§393.89 — Buses, driveshaft protection Any driveshaft extending lengthways under the floor of the passenger compartment of a bus shall be protected by means of at least one guard or bracket at that end of the shaft which is provided with a sliding connection (spline or other such device) to prevent the whipping of the shaft in the event of failure thereof or of any of its component parts. A shaft contained within a torque tube shall not require any such device.
[33 FR 19735, Dec. 25, 1968, as amended at 53 FR 49402, Dec. 7, 1988]
§393.89 — DOT Regulatory Guidance
Question 1: For the purposes of §393.89, would a spline and yoke that is secured by a nut be considered a sliding connection? Guidance: No. To be considered a sliding connection, the spline must be able to move within the sleeve. When the end of the spline is secured by a nut, it no longer has that freedom.
Question 2: On multiple drive shaft buses, does §393.89 require that all segments of the drive shaft be protected no matter the segments' length? Guidance: Yes. Each drive shaft must have one guard or bracket for each end of a shaft which is provided with a sliding connection (spline or other such device).
Question 3: How does an existing pillow bearing (shaft support) on a multiple driveshaft system affect the requirement? Guidance: It does not affect the requirement. It is part of the requirement.