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5. Helical Gear Set

Introduction Unfortunately, it is not uncommon for the teeth of VEX spur gears to break under high loads. Even the high strength gears have been known to crack under pressure. With our new gear set, teams will be able to build gearboxes that can handle heavier loads than ever before. Our new gear set contains helical gears. Helical gears have slanted teeth. This key feature gives helical gears many advantages over spur gears: helical gears have higher torque capacity than spur gears helical gears have less vibration that spur gears helical gears can transfer power between non parallel shafts It is no wonder that helical gears are the ideal choice in industry applications.     Application The set contains the following components. Right and Left Hand 12 Tooth Helical Gear Simple 12 Tooth Helical Gears with 10 degree angles Right and Left Hand 36 Tooth Helical Gear Simple 36 Tooth Helical Gears with 10 degree angles Right and Left Hand 60 Tooth Helical Gear Simple 60 Tooth Helical Gears with 10 degree angles Right and Left Hand 19 Tooth Rack Helical Gear Simple 19 Tooth Helical Gears with 10 degree angles. Right and Left Hand 12 Tooth - 36 Tooth Helical Gear The helical gears will often be under high torque. The helical gear adapter is able to take advantage of the additional strength that the metal 12 tooth gear offers. Our gear set allows teams to build many interesting gearboxes. Helical Gearbox A simple helical gearbox is two helical gears transmitting power between two axles. Every helical gear, in the assembly, must be meshing with the opposite type of helical gear; two left hand helical gears cannot mesh. A simple helical gearbox can handle greater loads than a spur gear box of the same ratio and build quality. Helical gears have one noticeable side effect. They generate a small axle force in the direction of the teeth. This byproduct can be removed with a herringbone gearbox. Herringbone Gearbox A herringbone gearbox is also called a double helical gearbox. The gearbox has both a left hand and right hand gear on each axle. Helical gears generate an axial force in the direction of the slant. By having two inverted helical gears on the same axle, the gears generate forces that cancel out. The herringbone gearbox has a greater torque capacity than a spur gearbox with the same gear ratio, build quality, and number of gears. Rack and Pinion Gearbox A helical design is optimal for a rat and pinion gearbox. Rack gears generally carry high loads. The helical tooth design increases the torque capacity of the gear. Helical rack gears are less likely to crack while lifting high loads than traditional rack gears. Explanation Helical gears are stronger than spur gears. The angled teeth helical gears ensure that there is more contact between two gears. A greater contact area allows helical gears to carry greater loads. The minimal vibration of helical gears is also caused by the angled teeth. The teeth of the helical gear gradually comes into contact. Helical gears are also always engaged to part of more than one tooth at a time. These qualities ensure that helical gearboxes are very quiet.    CAD Explanation and Design Process We used Autodesk Inventor 2015, Autodesk 123D, and buckets of whiteboard markers for our VEX CAD Engineering Project. We started off by researching helical gears and helical gearboxes. We finalised an optimal tooth pitch for VEX components. Then, we modified VEX spur gears to have this tooth setup. We used the coil tool to make the tooth feature. After, we assembled the gears in various gearbox assemblies. We animated the assemblies to provide a clear and thorough understanding of how the gearbox worked. We decided to physically make the Simple Helical Gearbox. We exported the gear part files as stl files and modified them in Autodesk 123D. We then printed the required parts. We built the gearbox and then applied a force on the gears until the teeth crack. We measured the approximate amount of force required to break the teeth. We repeated the process with spur gears. We found that spur gears broke under less force than the helical gears.   Conclusion and Improvements The VEX CAD Engineering Challenge was a great experience. We learned many useful design skills while making our helical gear set. Previous to the contest, we had never done animation work in Inventor. Now we feel comfortable with many of these complex tools, including Drive Constraints, Inventor Studio, and Exploded Views. We definitely plan on using Inventor, and CAD in general, more often in our robotics club. A lot of resources are saved by designing robot components virtually before physically. Next year, we will encourage our club teams to CAD their robots before ordering new parts. This new rule implementation will definitely prevent teams from buying excess and unnecessary parts. We hope you find our helical gear set to be a necessary addition to the VEX Robotics Inventory. We are certain that your curiosity is intrigued by the potential robot designs that gear set makes available.