Did altitude just blow out 2 MPS's?, Put the in my checked baggage...now won't hold vac. Options

[JeffBowlsby]

With nothing else to do on this front, I decided to see if I could improve the MPS that I put back together recently. It was leaking down vacuum a little faster than I liked.

First task was to dismantle the one that would not hold ANY vac. See the pic. I'm pretty sure the diaphragm had a leak. (IMG:style_emoticons/default/lol-2.gif)

So after Frankensteining the two and using what I thought was the best parts, I ended up with an MPS that holds solid vacuum and is calibrated to factory specs. I know it will still need adjustment but this is a really solid (re)starting point going ahead.

Couldn't have done it without the VAST knowledge and skills on this board - big thanks.

Was this one of the damaged diaphragms from the plane ride?

[FlacaProductions]

It was. This one obviously bad. Came out of the unit just like that - in two pieces.
Other diaphragm is ok but ended up that the case and or main o ring seal was not totally sealing.

New combo of parts yielded a well sealed, well bench-adjusted unit.

I’ll see if a new diaphragm yields a second working unit when they become available again.

[emerygt350]

What does the curve look like?

[FlacaProductions]

I've set it at
0hg:1.47h
4hg: 1.11h
15hg: .75h

Should I plot more?

[JeffBowlsby]

It was. This one obviously bad. Came out of the unit just like that - in two pieces.
Other diaphragm is ok but ended up that the case and or main o ring seal was not totally sealing.

Wow. Looks to me that the aneroid cell expanded, which displaced both the plunger on both the diaphragm and the coil, resulting in the failed diaphragm from excessive deflection.

[Superhawk996]

Very common failure mode for the diaphragm to split into two pieces like that.

[emerygt350]

I've set it at
0hg:1.47h
4hg: 1.11h
15hg: .75h

Should I plot more?

Yeah, do a measure for every 1 hg change.

[wonkipop]

It was. This one obviously bad. Came out of the unit just like that - in two pieces.
Other diaphragm is ok but ended up that the case and or main o ring seal was not totally sealing.

Wow. Looks to me that the aneroid cell expanded, which displaced both the plunger on both the diaphragm and the coil, resulting in the failed diaphragm from excessive deflection.

don't have D Jet, but this has been a fascinating topic to read.
seeing inside these amazing little devices from early days of tech.

i wonder if its not a case of excessive deflection so much as two devices,
though initially working, nevertheless worn and aged. the diaphrams having been through many cycles along with the aneroid chambers and then this flight happened to take them sufficiently up range that at least one of the devices finally reached its "worn" breakage point.

im looking at cabin pressure which is cargo hold pressure. thats usually 8,000 ft above sea level as the upper limit. often a bit lower than that. can be somewhere between 6,600 and 8,000 depending on the plane, route etc. but 8,000 is the usual.

and quick google says highest paved road in europe is just over 9,000 ft and highest in USA is 14,266 ft. (14,000 ft is pretty high too for your average person, you would feel that, but apparently you folks have a paved road that high up. (IMG:style_emoticons/default/biggrin.gif) )

fair to say that when new units probably designed to reach this limit with diaphrams and aneroid chambers etc with maybe a small engineering safety factor.

but everything changes as the units age. repeated cycling would gradually reduce the flexibility limits for the items.

i think what has happened here is one of those units was sufficiently at the point of age and use that taking it to 5,000 - 8,000 ft was enough to hit that limit and it cracked the diaphram. same thing would probably have happened if you drove it up to 8,000 feet on a mountain road. would have failed? probably could have pottered around at sea level or lower altitude for a bit longer in time as it was not stretched so far. but ultimately as time went on the limit of its movement would have continued to diminish and it would have failed at some point in the near future.

transporting these now very aged units even in cabin luggage would not make a difference. the whole plane is pressurized equally and temps are also maintained in the cargo holds to something close to cabin temps. there are often animals down there being transported so it does not get too cold.

i think thats what has happened here. the stress limit for an aged unit was found at 8,000 feet above sea level atm pressure. a brand new unit back in the day probably could survive much higher altitude - lower atm pressure.

[wonkipop]

double post delete.

[FlacaProductions]

so here's the next, obvious question then: how do I get them back?!

Should I dismantle them (the good one, anyway at this point) and take the diaphragm out so that it's not subjected to any pressures?

[Superhawk996]

You all lost me - the only take a way I got was that nothing was damaged by altitude. (IMG:style_emoticons/default/idea.gif)

[windforfun]

so here's the next, obvious question then: how do I get them back?!

Should I dismantle them (the good one, anyway at this point) and take the diaphragm out so that it's not subjected to any pressures?

At this point... Fuck it. Buy what you need from George at AA. IMO, the objective here is to get the car back on the road & have fun. Not all problems can be solved. But some extra cash can sure help.

(IMG:style_emoticons/default/beer3.gif) (IMG:style_emoticons/default/beer3.gif) (IMG:style_emoticons/default/beer3.gif)

[ctc911ctc]

Earlier in this thread I took the same path and though I have a great deal of experience with these devices I forgot a crucial fact. If both ports are open there is no pressure differential. Meaning; both sides of the diaphragm are exposed to the same pressure.

Soooo, though intriguing and I agree with everything you wrote (almost my words to a "T"), we both got snookered with the idea of an airplane being involved.

It was. This one obviously bad. Came out of the unit just like that - in two pieces.
Other diaphragm is ok but ended up that the case and or main o ring seal was not totally sealing.

Wow. Looks to me that the aneroid cell expanded, which displaced both the plunger on both the diaphragm and the coil, resulting in the failed diaphragm from excessive deflection.

don't have D Jet, but this has been a fascinating topic to read.
seeing inside these amazing little devices from early days of tech.

i wonder if its not a case of excessive deflection so much as two devices,
though initially working, nevertheless worn and aged. the diaphrams having been through many cycles along with the aneroid chambers and then this flight happened to take them sufficiently up range that at least one of the devices finally reached its "worn" breakage point.

im looking at cabin pressure which is cargo hold pressure. thats usually 8,000 ft above sea level as the upper limit. often a bit lower than that. can be somewhere between 6,600 and 8,000 depending on the plane, route etc. but 8,000 is the usual.

and quick google says highest paved road in europe is just over 9,000 ft and highest in USA is 14,266 ft. (14,000 ft is pretty high too for your average person, you would feel that, but apparently you folks have a paved road that high up. (IMG:style_emoticons/default/biggrin.gif) )

fair to say that when new units probably designed to reach this limit with diaphrams and aneroid chambers etc with maybe a small engineering safety factor.

but everything changes as the units age. repeated cycling would gradually reduce the flexibility limits for the items.

i think what has happened here is one of those units was sufficiently at the point of age and use that taking it to 5,000 - 8,000 ft was enough to hit that limit and it cracked the diaphram. same thing would probably have happened if you drove it up to 8,000 feet on a mountain road. would have failed? probably could have pottered around at sea level or lower altitude for a bit longer in time as it was not stretched so far. but ultimately as time went on the limit of its movement would have continued to diminish and it would have failed at some point in the near future.

transporting these now very aged units even in cabin luggage would not make a difference. the whole plane is pressurized equally and temps are also maintained in the cargo holds to something close to cabin temps. there are often animals down there being transported so it does not get too cold.

i think thats what has happened here. the stress limit for an aged unit was found at 8,000 feet above sea level atm pressure. a brand new unit back in the day probably could survive much higher altitude - lower atm pressure.

[emerygt350]

so here's the next, obvious question then: how do I get them back?!

Should I dismantle them (the good one, anyway at this point) and take the diaphragm out so that it's not subjected to any pressures?

I would probably disassemble just to be safe.

[FlacaProductions]

Well, the airplane ride was key as that's what got the units to an altitude (real or contrived via cabin pressurization) where at least one of the diaphragms failed.

The other....again, I think the relatively pressure of the pressurized cabin caused it to perform at less than optimal levels.

It COULD have been a result of physical abuse when the bag was thrown around but - and I guess all that really matters is - I'm back to good on one unit and awaiting the production of new diaphragms to bring the 2nd unit back.

I'm just trying to avoid damaging any more units.

I guess I'll just carry them on and hope for the best. (what's funny is, both of those units were shipped to me in the recent past but apparently this trip was a bridge too far)

oh - and I'm fine with buying a refurbished units - i've looked into it - but I can say it most likely won't be from AA. But that's another conversation that's already been beaten to death here. Part of the fun for me is the problem-solving.

[wonkipop]

You all lost me - the only take a way I got was that nothing was damaged by altitude. (IMG:style_emoticons/default/idea.gif)

well. altitude was the trigger for an old but still functioning unit at sea level or thereabout to finally fail. a bit of both really.

i see two parts which have to gradually degrade with time and use.

a membrane. eventually loses its flexibility by small degrees with cycling and with material degradation.

an an aneroid chamber which is i understand an accordian folded metal chamber with a vacuum inside. although maybe i am misunderstanding that particular part. never seen one, not a D Jet man. but if it is what i have said it is, those folds must gradually become less and less firm over time as the chamber cycles and weaken. the chamber would naturally begin to extend/expand further than its initial design parameters when manufactured.

put both together, a chamber that extends more than it did when new and a membrane that degrades with age and use and at some point a limit of extension is reached.

i think its amazing the devices have gotten to this point in time.
half a century. bosch would never have imagined them going this long.
testament to the german engineering standards at that time.

if i was travelling in a plane to transport them at this point in time, i probably would dismantle them. at least they won't fail due to "over-extension". it extends the borrowed time i imagine all such original units are now finally in.

[wonkipop]

Earlier in this thread I took the same path and though I have a great deal of experience with these devices I forgot a crucial fact. If both ports are open there is no pressure differential. Meaning; both sides of the diaphragm are exposed to the same pressure.

Soooo, though intriguing and I agree with everything you wrote (almost my words to a "T"), we both got snookered with the idea of an airplane being involved.

It was. This one obviously bad. Came out of the unit just like that - in two pieces.
Other diaphragm is ok but ended up that the case and or main o ring seal was not totally sealing.

Wow. Looks to me that the aneroid cell expanded, which displaced both the plunger on both the diaphragm and the coil, resulting in the failed diaphragm from excessive deflection.

don't have D Jet, but this has been a fascinating topic to read.
seeing inside these amazing little devices from early days of tech.

i wonder if its not a case of excessive deflection so much as two devices,
though initially working, nevertheless worn and aged. the diaphrams having been through many cycles along with the aneroid chambers and then this flight happened to take them sufficiently up range that at least one of the devices finally reached its "worn" breakage point.

im looking at cabin pressure which is cargo hold pressure. thats usually 8,000 ft above sea level as the upper limit. often a bit lower than that. can be somewhere between 6,600 and 8,000 depending on the plane, route etc. but 8,000 is the usual.

and quick google says highest paved road in europe is just over 9,000 ft and highest in USA is 14,266 ft. (14,000 ft is pretty high too for your average person, you would feel that, but apparently you folks have a paved road that high up. (IMG:style_emoticons/default/biggrin.gif) )

fair to say that when new units probably designed to reach this limit with diaphrams and aneroid chambers etc with maybe a small engineering safety factor.

but everything changes as the units age. repeated cycling would gradually reduce the flexibility limits for the items.

i think what has happened here is one of those units was sufficiently at the point of age and use that taking it to 5,000 - 8,000 ft was enough to hit that limit and it cracked the diaphram. same thing would probably have happened if you drove it up to 8,000 feet on a mountain road. would have failed? probably could have pottered around at sea level or lower altitude for a bit longer in time as it was not stretched so far. but ultimately as time went on the limit of its movement would have continued to diminish and it would have failed at some point in the near future.

transporting these now very aged units even in cabin luggage would not make a difference. the whole plane is pressurized equally and temps are also maintained in the cargo holds to something close to cabin temps. there are often animals down there being transported so it does not get too cold.

i think thats what has happened here. the stress limit for an aged unit was found at 8,000 feet above sea level atm pressure. a brand new unit back in the day probably could survive much higher altitude - lower atm pressure.

i might be wrong about this.
(IMG:style_emoticons/default/biggrin.gif)
possibly will be wrong not being a D jet man.

but the aneroid chamber will expand?
its barometric.
thats the bit i am thinking about.
and i'm thinking that is coupled with it degrading as a device with cycles and ageing.
the folds in the accordian like construction (if i have that bit right?).
so its the bit that over extends due to lower atm pressure.
and it does not matter if the pressure is all atm or lower atm pressure both sides of the device, its that the lower atm pressure causes the aneroid chamber to activate.
and it is what damages the membrane.
---
but i could be completely arse about on that and not really understanding the device properly.
just a suggestion really for you experts to dismiss or consider. (IMG:style_emoticons/default/beerchug.gif)

[wonkipop]

I guess I'll just carry them on and hope for the best. (what's funny is, both of those units were shipped to me in the recent past but apparently this trip was a bridge too far)

Part of the fun for me is the problem-solving.

yes, thats not an unreasonable thought.
they probably spent most of their lives operating or being stored at low altitude, far closer to sea level.
and survived one shipping, but were stressed by that.
and the second exercise took at least one of them past the point of no return.

problem solving is fun -- but also makes you not make the same mistake twice.
you know something happened to them as a result of that plane flight.
it may be hard to assertain for sure exactly what it was.
but it was something to do with the flight.

[JeffBowlsby]

Google this:

Does an aneroid cell expand when ambient pressure drops?

[Superhawk996]

Ya all smoking the crack (IMG:style_emoticons/default/smoke.gif)

Anders has tested & shown the growth of the android cell is 2.5mm at 15” Hg of Vacuum. 2.5mm =0.0984 in. And that’s with 15” of VACUUM guys.


https://members.rennlist.com/pbanders/manif...sure_sensor.htm

Even at top of Pikes Peak (14,115’) I assure you there is still positive atmospheric pressure. I’ve been there, survived, and can confirm there is no vacuum there. (IMG:style_emoticons/default/beerchug.gif) Translation: even at top of Pikes Peak there is positive atmospheric pressure and the expansion of the aneroid chamber will be far less than 2.5mm. A trivial amount.


Note: 100 kPa at sea level = 29.53” Hg of positive atmospheric pressure.

The atmospheric pressure of an airline cabin as discussed is 8000 feet or so and again is more positive atmospheric pressure (not vacuum) than you would experience in the parking lot at the top of Pikes Peak.

The vacuum the engine develops against a closed throttle idling is 15” Hg or more. The stress and growth of the aneroid cell in a plane cabin that has positive atmospheric pressure is trivial compared to what it experiences when it is exposed to 15” Hg of manifold vacuum.

Let’s not be creating new mythology of blowing out & damaging MPS’s from plane transport.

To quote the White Stripes: “you just can't take the effect and make it the cause”.

https://www.youtube.com/watch?v=STSkGSTMr9Y?si=TVblQRUKQltEj7gq