Ultra rare U-Boot navigation instrument

[Michel]

Hello,

That is probably one of the most rarest U-Boot navigation instrument.

His name is : "Höhenrechenschieber HR 2"

Since I collect the U-Boot militaria, I have only ever observed two HR2, that may be examined in the German Naval U-Boat Archive at Murvick – Marine Schule, and the second in a US museum.

The instrument measures 17” x 7” approx. with a total extended length of approx. 27”, height 7” and comprises:
Black anodized alloy frame and base with KM I/D plate to front marked “Hohenrechenschieber HR 2 “ with Military code gwr for Dennert & Pape Hamburg,instrument serial Nr and KM property marking Eagle /Swastika/M.
Applied paper printed declination tables to front, alloy vernier knobs left and right marked “Feinstellung nach klemmung” bright plated clamping knobs to left and right hand side, these enable the verniers.
Curved Plexiglas viewing shield, further diagrams for guidance and notes.
Dual Concentric spiral scaled tubes, tube locking lever to left-hand end .

Michel

[Michel]

2

[François SAEZ]

So I will be the first to ask - what is the use of this beautifull instrument? Specific U-boot?

[Michel]

Hello François,

Yes it's typical for U-Boot.

The HR2 is a development and substantial refinement based on a Bygrave rule invented in England in the 1920s and designed to solve the PZX triangle.

The First German Version type HR1 was a simple dual concentric cylinder though a progression from the original Bygrave invention.

The German Navy required ever greater accuracy for position fixing in special circumstances, one of which was covert opperations, the HR1 was developed to a point where a solution with an error of less than ½ a minute of arc or within about 1 ½ minutes could be calculated.

Best,

Michel

[Michel]

A

[Gordon Williamson]

A salutory lesson for anyone thinking of starting to collect U-Boat material. Don't bother, Michel already has it ALL!!!!!

[Michel]

Thank you for the compliments Gordon, I am all red of confusion but I have again many dreams...

[Langemark]

Thank you for the compliments Gordon, I am all red of confusion but I have again many dreams...

What kind of dreams exactly ?
Mark

[glaser]

Kriegsmarine ultra rare HR2 Höhenrechenschieber

[ATTACH]2443122[/ATTACH]

[glaser]

Kriegsmarine HR2 utra rare Höhenrechenschieber PICS?

I am looking for pictures of an HR2 in use, any help appreciated!