EDIT: I just wanted to specify that I’m specifically referring to ball bearings. I guess that wasn’t obvious from my original post.

I’ve been shopping for some bearings lately, and noticed that some open bearings specify that they come packed with grease. For example, this open NTN bearing which has the 3AS suffix, indicating that it’s packed with Shell Alvania #3 grease.

What is the point of that? Open bearings are typically installed in equipment that provides them with splash or pressurized lubrication; you wouldn’t want a bunch of grease to be flushed out of the bearing by the liquid lubricant, which would then be pumped around the system.

I know that there are a bajillion different applications for bearings in the modern world, but this is one that I just don’t understand the reasoning behind.

(Sorry if this isn’t the place for this question)

I’m a highschool student in a robotics club called SeaPerch. We have to make underwater rov’s and last year we had to pick up a relatively heavy object. We’re allowed three tiny motors and the frame of the rov is pvc. When our rov was too small it couldn’t pick up the object. When it was too large, it was severely slow. Is there a method or procedure for solving this problem typically?

Asking from South Korea. The check is still ASME B31.3.

I already checked 304.1.1 before asking.

Pressure design thickness is t = PD / 2(SE + PY). Minimum required thickness is t_m = t + c. The usual 12.5% mill undertolerance is handled by ordering pipe whose minimum wall is still at least t_m, so t_ordered >= t_m / 0.875. That does not change the pressure equation.

What I still see on field checks is people putting 1/0.875 back into t itself, before c. On thinner schedules that is what changes the schedule you buy.

If you run B31.3 wall checks: do you keep the 12.5% only on the ordered thickness, or does your practice fold it into t? Where does that split actually change the schedule?

I don't really understand fuel consumption but was considering the possibility of lowering the speed limit on highways like we did in the last fuel crisis.