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  • Pedal drive propeller system

    Discussion in 'The main mechanical design forum' started by Chikokishi, Oct 3, 2012.

    1. Chikokishi

      Chikokishi New Member

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      Im trying to design a pedal drive for a small boat propeller, but as it turns out the only *real* chain gear system knowledge i have is with mountain bikes. Im a senior in mechanical engineering, and this is my senior design project. Anyway, iv been everywhere trying to find a good reference to teach myself types of gears, connections, etc. But because i dont know what things are called i cant search for them. Of course i know a sprocket holds the chain and such, but how do i attach it to drive shaft, what are the sprockets that only work in one direction called, whats the proper word for a gear that works at a 90 degree angle? Etc etc. My mech design book tells me all about how to calculate spines and forces, but nothing like a list of words and what they do.

      Thanks for leads!

      Chiko
       
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    3. MSBT

      MSBT Member

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      Hi,
      Apart from being very surprised that a "senior" student has never heard of a bevel gear to transmit rotation orthogonally, (or why you haven't simply asked your tutors or faculty-technicians), I suggest you do a bit of reading in this area.
      Both of these documents specifically refer to pedal-powered marine-propulsion and you should be able to find a lot more info on various gearing systems in similar sources that could be of use to you:

      http://worldwide.espacenet.com/publ...T=D&ND=3&date=19841002&DB=EPODOC&locale=en_EP

      http://worldwide.espacenet.com/publ...T=D&ND=3&date=19210615&DB=EPODOC&locale=en_EP
       
    4. Chikokishi

      Chikokishi New Member

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      Yes, well, I DO go to one of the nations top accredited colleges. And its completely worthless. Long story short, this school sucks terribly and i feel completely adequate to walk out of here and fail miserably at any job I go to. The beveled gears that i should know about as a senior in mechanical engineering is part of a class taught by a teacher who cant even correct his own homework that he assigns. Followed by asking us questions such as "what is a torque on the bearing in this system?"

      Anyway. I am here to read and learn about these gears, and the two links you gave looked helpful. I will look at them tomorrow when i have time. However, what i still need is a good reference for the types of gear available. Like.. a reference card with pictures and uses listed for the various (general) kinds of gears out there.

      Also, please don't refer to me as a "senior" as if im lying. I came to this forum because the last forum i was in continually attacked me for not being "smart enough" to design a device on my own, and kept telling me to just buy something on the market, or just give up. I don't want that happening again here.

      Chiko
       
    5. Chikokishi

      Chikokishi New Member

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      To be a bit more descriptive, I am looking for a reference that will allow me to find the name of a gear type based on what its used for, and how it controls its relative chain. For example, if im looking for a gear that pulls chain one direction, and if the chain goes backwards it will ratchet or free wheel. Such as the cassette on the rear of a bike. What would that be called?

      Of course if i could walk into a gear shop and look at the gears i could learn it all on my own. But as i am going to be shopping online i would like to know the names of gears so that i may search for them.

      Chiko
       
    6. Dana

      Dana Well-Known Member

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      There could be many ways to attach a sprocket to a shaft: key/keyway, taper bushing, pin, weld, etc. Right angle gears are "bevel gears", though helical gears could also be used. A freewheeling sprocket could be a ratchet and pawl, but you could also use a "sprag clutch" or a "one way bearing" (also called roller clutch).

      I suggest getting catalogs or looking at the website for Stock Drive Products, Boston Gear, Timken (bearings including roller clutches), and W. M. Berg. All of these have extensive engineering sections


      Unfortunately, most engineering schools today are heavy on theory, weak on practical application. Unless your professors have worked in industry before taking up teaching they probably are weak on practical application themselves. This is nothing new; it was no different in the 1970s when I was in school. But don't worry too much, you won't use much of what you learned in school but you should have the skills necessary to learn what you need to know. You won't be thrown on your own on your first job; you'll almost certainly be guided by engineers experienced in the area you're working in. When I graduated I really had no clue what an engineer actually did day to day, but on my first day on the job I was given a simple design to rework, next was a new design but loosely based on some existing equipment, working up from there.
       
    7. Chikokishi

      Chikokishi New Member

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      Dana,
      Thats good to hear! As you can see with my first actual design project, i feel like i dont know anything. And thats exactly right, i can calculate all sorts of things... But what IS it that im calculating?

      So you suggest that i just browse catalogs and look at things? Ill do that when i get some free time this evening. Thanks for the reply!

      I attempted to read my mechanical design book again today to see if i could learn from it. It tells all about how to calculate pitch, pressure, resistance, torque, fracture, etc of a gear. Nowhere does it mention gear types and uses. Frustrating.
       

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