Toastmaster: Toasting in Style! - Revision history

Jgutshall at 02:46, 26 March 2007

2007-03-26T02:46:44Z

Jgutshall at 00:00, 26 March 2007

2007-03-26T00:00:19Z

Jgutshall at 23:59, 25 March 2007

2007-03-25T23:59:46Z

Jgutshall at 23:58, 25 March 2007

2007-03-25T23:58:57Z

Jgutshall at 23:58, 25 March 2007

2007-03-25T23:58:24Z

Jgutshall at 23:57, 25 March 2007

2007-03-25T23:57:03Z

Jgutshall at 23:55, 25 March 2007

2007-03-25T23:55:58Z

Jgutshall at 23:54, 25 March 2007

2007-03-25T23:54:57Z

Jgutshall: /* Time to toast */

2007-03-25T19:35:04Z

Time to toast

Jgutshall: /* Time to toast */

2007-03-25T19:34:04Z

Time to toast

@@ Line 331: / Line 331: @@
 '''Discussion'''
-The maximum height of the toast upon release of the electromagnet (at the toast exit) was the engineering specification related to the ‘force and motion control' and 'safety' user requirements.  It is desirable to minimize the maximum height the toast will reach upon exit.  Minimizing the meximum height of the toast may be accomplished through increasing the mass of the system or by decreasing the spring stiffness or spring deflection.  The maximum height of the toast (4.93 cm) that was found through this procedure is approximately what would be expected from a toaster and what was observed while the toaster was in operation.
+The maximum toast height at exit was found to be 4.63 cm which is reasonable.  To check that the analysis produced accurate results, the spring force was calculated to make sure that it was greater than the force from the weight of the system (so the bread would pop up again).  The force of the spring was found to be greater than the system weight.  The maximum height of the toast upon release of the electromagnet (at the toast exit) was the engineering specification related to the ‘force and motion control' and 'safety' user requirements.  It is desirable to minimize the maximum height the toast will reach upon exit.  Minimizing the maximum height of the toast may be accomplished through increasing the mass of the system or by decreasing the spring stiffness or spring deflection.  The maximum height of the toast (4.93 cm) that was found through this procedure is approximately what would be expected from a toaster and what was observed while the toaster was in operation.
 '''Improvements'''

@@ Line 32: / Line 32: @@
 | align="center"|Houses all inner components, protects user, and provides aesthetic appeal
 | align="center"|Polypropylene (Recycling code: #5)
-| [[Image:DSCN0948.JPG |center|50px]]
+| [[Image:DSCN0948.JPG |center|75px]]
 |-
 ! 2
@@ Line 67: / Line 67: @@
 | align="center"|Catches and supports bread for toasting
 | align="center"|Treated steel
-| [[Image:DSCN0968.JPG|center|50px]]
+| [[Image:DSCN0968.JPG|center|75px]]
 |-
 ! 7

@@ Line 39: / Line 39: @@
 |align="center"|Operates and provides controls to heating elements, supports other components (circuit boards), and provides structural support
 | align="center"|Polypropylene (Recycling code: #5)
-| align="center"|[[Image:DSCN0957.JPG|center|50px]]
+| align="center"|[[Image:DSCN0957.JPG|center|75px]]
 |-
 ! 3
@@ Line 46: / Line 46: @@
 | align="center"|Supplies heat to toast bread to perfection
 | align="center"|Mica sheets, nichrome wire
-| [[Image:DSCN0958.JPG |center|50px]]
+| [[Image:DSCN0958.JPG |center|75px]]
 |-
 ! 4
@@ Line 60: / Line 60: @@
 | align="center"|Positions and clamps bread for toasting
 | align="center"|Treated steel
-| [[Image:DSCN0969.JPG |center|50px]]
+| [[Image:DSCN0969.JPG |center|75px]]
 |-
 ! 6
@@ Line 74: / Line 74: @@
 | align="center"|Clamps to hold bread; also heats to help toasting
 | align="center"|Steel
-| [[Image:DSCN0960.JPG |center|50px]]
+| [[Image:DSCN0960.JPG |center|75px]]
 |-
 ! 8
@@ Line 81: / Line 81: @@
 | align="center"|Holds together cover and base; holds in electrical components
 | align="center"|Steel
-| [[Image:DSCN0944.JPG  |center|50px]]
+| [[Image:DSCN0944.JPG  |center|75px]]
 |-
 ! 9
@@ Line 88: / Line 88: @@
 | align="center"|When handle is pushed down, springs pull together to close wire bread clamps
 | align="center"|Wire
-| [[Image:DSCN0963.JPG |center|50px]]
+| [[Image:DSCN0963.JPG |center|75px]]
 |-
 ! 10
@@ Line 95: / Line 95: @@
 | align="center"|Holds heating elements in place; provides connection between inner components and plastic base.
 | align="center"|Treated steel
-| [[Image:DSCN0952.JPG  |center|50px]]
+| [[Image:DSCN0952.JPG  |center|75px]]
 |}

@@ Line 53: / Line 53: @@
 | align="center"|Provides anchoring point for toast holding troughs; moves up and down with handle mechanism
 | align="center"|Steel
-| [[Image:DSCN0967.JPG |center|50px]]
+| [[Image:DSCN0967.JPG |center|75px]]
 |-
 ! 5

@@ Line 365: / Line 365: @@
-[[Image:Toaster Front.JPG|left|200px|Figure 8: Front view]]
+[[Image:Toaster Front.JPG|left|thumb|200px|Figure 8: Front view]]
-[[Image:Toaster Front Down.JPG|left|200px|Figure 9: Front view, deflected]]
+[[Image:Toaster Front Down.JPG|left|thumb|200px|Figure 9: Front view, deflected]]
-[[Image:Toaster Right.JPG|left|200px|Figure 10: Right view]]
+[[Image:Toaster Right.JPG|left|thumb|200px|Figure 10: Right view]]

@@ Line 208: / Line 208: @@
 '''Discussion'''
-The time to toast, or the time it takes between turning on the toaster and the bread product reaching the temperature needed for the surface to begin browning, was the engineering specification related to the ‘ease of sensing and controlling state’ user requirement.  It is desirable to minimize the time to toast.  Minimizing the time to toast can be done through increasing the efficiency of the toaster, or the ratio of the heat transfer into the bread product to the power input into the heating elements.  This can be increased or decreased by changing the geometric or thermal properties as described above.  For example, decreasing the toast slot opening will decrease the convection constant, therefore decreasing the amount of heat lost through the top of the toaster to the environment.  Or, a different material for the heating element wire could be chosen with a higher emissivity so there is more heat transfer to the bread by radiation.  The conduction constant of the insulation should likewise be high so as to decrease the amount of heat lost through the toaster. The time to toast that was found through this procedure is within the correct range observed through actually toasting slices of bread.
+The time to toast, or the time it takes between turning on the toaster and the bread product reaching the temperature needed for the surface to begin browning, was the engineering specification related to the ‘ease of sensing and controlling state’ user requirement.  It is desirable to minimize the time to toast.  Minimizing the time to toast can be done through increasing the efficiency of the toaster, or the ratio of the heat transfer into the bread product to the power input into the heating elements.  This can be increased or decreased by changing the geometric or thermal properties described.  For example, decreasing the toast slot opening will decrease the convection constant, therefore decreasing the amount of heat lost through the top of the toaster to the environment.  Or, a different material for the heating element wire could be chosen with a higher emissivity so there is more heat transfer to the bread by radiation.  The conduction constant of the insulation should likewise be high so as to decrease the amount of heat lost through the toaster. The time to toast that was found through this procedure is within the correct range observed through actually toasting slices of bread.
 '''Improvements'''

@@ Line 212: / Line 212: @@
 '''Improvements'''
-To improve the design, a material with a higher emissivity could be chosen for the heating element wire, this would allow more energy to be transferred to the bread through radiation.  The toast slots on top of the toaster could be made smaller or have a cover that slides over them while toasting so as to reduce the convection heat transfer constant by inhibiting air flow.  This would decrease the heat lost to the surroundings and more would be transferred to heating the inside of the toaster.  The current, which affects power input could be increased so as to provide more power which becomes heat transfer to the toast, although there are quite possibly safety regulations that this would violate.  The thermal conductivity of the mica insulation, assumed here to be ideal, could be increased since heat is lost through this, even though it was considered negligible here.  Cost is an important tradeoff as materials and manufacturing for creating a cover for the toast slots as well as a more insulating material for the heating elements are not cheap.  Geometrical values to keep in mind in the design include the dimensions of the heating element wire.  The surface area should be great enough to allow for maximum heat transfer to the toast, but not so large that the wire does not provide enough thermal resistance for optimal heat generation.
+To improve the design, a material with a higher emissivity could be chosen for the heating element wire, this would allow more energy to be transferred to the bread through radiation, but might also be more expensive than a material with a lower emissivity.  The toast slots on top of the toaster could be made smaller or have a cover that slides over them while toasting so as to reduce the convection heat transfer constant by inhibiting air flow.  This would decrease the heat lost to the surroundings and more would be transferred to heating the inside of the toaster, but it may be inconvenient to the user to have to work around these altered openings.  The current, which affects power input could be increased so as to provide more power which becomes heat transfer to the toast, although a trade-off is that there are quite possibly safety regulations that this would violate.  The thermal conductivity of the mica insulation, assumed here to be ideal, could be increased since heat is lost through this, even though it was considered negligible here.  Cost is an important tradeoff as materials and manufacturing for creating a cover for the toast slots as well as a more insulating material for the heating elements are not cheap.  Geometrical values to keep in mind in the design include the dimensions of the heating element wire.  The surface area should be great enough to allow for maximum heat transfer to the toast, but not so large that the wire does not provide enough thermal resistance for optimal heat generation.
 ===Maximum toast height at exit===