SRS custom builds 1U rack frame For Metawave

Edited by the Engineeringtalk editorial team Jun 1, 2000

Stoke-on-Trent based Metawave needed a particular type of 1U rack frame that would meet EMC regulations but no rack frame manufacturer has an off-the-peg solution. SRS produced one though.

Stoke-on-Trent based Metawave (formally Johnson Matthey Print Ltd) needed a particular type of 1U rack frame that would meet EMC regulations but no rack frame manufacturer has an off-the-peg solution.

This left the engineers at the company with two main options.

They could either buy a standard 1U rack and modify it in-house or they could collaborate with a rack frame manufacturer to produce a custom-built frame.

After an investigation into the expertise of design engineers at the various rack frame manufacturers, they decided to take the latter option.

SRS Products plc was contacted to provide a custom-built solution for the project which was to design a 1U rack frame to house a new range of serial digital interface products for use in the TV industry.

Metawave did not have the facilities to deal with the metal forming and machining required to modify a standard 1U rack in-house and SRS Products was chosen because of its willingness to work with the company prototypes.

SRS has developed an EMC 1U 19" chassis that accepts up to four rows of 3U Eurocards horizontally with up to 8HP of useable front panel width.

Plug-in cards interconnect with a horizontally mounted backplane fitted with I/O connectors.

These protrude through the rear panel to enable the fitting of external cables.

The unit is modular in design and can be adapted to suit PCBs 160mm and 200mm deep, 100mm (3U) and 233.4mm (6U) heights.

The chassis has a formed base and sides constructed from 1.6mm mild steel with a perforated ventilation pattern in the sidewalls to allow a good flow of air whilst maintaining an RFI screen.

Guide plates fitted to the base chassis provide guidance for plug-in Eurocards, whilst a staggered lead-in pattern enables easy alignment of the PCB and the runner slot.

The rear panel is a separate item, which allows different variants to be used and eases the assembly of the backplane connectors to the panel.

Access to the top of the chassis is via a one-piece removable cover while EMC shielding is achieved by fixings and conductive metal-to-metal contact of the mating components.

Shielding of the front panel aperture, however, necessitated a different approach, as the specification for the front panel requires it to hinge down, leaving access to the complete inner aperture.

It also has to contain four integral miniature axial fans to force air cool the enclosure and extend to cover the rack mount fixings to enhance the final appearance.

Shielding these has been achieved through a conductive inner panel trapping the fans against the outer panel.

The inner panel is also fitted with beryllium copper fingers which provide contact via a wiping action with the main chassis.

The outer panel extends to the full width and is fitted with captive fixings and a unique hinge that allows the panel to hinge clear of the aperture.

Metawave's executives are very pleased with the results.

Commenting on the final product, Mark Townsend said "We now have a fully compliant rack frame with integral cooling in the front cover that allows us to sell our products with confidence".