ELECTRICAL VOLUNTEERS REPORT SUNDAY 21st FEBRURY

[JONATHAN-BARNES]

I came in on Saturday. I cleaned and painted the three light fittings that we took down last week from under the canopy at Rammy.

On Sunday we had a full house. The fire alarms were tested as usual.

The Rawtenstall Christmas lights had been taken down by a member of paid staff who will remain nameless. He had managed to get them tied in knots and tangled up like a birds nest. We took them onto the undercroft where we had enough room to spread them out. It took some effort to get them unknotted and untangled before putting them into their container ready for next Crimbo.

The Rammy light fittings were converted to LEDs. One of these just needs some white paint on the inside and then they can go back up.

We did some work on the 1950s clock that we hope to install outside of the Trackside under the canopy. From the bits and pieces of two similar clocks we engineered (cobbled together) a motor and gear box that we hope will be OK. We fixed it in the clock and left it on test until next week.

The Standard 4 group have given us the components of a speed gauge (miles per hour) for their steam engine in the hope that we can restore it. This consists of a generator that produces a voltage proportional to speed and a moving coil meter. On inspection it was found that the windings of the generator were shot at. It would cost a fortune to have it rewound as the windings are segmented and complicated.

We contemplated the problem as we supped tea and ate jam cake and chocolate roll. One possibility is to replace the windings with Hall Effect transistors. These would produce a pulse of current every time the magnetic field from the magnetic rotor swept past them. The current could then be processed electronically to drive a moving coil meter calibrated in miles per hour.

What is the Hall Effect? I hear you ask. If a conductor with a current flowing through it is placed in a magnetic field that is at right angles to the conductor, an electric field is generated at right angles to both the current and the magnetic field.

In a Hall Effect transistor this electric field is used to control or switch the output of the transistor. This is not to be confused with a Field Effect transistor. This is a different animal and I can bore you about this some other day.

[martin_livingstone]

...like tomorrow?

Good post Jonathan!

[marflow]

The nameless paid employee shall be named. His name begins with "S" and ends with "imon" !!¡

The clock was very difficult to "cobble together" because somebody (who shall indeed remain nameless) didn't make enough notes on how it worked before dismemberment. By the time "they" had finished with it, the drive shaft was bent and was impossible to straighten. So we had to use the shaft from the other gearbox. From two halves, we have made a hole (ASB's spelling?) And somehow, a piece of chocolate cake got into the gears. Who did that? At least it wasn't gobs of Sarah's eggs!


SPEEDOMETER for 80097 not 80!
Hall effect Transistors come in various guises: latching, north pole sensitive, south pole sensitive, either pole sensitive. So there will have to be some research. The caboodle needs powering and steam will not do! A completely different idea would be a dynamo from a bike??

The dial we were given was just a mass of rust inside. Nothing approaching the highly sensitive moving coil meter it used to be.

If the Victorians had tried to use less weight (each of the parts of the speedo weigh about 60Lbs), they could have saved a fortune on coal.

Ideas on a postcard please.

[Union Pacific]

Have you tried contacting 'The Standard Locomotive Owners Association' for a speedo ? you never know, somebody might have a spare.

[asbibby]

SPEEDOMETER for 80097
Hall effect Transistors come in various guises: latching, north pole sensitive, south pole sensitive, either pole sensitive. So there will have to be some research. The caboodle needs powering and steam will not do! A completely different idea would be a dynamo from a bike??

[Wizzo]

Pedalled by the fireman ??? The faster the engine goes the faster he has to pedal. Or would it be t'other way round ?


Bret