Odds and ends

[Mark]

Here's another one just recently made, I was wondering how many Hz it's cycling at, or if the sound would somehow reveal it? It was weird how when I thought to try using a magnet to hold the jumper down, how unexpectedly fast it seemed to run, how peculiarly it suddenly catches the rhythm when I go to start it.
https://youtu.be/KfbRd5LtIxc

And this one just very simple.
https://youtu.be/ZiBcnxdmY7Q

Here's the video that kind of got me interested in jumpers, it's a good video on how to make one and a fair amount of interesting data in French and English.
https://youtu.be/QYZje3YfuO8

[Mark]

Another jumper that was minimalistic.

Easy Balloon Three Piece Stirling Hot Air Jumper
https://youtu.be/B547cKwERzI

[Mark]

A fast one. At the 1:14 mark it appears stretched and frozen for a few seconds.
Speed Test of a Stirling Engine Hot Air Jumper
https://youtu.be/ciHfynKzFE0

[Mark]

A silicone condiment container jumper or making things with odd things.
https://youtu.be/b1KA3NQcQYg
https://youtu.be/WnteuWwNKAw

[Mark]

Another odd thing to use to make a jumper.
Stirling Hot Air Jumper with Sippy Cup Lid
https://youtu.be/SbBvBssQw8M

[Mark]

This is a toothbrush holder I bought long ago thinking it might be useful for a jam jar jet or something but instead this simple three piece engine made by adding a silicone jar lid and some steel wool.
https://youtu.be/qn9DUPrqUVw

[Mark]

Martini Glass Stirling Hot Air Jumper
https://youtu.be/7UkkXHwxR9Q

And a bit faster.
https://youtu.be/PA0hhiqEhFg

[Mark]

It seemed like there was an outside chance I might have been heating this a little too much. It's a lot of mass slinging up and down being held with two magnets and a stretch press-fit wobbly drill dust catcher bellows. Living on the edge. ha

Pressure Loss on a Stirling Hot Air Jumper
https://youtu.be/WXUVMTi8cZU

Film Developing Tank Engine Parts
https://youtu.be/rBeaZNxOQYc

[Mark]

I saw this engine which is just a can with a glass tube and some steel wool wrapped around the bottom of the tube and the tube attached to a diaphragm. Also a little pan of cold water jackets the top region for cooling. For some reason it brought to mind my snorkelers, for it breathes in and out even though it's an external combustion engine. It's kind of interesting how expansion and contraction here have some commonalities with a jam jar jet snorkeler even though evolutionarily on a different branch. Perhaps it might be possible to make a jam jar jet snorkeler with a flexing up and down snorkel.
Free Piston Hot Air Engine - Torque adjusting
https://youtu.be/-3E8TldOFcU

What I found interesting when experimenting with a steel wool displacer or very loose-fitting piston in a sense, is that in a large quartz test tube over a liter in volume is that if you heat the bottom and have a diaphragm at the opposite end, if you tilt the steel wool so that it slides to the hot end the diaphragm pulls in and likewise when the steel wool is tilted so it slides to the cold end the diaphragm puffs out. It's just kind of interesting to think about.

Rolling-down diaphragm piston vs. Hot Air Engine (Metronome)
https://youtu.be/l572pE3bA4I

The Hot Air Engine that You Never Did Before - tutorial with tin cans and spider
https://youtu.be/A6IB1wwA0_A

[Mark]

This little heat engine was cobbled together with simple parts and has an odd characteristic for creating motion. Finally something that runs well and not so fragile or fussy.
Flame Driven Pendulum Rocker
https://www.youtube.com/watch?v=eriiZBtj5SI

PHILOSOPHICAL TRANSACTIONS
"On the Vibrations and Tones produced by the Contact of Bodies having different
Temperatures"

"In the year 1829 Mr. Arthur Trevelyan was engaged in spreading pitch with a
hot plastering iron, and observing in one instance that the iron was too hot, he laid it slantingly against a block of lead which happened to be at hand. Shortly afterwards he heard a shrill note, resembling that produced on the chanter of the smaller Northumberland pipes, an instrument played by his father’s gamekeeper. Not knowing the cause of the sound he thought that this person might be practicing out of doors, but on going out the tone ceased to be heard, while on his return he heard it as shrill as before. His attention was at length attracted to the hot iron, which he
found to be in a state of vibration, and thus discovered the origin of this strange music."
https://royalsocietypublishing.org/doi/ ... .1854.0001

[Mike Everman]

Hi Mark, Happy '24!
That paper was a good read. I think it suggests this works in a vacuum, correct? So, not a convection effect, but purely conductive, which makes some sense, where the heat bleeds out at the contact, which slightly contracts that side, which makes a teensy upward bow, that makes it raise up a bit, adding to the instability. That's the way I'm seeing it in my head, at least...

[Mark]

I was interested in these speaker spikes for some experiments. If you watch from just before the 3 minute mark up to around the 7 minute mark it had some food for thought on coupling and filter effects, maybe of interest.
Why You Want to Decouple Instead of Using Spikes for Vibration Control - AV Room Service - THE Show
https://www.youtube.com/watch?v=s6Ucek7OqBg

As an aside, I was filming some high pitch resonance and when reviewing the video my camera imparted a sudden, short but strange effect in one second to the video, a buzzing blurr with sound effect and then it went away. It has never done that before and never again but could a high pitch sound affect the camera workings in some way I wonder? The sound/culprit in question was like this high pitch resonance near the end of the clip.
https://www.youtube.com/watch?v=7InFwKHOi38

[Mark]

Hi Mark, Happy '24!
That paper was a good read. I think it suggests this works in a vacuum, correct? So, not a convection effect, but purely conductive, which makes some sense, where the heat bleeds out at the contact, which slightly contracts that side, which makes a teensy upward bow, that makes it raise up a bit, adding to the instability. That's the way I'm seeing it in my head, at least...

I thought that paper was a riot how many different materials they tried, and rock salt no less. I've tried my gold wedding ring, platinum metal, silver, the element silicon,etc. I wonder where the line of demarcation is between expansion and contraction and the metal just resonating? It's tricky finding two metals that work well together, it's not always going to do what you want, I've found it can be a lot of trial and error.
Happy 2024 too!

[Mark]

Tidbits
Melde's Experiment with the Trevelyan Rocker
"The usual explanation of the phenomenon is that the lead is heated as the iron strikes it, and throwing up little elevations,
first at one and then at the other corner of the bolt, under thermic expansion, keeps the bolt in oscillation."
https://scholar.archive.org/work/qbd2us ... owdst6y66m

"The topic of Tyndall’s career-establishing Friday Evening Lecture had been an acoustic one, examining the sounds produced through heated metals, which Trevelyan, Faraday, and Forbes had investigated during the 1830s. Tyndall had first approached this subject under Magnus in Berlin during 1853, before developing these experiments into a Royal Institution lecture in the same year.22 He observed that a Saxon, M. Schwartz, had first discovered this sonorous phenomenon in a smelting works, during the process of solidifying silver by placing it on an anvil to hasten its cooling. Although Trevelyan had come across this phenomenon several years later, it was he who realized its importance for the study of heat as a demonstration of the transformation of energy into sonorous vibrations."

[Mike Everman]

I feel like it would also work with a straight cylinder that is imbalanced so it rocks on a flat plate. If my thoughts on thermal bow are correct...

Seems you would want high thermal conductivity at the contact, and low emissivity of the rocker so it does not lose too much to the environment, and high thermal expansion coefficient for the rocker.