{"id":90,"date":"2018-08-10T13:48:25","date_gmt":"2018-08-10T13:48:25","guid":{"rendered":"http:\/\/commons.princeton.edu\/63-tiger-cub\/?p=90"},"modified":"2019-04-01T20:36:07","modified_gmt":"2019-04-01T20:36:07","slug":"22-february-2018","status":"publish","type":"post","link":"https:\/\/commons.princeton.edu\/63-2-tiger-cub\/2018\/08\/10\/22-february-2018\/","title":{"rendered":"22 February 2018"},"content":{"rendered":"<p>Notes by Noelle Goudy<\/p>\n<p>Assignment for Tuesday: Think of questions for Professor Martinelli<\/p>\n<p>Assignment for Thursday: Introduction and chapter 1 of\u00a0Shop Class as Soulcraft<strong><br \/>\n<\/strong><\/p>\n<p>&nbsp;<\/p>\n<p>Announcements:<\/p>\n<ul>\n<li>Get stuff to be powder-coated or chromed together\n<ul>\n<li>We might be missing frame parts<\/li>\n<li>Make sure we have anything that will be painted ready to be powder-coated<\/li>\n<li>Example: battery box<\/li>\n<\/ul>\n<\/li>\n<li>Next Tuesday: Professor Martinelli\n<ul>\n<li>Come up with a set of questions for him<\/li>\n<li>Week four scribe: take notes next week<strong><br \/>\n<\/strong><\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p>Housekeeping:<\/p>\n<ul>\n<li>Ricky: Found a taillight at the bunker and got that working; checked the spark plug on the red motorcycle<\/li>\n<li>Noelle: With Alex, assembled carburetor; flooded the carburetor and it leaked; lathed out the top plate because it was warped; reattached it and it no longer leaked<\/li>\n<li>Eric: Determined which front and back hub to use; began plugging it up for powder coating<\/li>\n<li>David: With Alex, found that half of a split-ring washer is missing (but there was one at the bunker)<\/li>\n<li>Connor: With Grace, cleaned the engine plates and put them back together; going to sandblast it today<\/li>\n<li>Charlie: Tried to disassemble the headlight; put it in a new chromed case<\/li>\n<li>Brendan: Cleaned the light; organized parts for powder coating<\/li>\n<li>Alex: Worked with Charlie<\/li>\n<li>Grace: Worked with Connor<\/li>\n<li>Jordan: With Emily, put together the jacks for the wheels<\/li>\n<li>Julianne: With Charlie and Ricky, went to the bunker; finished cleaning top end parts<\/li>\n<li>Sarah: With Ricky, attached the light and tested it; watch the dem for the spark plug<\/li>\n<li>Jake: Searched on ebay<\/li>\n<li>Hannah was out<strong><br \/>\n<\/strong><\/li>\n<\/ul>\n<p>Tiger Cub Engine Calculations Reading:<\/p>\n<ul>\n<li>Octane is C8H18<\/li>\n<li>Air is 20% O2<\/li>\n<li>Nitrogen goes in and out of engine\n<ul>\n<li>While it is a spectator, it still starts to react to form NOx<\/li>\n<li>A problem with engines<\/li>\n<\/ul>\n<\/li>\n<li>Sulfur present &#8211; emissions<\/li>\n<li>Carbon dioxide and water vapor are also products<\/li>\n<li>Energy release is 44,400 J per gram octane<\/li>\n<li>Air to fuel ratio is about 15:1 by weight\n<ul>\n<li>14.7:1 grams in industry<\/li>\n<\/ul>\n<\/li>\n<li>What limits the amount of power output is the amount of oxygen\n<ul>\n<li>Could make the engine larger<\/li>\n<li>Compress the air\n<ul>\n<li>Super\/turbocharging<\/li>\n<\/ul>\n<\/li>\n<li>Use pure oxygen or\n<ul>\n<li>Nitrous oxide<\/li>\n<li>Nitromethane<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/li>\n<li>\u2155 liter -&gt; .257 g of air and \u00a0.0171 g fuel yields 759 J<\/li>\n<li>37,950 Watts out of the engine (100% efficiency)<\/li>\n<li>50.9 horsepower (if the engine was fully efficient)<\/li>\n<li>Engine has about 20% efficiency in actuality<strong><br \/>\n<\/strong><\/li>\n<\/ul>\n<p>Demo:<\/p>\n<ul>\n<li>Two cylinders (pipettes) with a platinum wire\n<ul>\n<li>They are bubbling with the top open<\/li>\n<\/ul>\n<\/li>\n<li>When the top is closed, the bubbles cannot escape\n<ul>\n<li>The gas inside the left cylinder is going down more quickly than the right\n<ul>\n<li>This cylinder holds the hydrogen (H2O -&gt; two moles hydrogen for only one mole oxygen)<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/li>\n<li>When the hydrogen got to the bottom, a spark was lit and the ping pong ball moved upwards about a foot and a half\n<ul>\n<li>The product is water<\/li>\n<li>The pressure increases because of heat (PV=nRT)\n<ul>\n<li>Thus, the ball is launched<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/li>\n<li>On the second launch, the ball went up about three feet<\/li>\n<li>On the third launch, the ball went up about two and a half feet<strong><br \/>\n<\/strong><\/li>\n<\/ul>\n<p>Brake dynamometer:<\/p>\n<ul>\n<li>A device that allows you to figure out the torque and power of a motor<\/li>\n<li>A rope is wrapped around the shaft of the motor (called a rope brake)\n<ul>\n<li>This motor is an electric motor<\/li>\n<\/ul>\n<\/li>\n<li>The ropes are pulled tighter and the differences of the tensions in the ropes will allow you to find the torque as a function of speed for this motor at a certain voltage\n<ul>\n<li>The speed of the motor will also be recorded<\/li>\n<\/ul>\n<\/li>\n<li>As the rope is pulled tighter, the engine slows down<\/li>\n<li>For an electric motor, torque vs speed is linear\n<ul>\n<li>The torque is greatest at stall<\/li>\n<\/ul>\n<\/li>\n<li>Power = Force (Torque) * Velocity<\/li>\n<li>To get a power vs speed graph, multiply the two axes together and graph with respect to speed\n<ul>\n<li>The graph is a parabola (opening downwards)<\/li>\n<li>The greatest power to the motor will be at the center of the parabola, which is half of the possible velocity<\/li>\n<\/ul>\n<\/li>\n<li>Homan force vs velocity is called the Hill Curve\n<ul>\n<li>Concave and with a downward slope<\/li>\n<\/ul>\n<\/li>\n<li>The power vs velocity graph for a human on a bike also has a peak, where it will be easiest to get up a hill<\/li>\n<li>Efficiency of an electric motor would be the power curve divided by the force (torque) curve\n<ul>\n<li>Graphed with respect to velocity, it is a straight line with a positive slope<\/li>\n<li>The most efficient is using the least amount of energy<strong><br \/>\n<\/strong><\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p>Questions for Professor Martinelli:<\/p>\n<ul>\n<li>Where does air flow play a role in our motorcycle?\n<ul>\n<li>Carberation<\/li>\n<li>Cooling<\/li>\n<li>Windage in the engine<\/li>\n<li>Exhaust<\/li>\n<\/ul>\n<\/li>\n<li>Aerodynamic drag\n<ul>\n<li>Streamlining shapes<\/li>\n<li>On the wheels<\/li>\n<\/ul>\n<\/li>\n<li>Fluid in the engine\n<ul>\n<li>Lubrication<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<h3>27 February 2018<\/h3>\n<p>Notes by Eric: Professor Littman was not here today. \u00a0In his absence, we were joined by a guest: Professor Luigi Martinelli<\/p>\n<ul>\n<li>\u00a0\u00a0\u00a0\u00a0\u00a0 Broad overview of the role of fluid mechanics, and more generally whatever happens when you try to move against air or water<\/li>\n<li>\u00a0\u00a0\u00a0\u00a0\u00a0 Whenever you are doing mundane tasks, you are dealing with fluid flows.\u00a0 Either they are opposing your motion or helping you.<\/li>\n<\/ul>\n<p>o \u00a0\u00a0 Two regimes\u2014organized (laminar) and chaotic (turbulent)<\/p>\n<ul>\n<li>\u00a0\u00a0\u00a0\u00a0\u00a0 Chaotic flow will offer more resistance to the motorcycle<\/li>\n<li>\u00a0\u00a0\u00a0\u00a0\u00a0 Cost of turbulent flow vs. closing the wake is a tradeoff constantly considered.<\/li>\n<li>\u00a0\u00a0\u00a0\u00a0\u00a0 Distance between back of ride and wake seeks to be minimized.<\/li>\n<li>\u00a0\u00a0\u00a0\u00a0\u00a0 Some helmets are designed to minimize the gap between the rider and the air flow<\/li>\n<li>\u00a0\u00a0\u00a0\u00a0\u00a0 Often propulsion requires a working fluid<\/li>\n<\/ul>\n<p>o \u00a0\u00a0 The flow rate\u2014the amount of fluid that can go in or out\u2014is determined by the shape of the valve.<\/p>\n<p>o \u00a0\u00a0 The sizing of the fin is determined by the property of the flow of the engine head; therefore, the extent of the fin design of an air cool engine<\/p>\n<ul>\n<li>\u00a0\u00a0\u00a0\u00a0\u00a0 Sometimes the two combine<\/li>\n<\/ul>\n<p>o \u00a0\u00a0 In a sail boat, the systems are integrated\u2014balance, steering, and other properties of the sail<\/p>\n<p>o \u00a0\u00a0 Other, seemingly more complex systems, such as a rocket, are actually simpler.<\/p>\n<ul>\n<li>\u00a0\u00a0\u00a0\u00a0\u00a0 Two vs. four stroke.\u00a0 Two-stroke\u2014as you draw in fresh mixture, you exhaust from the previous combustion; the two-stroke exhaust may let out unburned fuel.\u00a0 If you solve the environmental problem, you would have a lighter engine because you do not need a valve. In a four-stroke engine, one stroke pulls in and compresses fuel then ignites it (power stroke), then the next stroke pushes out the exhaust.<\/li>\n<\/ul>\n<p>o \u00a0\u00a0 The Tiger Cub has two valves to have a desirable mass flow rate.\u00a0 The cam controls how quickly the valves open and close<\/p>\n<ul>\n<li>\u00a0\u00a0\u00a0\u00a0\u00a0 Engine cooling\u2014require heat exchange between the engine and the outside air<\/li>\n<li>\u00a0\u00a0\u00a0\u00a0\u00a0 Overview of aerodynamic forces on ground vehicles<\/li>\n<\/ul>\n<p>CARBURATION<\/p>\n<ul>\n<li>\u00a0\u00a0\u00a0\u00a0\u00a0 Venturi effect: for an incompressible flow, a reduction of area causes an increase in local flow velocity and a consequent decrease in pressure.<\/li>\n<\/ul>\n<p>o \u00a0\u00a0 Always have high velocity, low pressure<\/p>\n<ul>\n<li>\u00a0\u00a0\u00a0\u00a0\u00a0 The carburetor then fulfills 3 primary functions:<\/li>\n<\/ul>\n<p>o \u00a0\u00a0 Control engine power by adjusting the air intake flow<\/p>\n<p>o \u00a0\u00a0 Meter the fuel flow in the air flow aspirated maintaining the ratio air\/fuel to optimal values throughout the engine operating range<\/p>\n<p>o \u00a0\u00a0 Homogenize the mixture of air and fuel to enable the subsequent combustion<\/p>\n<ul>\n<li>\u00a0\u00a0\u00a0\u00a0\u00a0 It is possible to obtain optimal thickness, spacing of the fins by mathematical computations<\/li>\n<li>\u00a0\u00a0\u00a0\u00a0\u00a0 There are two approaches to improving design: evolutionary and computational<\/li>\n<\/ul>\n<p>External aerodynamics<\/p>\n<ul>\n<li>\u00a0\u00a0\u00a0\u00a0\u00a0 Even with seemingly benign topics, it is hard to optimize,<\/li>\n<li>\u00a0\u00a0\u00a0\u00a0\u00a0 Hybrid between electric bike and moped is most efficient<\/li>\n<li>\u00a0\u00a0\u00a0\u00a0\u00a0 The speed at which the oil moves around is quite low; our motorcycle has a dry sump reduces the complexity of the system; if we had a<\/li>\n<li>\u00a0\u00a0\u00a0\u00a0\u00a0 Land speed records<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>Notes by Noelle Goudy Assignment for Tuesday: Think of questions for Professor Martinelli Assignment for Thursday: Introduction and chapter 1 of\u00a0Shop Class as Soulcraft &nbsp; Announcements: Get stuff to be powder-coated or chromed together We might be missing frame parts Make sure we have anything that will be painted ready to be powder-coated Example: battery &hellip; <a href=\"https:\/\/commons.princeton.edu\/63-2-tiger-cub\/2018\/08\/10\/22-february-2018\/\" class=\"more-link\">Continue reading<span class=\"screen-reader-text\"> &#8220;22 February 2018&#8221;<\/span><\/a><\/p>\n","protected":false},"author":6,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3],"tags":[],"class_list":["post-90","post","type-post","status-publish","format-standard","hentry","category-diary"],"_links":{"self":[{"href":"https:\/\/commons.princeton.edu\/63-2-tiger-cub\/wp-json\/wp\/v2\/posts\/90","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/commons.princeton.edu\/63-2-tiger-cub\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/commons.princeton.edu\/63-2-tiger-cub\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/commons.princeton.edu\/63-2-tiger-cub\/wp-json\/wp\/v2\/users\/6"}],"replies":[{"embeddable":true,"href":"https:\/\/commons.princeton.edu\/63-2-tiger-cub\/wp-json\/wp\/v2\/comments?post=90"}],"version-history":[{"count":1,"href":"https:\/\/commons.princeton.edu\/63-2-tiger-cub\/wp-json\/wp\/v2\/posts\/90\/revisions"}],"predecessor-version":[{"id":91,"href":"https:\/\/commons.princeton.edu\/63-2-tiger-cub\/wp-json\/wp\/v2\/posts\/90\/revisions\/91"}],"wp:attachment":[{"href":"https:\/\/commons.princeton.edu\/63-2-tiger-cub\/wp-json\/wp\/v2\/media?parent=90"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/commons.princeton.edu\/63-2-tiger-cub\/wp-json\/wp\/v2\/categories?post=90"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/commons.princeton.edu\/63-2-tiger-cub\/wp-json\/wp\/v2\/tags?post=90"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}