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NH478 Haybine

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#1 Mferguson3525


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Posted 19 August 2012 - 03:07 AM

I have a NH 478 Haybine and have broken the roller chain for the bottom roller on the woble box side. When replacing the chain I noticed that the idler sprocket up above the double sprocket is off center. I assume that something has moved but dont see where anything looks worn. Where should I start to figure this out? I replaced the chain but it broke again.Thanks for any info....

#2 mike10


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Posted 19 August 2012 - 08:29 AM

There is a setscrew that holds the double sprocket in position by seating into a hole in the output shaft of the gearbox. Sometimes these set screws will fall out or more likely the pressure of the sprocket against the set screw will cause the setscrew to wear and the hole in the shaft to elongate allowing the sprocket to slip to the side. If the idler mounting tabs above the gear are not bent, which can happen when a chain fails, then I would look at the set screw.

Be sure after tightening the chains that the rolls are in time and not touching each other. You can install the lower chain and get the rolls out of time. When that chain is tightened there should be equal slack on the top side of the chain as there is on the lower side of the chain when pushed against. If one side is tight and the oposite side is loose you have the roll out of time.
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