Rubber Band Heat Engine

I've been made the Rubber Band Heat Engine, which is described by Richard Feynman in his book. As the rubber bands are heated by the lamp, they contract, moving the center of mass away from the center of rotation. This causes the engine to rotate!

Category:

Science & Technology

Tags:

• rubber
• band
• heat
• engine
• thermodynamics
• experiment

[Philip614]

Whats the title of the book he mentioned it in?

[checkmatedeepblue]

The Feynman Lectures on Physics

[PattyMMelt]

just for future reference, thats a LAMP, not a LUMP... i see you've misspelled it in several of your comments as well as your description

[checkmatedeepblue]

Thank you for your kind attention

[heloizyjhenifer]

The least energy efficient engine ever, but smart ;)

[tuffpee]

Almost, but backwards! When you heat a rubber band it actually contracts! You can test this by hanging a weight from a rubber band and bringing a flame close to it.

So what's happening here is the bands under the lamp are contracting. Assuming that the axis of the wheel is fixed, then the parts of the tire connected to the contracting bands get pulled closer to the center. This moves the center of gravity of the wheel to the (screen) right of the axis, and so the wheel rotates!

[st1cklebr1ck]

@kaulas123456789 The majority of the radiation coming from a filament lamp is in the infra red part of the spectrum. It is these wavelengths that will be doing the majority of the heating.

[st1cklebr1ck]

@mjinen as long as you stop the sun radiating on half of the wheel, yes it will work.

[st1cklebr1ck]

@osbiath Although heat is (energy) is always conserved, when ever you make it do work there is an increase in the total entropy of the system. The entropy is a measure of how much useful work the heat can perform. The only closed system is the universe as a whole and eventually all of the energy will no longer be able to do work because the system has reached it's maximum amount of entropy. This is known as a heat death and it is thought that this will be the ultimate fate of the universe.

[st1cklebr1ck]

@humperfier Indeed, making things cold does indeed make the majority of objects contract; but not rubber. Due to its polymeric structure, when you lengthen an elastic band you align the polymer fibres so they lay in the same direction. This corresponds to a lower state of entropy because it is more ordered. By removing heat from a material you lower its entropy. In the case of a rubber band, the lower entropy state is a longer, more aligned configuration.

[st1cklebr1ck]

@xijnnijx Exactly correct. Cooling the bands would allow them to lengthen on the opposite side to it would help shift the centre of mass even further from the axis creating a larger moment around the axis.

[xijnnijx]

so if you had something to cool it on the other side, would it be able to spin faster?

[theledkid2]

when it's cold you get increased electrical stimulation sent to your muscles to flex them to warm you up. its not contracting its twitching. sheesh

[humperfier]

@tuffpee im pretty sure cold makes things contract, that is why when its cold you have to stretch your muscles more

[Measonz]

Rubber Band Heat Engine is very good video

[scientificpages]

@checkmatedeepblue when i saw this I instantly think abouth Feyneman idea about rubber engine :) thanks for making it!