Roller Bearings in Meccano
There can be very few Meccano constructors who have not had to build a roller bearing. The two requirements are that they should be able to bear vertical loads with reduced rotational friction, and also to prevent unequal loading so that they resist tilt.
If they are small, then the complete Meccano Ball Thrust Bearing (part 168b,c,d) will be most useful, and it has the added advantage of a toothed component for a chain drive. The latter part (168b) could be replaced by a 3 1/2" gear wheel (part 27b) if a 1/2" pinion were required.
Even smaller or much larger bearings can be built, especially the giant roller bearing for a blocksetter using the 9 1/2" flanged rings. In the latter case some sort of spider will be required to provide support for the rollers themselves.
Added problems in roller bearing construction are the need to hold the whole construction together, to transmit a central drive, and also to provide for an electrical connection between the lower and upper parts of the model.
An interesting method of building a bearing will shortly be described (see photo). It relies on hook rollers to transmit the loads, and will be found to be extremely stable even under severe eccentric loading, as well as being self-centering. If two circular plates are locked together but separated from each other by a space which is just larger than the rollers between them, this principle can be used to make such a bearing. The plates would then be attached to one component of the model, say the base, and the rollers would be attached to the other part of the machine, say the under-side of the super-structure.
Roller Bearing Construction
The main section of the bearing consists of three gear rings (part 180), two hub discs (part 118) and two (flat) 6" circular plates (part 146). They are assembled using four 3/4" bolts. Ensure that the teeth of the gear rings correspond to each other before using them. A 1/2" pinion below the chassis will mesh with them. Assemble these components by passing bolts, introduced from above through the gear rings, then through one of the hub discs, then the two stacked circular plates (for strength), and finally the second hub disc. Ensure that the gear rings and the circular plates are concentrically located to avoid binding of the slewing gear. Bolt a wheel disc above using two screws for fixation.
Pass eight 1 1/8" bolts through the peripheral holes of the hub discs from above, and immediately tighten them securely on nuts below the lower hub disc. Now screw a further nut on each bolt almost up to the edge of the lower hub disc flange.
A second pair of flat 6" circular plates is joined together, with a bush wheel below, which holds a 2 1/2" rod projecting upwards (this rod is the central spindle of the roller bearing).
The distance between the two sets of stacked circular plates is critical. Thread nuts on the eight bolts, but do not tighten them. Use a 3/4" flanged wheel as a test gauge. The plates should be set apart so that the wheel does not touch both sets of plates at the same time. Use only four of the bolts set at 90 degrees from each other for testing, and turn the inside nuts up or down as required for the gauge, bringing the outside nuts to the lower circular plates as a lock nut. Keep testing the gauge continuously as this is done, until the lock nuts are tight and the gauge is correct. Continue round the plates at 90 degree intervals, testing continuously. Any widening of the gauge will allow the bearing to rock, and any narrowing of the gauge will cause binding of the 3/4" flanged wheels.
Build a square sub-frame from four 5 1/2" angle girders, flanges down, attaching them to each other at their ends by their oval holes.
Now thread this structure onto the remaining bolts of the bearing, and follow the procedure as previously outlined, testing the gauge continuously. The sub-frame will be used for attachment of the bearing to the sub-chassis.
Each of these consists of two 3/4" flanged wheels freely running on short threaded pins fastened in the end holes of two overlapped pre-curved 2" (five holed) perforated strips. The curve should follow the outside circumference of the hub discs. The perforated strips are very tightly fixed by their centre holes to the smooth end transverse bores of threaded couplings, with two standard washers intervening. Pivot bolts are used for this fixation, introduced from inside the couplings, then the washers, and then through the strips. The strips are very securely fixed to the coupling by a nut.
The pillar of each hook roller consists of the threaded coupling and two collars on a 3/4" bolt. It is emphasised here that the pillars must fixed to a very strong chassis in order to withstand superimposed loads. Such a structure might be built from a layer of flat plates and an angle girder above. The front pillars are located 4 1/2" apart from each other, while the rear pillars are 5 1/2" from the front ones.
Place the centre shaft placed through its bearing in the superstructure if one is used, taking care to ensure meshing between the gear rings and the slewing pinion. Now attach the hook rollers one by one to the underside of the superstructure. Introduce a 3/4" bolt from above through the chassis girder and flat plate, thread two collars onto it, and then screw it into the waiting central bore of the threaded coupling. Proceed around the bearing, attaching the other rollers, and then check for free running. Lubricate where necessary.
Once the bearing has been completed, it action can be clearly seen. When it is loaded in front, then the front rollers run against the lower plates. The rear rollers will run under the upper plates. Because the gauge has been so finely adjusted, almost no tilt will be apparent.
A much smaller bearing can be built, with 2" pulleys (part 20a) as the circular plates, and 1/2" pulleys used as the rollers