 Hi everyone. In this video I'm going to talk about bevel gears. Bevel gears have slightly different geometry from what we've been looking at with spur gears and helical gears in that the actual face of the gear itself where the teeth are is at an angle. And on the drawing that I've started here you can see that the angle that gives that orientation is labeled gamma and we have a face width of those teeth of b just like we've seen before but now noted that it just measures a little differently. So I've only drawn one gear in what would be you know a mating pair in a gear set. On this gear we have our similar forces. We have an axial force like we've seen before. We have radial force and now we're adding in what we'll call a normal force which is basically normal to that surface where the gears are gear teeth are located. Of course we would also have our transmission force but in this case our transmission force is perpendicular to the page so I'm not drawing it out here but it's coming into and out of the screen as we're looking at it. We still have a pressure angle fee generally around 20 degrees as a standard for that. I've also labeled some diameters here. One being this outer diameter which would be measured at the largest overall size of the gear and then the diameter that we'll end up using for a lot of our analysis which is the average diameter. The average diameter being somewhere in the middle here between this smaller inner diameter and this larger outer diameter on the bevel gear. So that average diameter we can quantify by saying it's equal to that outer diameter minus the face width times sine gamma so that's just the projection of the face width onto that that coordinate direction and if we were looking at a mating gear pair here we might be interested in the gear ratio and I want to write that down quick and that is omega p in ratio to two omega g so that's just like we've seen before the pinion in the gear and we can relate that to the number of gear teeth on the gear and the pinion the diameter we can also even relate it to the angle in this case the bevel angle which is kind of interesting of the gear or of the pinion where we have the cotangent of the pinion. All right so when it comes to looking at our analysis that we're interested in we want to do a force analysis usually. Typically the first thing we would need is a pitch line velocity if we want to look at the relationship between force transmission the transmitted force and the power and so just making a note as a reminder of what we've seen before that we can write pitch line velocity in terms of that average diameter pi d average times n and being rotational velocity then we can write the transmission force much as we've seen it before in terms of power and velocity now of course this 33 000 value in there is a English unit system you know conversion going on so now again kind of working from that transmission force we can write some of our other forces that we have we have the normal force that we've just described here the axial force which I could write in terms of the normal force and then also of course in terms of this transmission force and the radial force like that so we've got these various forces that we we might want to make use of and now actually in terms of stress our equation hasn't really changed much so I'll just kind of for iterative purposes write that down again and the main difference here is now we're going to pull j from figure 16.13 so we've got a new another new figure in order for finding that geometry factor and then we're going to pull this mounting factor from table 16.1 so this is a new a new source for the mounting factor other than that nothing else has really changed in terms of how we would analyze the system we've got a little bit of new geometry we've got a couple of new variables but otherwise everything else is is really very similar all right thanks