# Thread: Physics Question

1. ## Physics Question

I have a journal bearing (think of it as a circle) with a shaft through it (another circle inside the first). The bearing is about .020" larger than the shaft. When the machine is off the shaft lays in the bottom of the bearing. A sector of the shaft circumfrence is in contact with a sector of the bearing surface. I am trying to figure out what the length of this sector is to calculate the couple force required to overcome the force of static friction between the two. Does anyone have an equation or to for the sector length calculation above? Thanks

2. My first impression is to disagree with your premise. Unless the shaft or the bearing is deformable, the intersection of the two different circles is a single point, theoretically.

In practice, you probably can specify a space that counts as zero - small enough that it matters to no one that is really isn't. That would give you SOME area.

3. ## Physics Question

I would agree. I was not clear in the description. The circles contact on a single point. When the shaft rolls within the bearing it will travel a certain distance along the bearing surface before over coming the static friction and rolling. It is that sector and associated angle I seek.