How does my 1918 German barograph work? (Replogle mechanical drum)

On Thursday, October 29, 2020 at 3:16:14 PM UTC-4, Charles Gosse wrote:
I have a 1918 German barograph, photos are at the URL below. It appears complete but I do not know how to make it work. Apparently it has to be wound-up. I also have a photo of the underside of the metal tray, if you need to see that.

https://www.aeroconservancy.com/flugzeug

Hello Charles - this is indeed a piece of aviation history! It looks just like an early version of the popular Winter Barographs.
There has to be a clockwork located under the drum. If you could post a link to a picture of the underside of the tray, it most likely will show a hole for a key used to wind up the movement or a bail that folds out to wind it up.
Take a look into the drum. There is most likely a thumb-screw used to removed the drum.
Also, the front plate is labeled 'Umdrehungszeit 2' meaning the drum will turn once every 2 hours. The clockwork may have a lever to change the drum speed to go slower or faster.
Thanks for sharing this link!

Uli
'AS'