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

[FlacaProductions]

Brought two of my 3 MPS back to L.A. from Indiana while I await the arrival of my LCR55A so that I could do some bench plotting and tuning only to find that neither one of the now holds any sort of a vacuum.

Both ran fine in the car before flight - just needed some adjustment. One has the factory plug replaced with a Tangerine model - the other is still factory sealed.

Did being in the unpressurized cargo area in my checked baggage blow them both?

That would really stink....

Brian

[flipb]

The cargo hold in modern jets is pressurized. The round shape of the fuselage makes for a strong pressure vessel (vs a semi-circle if if was just the passenger compartment).

Could've been damaged in transit though. And most jets are pressurized to the equivalent of being at ~8000ft altitude, so I guess that could've been enough to damage them?

[FlacaProductions]

They were well packed and padded.
F me.

[ctc911ctc]

Considering that the ALPS and the Rockies were thought about in 1966-67 when Bosch was engineering that device, I would think that it would be good to 10,000 ft. AT LEAST. Add in the 100% German engineering user-error allotment and...........

If the cabin altitude was a little higher than that you would be offered oxygen.

I doubt the shock (Physical) would cause them to fail.

A sudden differential 10K to 2K cabin altitude in a minute or two may have an effect? (IMG:style_emoticons/default/confused24.gif)

This is an interesting issue - I would - if I were you - double check the test performed after the flight - perhaps it was an error within the experiment?

Good luck with this one - CTC

[FlacaProductions]

I just put two vacuum pumps on each one here in LA.
ZIP.
there is only one way to do this test, right?

Plug the hose on the nipple. Pull vac.
Done.

I don’t get it. They were both in the car on Friday.
I didn’t pull a vac there but the fact that the car ran and ran fine should be enough. Only reason I’m messing w them is to get the highway cruise temps down via my wide band. Was bringing them here to plot them w the LCR I just bought off of eBay that hasn’t even landed yet.

[emerygt350]

Considering that the ALPS and the Rockies were thought about in 1966-67 when Bosch was engineering that device, I would think that it would be good to 10,000 ft. AT LEAST. Add in the 100% German engineering user-error allotment and...........

If the cabin altitude was a little higher than that you would be offered oxygen.

I doubt the shock (Physical) would cause them to fail.

A sudden differential 10K to 2K cabin altitude in a minute or two may have an effect? (IMG:style_emoticons/default/confused24.gif)

This is an interesting issue - I would - if I were you - double check the test performed after the flight - perhaps it was an error within the experiment?

Good luck with this one - CTC

I think the danger would have been in the expansion of the cell rather than any stress on the diaphragm like part that normally breaks due to use/too much vacuum.

Well, you can pull apart the one with the tangerine mod and see what is up.

[FlacaProductions]

This might have just been a bridge too far for me.

[ctc911ctc]

Thinking back I broke one by selecting PRESSURE rather than VACUUM on my hand pump and it did not take much to break the diaphragm - perhaps 5lbs. Of course it was one that I had just purchased and was "new" (looking), I replaced the diaphragm and it worked great and is still working great.

Considering that the ALPS and the Rockies were thought about in 1966-67 when Bosch was engineering that device, I would think that it would be good to 10,000 ft. AT LEAST. Add in the 100% German engineering user-error allotment and...........

If the cabin altitude was a little higher than that you would be offered oxygen.

I doubt the shock (Physical) would cause them to fail.

A sudden differential 10K to 2K cabin altitude in a minute or two may have an effect? (IMG:style_emoticons/default/confused24.gif)

This is an interesting issue - I would - if I were you - double check the test performed after the flight - perhaps it was an error within the experiment?

Good luck with this one - CTC

I think the danger would have been in the expansion of the cell rather than any stress on the diaphragm like part that normally breaks due to use/too much vacuum.

Well, you can pull apart the one with the tangerine mod and see what is up.

[FlacaProductions]

that's the thing. no more diaphragms.

[ctc911ctc]

[/quote]

I think the danger would have been in the expansion of the cell rather than any stress on the diaphragm like part that normally breaks due to use/too much vacuum.

Well, you can pull apart the one with the tangerine mod and see what is up.
[/quote]


If the MPS was in a 10,000 cabin and then both sides of the diaphragm were then at 10,000ft, ( after a few hours of flight) the decent would look like pressure on the diaphragm - this would not be a good thing.

HOWEVER

If the two sides can normalize (establish the same pressure over time) this would not be a good thing........not sure what happened - please let us know.

[burlybryan]

Your bag wasn't searched and the MPS's "probed"? There is enough of a pressure difference in flight to have fluids squeeze out (and beer corks pop...ask me how I know), so it's certainly possible. That said, don't these just have a membrane that is not sealed like a pressure vessel, so there's really no ambient force to act on them?

[ChrisFoley]

Here's what I thought of:
The reduced atmospheric pressure resulted in expansion of the aneroid cell, which pushed the diaphragm outward, like happens during use on overrun, but with more force.

More than likely the diaphragms were close to failure already. They almost always fail at the edge of the supported perimeter area because the casting has a sharp corner there.

[emerygt350]

The whole thing is a sealed area. Two forms of movement, expansion and contraction of the diaphragm itself, and the vacuum driven movement of the whole thing.

[ChrisFoley]

The whole thing is a sealed area. Two forms of movement, expansion and contraction of the diaphragm itself, and the vacuum driven movement of the whole thing.

Both sides are open to atmosphere when it isn't connected.
The diaphragm doesn't either expand or contract. It simply flexes.
Once the diaphragm is against the part load stop, it doesn't move any further. All the additional movement comes from the aneroid cell expanding.

[FlacaProductions]

I’ll crack the unsealed one asap and report back.

[Spoke]

The MPS senses the difference in pressure from ambient to the intake (inside cavity) pressure. It seems if the pressure port is open then should be no pressure difference between the inside cavity and the ambient pressure.

[emerygt350]

The diaphragm itself is a sealed vessel. Containing a specific gas which expands and contracts at a given pressure. The other form of movement is from the entire sealed vessel moving within the mps, this is what most of you guys are referring to and is where the cracking comes in. Although the sealed vessel can fail, it isn't as common.

[FlacaProductions]

Here's the pics.
First time I've had one open but nothing looks amiss to me - tell me what I'm missing and what i should look at.

diaphragm appears in tact to me.
cell seems good...from what i can tell.

The ONLY thing that I can MAYBE see is that the 4 bolts holding it together didn't seem overly tight. They were tight - just not as tight as I thought they should be. Seemed well-sealed tho...and clean. I doubt the tightness of the 4 bolts had anything to do with it.

[attachmentid=951
886]

[FlacaProductions]

[FlacaProductions]

AND....how do i put it back together?!