Quick, Easy Stuffing Tube Construction

One of the early problems I had to solve when I built my first ship was the construction of stuffing tubes for the propeller shafts.  Stuffing tubes (or stuffing boxes) are needed to allow the rotating shafts to exit through the hull, while keeping water outside where it belongs.  They also serve to stabilize the prop. shafts and position them solidly where they belong.

What you basically need, is a hollow tube that is mounted in the hull.  A shaft is inserted into the tube, with a propeller at the outside end and a coupling to a motor on the inside end.  The tube is filled with grease to keep water out and also help lubricate the spinning shaft.  However, some kind of seal/bearing is needed at either end of the tube, for the shaft to ride on as well as to keep the grease contained within the tube. Randy Kehr’s Big Gun Page shows a method where successive “layers” of different-sized tubing is stacked up between the outer tube and the shaft, creating the bearings.  I have come up with a modified solution that is very clean, and can be done very quickly, with minimal cost.

This stuffing tube design is basically a brass tube, as may be found at most hobby shops and hardware stores (look for the K & S display rack).  For shafts, I used 1/8″ brass rod, also from the K & S rack.  Where this design differs is in the use of manufactured bearings; flange-type, sintered bronze bearings from Small Parts, Inc.

Figure 1.
Flange-type Bearing.Both of these part number have 1/8″ inside diameters, and 1/4″ outside diameters – the only difference is the overall length, which is 1/4″ for -2/4, and 3/8″ for -2/6.  Either works fine, and cost is only $1.36 each as of this writing.  Other sizes are available as well, and I have seen similar bearings at some hardware stores.

The outer tube needs to have an inside diameter that matches the outside diameter of the bearing, which would be 1/4″ plus the tube thickness, making a 9/32″, etc. a good fit.  Hint:  Take a bearing with you when you go shopping for the tube, and see what fits best!

Figure 2.
Stuffing Tube Assembly.As can be seen from Figure 2, assembly of the stuffing tube consists of merely inserting a bearing into each end of the tube.  Securing bearings with a drop of CA glue has worked fine for me so far.  As is noted, a small fill tube provides a convenient means to fill the stuffing tube with grease, and should be located far enough from the end of the tube that it clears the bearing.  In later versions of this stuffing tube, I’ve left out the fill tube – it’s easier just to pull the shafts to grease them.

Figure 3.
Final Assembly.Finally, the propeller shaft is pushed throught the assembled tube, and hooked up at either end.  My experience has been that these bearings are often a bit tight, requiring a few strokes of a miniature rat-tail file to ream out the inside before the shaft fits.  Other than this, they are virtually trouble-free, rock-solid, and can be assembled in just a few minutes.