how does a cam chain tensioner work?


4 replies to this topic
  • dirtbikesandlacrosse

Posted July 16, 2013 - 10:17 PM

#1

how does a cam chain tensioner work? Like how does it actually make the cam chain tighter?

  • KJ790

Posted July 17, 2013 - 05:04 AM

#2

Each company has a slightly different design, but they are all similar. Most have a spring loaded slider or wheel that pushes on the cam chain half way between the crank and the cams to take the slack out of the chain.

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  • grayracer513

Posted July 17, 2013 - 06:51 AM

#3

The most common design used today is essentially a spring driven worm and sector type set up. There is normally a housing that bolts to the cylinder in such a way as to bring the plunger of the tensioner to bear on a swinging tensioner shoe, as in the picture above. The plunger itself has an internal screw gear cut into it, and is keyed to the housing so that it cannot rotate along its length. A torsion coil spring is anchored to the housing and drives a shaft cut with a worm gear the threads into the plunger. This is the part that you turn to release tension when servicing.

As slack appears in the chain, the spring is able to rotate the internal shaft steplessly until the slack is gone, but if the chain tries to push back on the plunger, it cannot do so any more than you can pull a bolt out of a threaded hole without turning it; worm gears can't be back driven. Simple.

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Other designs include simple spring loaded arms or plungers, often with ratchets to prevent pushback, some driven by hydraulic pressure from the engine oil pump, etc.

  • dirtbikesandlacrosse

Posted July 17, 2013 - 11:18 AM

#4

O I get it now! So it pushes the cam chain inwards to increase the tension. Thanks!

  • TDW

Posted July 21, 2013 - 12:53 PM

#5

The most common design used today is essentially a spring driven worm and sector type set up. There is normally a housing that bolts to the cylinder in such a way as to bring the plunger of the tensioner to bear on a swinging tensioner shoe, as in the picture above. The plunger itself has an internal screw gear cut into it, and is keyed to the housing so that it cannot rotate along its length. A torsion coil spring is anchored to the housing and drives a shaft cut with a worm gear the threads into the plunger. This is the part that you turn to release tension when servicing.

As slack appears in the chain, the spring is able to rotate the internal shaft steplessly until the slack is gone, but if the chain tries to push back on the plunger, it cannot do so any more than you can pull a bolt out of a threaded hole without turning it; worm gears can't be back driven. Simple.

Posted Image

Other designs include simple spring loaded arms or plungers, often with ratchets to prevent pushback, some driven by hydraulic pressure from the engine oil pump, etc.


I like your explanation of how most of the tensioners work. I dont think alot of people understand that the tensioners are designed to only turn one way automatically, and not in both directions.




 
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