Split roller bearings help turn ordinary pipe into precision drive shaft

A couple of standard 2-1/2 in. schedule 80 pipes were quickly transformed into precision drive shafts for critical positioning equipment in the United States Navy Research Laboratory’s new Spacecraft Rendezvous and Docking Simulator with the help of split roller bearings.

The idea came from engineers at Craft Bearing Company Inc., who designed the large, state-of-the- art equipment to manoeuvre the full-sized spacecraft to simulate the terminal docking phase during rendezvous in space.

The Navy needed a long, rigid, lightweight drive shaft for the precision control of the docking spacecraft. Craft’s engineers developed an effective and inexpensive solution that could be applicable to almost any situation where line shafts are needed.

The engineers simply made the drive shaft from standard pipe, rather than solid machined steel. This was possible because the use of a Craft Split Bearing required machining only the area where the bearing was to be installed. The rough 2.875-in. outside diameter of the pipe was easily turned to 2.750 in. for about 6 in. near the centre of the 20-ft pipe sections. Each end was bored to 2.375-in. inside diameter to accept Trantorque keyless bushings.

The pipe sections were installed on either side of a girder-mounted, low-backlash, parallel shaft gear reducer. Short stub shafts at each end were fitted with drive sprockets. The standard Craft S1-212 BCH Split Roller Bearing was then installed around the shaft.

Due to the high lateral stiffness and light weight of the pipe sections, only one bearing was required at the mid-span of each pipe drive shaft.

Compared with a conventional 2-in. solid drive shaft, the pipe shaft was 28 per cent lighter, 70 per cent stronger and 140 per cent more rigid.

The ability of the split roller bearing to be assembled around the shaft saved hours of machining, reduced installation time and made the concept feasible.

For more details on this application, contact Craft Bearing at 757-247-6000, e-mail: info@craftbearing.com, or use the reader reply card number below.

Reader Service Card No. 310