Revival of the jumping disc

Abstract

Snap discs made of bimetal have many technical applications as thermostats. Jumping discs are a toy version of such snap discs. Besides giving technical information, we describe physical investigations. We show especially how, through simple measurements and calculations, you can determine the initial speed (∼3.5 m s −1 ), the acceleration (∼30 000 m s −2 ) and the lower and upper snap temperature (∼31; ∼99 • C). High speed videos give even deeper insight into the jump.

Strategies and techniques for fabricating MEMS bistable thermal actuators.

“…At low temperatures, these bimetallic discs have a concave shape which then snaps to a convex shape at higher temperatures. As is common in discontinuous phase change materials, the bimetallic disc demonstrates significant hysteresis behavior as shown in Figure 1.4 [5]. These and are defined the lower and upper snap temperature for the bimetallic disc and those two temperature values provide the sensitivity of the bimetallic disc [5].…”

“…The second layer is typically made from steel and is called the "active layer" because of its much higher CTE. The two layers are cold-welded together [5].…”

“…Invar was developed by the French physicist Charles Guillaume back in 1897 [5] and it is an alloy which has the composition of 36% Ni and 64% Fe. This ferromagnetic facecentered cubic alloy has a very small coefficient of thermal expansion in the wide temperature range between -100°C and +160°C.…”

“…This ferromagnetic facecentered cubic alloy has a very small coefficient of thermal expansion in the wide temperature range between -100°C and +160°C. Since its CTE is almost invariant, the material became known as invar [5].…”

“…As is common in discontinuous phase change materials, the bimetallic disc demonstrates significant hysteresis behavior as shown in Figure 1.4 [5]. These and are defined the lower and upper snap temperature for the bimetallic disc and those two temperature values provide the sensitivity of the bimetallic disc [5]. In this research, we strive to develop a novel microfabrication process for making miniature versions of these thermally-actuated snap discs using MEMS technology.…”