mech 153 - mechanical components (lecture part) mechanical engineering technology, camosun college
notices Solutions to assignments 1, 2 & 4 have been posted. See below. (These are the ones you will need for the upcoming midterm test so take a good look at them.)
Final Project Here is description of the Mech 153 Final project ... Click Here.
14 March 2010 Project Belt Note It has been pointed out to me that the "Calculating pulley diameter of drive shaft and belt cross section" text table (Table 20-2) does not have the range to allow the design of the bike transmission to proceed easily. In searching the web for solutions it occurred to me why this table is having a problem We are trying to transmit a moderate amount of power (950 Watts or 1.27 HP) over a system that is not rotating very fast (100 to 300 rpm depending on where you look at rpm). To do this successfully on a smallish pulley we need to develop fairly high friction forces between the belt and the pulley to create enough grip to transmit the required power. You can develop enough belt/pulley grip force if you tension the belt around the two sheaves to a force that is higher than normal. The text's problem is that, in Table 20-2, it assumes that the belt is tensioned to some standard and normal force. We need more, more, more ... tension! That will allow us to use a smaller sheave and make the system look more practical.
By far the easiest way to work this out is to use a set of belt/pulley equation, but you won't learn these until second year. The next best way is to use one of the online belt/pulley calculators. These tend to be in US units of Horsepower. That's why I converted 950 Watts to 1.27 HP in the paragraph above.
Try this calculator our (click here ...).
They have a nice explination of what going on and how to load numbers into the calculator. Note how high the belt tension force is. It get pretty big. The nice thing about this calculator is that it will give you a solution for almost any design. It also works out the belt length. The only thing it does not do is tell you what type of belt to use. I can live without you speciifing the belt length in your report, so don't sweat it.
By the way, if you have come up with another way of dealing with lacking in the textbook feel free to use it. All I ask, for any method you use, is that you spell out what you have done and how/where you got your answers. Oh ya, they need to be correct too.
Take a look at this fun video. These folks have gone kind of nuts! (Click Here ...)
notes & files
links Belts: Have you ever seen something as amazing as this? (Click Here ...) Camera: Take a few minutes with this video. It is wildly interesting and a really wonderful job of 3D computer work. (Click Here ...)
project
assignments & labs
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