but awful for transferring the ginormic amounts of current that the lamp needs. The split washers are no good either since…well, they're split washers. For small screws that don't really see much vibration or anything, they're all right. But large ones on giant threads are more of a party favor. I've yet to see any of these connections come loose when they're just torqued properly with large flat washers. Don't forget, that increased surface area also means more friction holding it in place.  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 06-05-2016 07:56 PM                     They had STAR washers, never split washers. As for split or wave washers, their vailue has only been proven by oh about 50 years in xenon lamp usaage. The purpose of the split or wave washer is to prevent loosening. The problem with the star washer in this application is that it will reduce contact area AND they will dig into the silver (a relatively soft metal). In fact, they also removed one of the flat washers on the "C" lamphouse but kept both in for the B lamphouse so on one side, you only have the nut's contact area to transfer the current. You should have a flat washer on both sides of the ring lug for maximum contact area and the flat washers don't get their suface damaged since they only contact the ring lug. Then put a split washer (or wave washer) and then the nut to finish the connection. Then you have maximum contact area for current transfer and a mechanical connection that is going to be more secure and survive heating/cooling cycles better than mere torque.  |  IP: Logged Monte L Fullmer Film God Posts: 8367 From: Nampa, Idaho, USA Registered: Nov 2004 posted 06-08-2016 03:59 AM                     quote: Steve Guttag You should have a flat washer on both sides of the ring lug for maximum contact area and the flat washers don't get their suface damaged since they only contact the ring lug. What would be the recommendation on this - can one use a copper washer as the second (which one can readily find in hardware stores), or stay with the silver alloy as the second washer? I presume that a regular steel washer isn't the best choice due to current flow. thx - Monte  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 06-08-2016 04:37 AM                     The recommendation?...Well Barco has already recommended and I will not provide a how-to that contradicts the manufacturer. My critique was just that. What the current design provides is a semi-precarious connection that is dependent on semi-precise torque to prevent failure. When mixing metals, one has to be a bit careful as they do not always react well together. I would also say that merely adding the second washer without taking into account the potential change in torque requirement isn't advised (you now have another semi-resilient item to account for (Barco had it on the "C" lamphouse and removed it, yet retained it for the "B" lamphouse). The addition of an appropriate wave washer (or split) would put the burden of maintaining the mechanical connection more onto the properties of the wave/split washer (still needs to be torqued but more forgiving).  |  IP: Logged

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