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Car engine component standards. Where can i find?

  1. Dec 17, 2011 #1
    I am designing a car engine water pump and I want to know where i can find the standards of engine components that i can relay on. I mean what safety factors of stresses ,pressures temps and so on need to be accounted for.
     
  2. jcsd
  3. Dec 17, 2011 #2
    Huh. Would you want to buy a vehicle that had a reputation of systems and components failing and having to be repaired every six months?

    Nontheless, it is a very good question. It addresses what goes into the design of a part to fulfill expectations of users.

    I am not sure if there is a specific guide for the design of machine parts for automobiles.

    In any case, following basic machine design would be most practical. You would set a timelife ( is that a word ?) for the housing , seals, gasket, impeller for example. You would take in account vibration fatigue, temperature stresses, pressure fluctuations.
    Some design criteria would be more exacting than others which might entail "best guess".
    A reason I do say "best guess" is that they have been manufacturing cars for a hundred years or so and still components fail - especially a component so simple as a water pump.
    A previous design would serve as a model that could be tweaked to eliminate some metal and weight here and there, a change in casting procedure, alloys, performance criteria, and cost.

    I would consult your machine design book to find out a general safety factor and guidelines for fillets, bolted connections for example as a start.
     
  4. Dec 18, 2011 #3
    Thanks for the response, I understand the basic principles of basic machine design (like you mentioned- time life, fatigue and stresses. I just thought that there would be some standards when designing car components like there are when designing buildings, planes and elevators, and that these standards would be the rough outline or guide lines for my first layout.

    Buy the way, I believe that car manufactures invest time and money in calculating when is an appropriate time for a part to fail. I mean the spare parts market is huge and if they built fail free cars and parts it would cost many people there jobs and others would just lose tons of money.
     
  5. Dec 18, 2011 #4
    Well certainly don't start with anything that moves if you want to learn to design something.

    People don't design 'water pumps' 'transmissions' (they do, but it doesn't work for my examples, you'll have a chief engineer making system decisions). They design shafts, seals, clips etc. That come together to form a machine.

    You have to start from the ground up, looking at single components to begin with. There aren't really any standards, beyond internal company standards.
     
  6. Dec 18, 2011 #5
    xxChrisxx, I understand what you mean and it makes sense. Although I'm trying to find some sort of safety factor or some work cycles minimum for car engine components. Like i mentioned I know that in aviation these things are very clear and easy to find. This will be my starting point and from there i will design each component with that factor as the final goal of the multiplication or sum of each of smaller parts factors.
    I thought it would be pretty easy to find, turns out i was wrong.
     
  7. Dec 18, 2011 #6
    I an not sure what you are saying there. I doubt if Pratt and Whitney shares its design criteria for engine components with GE or Rolls Royce. As a whole when the engine is completed it has to go through certification for air worthiness. In an airplane, if a part fails, the airplane cannot just pull over to the side of the road and wait for a towtruck to arrive, so parts are designed to be fail safe and operable until the next engine overhaul will occur. Airplanes do not have such a thing as a warranty.
    Bolts from a bin for an aircraft engine are selected so that all bolts meet a minimum criteria - anything above is OK, anything less than is not. ( Thus you have higher military specifications, aviation specifications etc for parts and material selection than general )

    For a car, as a whole it must meet certain safety considerations on the road, such as brakes never failing, handling, etc. A non-life threatening component could be designed for a 1 to 2 year life such as wiper blades, or a 5 year life such as belts (maybe ). The powertrain ie engine, transmission, axles - is now probably "overdesigned" beyond the life of the car for obviious reasons. Other components on the engine might have an maximum expected life ( to last at least a certain number of years or cycles ) So thus you have the warranty thing to take into account when designing your water pump, but obiously there is not a one to one relationship of course - the pump just doesn't fail the day after warranty expiration.

    You could design your water pump to have an expected life of 25 years if a seal can last that long, but what would be the point in that if the car is going to be scrapped after 10 years. A $500 water pump would just add to the initial price of the car and for very few people this would be important buying/selling feature.

    for the bolt example - the bolts are selected so that an average, or 80% on a bell curve, or a certain number of standard deviation of the bolts meet design criteria so the selection is more relaxed.

    I hope that explains it some more for you.
     
    Last edited: Dec 18, 2011
  8. Dec 18, 2011 #7

    AlephZero

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    OK, there probably isn't one single "warranty deal" for a complete aircraft, but individual components certainly have warranties. For engine parts, that often means a free replacement if they fail before they are supposed to be replaced during scheduled maintenance.

    These days the warranty is often built into a fixed price maintenance contract (or "power by the hour"). The airline pays a set price for the standard scheduled maintenance that is required by law to keep the plane airworthy. Anything beyond that counts as "free replacement under warranty".

    The regulations (FARs, JARs, etc) only tell you what you have to demonstrate, and (sometimes) what you have to do you have to demonstrate it. They don't tell you anything about how to design the aircraft or engines. In fact it works the other way round: once the design is more or less fixed, there is usually a discussion with the regulators to agree up front how the regulations will be applied to it, because no set of printed regulations can cover every new idea that a team of design engineers will think up.
     
  9. Dec 20, 2011 #8
    i just hope my post is not late, i feel when you are designing your water pump. your starting point will be your input/output: how much output power are you trying to achieve (or flow rate) from that everything falls in place as in the pressures that are going to be experienced. As for the stresses and failures you might experience i dont think u should worry alot because a car is generally going to be in a stable enviroment (unless its for an off road vehicle then your considerations might differ a bit).
     
  10. Dec 21, 2011 #9
    Try the SAE website (Society of Automotive Engineers). I think most vehicle standards come from SAE.
     
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