A ROLLER having the same diameter as a corresponding ball and a length equal to the ball diameter has approximately four times the carrying capacity of a ball, according to Mr. Hermann. The data presented on cageless roller bearings are based upon knowledge of the carrying capacity and life of the ball bearing.
The reason for the increased carrying capacity of a roller over that of a ball is due to the distribution of the load over a line of contact rather than at a point of contact. The roller bearing increases the number of such line contacts and therefore further distributes the load to the raceways. By increasing the number of line contacts, the cageless rollers reduce the stress per roller and failure due to fatigue. The fatigue factor is reduced 40 per cent, comparing a cageless with a caged roller.
Formulas are presented which are based on ball-bearing data so that the load-carrying capacity at the various speeds of rotation will give the same life to the cageless roller bearing as would be experienced with the proper ball bearing for the same load and speed.
Hardness of the raceways is discussed and data necessary to apply cageless roller bearings are presented. The methods of assembly are stated.
As to roller specifications and requirements, the rollers are made from wire having an S.A.E. 52100 analysis. The process of manufacture is described and the allowable tolerances are given. Insufficient data are as yet available regarding just how little lubricant is necessary but, thus far, Mr. Hermann says that the installations are running on almost every kind except water.
Car manufacturers using cageless roller bearings for universal-joint trunnions say that lubrication is necessary only after 20,000 miles, or a period of one year. They are lubricating then more as a precautionary measure than as a necessity.
In the discussion, the experience of the manufacturer who pioneered the cageless roller bearing on a universal-joint trunnion is recounted.