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28. RC for Lady Sarah (3)


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This picture shows the servo linkage after modification to its final form. (Compare this with the prototype version on page 26!) I've cut away surplus length from the horizontal linkage and reduced the length of the regulator arm. All that remains is to spray all the aluminium components matt black to make the whole assembly less obtrusive, and, finally, to add a driver.

The servo casing is positioned between the steam outlet pipe and the water inlet union with a gap of 3/16" at each side, taking care that no part of the casing is in direct contact with any hot surfaces. I considered fitting an aluminium heat shield between the boiler parts and the servo, but after two 1 hour continuous steam-ups this has so far proved not to be necessary.

The servo connector cable is ready to be plugged into one of two connector pin sets mounted in a veroboard panel under the front edge of the tender floor. This means that the engine and tender do not have to stay permanently attached. The electrical connections are simply unplugged enabling the engine and tender to be separated for transportation and maintenance.

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At the front of the tender there's a slider switch and a power-on indicator lamp.

The holes in the lower front section are for the two 6BA bolts that normally hold the tender body in position.

Under the front edge of the tender floor is a panel made from 0.1" pitch veroboard with pcb pins fixed in two sets of three. This forms the servo connector panel. The pitch of these pins matches the connector at the end of the servo cable. Connecting wires from the receiver and anti glitch unit have been soldered to the appropriate pins. This allows the servo connectors from the engine to be pushed directly onto the set of pins for the required RC channel making all necessary electrical connections between the loco and the tender.

I've sited the servo connector panel as close as possible to the loco-tender linkage pivot to help minimise strain on the electrical connections as Lady Sarah negotiates curved track sections.

The photographs and text on this page are copyright (c) Paul Backhouse 2000 and may not be reproduced or distributed without the owner's permission.

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