People cryo-freeze their body, hoping to be revived at some later point in time, to achieve immortality. That same concept is now applied to piston engines, for example by Victor Aviation. The goal is not to achieve engine immortality, but longer engine life time. Observed changes include: Stress relieve, increased resistance to abrasion, change in vibrational damping, anecdotal evidence of changes in heat transfer, stabilization of metals to reduce warping under heat, stress, and vibration. That sounds all like music to my ears, but is it true? I have never heard of cryo-feezing an aircraft piston engine until now, and my first thought was that this is all marketing BS. But after digging deeper into it, I am not so sure anymore. The owner of Victor Aviation, Victor Sloan, contributed to Low Temperature Materials Mechanism, and cryogenics appears to be used in car racing.
Some literature and sources:
Cryogenics Explained – Hekimian Racing Engines
Discovery Channel Next Step : Cryogenics!
Aircraft Engine Overhaul – Victor Aviation -
ColdFacts – Magazine of Cryogenetic Society of America
Opinions?
I have no idea how it would benefit as part of the overhaul process.
One thing I did read, was that in Alaska back in the day they didn’t keep aeroplanes in hangars. The aeroplane needed to acclimatise to the cold otherwise everything would break. Things like certain hoses, tires, vapour lines could freeze up and it was very much a part of their maintenance to have the aeroplane adjusted for the cold temperatures.
Imagine lighting a fire under your engine for 4 hours before you could start it…. That was their daily task back in the 50’s. It was cold on a level most of us will never know.
If done immediately after the engine overhaul, when many moving surfaces will be overtight, and rough, what will happen? Have the designers allowed for the differential contraction of dissimilar metals at temperatures far below design storage temp?
I’d suspect results might be highly variable and unpredictable.
Proper cryogenic processing should be a part of the manufacturing process, and it’s not about stress relief – quite the opposite, it’s similar to quenching in that it “strategically disturbs” the metal structure.
should be part of the manufacturing process
But is it?
it’s not about stress relief
That is one out of many advantages claimed, i.e. see two of the sources above
Interesting.
Why is this not widely used?
Obviously one would do individual parts; not the assembled engine.
-184 deg C ! That’s not cheap.
Perhaps this is relevant?
That video is excellent.
One thing which amazes me is the timescales on which this works. Normally, in hardening and subsequent tempering, it is done very fast; generally on a timescale of seconds.
But isn’t there the same tradeoff between toughness and hardness? In piston engines this is normally addressed with case hardening (nitriding) which gives a hard surface. It is possible that what this guy was really doing was trading up the hardness/brittleness scale, and because he had a well controlled tool feed rate the drill didn’t just snap.
I use solid carbide milling cutters and I have some solid carbine twist drills but they are quite delicate.
But isn’t there the same tradeoff between toughness and hardness?
According to the links above and below apparently not.
Harder or Tougher? One common fear is that cryogenic treatment increases the tool’s hardness, which equates to brittleness. Not so, according to Bond.
This process doesn’t make tooling harder,” Bond said. “In fact, some customers request that I raise the tool’s hardness, but I have to turn them away
