Entry ID #: 5795
Created: Tue, Jan 8, 2019 9:48 AM
Why the Insert Lock?
This year, we have spent a lot of time working with flywheels. We’ve done our best to minimize our flywheel’s footprint and friction in order to make it best work with the rest of our robot. However, the spacing necessary to fit the required gears was more than we would have liked, so we explored ways to decrease the amount of spacing needed between gears. The insert lock does just that, while tightly holding the gear tight so that there is no slippage between the axle and the gear.
How the Lock Works
The lock is relatively simple. It involves the long insert piece and the end cap. The long insert fits tightly inside of high strength gears by using the high strength axle hole. It also has thin extensions on the side which flex in and press against the inside of the hole. This gives the tightest fit possible to avoid any lag in the transfer of power from the axle to the gear. Once the lock is in a gear, the cap is used to cover the other end. The design of the cap is made to easily accept 8-32 screws that pass through it and the insert to clamp down on the axle. The use of 8-32 screws (we prefer star drive), as opposed to the set screws from shaft collars, allows much more torque to keep the assembly tightly attached to the axle. This also solves the problem we have had with set screws being loosened by the constant vibrations within the flywheel.
How the Lock Was Made
After isolating the problem we wanted to solve, we then devised a few ideas to fix it. After quickly sketching each of our possible solutions, we came to the conclusion that this part would best solve the problem. It would be most effective at achieving our main goals for this part and at being effective in other ways. We took some measurements of a High Strength gear to find out how the part had to be fitted before starting the design of the first part in Autodesk Inventor. The long insert started very simply with a square extrusion to fit in the gear and an end which held it from sliding out on one side. We cut a hole through the center for the axle then moved onto the first version of the cap. We then designed the end cap to secure the gear to the axle. We then placed the hole in the cap in a location that affords enough space to fit the 8-32 screws. After printing both parts and testing their size and functionality, we decided to create a few more additional features. We added a few filleted edges to make the assembly of this part easier and then decided to find a way to create a tighter connection of the insert on the gear. We cut a rectangle centered in each side of the insert. After this, we extruded thinly curved segments within each of these cuts that extended slightly past the surface of the insert. Although the addition of the ribs makes the insert larger than the hole, the ribs are designed to flex in and keep pressure against the interior sides of the gear.
Overall, this project taught me a lot. I had never used Inventor before, so it took some time to get used to that, but I learned the basics of a new CAD program. 3D design has been and is very useful for robotics as it allows us to plan and design our robot before building it. I have grown to really appreciate and enjoy CAD programs, so I know I will definitely be using them in the future. I am going to major in civil engineering, so I will likely be using multiple Autodesk programs used in some form for structural design. I know these other CAD programs will be invaluable, and I can’t wait to use them in my future career.