As an engineer at Robotzone my job is to design innovative parts. The innovation many times stems from frustration with parts that are currently available on the market – either the available parts won’t allow users to build something a certain way or the available parts can be a weak link or point of failure. That's why we are excited to launch the new D-hubs into the ever-growing line of Actobotics® parts!
Set Screw Woes
Cylindrical bore set-screw hubs have a primary intent of going onto a shaft with a flat on one or multiple sides. The set-screw puts pressure on the flat surface of the shaft to lock the hub and the shaft together. There are two issues with this approach. First: the set-screw and shaft that it contacts are prone to wear in high-use and high-torque applications. As the set-screw wears on the shaft and vise-versa, there is the possibility that the hub can become loose. Second: if the set-screw does become loose it can cut into the shaft as it rotates around, marring the shaft and making it very difficult to get the hub (and other items on the shaft, such as bearings) very difficult to remove.
Clamping Hub Challenges
Clamping hubs, when tightened, squeeze down onto a shaft to create a no-slip connection between the hub and shaft. Although they are more commonly used with round shafting, some builders, hobbyists and FIRST teams have made the migration from set-screw hubs to clamping hubs even for use on D-shaped shafting in hopes of solving their set-screw woes. However, there is a potential issue with this approach as well. Since the shaft is D-shaped and the bore of the clamping hub is cylindrical, there’s a chance that the shaft can spin inside of a standard clamping hub since there’s not 100% contact between the two parts.
In order to solve those issues we’ve designed hubs that have a D-shaped bore to perfectly match the shaft profile of popular gear motors and shafting used within the robotics market. Like their cylindrical bore siblings, the D-hubs are offered in two varieties; set-screw and clamping. We challenge you to get either version to slip!
The symmetrical profile provides for a nearly perfectly balanced part, excellent for high speed applications. The profile of the bore alone would keep the hub from slipping on the shaft but the set-screw keeps the hub from sliding up and down the shaft. The set-screw will put a mark on the shaft (as the cupped point is intended to dig in and hold tightly), but on the non-cylindrical surface. This is key to a properly manufactured D-hub as running a set-screw down onto the rounded profile of a shaft would mar the shaft and make installing/removing of future parts a battle.
The clamping D-hubs are the absolute brute of all hubs. They’re non-marring which means you can install and remove anywhere along a shaft with no evidence left behind. The bore is only a few thousandths larger than the diameter of the shaft so they squeeze down on the shaft with the minutest amount of distortion to the pattern on the hub. They clamp so tight they’ll never move during use - they release easily by loosening the 6-32 pinch bolt.
If you've ever had trouble with slipping hubs or marred shafts from set-screws, try our new D-hubs. You will be glad you did!
by Kyle Lewis