Bevel Gear Thrust Loads on Bearings

Hi,
I’m on team 4926 GalacTech and this off-season we are attempting to build a swerve drive. Although I will probably post the final design on here for feedback when it is done, I would appreciate some of your input on the axial/thrust loads cause by bevel gears (our current path is coaxial).

Through some calculations from a PDF I found online, I determined the axial load from the vex bevel gears and a NEO with a 3:1 reduction is about 48.6 N on the bearing that will be containing the gear. My calculations and the PDF I got my formulas from are attached (Please let me know if any part of my calculations are unclear). This result is also fairly close to the 50 N force that was calculated by the KHK gear calculator. Does this seem like a reasonable result?

Also, would a typical andymark flanged 1/2 inch hex bearing be able to take this kind of axial load? I couldn’t find any axial load data from the andymark or vex websites on this type of bearing but maybe some of you have some personal experience.

If the bearing can’t support the axial load, I will probably just put a washer between the thrust bearing and radial bearing that spreads the thrust load across the flange of the bearing rather than the inner race.

Thanks for your help!!

Screenshot_20190522-133218|690x388

Timken_Eqns (1).pdf (135.6 KB)

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We use these and have had no issues:

The link just takes me to a overview page for bearings. Do you have a specific part number?
Thanks

5906k515 and 5906k516 are the two we have used - 1/16 and 1/8 thickness depending on stack.

I think you may have misunderstood what I meant. I was wondering how your radial bearings, not thrust bearings, have handled the thrust loads from the bevel gears. Did they ever break or lose performance?

Here is the radial bearing we were planning on using:

I’ve seen people use all kinds of bearings to take the load. 50 N is about 12 lbf, which is very little load to put on a run-of-the-mill radial bearing. The AM bearings should be fine.

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That’s good to hear. Thanks!

Probably fine but we have always included the thrust washers that I indicated, needed the spacers anyway so no negative -

Yeah I plan on including a thrust bearing as well to reduce friction from the thrust load.

It’s been a few years now, but I learned in mechanical engineering school that traditional radial bearings are generally good for about 20-25% of their radial load capacity in axial loading. Beyond that, this is why they make angular contact bearings and thrust bearings.

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Yep, deep groove bearings are good for 25% thrust. http://www.rbcbearings.com/ballbearings/axial.htm

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That’s an interesting relationship between axial and radial load. Is there a reason for the proportionality between these two values?

Quick question: Do oilite bearings ever “run out” of the lubricant, or are they just a drop in and forget about it solution. If they do require replacement, how often do you guys replace them in a competition season?

We never replace them and have even reused them for multiple years. We can’t really say if they are absolutely necessary even (per other posts) and know of teams that do not use them, but we will likely continue to as long as they just fill a space where we would otherwise need a spacer. With them the ball bearings also exhibit minimal wear through 6 to 7 events plus hours and hours of practice and demonstrations.

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