Originally Posted by fliz
Quick question regarding these two paragraphs.
I broke an aftermarket gearset. Since it's no longer manufactured, I had to have a custom replacement made. The original was helical, but I asked for a straight cut second on the new shaft. I was under the impression that spur gears are stronger, ince they don't produce the axial loads that a helical gear design does. Is a spur gear design less likely to produce shaft flex?
If the spur design is not going to be as strong...I may have to call and change my order.
Yes, a spur gear produces much less axial load than a helical gear. The axial thrust loads must be absorbed by the bearings. The high thrust loads create increased frictional losses which is why most racing gear sets opt for a spur gear (more power delivered to the wheels basically). But in terms of the actual strength of the gear....a helical gear is stronger than a spur gear all other things being equal.
A spur gear is actually going to create more shaft flex because nearly all the reaction forces are going to be in the direction that would bend the shaft. A helical gear, as mentioned, has a portion of those forces going along the length of the shaft in the axial direction. However, I believe that a spur gear can operate with less critical gear mesh so the gears need to separate more for it to become a real issue.
If you have this gear made I would suggest consulting an engineer to make sure that the gear being produced is as strong or stronger than the gear it is replacing.