Bearings

Spherical Bearings and Rod Ends

• Rod ends for racing

Radial Bearings

Most common type of bearings for shafts. Typical unit has a hollow cylinder shape, with spherical balls or cylindrical rollers inside.

Bearing Selection Tools

Pre-Selection: Type of Bearing

• The Schaeffler Pre-selection Chart on page 30 of the HR1 handbook provides a useful overview of the different types of bearings.
• Ball bearings are usually lighter, can run at faster speeds, and are lower friction than roller bearings, but also have lower load capacity.
• Single row deep groove ball bearings come with different sized balls (and corresponding weights and sizes). From smallest to largest: 618XX, 619XX, 60XX, 62XX, 63XX.
• Suggestions from a FS Wiki Author of what teams could use:
  • Bellcranks: Deep groove ball bearings
  • Steering: Deep groove ball bearings, or needle bearings (in areas with 0 axial force)
  • Drivetrain (such as differential mounting): deep groove ball bearings or roller bearings
  • Wheel Hubs: Angular Contact ball bearings or tapered roller bearings in an X or O configuration, Or buy an off-the-shelf wheel hub.

Picking the Specific Size

• SKF Bearing Selection Tool
• Schaeffler Bearing Selection Tool

Suppliers

• Schaeffler (Includes FAG, and INA)
• NSK
• SKF

Tolerances and Fits

Section 8.3 of the Schaeffler HR 1 Catalogue is the best available source.

1. Search for the supplier part number on a supplier's catalogue like Schaeffler's Medias Catalogue. Bearings have standardized supplier part numbers across all suppliers, so it will be the same part number on SKF or NSK's website as well. Searching without the suffix for the seals (ie. "-ZZ" or "-2RS1") will improve the chances of at least finding the bearing of the correct size.
2. The catalogue page for the specific bearing (like Schaeffler's Medias) should state the basic dimensions, and min/max radii of the housing etc. It may not contain the tolerances.
3. In section 8.2-8.3 (pg 145) of the Schaeffler HR1 handbook there will be tolerance info for the housing and shaft. Start with Table 1 to determine the loading condition. Then for radial bearings (the most common type) look at Table 2 for the shaft tolerance, and Table 4 for the housing tolerance.
4. In the same Schaeffler HR1 handbook, Section 8.6 has the more advanced GD&T (Table 10, Assume a bearing tolerance class "Normal"), then Table 11 has the surface roughness tolerance (The diameter tolerance grade is from 4th column of Table 10).

Tolerances note:

Looser tolerances than those recommended by the manufacturer may be possible.

For drivetrain and wheel assemblies, an increased interference may be possible when seating bearings into aluminum housings. Aluminum's high coefficient of thermal expansion allows it to expand significantly when heated. Do not wreck the heat treatment of the aluminum though. Additionally, having thin, lightweight aluminum bearing seats limits the residual stress from the press-fit and minimizes dimensional changes of the steel bearing race (compared to the same press-fit into thick steel housing), which would cause bearing issues such as friction and wear.

For bellcranks an increased interference may be possible for the same reasons as above. Additional clearance is possible due to the bearings moving at low speeds, only ever rotating <90deg and always being under preload. When in doubt, follow the manufacturer's recommended tolerances.

Just give me some tolerances

If you want some housing and shaft diameter tolerances from strangers on the internet:

• Wheel Bearings: N8/k6
• All Other Bearings: H8/h7

If you run into issues, you have no one to blame but yourself.

See Also

Compliance