Vintage Kollsman Altimeter Repair

[@EdwinSteiner]

It really takes balls of steel to attempt such a repair.

[@harmlesscreationsofthegree1248]

Albeit very small ones

[@Calamity_Jack]

I'm glad he got his ball in there.

[@chaoticsystem2211]

@@harmlesscreationsofthegree1248 it's about density

[@zyeborm]

@@Calamity_Jack two balls, after his first one broke ;-)

[@adrian.parano]

and more balls to place it back to the plane and fly with that repaired instrument 😂

[@orbitingeyes2540]

I worked my way through college in part as a repair technician at Unisys. I once witnessed a FedEx driver loading a shipment of workstation PCBs ($44k each in 1988) by throwing the flat boxes like Frisbees into the truck. When I reported the incident, mgmt was not amused. FedEx had to pay for re-testing and replacement. It cost FedEx several years' salary for that driver, and needless to say, he was no longer employed. We appreciate our delivery drivers, and while accidents do happen, respect and care are a must, and are very much a two-way street!

[@snooks5607]

and these days that's just a standard operating procedure of any courier. if one wants to have their package not kicked around they better deliver it themselves

[@Obladgolated]

Beautifully done! I liked how you just took a moment to enjoy its motion after it was clear that it was actually working again! As you worked on it and described the fine details of its operation, I found myself thinking that - once upon a time - there was undoubtedly a workbench somewhere in the Kollsman factory, possibly in Brooklyn NY, or perhaps in California, and a man who worked every day at that workbench, who could have diagnosed the problem in a few seconds and (probably) repaired it in a few minutes. He would have had containers of tiny parts all around him, carefully organized, and would have known (from long experience) exactly which parts needed to be replaced and which only needed to be cleaned and adjusted. That bench, and that man, are probably long gone. Whoever he was, he had a family, and problems and triumphs of his own, and a background, a life story, and a long history of coming to work every day at his bench. After years of toil, he knew everything that it was possible to know about Kollsman altimiters. His knowledge was very valuable in its time, and kept him employed for many years. Blessed are those who work to decrease the entropy of the world.

[@gvii]

Heh. An incredibly delicate device, yet built robustly enough to survive in an aircraft while getting the snot knocked out of it in turbulence, microbursts, on landing or takeoff. But one trip on a FedEx truck kills it dead. Fortunately, not beyond repair, but still... Good ol' FedEx. What would we do without you. Lol.

[@supercompooper]

fedWrecks

[@aserta]

If they don't steal it, they break it, and if they don't break it and don't steal it, they lose it.

[@marcusdamberger]

FedEx comes into it for sure, but so many sellers have no clue how to pack anything to take the rigors of FedEx. You would think them getting so many complaints and requests for refunds because the item they sent got trashed they would learn the problem isn't always FedEx but their poor packing and little effort in doing so..

[@fastradioburst253]

Wow! This takes me back lots and lots of decades ago when I worked for Kollsman Instruments testing these very instruments. My job specifically was testing and calibrating the "pressure discs" you talk about. It's been so long that I don't even recall what we called them. In fact, I'm kinda triggered right now by even looking at them because that's when some co-worker stole my girl. Worked out okay though, so I guess I'll watch the rest of the video. 😃😃😃

[@prillewitz]

You will need an watchmakers lathe to work on that screw Marc. Another interesting video, thanks! It’s almost midnight here, so I always enjoy when your videos appear!

[@GliderSteve56]

Yes, any competent watchmaker could re-pivot that screw for you

[@CuriousMarc]

Where is Clickspring when you need him!

[@sheerluckholmes5468]

@@CuriousMarc Still in beautiful ☀sunny Cairns.

[@kemi242]

I absolutely love the look of those vintage aircraft instruments from inside and outside.

[@SeanBZA]

You can also make a test port using the good old fashioned method, using a glass manometer tube with a mercury fill, and using the good old fashioned u tube manometer as on the ones I used in the instrument trade.

[@EricJorgensen]

Some of your more hotshot watchmakers can re-pivot a balance in a fraction of the time it takes to turn a new staff. Drill hole, insert carbon steel pin. The pivot screw is big enough that it may be a fairly simple operation to drill an 0.5mm hole in the end of the screw and install a pin in it.

[@jeffhiner]

That may be true, but are they able to reticulate the malleable logarithmic casing in such a way that the two spurving bearings are in a direct line with the panametric fan? Without such a fitment, the ambifacient lunar waneshaft may not effectively prevent side fumbling.

[@bennylloyd-willner9667]

How great to see a situation where tapping on the instrument actually works 😊

[@larryscott3982]

I see that the altimeter is labeled ‘CABIN ALTITUDE’. I believe that for the cabin pressurization system.

[@mikebarushok5361]

Yes, it's for monitoring the cabin pressurization system. As such it probably doesn't have much accuracy above 18,500 feet (iirc).

[@gcewing]

So to test it properly you need to take it to a log cabin in the woods or something like that.

[@Lightning_Mike]

Heh. Poor Marc lost his pressurization at the end there

[@jeffhiner]

No, this is cabin altitude for an unpressurized aircraft. There's no other reason for it to have a Kollsman window for altimeter setting-- cabin altitude in a pressurized aircraft doesn't need to be that precise, so the gauges are smaller and don't have a fine adjustment.

[@gcewing]

But then why bother labelling it "cabin altitude"? Unless you have a VERY unusual aircraft, the cabin is at the same altitude as the rest of the aircraft!

[@draygosmith]

One of the things I admire about you is that you always maintain a positive altitude! :)

[@GordonjSmith1]

My son and I built a watch at home last year (from parts) and this truly reminded me of it! Nice work.

[@Karl-P]

I used to fix this kind of equipment professionally and Heli overhaul service for few years. Those Fancy calibrated units to use for testing its nothing else just a T junction for Atmospheric and Vacum lines that switched over on different pressures, to different barometer .You are good to go with a properly calibrated altimeter. just take into account deviation in between 0-100-300 and every 300m points. if its more than 30m +/- not good if remember correctly. Also You really need that screw to rest on that jewel otherwise deviations will be too great. just because there gears it amplifies everything.

[@DerekHerbst747]

I wouldn't mind owning one of these. I spent 9000 hours as a 747 flight engineer and this would make a great souvenir. I already own a cockpit clock. Mechanical altimeters often include a vibrator device which taps on the case at about 15Hz to make the pointer move smoothly. It might be there, possibly in the bezel, powered by the lighting system. That would make it more accurate.

[@TheJimbodean67]

The fiddly bits are no match for your micro engineering skills! Instruments like that are usually shipped in a triple padded container with shock sensors and hand carried with both hands until installed. At least that’s how we did it in the military. Great job and thank you for sharing.

[@stevedowns5633]

All the pivots in a Kollsman Altimeter are hardened steel shafts. Looks like someone dropped this altimeter and the force broke the pivot off at the tip of the pivot screw. On the sector shaft there is a glass jewel that the pivot goes into. Adding a ball to be the pivot may work but dont expect it to work for long. Also, be carefull changing pressure too quickly or you will damage the instrument. I spent 20 years as an FAA Repairman for Aircraft Instruments and have repaired and calibrated a lot of Kollsman Altimeters.

[@AppliedCryogenics]

Yes! A lazy Sunday with CuriousMarc and Master Ken! And archaic mechanisms! ❤

[@Kevin75668]

You should invest in a Sherline lathe. Makes working with stuff that size a joy, especially with a DRO. I can't count the number of unavailable parts I've repaired or made replacements for with mine. One of my Fluke meters is only still alive today because of it, after breaking the no longer available range switch shaft. Took about 30 minutes to measure up the old one, make a new one, and install it. I wasted at least twice that long trying to find the part for sale.

[@jadney]

Replacing a worn or broken pivot is a common watchmaker's job. They drill a hole in the shaft (in this case, your screw) and insert a short length of the correct diameter of polished music wire, secured with a tiny bit of Loctite. He or she would need the screw and also the jewel to determine the correct diameter of music wire. Of course, if you still have the old broken pivot, that could simply be measured.

[@_a.z]

Wow I bought one off ebay last month and had the same fault! I carefully filed a point on the screw and it works well! I used to own some Texas instruments bourdon tube pressure metres years ago! They are well worth a look out of interest!

[@CuriousMarc]

Actually that is a good idea. Starting from an already machined screw and turning the end is way faster than trying to make the whole screw again. I might give it a try!

[@rhr-p7w]

This is the perfect opportunity for a collaboration with KZbinr Clickspring!

[@justforfunvideohobby]

Decades of machining skill really showing here. Marc only needs a couple of seconds to see something is up.

[@marianaldenhoevel7240]

Watching an altimeter unwind at that impossible rate - even on a bench - makes this pilot's sphincter clinch.

[@BarryRowlingsonBaz]

My ears popped on the way up.

[@raymitchell9736]

That's some very tiny things to work on and your hands are so steady... Wow! I've had the awesome delivery from FedEx as they hucked the package out of the truck onto my front porch... SCORE!!! As I'm sure he said as he gleefully drove off... But the dumb dumb probably didn't notice that I have 4, yes FOUR!!!, video cameras covering my front yard and porch from multiple angles?? Well, I caught the whole thing on video so I don't have to guess how the thing I ordered got broken... LOL.

[@lwilton]

I have a fence on the front of my property with a gate that trivially and obviously can be opened, and has a sign on the outside that says "DELIVERIES: OPEN GATE AND PUT PACKAGE INSIDE. DO NOT THROW OVER GATE!" The video cameras catch FedEx and Amazon just tossing stuff over the 6 foot high fence onto the pavement all the time.

[@raymitchell9736]

@@lwilton I have no fence or gate, simple access just walk up maybe 25 feet from the street and set on porch... too lazy to do that.

[@simontay4851]

Next time you're expecting a delivery and you catch the driver about to throw it over the fence, run out of the gate, grab his head, turn him to the sign and make him read it out loud to you. "WHAT DOES THE SIGN SAY? READ IT OUT LOUD TO ME!" Once he's read it, say to him: "THEN FKIN DO AS IT SAYS, YOU LAZY BASTARD! UNDERSTAND? If i had a high fence and a sign saying not to throw packages over but delivery drivers kept throwing them over anyway, i would be absolutely livid with rage. Fortunately i don't have a fence.

[@radarmusen]

Nice mechanics, sometimes there is a vibrator for smooth movements. (a automatic finger tapper)

[@TheEmbeddedHobbyist]

I can remember being told that the VSI was an instrument that's not needed much so in the event of a blocked static port. you would break the VSI glass to let the cockpit air pressure supply the static system. never got to break one to find out if it worked. 🙂

[@howardrowland6371]

I remember the same instructions from my flight instructor back in the 80s. I bought a used 1971 Cessna 172 in 1989, it had a knob that you could pull to vent the static system to the cabin in case the static port became blocked or iced. Never had to use it!

[@freednighthawk]

Honestly, I would mark the case as not flight worthy. You never know where something might end up.

[@MarcelHuguenin]

You have amazing skills and endurance Marc. I think this is an awesome repair. In the mean time it is fantastic to see how the diagram I knew for a long time is translated to the real deal and you showed it perfectly up to the nitty gritty parts that matter. Thank you for another great video!

[@davewright3088]

Well done..! A simple homemade Mercury manometer will give you a primary reference standard for pressure calibration. It will be as accurate and precise as your measurement of column height and temperature. Yes, be careful with Mercury. But, you know how to do that...

[@CuriousMarc]

I know. I need to drink the mercury shaken, not stirred.

[@Allan_aka_RocKITEman]

FWIW: Regarding that sea-level pressure adjustment Marc mentions, made to an altimeter when on the ground, in the USA it is calibrated in inches of mercury {i.e., Imperial units}. Example: *_"29.92,"_* which is called 'standard day conditions'. In other parts of the world, millibars are used. I THINK *_"1014"_* is the standard day reference in metric units.

[@Blade-420]

I have always wondered how an Altimeter works mechanically. very interesting innards, I imagine that if any adjustments / calibrations were needed when this was in service, they would be extremely Fiddly. thank you for posting 😃

[@johncloar1692]

If it is a pivot screw you may get a clock maker to repair or make one for you... Just a though.

[@jw0stephens]

My dad fixed an Altimeter which was the atmospheric pressure type. He had to fab up a staff on his lathe. He was a very experienced watchmaker but had wanted to work on instruments in the Navy. However there were no positions at that time, and he went to mechanic school. Later watchmaker's school in late 40's. So this was a taste of what he wanted to do.

[@douro20]

I wish old GE "Selsyn" motors weren't so expensive on the surplus market. They're used a lot in heavy industry to transmit the position of valves or gates.

[@QuintinMassey]

Well done!! I thought it was a goner but you got it! 👏

[@cvkline]

I'll have to show this video to my flight students. It's the next best thing to taking one apart themselves!

[@thesteelrodent1796]

Someone clearly didn't follow the shipping instructions that are printed on the side of the altimeter itself. Although you got it to work, more or less, I believe for longterm use it's better to get that pivot done correctly. Ball bearing joints are not really used in clock-like mechanisms, even today - it's very difficult to make a ball joint move accurately enough

[@ludmilascoles1195]

Well more like 'Ace Watch Repair' than vintage electronics but nice example of a true analog instrument. My first guess was a broken pivot so I guess I did learn something from all those hours hanging out with my dad in the hanger where he keep his Cessna. Especially when he scolded me about touching the altimeter because I will break the pivot

[@Ranger_Kevin]

The mechanism is surprisingly simple (although very delicate).

[@Damien.D]

Really nice job, with all the required perseverance and even taping on it at the end. The downside is that you made the FedEx gods very angry....

[@tekvax01]

Marc, maybe a watchmaker could source the parts for you. Another very excellent repair.

[@michaelcox436]

Hey I've got one of those Geiger counters. Very cool.

[@markr.1984]

You adjusted the Kollsman window to the correct local pressure but you should have also pre-positioned the hands to the of the elevation of your workshop. If you shop is at exact sea level then you're okay. But other than that it's not going to show the correct elevation altitude.

[@jbtoby8585]

Your emco lathe is stamping its feet in the corner....turn a new pivot 0:11 screw out of silver steel....harden and lap the tip...great content..

[@wolvesone]

I have the baby sister of that geiger counter the gmc500+ which I moded with an lnd712 tube so it can get alpha beta and gamma works great

[@KeritechElectronics]

FedEx: Dislodging pivots and botching instruments since I don't know when. Nice fix of a lovely instrument. Those teeny tiny balls... and flying high on a vacuum pump, haha!

[@ifitsrusteditsmine]

This guy is the Michelangelo of the screwdriver

[@Enjoymentboy]

I came for the electronics but stayed for the clockworks.

[@mrluckyuncle]

Cool. I was wondering how you were going to deal with providing test inputs for air pressure, etc.

[@Sean006]

Marc's tiny balls of steel saved the day. 👍

[@lwilton]

Now you just need to put it and the other altimeter in parallel and see if they even slightly agree. 🙂

[@zyeborm]

honestly I was pretty surprised he didn't. Bet we get to see it in the next video though

[@ropersonline]

That thumbnail caption = Bob the Builder vibes.

[@andreas9238]

Good to see you using a geiger on those instruments. Better safe than sorry.

[@RingingResonance]

yeah got to watch out for the ones that use radium paint for their dial faces! I have one in my garage. Fun to show people with the old geiger counter. I don't keep them inside even if it's far away. Radium decomposes into radon gas. Typically the radium has burned the paint so badly that it appears very yellow/brown in color and no longer glows on it's own. Sometimes you can make it glow a little if you shine some UV light on it. If it were radium, it would trigger your counter through the glass, and without the glass it's about like having a chest X-ray every hour of direct and close exposure.

[@parkerlreed]

I feel like at that small of a concentration on the hands it wouldn't be an issue. Is it really a concern in that case?

[@RingingResonance]

@@parkerlreed If you have it right up to your skin for more than a few minutes, or on your bed side table while you sleep there for weeks on end, or in the same room you work or sleep in for the next 10 years, and that's all with the glass in place. Oh, and when I measured mine, it was missing it's dial face. It only has it's hands and the word 'Altimeter' markings. No idea what happened to the dial face as it was missing when I acquired it. I can imagine a complete unit would read much higher than mine; which is where I got the approximate 'chest X-Ray equivalent' calculation from.

[@kevincoulombe6742]

NIce Job Marc!

[@rsmrsm2000]

Amazing

[@leonerduk]

I will never tire of listening to a French person saying the word "Pitot"

[@skizzofly]

Great Job!!

[@agranero6]

Wow it was expecting electronics and it is an aneroid pressure sensor. Coolest yet.

[@crono331]

I have an electric artificial horizon off a jet fighter. It works but it drifts. If you want to have a go, ill send it over.

[@OmegaSparky]

I have a broken altimeter with the same exact problem identified at @11:00.

[@SLYKER001]

Russian Post uses similar legendary extra careful methods to deliver things :D

[@markmuir7338]

That's an amazing rate of climb! Your workshop must be on Starship! 😅

[@Blade-420]

and when he released the pressure, I was Imagining someone on the radio yelling "Your descending too fast! Pull your nose up! PULL YOUR NOSE UP!"

[@wtmayhew]

The broken instrument with the TWA property tag on it appears to be a Cabin Differential Pressure Gauge, possibly intended for monitoring the effective elevation above ground pressure equivalent inside an aircraft. Commercial passenger aircraft are typically pressurized to about 6,000 feet in the cabin. I’m not sure such a gauge is intended to indicate all the up to the ~30,000 feet it received on the post-repair trial.

[@jadney]

I once flew overseas with a coworker who had an altimeter on his watch. We watched to see how "high" the cabin pressure went. It topped off at 10,000 ft.

[@mikebarushok5361]

A cabin differential pressure gauge is a different instrument.

[@wtmayhew]

@@jadney Wow, 10,000 feet is some pretty thin air. It was quite a few years ago, but I believe it was a Delta in-flight magazine where I picked up the number 6,000. 10,000 would save the airline money, but it doesn’t sound good for people with medical issues of the lungs.

[@wtmayhew]

@@mikebarushok5361 The guts look like an altimeter, but the dial is labeled cabin altitude. I looked up, but admittedly not exhaustively, Kollsman instruments and didn’t se one exactly like the one in the video.

[@mikebarushok5361]

@@wtmayhew Yes, it is labeled cabin altitude and measures pressure altitude corrected for local barometer. It has one port. If that port is open to the cabin pressure it measures cabin altitude, but if you ran a line from the instrument's port to a static pressure port you would be measuring the same thing as any altimeter. A cabin differential pressure gauge conceptually measures the difference between the cabin pressure and the outside pressure and therefore has two ports. An unpressurized airplane or a glider or open gondola hot air balloon would be examples of where the cabin altitude and vehicle altitude are the same barring ram air effects or Bernoulli's law effects and should always have zero cabin differential pressure, but would have cabin altitude increasing with height. Not that it has any bearing on the nomenclature, but I did work for Kollsman assembling and testing instruments including altimeters, air speed indicators mainly.

[@FaithyJo]

Because of course one of you would have a Geiger counter at hand!

[@ShainAndrews]

Solder... maybe silver solder is more than sufficient to retain your the ball on the end of the screw for your application.

[@spacemanmat]

Pretty sure that cavity in the broken screw isn’t going to be perfectly concentric not surprised it’s not running smoothly.

[@aamiddel8646]

Nice to use a manual shaker...

[@gower1973]

I still don’t get how the linear movement of the aneroid plates expanding gets converted into the rotation though?

[@bigsarge2085]

👍

[@sgtellioman]

I have a gyro from a Huey Helicopter that needs some love

[@ianeyolfson6525]

Good enough for me too

[@electrofan7180]

I'm sure any watchmaker can repair it with no problems.

[@zebo-the-fat]

How do they make those tiny steel balls???

[@oldavguywholovesRCA]

That pivot screw could probably be duplicated by a watch maker or watch repair person. Who knows.

[@aserta]

You can work on it even if it's radium. Just don't scrape it, don't chew on it like the end of a pen and don't place it inside your glass of water for sudden vigor and vitality.

[@FourthWayRanch]

probably not good to spin it so fast with the vaccuum application, maybe put a restriction in the vac line

[@CaptainRon1913]

Thats exactly how Fedex would deliver my packages. Drive up the driveway, throw them out the window onto the gravel driveway, and leave. They did that with a new laptop computer one time. It sat in the pouring rain for 4 or 5 hours before I got home. Fedex drivers were too fkng lazy to walk 30 feet to my covered front porch.

[@Allan_aka_RocKITEman]

*_"...and the legendary extra careful_** FedEx **_handling..."_* 🤭🤭🤭🤭🤭🤭🤭

[@Allan_aka_RocKITEman]

Starting at about 15:20 in this video: Marc _getting high_ for YT views...😉

[@fragdude]

Couldn’t you have drilled a little dimple into the “set screw” to cradle the ball better?

[@CuriousMarc]

Could certainly have been worth a try!

[@jaysonpida5379]

Wow...to do that damage someone hit it with a baseball bat or dropped it from a roof. Very surprised the glass wasn't shattered. Someone at FedEx doesn't like altimeters ;)

[@jensschroder8214]

amazing

[@Dsschuh]

I went to look for parts one and two and cannot find anything with a similar title…

[@CuriousMarc]

That would be this playlist: kzbin.info/aero/PL-_93BVApb59k-GD2e83E6prrhm5fobtV

[@danielepatane3841]

You may try to put a minuscule drop of cyanoacrylate in between the screw and the ball before tighten it? would it works?

[@ShainAndrews]

Please don't....

[@danielepatane3841]

@@ShainAndrews is silver soldering a minuscule ball on top of a minuscule screw safer than a tiny drop of cyanoacrilate? . Just to let you know cyano can be safely removed with a bit of heat (less than 200 degrees Celsius) whereas silver soldering a screw like that can potentially destroy it because of heat. Considering also that when you heat a piece of metal it will oxidize very fast so that minuscule thread will be gone forever.

[@oetken007]

I would not put my ball in there.😂

[@codertao]

... that is a concerning rate of climb...

[@trex70]

29.92 inHg is normal Pressure

[@NoEngine]

Sounded to me like the aneroid popped during the first vacuum pump run - I test altimeter with hand pump only so it was fun watching it done by machine

[@viperwizard491]

I guess that amount of radium is not dangerous unless you eat it or inhale. smoke alarms emit radiation at much higher levels

[@bradnelson3595]

I thought the shtick from Jim Carrey posing as the delivery guy in Pet Detective was hilarious, and likely over the top, of course. But maybe not.

[@lukemaney645]

No wonder so many planes have crashed through the years with fragile instruments like this altimeter to read altitude? One good bump and the whole thing is outta wack. I think I will stay off of aircraft and just stick to my trusty old pickup for travelling.

[@sweetpeaz61]

just macine a point on the screw you have

[@phatcowboy76]

Or if the ball would be temperature stable enough to not change at altitude. Also the circular watch spring could also be a temperature compensation for mechanical growth or shrinkage of metallic pieces moving with the bellows or diaphragms (aneroid capsules).

[@MoritzvonSchweinitz]

How would these precision mechanical instruments work in an old jet fighter, which might be subject to significant G loads?

[@stargazer7644]

They worked just fine for decades.

[@MoritzvonSchweinitz]

@@stargazer7644 yes, but how? Unless everything is perfectly weight balanced in all possible axis, G forces should affect these instruments!

[@stargazer7644]

@@MoritzvonSchweinitz If they work correctly at 1G, they'll also work correctly at 9G. It's not like these are pendulum clocks and have anything in them that depend on the value of G.

[@74HC138]

They work fine with the G loads, at least any G load a pilot could tolerate. What they don't tolerate are sudden shocks - falling to a hard surface makes a momentary shock well in excess of what any aircraft would ever experience while remaining in one piece. It's not so much about magnitude of forces but the rate in change of forces that will break an instrument. A fighter pulling 9.5G will go from 1G to 9.5G slowly and smoothly. An instrument falling to the ground will go from 0G to 200G and back to 1G in a few milliseconds when the unyielding metal instrument case it hits the unyielding concrete. The forces it will feel will be more like catastrophic air crash forces rather than flying forces.

[@jimballantine4408]

I would not be surprised if this was a scrap item. Could be crash recovered or might have suffered a 'rapid vacuum loss event' during testing 😂. Thing is on a serious note some cheeky monkies 'fix' these things and sell them on as genuine parts. With forged paper work they can be worth many many times what you got it off Ebay for see 'The problem of bogus parts' by the UK CAA to get an idea of why repairs of a non approved standard are a nightmare for commercial aviation. Anyone minded to fiddle with units that can still be found in operating aircraft please please make sure you never let it loose back into the wild!!! You may be acting on good intentions but the people who say may take it off your hands maybe are not so honourable.

[@johnmf6096]

A bad ebay shipper? Imagine my shock.

[@Rosseloh]

A cabin altitude gauge with a 50,000 foot needle? What in the heck? I guess if it was from a *really* high performance test plane intended to go above 100k it would sort of make sense......Airliners (which is what I'm familiar with) tend to not have cabin altitudes above 10,000 - most of the ones I know, alarms will start going off at 10k, and once you hit 14,000 is when the oxygen masks automatically drop.

[@wgmskiing]

This is a very old instrument from before certain improvements were made to the three handed designs. Airliners have pressurization failures and it is important to know if the cabin altitude is at say 14500 feet (you can legally operate without oxygen for the passengers) or 22,000 feet. I suspect this would have been at a flight engineer's station. Most aircraft post WWII had differential pressure gauges for the cabin altitude, showing both the cabin altitude and the differential pressure vs the aircraft altitude on one instrument.

[@Rosseloh]

@@wgmskiing Yes, all of this I know - apart from how old this specific unit is, of course. I agree that this is probably off an engineer's panel.

[@74HC138]

It's probably a bog standard altimeter with the words "cabin altitude" printed on the face instead of just "altitude". Cheaper/easier than designing a whole new instrument - just use a regular altimeter and change what's written on the face.

[@Rosseloh]

@@74HC138 You're probably right - at first I was trying to think of why that would matter, but yeah, if it was a standard low-res altimeter for a high performance plane (hence having a 50,000 foot scale), just slap Cabin on it and call it a day (you don't necessarily care about the hundreds when you're dealing with pressurization...I mean, you do, but you can get sufficient resolution there just by looking at where the thousands needle is). On the other hand, all it takes to change the needle resolution is different gear ratios, so IDK. For a modern commercial jet, sure, there's a lot of regulatory specs they'd need to hit which makes the design process more involved, but for something this old in what I assume was a military plane? I'm not sure... Just guessing, don't take any of this as fact.

[@camhyde9701]

maybe get a watchmaker to have a look at replacing the bearing? very upsetting fedex footage... puzzled how you are using a compressor to test it... i would have through you would need vacuum not compression

[@bichela]

He is using vacuum pump

[@camhyde9701]

@@bichela Yes however he said 'compressor'... i was teasing