From: Gordon,Ian [mailto:[email protected]] Sent: Thursday, August 26, 2004 2:03 AM To: 'IEEE EMC-PSTC GROUP' Subject: Turntable design/construction
All I am considering making a turntable for EMC testing. However, the maximum load on the table would be up to 700kg evenly distributed. Thus the bearings in the device would need to be extremely strong and furthermore these would ideally be made of non-metallic material. The Radio Spares website, http://rswww.com shows a "Euro unit" (RS part number 887-843) which would be ideally suited as regards loading but it is made of steel and thus not ideal from an EMC view point. Does anyone know where I may find non-metallic units with similar loading performance? The other way of looking at this issue is by asking what effect the presence of 4 or perhaps 6 small (55x37mm) totally isolated metallic units built into a solid wood table approximately 1m diameter is likely to have on any measurements taken within a fully anechoic chamber with an EUT size of approximately 1x0.5x0.75m. The cost of purchasing a proprietary turntable would be prohibitive. Any opinions gratefully received. Ian Gordon *********************************************************************** Ian: If the turntable merely sits on the floor of the shielded enclosure, then I would think that a carousel-style bearing wouldn't be too obtrusive, since I have used bearings like this (12" diameter by 5/16" thick) for quite heavy loads. These are not precision devices, but low-tech & cheap. See McMaster-Carr http://www.mcmaster.com/ , part # 6031K19. Although this is rated for 1000 pounds, for slow-speed operation, you can overload it a lot more. Cost is about $9 each. For absolute non-conductivity, I really like Mike's suggestion about billiard balls. Just get a couple of 4' x 4' sheets of marine-grade plywood, drill a hole in the center for a heavy threaded rod, and screw on a nut from each side. Rotate the rod rapidly while holding a wood chisel against the face of the plywood. After a while, you will have a decent ball-race. Repeat with the other sheet of plywood. The race faces can be made harder by painting them with epoxy. Take pictures for bragging rights! Or insurance claims. :( Ed Price [email protected] WB6WSN NARTE Certified EMC Engineer & Technician Electromagnetic Compatibility Lab Cubic Defense Applications San Diego, CA USA 858-505-2780 (Voice) 858-505-1583 (Fax) Military & Avionics EMC Is Our Specialty This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
