Build a Quality Bearing
Ian Mordue
When Frank Hornby came up with his idea for Meccano, I don’t think he could have anticipated the sophisticated applications that modellers found for the parts he introduced to the system. One of the most innovative was (as far as I am aware) first suggested by Bert Love in his book “Meccano Constructor’s Guide”. In this he described the combination of two 6” circular plates inside two 7 ½” circular strips, carefully separated by washers and holding 52 Meccano ball bearings to form a very effective ball bearing race. This was capable of supporting and turning very large rotating superstructures without any “tilting”, since the play in the bearing could be kept to a minimum by patient adjustment. The nature of this design of bearing was such that the use of both the GRB and the smaller part 168 (ball thrust bearing) was marginalised for serious builders to models where all the thrust was at 90’ to the bearing plates or where the size of the model meant that the 7 ½” diameter of the completed unit was inappropriate for scale purposes.
Now that the range of Meccano has been much extended by producers of reproduction parts, the option for creating similar bearings in a variety of sizes is open to builders. Given that the difference in size between the outer and inner parts of the bearing is 1 ½” this gives the following possibilities:
5 ½” circular strips (or 5 ½” circular girders) with 4” circular plates creates a 5 ½” diameter bearing
4 ½” circular strips with 3” circular plates creates a 4 ½” diameter bearing
3 ½” circular strips with 2” circular plates creates a 3 ½” diameter bearing
2 ½” circular strips with 1” bush wheels creates a 2 ½” diameter bearing
This wide range of choices now offers a quality engineering solution to producing smooth rotation in any plane for virtually any model where circular movement is necessary.
The example below was used by me in a small service crane on top of a much larger crane to permit slewing of the jib of the service crane. This particular bearing uses 3 ½” diameter circular strips with 2” circular plates in the centre. This size was chosen as it was in scale with the small crane itself and a 3 ½” gear ring could be neatly fixed to the base of the bearing. The crane superstructure could slew round this gear using a ½” pinion fixed in the end hole of the 3” x 1 ½” plate fixed to the centre of the bearing and as shown in picture 1. The 3” x 1 ½” plate would form part of the base of the crane superstructure and the collar holding the ½” slewing gear in place would be replaced with a gear being driven by a small motor in the cab of the crane. In picture 2 the underside of the bearing is shown with the gear ring attached. The four bolts going through the gear ring would be fixed to the crane base. Picture 3 shows a side on view of the bearing so that the spacing apart of the various elements of the bearing can be seen. When constructing the bearing, the two circular strips are only loosely connected initially so that the balls can be squeezed between them. Once all the balls are in place then the bolts joining the circular strips can be tightened up and the smooth rotation of the bearing tested. If the bearing becomes “sticky” as the bolts are tightened, then the thickness of the washers separating the circular strips will need to be adjusted (a mix of standard Meccano and commercially available 4 mm washers will usually provide enough options to reach an optimal compromise between freeness and lack of play).
Picture1
Picture 2
Picture 3