Heat Effects on Spirit Levels

[vtcnc]

Found this on Instagram this morning. Pretty interesting and disturbing at the same time.

Instructor Adam B on Instagram: "4 Things You’ll Wish You Didn’t Know About Levels - Part 1 Digging ever deeper into the surprising world of spirit levels, I stumbled across a few bizarre phenomena which affect level readings There’s so much intere

429 likes, 27 comments - laneymachinetech on November 24, 2021: "4 Things You’ll Wish You Didn’t Know About Levels - Part 1 Digging ever deeper into the surprising world of spirit levels, I stumble..."

www.instagram.com

 

[RJSakowski]

My level is encased in about 2 lbs. of iron which will go a long way toward eliminating the thermal effects. Interesting though. Metrology labs never make precision measurements or calibrations without allowing a devise or an object to normalize to the room temperature. My shop is fairly well temperature controlled, never varying by more than a few degrees year around. A garage shop would be an entirely different story.

 

[RJSakowski]

Items 3 and 4 would be a non-issue. Level would be defined by your particular location. Level as defined by a plane perpendicular to a plumb bob or to a plane parallel the surface of a liquid wouldn't measurably change over a short distance. It's a known fact that a nearby mass such as a nearby mountain will pull a plumb bob towards it but all measurement will experience the same effect.

 

[tweinke]

That was very interesting. Makes me wonder how many people leveling a machine could have been bitten by the heat bug while trying to get good readings.

 

[vtcnc]

That was very interesting. Makes me wonder how many people leveling a machine could have been bitten by the heat bug while trying to get good readings.

That is what I found interesting while thinking about this as well.

 

[sdelivery]

I am a professional who has used his spirit levels for decades.
I always give my instruments time to acclimate to the temperature of the object by placing them on the machine..
I have seen a garage door opening and closing change my level.
I have seen guys wipe the dirt off the vial of a starrett level and change the reading!
Like most tools there are idiosyncrasies to achieving accurate results.

 

[tweinke]

All so very true. Mear mortals like us home shop/ beginners forget to apply all the factors to things that a true professional does as a matter of course. That is why i like to come here, the knowledge of the guys here can solve problems that are overlooked by those that do not know.

 

[sdelivery]

Mear mortals! Luv it!
Aren't we all ? Just in different venues?

 

[graham-xrf]

Items 3 and 4 would be a non-issue. Level would be defined by your particular location. Level as defined by a plane perpendicular to a plumb bob or to a plane parallel the surface of a liquid wouldn't measurably change over a short distance. It's a known fact that a nearby mass such as a nearby mountain will pull a plumb bob towards it but all measurement will experience the same effect.

Yup - this happens! My Dad (builder) had a traditional lead plumb bob set into a "teardrop shaped" cutout in a hardwood plank, and with a fine V-line cut into it. The whole thing, which stood as high as a man, had a cover box that could be removed sideways, with viewing aperture, all to stop air disturbances. He told me the same thing about Table Mountain (Cape Town). The middle of that peninsula mountain is made of iron, or something dense, because all the buildings stand slightly off true geographic vertical, and plumb bobs hang slightly pulled toward the mountain.

Not a problem for building purposes, because the forces in the buildings are still properly catered for by regular spirit levels. I expect any satellite tracking dishes in the region would have to correct for clinometers being somewhat untruthful. The messed up way levels worked in Cape Town has been well known since back in the 19th Century because of the importance of the Observatory in Cape town, and the huge efforts to establish the Southern Arc of the Meridian, and prove the Southern half of the Earth oblate spheroid was the same shape as the Northern half.

The deviations from vertical were known as "La Caille’s discordances". I am not sure it is true that at the base of the mountain, coffee in a cup will look slightly skewed off level. I never noticed anything like that, and I lived for a while in a University residence on the slopes of Table Mountain.


Great history and pictures here -> Arc of the Meridian Survey

 

[addertooth]

I am so sorry, but you summoned the physics genie.
Yes, mass, height from center of Earth, and time all impact gravity (and perceived level).
I worked in a physics lab for a lot of years. It is a well proven maxim that a large mountain nearby can create a sideward pull.

Now for the real mind-blower, which has been well-proven by experiments. Time on the surface of the earth is slower, than time up at the distance that geostationary satellites orbit.

Now for the more significant issue. Level is not as critical as you think, as long as you are not introducing a bow or a twist in your machine tools. There are lathes and mills on heaving and bounding ships, which still produce very accurate bearing surfaces. The lathe on my SEORTM (gooney-bird, Batmobile), was quite accurate, but almost never level (The SEORTM is a machine shop on an extended 5-ton Army truck).