Question 431Motor Plants - Assistant Engineer

The correct answer is C) renewing both driving and driven gears as a set. When the timing gear backlash for a Roots-type blower becomes excessive, the proper repair is to renew both the driving and driven gears as a set. This is because the excessive backlash is likely caused by wear on both gears, and simply replacing one gear will not properly address the issue. Renewing the gears as a set ensures that the new, matched gears have the correct fit and backlash, restoring the proper operation of the Roots-type blower. The other options are not correct because they do not fully address the root cause of the problem. Renewing only one gear (options A and B) does not account for the wear on the other gear, and shimming and pinning the gears (option D) may only be a temporary fix, as the underlying gear wear would not be addressed.