If you are seeing lower than normal compressed air output, yet the compressor still magically puts out about 20 bar, this is a classic sign that the coupling has sheared. Friction between the rivets is sufficient to make that much air - but no more.
The coupling should be replaced.
A popular jibe during the Space Race was that while the US had spent millions of dollars to develop a suitable writing implement for their Astronauts which could be counted on to perform in zero gravity and other environmental challenges of outer space.. the Russian Cosmonauts “used a pencil”.
This expression has come into the language as a metaphor for not overthinking stuff.
In a parallel urban legend, we understand DOSAAF mechanics would temporarily fix one of these sheared Air Compressor couplings in the field - using a common nail.
It's early October 2021 and global supply chains are not in good shape, with over 70 freighters at anchor outside LA and Long Beach alone, waiting to unload.
That 'nail' clue was our starting point in developing rivets to 'on-shore' the refurbishment of these Shear couplings. The correct ductility of the rivet needed to be determined by multiple hardness tests, the correct length by trial and error, since on both sides the rivet head must sit slightly below the coupling surface.
Once the rivet has been closed, the coupling parent metal gets staked on either side to retain the sheared rivet halves, (so they can't take a voyage inside the motor or compressor.)
Older couplings appear to be drilled for a 4mm diameter rivet - this diameter dropped at some point to 3.5mm - the same time that coupling halves started to appear in a brighter grade of stainless. We have developed both rivet diameters and the refurbished coupling shipped to you may have either 3.5 or 4mm diameter rivets.
TYC's shear couplings come with a 1 year / 100 hour warranty.
We have no idea why these couplings have three pairs of rivet holes.
Our Vedeneyev engines were not only used in airplanes. Did a ground-based pumping engine use what we call the "air compressor drive" for a higher shear load accessory that justified multiple rivets in this shear coupling ?
And why are the pairs of holes unequally spaced? Protection against some funky rotation harmonic ?
Perhaps we are just overthinking it.
You can always tell a corny TV science documentary is wrapping up without much of a conclusion when the voiceover drops the hackneyed “while great strides have been made in this area, there is so much researchers STILL do not understand about…”.. or perhaps the deep voiced presenter will go with “what Scientists NOW believe …”
Nevertheless, we’d love to know if you have the answer to any of these shear coupling mysteries. Pick up a pencil ( or keyboard) and drop us a line!
And before we go....We need your cores!!
Don’t let those sheared, unloved couplings sit on your hangar shelf - support on-shoring, support faster deliveries to viewers like you - the Yak community - and cash them in! Call us at 619 933-2571 for details.
If you are buying one, the price shown includes an immediate $35 electronic refund as soon as we receive your sheared core.
John flies out of KSEE whenever he can scrape together a few bucks to fill the tanks