TempMeter : Measuring Temperature with a Brass Rod

RE: TempMeter : Measuring Temperature with a Brass Rod

aspork42 — Fri, 23 Oct 2020 05:35:06 GMT

Cool experiment!

Thermal expansion is one of those things that I’ve often wondered about and not considered “solved”. Things like bridges just are forced to “deal with it” by using expansion joints. But we’ve also learned how to use it to our advantage with things like bi-metallic strips in thermostats...

RE: TempMeter : Measuring Temperature with a Brass Rod

jw0752 — Sun, 09 Aug 2020 03:21:26 GMT

Hi Dubbie,

I had a good time this evening duplicating your experiment. If you would like to see some pictures message me your e-mail

John

RE: TempMeter : Measuring Temperature with a Brass Rod

phoenixcomm — Sat, 08 Aug 2020 16:52:46 GMT

[mention:d25512d61e65470296ce2f82f47741ab:e9ed411860ed4f2ba0265705b8793d05] Great article on thermal expansion. When I was in the AF I was a crew chief on a BlackBird, on the ground it looked like corrugated titanium. After M2 it smoothed out like a baby's ass!

~~Cris

RE: TempMeter : Measuring Temperature with a Brass Rod

jw0752 — Sat, 08 Aug 2020 01:46:37 GMT

I like your experiment. How about putting the experiment up on two pillars of books with a sheet of very level glass under the small diameter roller. That way you could heat the brass rod between the book pillars without heating the table. It would also isolate the brass rod in open air and you could apply a lot higher heat level with the hot air gun. The glass plate would provide a smooth surface so that the small axle could roller smoothly. Also it will be important that the indicator on the end of the axle rod is very balanced and very low mass. This will minimize any force that would result if we were dealing with raising or lowering a center of gravity. Since it is a small value measurement there are a lot of small factors that can interfere with it.

Excellent challenge and I look forward to seeing what you come up with.

John

RE: TempMeter : Measuring Temperature with a Brass Rod

DAB — Fri, 07 Aug 2020 18:48:43 GMT

Very good experiment.

I ran into a real world issue about thermal expansion back in my younger days working in a laser lab.

We had connected a camera and lens assembly with aluminum bars and discovered the focal length changed when the room cooled or heated.

DAB

RE: TempMeter : Measuring Temperature with a Brass Rod

beacon_dave — Fri, 07 Aug 2020 17:20:52 GMT

You could perhaps use a rack and pinion arrangement at the end of the rod to translate linear to rotary motion with less potential for slip (but more potential for backlash / zero travel)

RE: TempMeter : Measuring Temperature with a Brass Rod

genebren — Fri, 07 Aug 2020 15:39:07 GMT

Very cool (or in this case hot)! Very interesting experiment. Funny how some ideas stick in your mind for years and years, only to pop up and be the inspiration for an experiment.

Well done!

RE: TempMeter : Measuring Temperature with a Brass Rod

dougw — Fri, 07 Aug 2020 15:35:09 GMT

Great demo of thermal expansion.

You mentioned the expansion of the table. Would it be more accurate to subtract the table coefficient from the brass coefficient - and using the differential coefficient in your calcs?

I like the simplicity of using a big wheel on a small axle to amplify the movement (demonstrating another principle), although it would be interesting to see your rod connected to a digital caliper.