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Correct clearance of engine parts

  1. Dec 4, 2013 #1
    hello friends,can you explain what is correct clearance of engine's moving parts,giving examples.
  2. jcsd
  3. Dec 4, 2013 #2


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    This is incredibly vague. What engines? What parts?
  4. Dec 4, 2013 #3
    it is implication of clearance of an automative engine's static and moving parts.
  5. Dec 4, 2013 #4


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    Too loose is no good.
    Too tight is no good.
  6. Dec 5, 2013 #5

    Ranger Mike

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    In the beginning ....pre-industrial revolution..things were made one at a time. Clocks, table plates, glasses..pretty much everything was made by craftsmen..one at a time. The need for mass production came about thru...WAR... you were not going to beat your enemy if you had bow and arrow and he had flintlock firearms...and if both sides had fire arms.. the man with the most was going to win. In fact the first know quality control gage was a cannon ball gage. This was a simple round ring with a handle and the cannon ball either fitted thru the gage or it did not. This go-no go gage was the forerunner of all kinds of neat things in measurement. The cannon ball maker would cast many cannon balls and those that fit got shipped, those that did not went back to the furnace for remelt. So we have a “ nominal” dimension (ideal size as designed) and a working “tolerance” or acceptable deviation from the nominal size. As production refinements evolved this tolerance became smaller and smaller. measurement techniques and equipment also became more accurate and precise.
    Enter todays production automobile engine. We have mass production capability for machine metal parts to very high accuracy. Typically the manufacturing tolerances are to .0005” (.0127mm).
    getting back to your initial question- an internal combustion engine is one big air pump. It takes in gasoline and air , compresses it and ignites the mix thus causing linear motion of the piston rod assembly that becomes rotary motion via the crank shaft. Except for the piston ( aluminum) all other parts are either iron or steel. ALL of these items have a coefficient of thermal expansion. They get hot and the size increases ( thermal growth). If we had no " clearance” things would seize up. We have clearance to compensate for thermal expansion AND provide a small amount of room in the assembly to hold lubrication ( motor oil). If the clearance is not enough, the result will be metal to metal contact and eventually the resultant friction will be fatal. If we have too much clearance the parts will be banging together and the gap will widen and we have fatal attraction!!
    my opinion
    Last edited: Dec 5, 2013
  7. Dec 6, 2013 #6
    A really good explanation.but how can i find pictures about clearance,good clearance and bad clearance,failure of bad clearance,clearance examples.
  8. Dec 6, 2013 #7

    Ranger Mike

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  9. Dec 6, 2013 #8
    thanks again.you are a very experienced person.
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