Low Profile Single Hole "Auto Align" Bearing
Entry ID #: 3890
Created: Wed, Jan 11, 2017 7:37 PM
Single Hole Bearing Introduction The current VEX bearing flats have four small nubs surrounding each hole so that they align properly in the square holes found on VEX metal parts without excessive effort, however over the course of development of VEX rocotics, mechanisms have become, and are ever-increasingly high torque and/or delicate. The current VEX bearing flats, which were not designed or intended for use in the way that competition currently demands, are failing to keep up with the stresses necessary to preserve the efficiency of power transfer. Bearing Failure VEX bearing flats are likely to fail in 3 main ways: Heavy Load/Shock Load Heavy loading or sudden force on a VEX bearing flat can cause it to slide out of place, often stripping the nubs used for alignment. This causes unnecessary friction, and in serious cases shaft locking, which occurs when the sqare shaft rests flush against the side or in a corner of the square holes. Torsion While Steel and aluminum are more torsion resistant than the VEX acetal bearing flats, they are still not entirely rigid. VEX steel or aluminum at stock length is more than long enough to flex and twist. Torsion does not cause the bearing to change orientation realtive to the structure it is mounted to, but rather the shaft it is supporting, resulting in unnecessary friction. Poor Alignment Although VEX bearing flats work well in the simple scenarios they were intended for, delicate mechanisms as well as low torque/high rpm applications rquire perfect alignment, which as previously stated is failry easy to lose. Once a bearing has had its nubs damaged or stripped it is effectively impossivble to align, and given that high rpm mechanisms are prone to shock loading, there is a high likelyhood that this will occur somewhere in the system, introducing friction which will multipy power loss by the factor of each compound between the output and the disturbance. With the growing need for high fidelity bearings has promted a number of teams to go to great lengths to remove them from their mechanisms wherever possible, but this practice can only go so far given that bearingflats can not be properly avoided in the cases of compounding and outputs that require a shaft input. The first thought that comes to mind when seeking alternatives is a ball or roller bearing, as they are durable precision parts that are designed for professional applications far beyond the limits of VEX robotics, however the cost of manufacturing stainless steel or ceramic bearings is too high to compete with the affordability of the current acetal bearings. The answer to introduce a new plastic bearing that can offer the strength and torsion resitance of a ball or roller bearing as well as the ease of use of VEX bearing flats whithout breaking the bank. The solution is a single hole bearing that utilizes the rigidity of the metal it is mouted to in order to resist torsion and set inside a hole in the metal to maintain alignment without having to rely on easily stripped nubs or compression from fasteners to keep it in place. Part Design and Specs The part istelf is a 3D printed cilynder (modeled with Autodesk Inventor Professional 2016) with a wider lip at the bottom and a 0.13" diameter hole in the center (the same diameter as the VEX bearings). The part is pressed into a 5/16" diameter hole drilled in steel or aluminum structure, no screws or rivets necessary, keeping the instalation process quick and easy. The new bearing solves the 3 largest problems with VEX bearing flats through the application of these key design features: Support utilization of Stucture 1. The new part rests in a hole with substantial overhang, preventing it from becoming disoriented by load. 2. Since the bearing is two-thirds shorter than a conventional VEX bearing flat, it is effected significantly less by torsion. Outer Lip Alignment The lip at the end of the part, when pressed flush to the mounting surface, ensures perfect alignment no matter the conditions as well as preventing it from sliding out of its hole. Conclusion Initial tests indicate that the part is significantly more robust than the current VEX bearing flat, and fully capable of being used in high stress applications as well as being accessable as a 3D printable component and CAD model, which can be edited to the users' need and preference. Although it is very simple, bearings are vital to the function of any VEX robot, and the improvment of a part so simple can make complex mechanisms more accessible and mechanical efficency easier to acheive.