Featured Shaft speed indicators

It's been kinda quiet lately so I thought I would post a photo of some of my speed indicators. I have a lot more larger ones, most of them boxed. They can get quite complex. Dennis

 

Think you will have to enlighten us.
I have no idea what a shaft speed indicator is.

Unless it is to indicate how fast you are falling down the mine shaft.
They look interesting.

 

Machinist speed indicators.
This might explain it easier.

Cheers
Stephen

 

I've seen these at estate sales and never really knew what they were. Thanks for posting.

@springfld.arsenal would probably appreciate seeing these as well.

 

Sorry for leaving you hanging! These speed indicators became helpful towards the late 1800s as better tooling and faster turning speeds required a specific rpm on the lathe to produce the best results. Water powered equipment had a variable speed and even steam engines needed the various belts shifted to vary the speeds.

You simply hold the point against the end of a shaft and count revolutions on the wheel as you time it. Most shafts have a center point left over from the machining and this helps. Indicators may have optional ends that press over the point. These include a rubber tip for shafts with no center divot and a small calibrated rubber wheel that you press against the side of the shaft to get surface speed instead of rpm.

One improvement was to have a small bump on the count wheel so you could count each revolution as it passed under your thumb. This helped with higher speed shafts. The count wheel revolves one turn for every 100 turns of the machinery you are measuring. Even better were the ones with a second geared wheel that counted how many times the first wheel turned.

Fancy versions came in fitted cases and had glass dials like a dial indicator or pressure gauge. These included a rapid reset. The early versions had to be spun until they were at zero each time. I have one with 3 inputs shafts and you select the one that gives the proper speed range.

Virtually all of these are derived from Woodman's 1876 patent that fathered them all. Starrett improved them in 1896 and are so marked. As electric motors replace other forms of power their fixed speed relegated the shaft speed indicator to the scrap bin. Starrett had 4 models, the 102, 104, 106 and 107, and still made them up to about 2000. They are featured in the National Museum of American History. Dennis

 

Thank you.
Not sure I understand everything you said. But I get the gist of it.

 

nice group ,never thought to look it up on utube,,,sold a few of these in bad condition

 

Interesting. I use a pistol-like laser version now. You put one piece of reflective tape on the spindle and the pistol thing gives a digit readout of the rpm.