Odd (optical?) item I picked up

[drykid_]

Picked this up for the princely sum of £2 from the local auction, one of these occasions where I figured if I didn't buy it and take some proper photos I'd never get to find out what it actually is. For what it's worth it came with a pair of vintage (judging by the cases they came in) Hilger & Watts diffraction gratings, one of which has "TRANSMISSION TEST" crudely scratched into its surface. Though these may be something unconnected that was just bundled into the same lot.

Not much else to say about it really, it seems to have some kind of prism mounted at a 45 degree angle to the the main assembly. There are two wheels on one side that appear to be shaped with the intention of being driven by a belt of some kind (and with a finely-toothed geared rack inbetween them.) Also a single smooth wheel on the opposite side. The centre part is - I assume - some kind of motor with two magnets mounted at a slight offset to each other and connected to some electrical terminals. (Sorry for being so vague!) Attached to the base is a metal tube with some kind of lens inside.

Maybe some kind of lab gear? Interested what people think anyway.

[drykid_]

Two more photos

[paulsherwin]

Teaching equipment of some kind? An alignment jig?

[G6ONEDave]

It seems to have some similarities to a cine film projector. Perhaps as Paul suggests a teaching aid. Or something custom made for a specific type of film or to add sound.

Dave

[matthewhouse]

I would think the 2 wheels would run on a track or round rail and the unit wound along with the rack on the side, perhaps with a pinion attached to a handle. The smooth wheel just running on a surface?

No idea what it is but it looks cool though.

[Graham G3ZVT]

Could it be an instrument for measuring the tensile strength of yarn?
The optical parts might simply project a spot of light onto a scale

[Andrew2]

I'd go with the teaching aid, but quite what is a mystery. At school in the 60's, in the physics lab there was a microwave demonstration unit which had a source of 10 GHz RF (a Gunn unit I think) fitted with a small horn and a detector. There were moveable reflectors and everything was on calibrated tracks. Construction was mostly aluminium extrusions and Tufnol stand-offs etc. Very much like this item.

[McMurdo]

Reminds me a bit of a mirror galvanometer, maybe records something on light sensitive paper?

[tobytronic]

A Universal Bend Test Machine? Doesn't account for the prism, though.

[mark_in_manc]

I wonder if the tube with a lens ('underneath') takes a bulb. There seems to be a mirror at the end of the tube at an angle, which perhaps projects light through the slit in the base plate. There seems to be black tape applied to the block which holds the prism, and also to the top of the alu base plate, perhaps to calm down stray reflections. This would then shine a light via the prism and its tube onto whatever the thing which looks like a solenoid is.

I wonder if there was a vibrating thing partially in the way of the light beam, and if you drove the solenoid at a known frequency, you could use aliasing to work out the frequency of the vibrating thing. The suggestions up thread about the grooved wheels running on a track, and the smooth one not, make sense - perhaps to find an antinode in the modeshape of the vibrating thing?

I should add that all this might be a massive lump of confirmation bias, given what I used to do in a laboratory!

ETA - it reminded me of 'taut wire methods' which are a rather out-of favour method for measuring micro-strains, such as described below (scroll down to Fig 3). The wire is tensioned up to a given 'twang', and then when its anchor points move, the change in pitch (freq) can be used to work out the amount the anchor points have moved. In this case, the taut wire might be the thing which interrupts the light beam.

https://www.sciencedirect.com/scienc...43816613000766