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

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Old November 1st 20, 03:52 AM posted to rec.aviation.soaring
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Default How does my 1918 German barograph work? (Replogle mechanical drum)

On Saturday, October 31, 2020 at 1:54:45 PM UTC-4, Charles Gosse wrote:
On Friday, October 30, 2020 at 8:17:05 PM UTC-4, AS wrote:
On Friday, October 30, 2020 at 7:29:55 PM UTC-4, Steve Leonard wrote:
On Friday, October 30, 2020 at 4:33:06 PM UTC-5, wrote:
On Friday, October 30, 2020 at 4:45:30 PM UTC-4, AS wrote:
On Friday, October 30, 2020 at 2:56:53 PM UTC-4, Charles Gosse wrote:
On Friday, October 30, 2020 at 2:27:19 PM UTC-4, Charles Gosse wrote:
On Thursday, October 29, 2020 at 6:10:20 PM UTC-4, Herbert Kilian wrote:
On Thursday, October 29, 2020 at 2:16:14 PM UTC-5, 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.

That's the kind of device you'd expect hanging above the basket of a hydrogen balloon. A precious piece of aviation history!
Hello Herbert,
I am really unfamiliar with google Groups. After you responded here I received an email with your response, as well, and tried to reply to that in gmail with photos but Google responded that they couldn't find the rec.soaring address. Anyway,I can't figure out how to add a photo here. Can you tell me?
Here is a photo of the underside. The green arrow points toward a clock-work mechanism that seems completely turned tight. What action or button starts the drum to turn?
Here is a photo looking down at the drum.

thanks for the picture of tray's underside. You are correct - the key is used to wind the clock.
If you look at the front side of the Barograph - the one that has the handle on it, you can see a sliding lever in the lower left corner. Slide that lever to the left until it snaps upwards into the detent. That starts the clockwork. The detent prevents an accidental stop of the recording. The second function of that lever is to move the recording arm onto the drum to create the trace. In your case, it looks like there is a small ink reservoir at the tip of the arm, which draws the line. Other options were a stylus, which scratched the trace onto a waxed paper or onto a layer of soot on an aluminum foil, etc.

Let us know if you can get the clock to tick. ;-)

I slid the lever over to the left but I can't raise it up into the detent because there's this other metal arm in the way.
I flipped it over and took a photo of the underside. On the right is the lever and on the left is the thing in the way.
I'm clueless.
Looks like the lever slides over, and then would get safety wired in place. Guessing it did not start ticking when you slide the long lever over to in line with the short lever, lining up the holes? If it doesn't start ticking, try turning the drum clockwise as viewed from above. You might also hold the drum and see if you can turn the knurled knob inside the drum so you can remove the drum and have a look at the clock mechanism. Sometimes, those old clocks need a little "boost" to get started again after sitting for many years.

Steve Leonard

I concur with Steve on the second metal arm being there to provide a safety for the moving arm, either by a wire or a cotter pin.
The picture from underneath shows that the arms are all in place and connected. I would have a clockmaker, who specializes in cleaning and restoring old clocks, take a look at it. It is a very simple mechanism and I am sure it can be restored.


I tried turning the drum clockwise to see if the mechanism would start but no luck.

Here is the device with the drum removed. The green arrow points to a metal enclosure within the drum. Not sure what to call this but I think this is where the metal coil is wound up.

Here is the underside again. The three green circles indicate three bolts that hold down that drum-within-the-drum.

Should I untighten these and try to lift the mechanism off and see if it is binding or should I just take this to a clock repair person?

Hi Charles,

if it was me, I would have a professional take a look at it. One possible reason for the clock not working despite being fully wound is that the clock-spring got wound tight and then rusted/fused together. For the spring to release its stored energy, its layers have to move relative to each other.
Let us know how it turns out. It would be so cool to take this 100+ year instrument up for a flight and create a trace.


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