Revved Up

-


Pictured is a little gadget I picked up yesterday at the indoor antiques market in Church Stretton, along with the patience cards I mentioned in Deck of the Week, for the princely sum of eight quid. Since the failed experiment with the flaky digital tacho I got off the 'net which lasted precisely one hour before dying, I've been looking for a reliable way of determining the rotational speed of the bench tools in the workshop. I was aware of the type of tacho shown from articles in the Model Engineer mags that I've been triaging - a simple mechanical solution to a basic mechanical problem. This particular model is by Moore & Wright of Sheffield, which judging by its style, construction and the 'spectacle' case, is around sixty or seventy years old.

The method of use is simple: you just select one of the two removable 'ends', shown left and place it over the end of the rather beautifully ground shaft of the device. The pointy one is to locate in the centre drilling of a shaft or the workpiece, and its partner takes the point of a dead centre: in the mandrel of the lathe, say. The outer scale moves one mark per revolution of the shaft, showing one hundred revolutions of the shaft per each complete turn of the dial; which then moves the inner dial by one notch as it passes zero: the entire revolution of this second dial representing ten thousand revolutions of the shaft. Timed against either a stopwatch or the second hand of a wristwatch, the number of revolutions per minute at the shaft or chuck can be gauged. Simple, indeed, and no electronics or lasers to snuff it unexpectedly.

Comments

Post a Comment

Popular posts from this blog

Of Feedback & Wobbles

-
Image
Many years ago I came up with an analogy for poorly damped feedback loops. The feedback loop that prompted this frankly tart analogy was indeed a horror. Anyone who remembers shame-faced their first attempts at clutch control resulting in the good old kangaroo launch across the lights only to stall in the middle of the crossroads will have some idea of the kind of data transfer lag involved in said system. The analogy I made was that of a large blancmange. Untouched, a model of stasis and eminently stable and predictable; but prod the bugger and the resultant chaotic behaviour needs a very complex physical model and some very decent computing horsepower to predict its outputs, if at all. The system in question was a large and complex audio-visual display at what eventually became 'The Electric Mountain' in Llanberis. We were ultimately contracted to maintain the thing having been witness to and peripherally involved in its installation. Certainly not involved in its des
Read more

Sister Ray

-
Image
Ray Keats - aka Ann Key - local artist & family friend, died this morning. She'd been ill for some years, but never let it get in the way of her work or of tending to the massive network of friends, colleagues and fans she had accumulated over the decades. Her house on the High Street of Rachub, just below where we live - a former cockle factory(!) - bought many years ago when she and her late husband Ronald moved here from Manchester to set up home in Yr Achub, is currently still home to her paintings and drawings, and the front window displays her work, including the last drawing she made in hospital, just days before she died. Her good friend Colin has been a diamond in her latter years, looking out for her and just being there when she needed him. She will be much missed by this tiny community of ageing bohemians up here in the hills, but suffice it to say, George, her cat, will be well looked after now she's gone.
Read more

A Time of Connection

-
Image
I was just reflecting on the vacuum of continuity that's left behind when someone dies: that sudden sense of disjoint, of fracture, in one's personal history that takes one completely by surprise at the oddest moments. These pinch-points in memory can often yield some surprising revelations of fact about periods in one's past. One such occurred to me tonight, tending my rather lazy meal of pizza in its journey from shrink-wrap to mouth via the oven. Al's recent demise still catches me out from time to time: the space he left bounded by forty plus years of friendship. But the thing that struck me tonight was just how much change was happening on a personal and social level in the very early years of our acquaintance. Between moving here from Birmingham in September 1980 and our buying our first proper house eighteen months later, all manner of things occurred that would chart the course of our lives to the present day. At around the time of our meeting Alan & Irene [
Read more