Junkers JU 52 Gauge Identification

[100Coogn]

Does anyone know what this gauge is/what it's for?     It's on the Junkers Ju 52.





Coogan

[Rocco]

It's a pressure gauge but not sure for what. Something really low pressure, 0.5 kg/cm is about 7psi

I'm thinking vacuum gauge?

[100Coogn]

I thought at first, maybe a fuel pressure gauge.  Then like you, noticed the low reading on it. 
I'm curious, because somebody brought up the forums on MSFS 2020 and at the time of posting this, nobody has an answer.

Coogan

[Rocco]

Interesting. Any idea where in the cockpit it is?

It's the right range for the gyro suction gauge, top end a little higher than most suction gauges these days but not much. I can't really think of anything else that deals with such low pressure in an aircraft.

[100Coogn]

Interesting. Any idea where in the cockpit it is?

It's the right range for the gyro suction gauge, top end a little higher than most suction gauges these days but not much. I can't really think of anything else that deals with such low pressure in an aircraft.

I'm still trying to find a good photo of the cockpit of one of these planes.  All the ones I'm seeing are too far away to identify the gauges.
I'm going to keep looking...

Coogan

[Treize69]

i believe that's one of the three kraftsoffdruckmesser (fuel pressure gauges), the diagram shows them having a max reading of 0.5kg/cm2. Number 20 on the diagram.

[100Coogn]

i believe that's one of the three kraftsoffdruckmesser (fuel pressure gauges), the diagram shows them having a max reading of 0.5kg/cm2. Number 20 on the diagram.

(Image removed from quote.)

(Image removed from quote.)

The ranges on the gauge does appear to be correct.  I'm looking at #20 of your image.
I wonder how that would convert to US lbs...  I think the fuel pressure on my truck is around 50psi or more.

Coogan

[alkali]

Fuel gauge if my German does not fail me.
Pages 184 and 185 of the 1939 user manual to be found here: https://stephentaylorhistorian.files.wordpress.com/2020/04/ju52-betriebsanleitung-1939.pdf (from this site https://stephentaylorhistorian.com/2020/04/16/ww2-aircraft-manuals-downloadable/ )
It does state the 0 to 0,5 kg/cm2 pressure range.
Best,
Marc

[alkali]

Ach! Didn't see Treize69's answer posted above - looks like we're on the same page anyway.

[Treize69]

I agree that the range seems very low for a fuel system, but that is what the diagram key seems to indicate. Nothing else has that range of readings.

[100Coogn]

Ach! Didn't see Treize69's answer posted above - looks like we're on the same page anyway.

That's just confirmation to me.  Always welcome.
Thank you guys for clearing this up.   

[Edit]  It looks like some of the guys on the MSFS 2020 forums are leaning towards fuel pressure too.  MSFS 2020 Forums

Coogan

[Rocco]

Good find! Yeah by that diagram the suction is #10 and it's in atu.

Definitely low for modern fuel pressure but I guess right for 80yrs ago.

[alkali]

Section 10-16 of the manual reads that fuel pressure must be between 0,14 and 0,25 atü, leaded 87 octane.