Flap push rod end bearings

Anyone out there able to explain to me the difference between a CM-4M and a CM-4MS rod end bearing? Aircraft Spruce lists a CM-4S (right) and a CM-4B (left) but no CM-4M or CM-4MS and the Van's store has no description. Thanks.

Hangar 1271 said:

Anyone out there able to explain to me the difference between a CM-4M and a CM-4MS rod end bearing? Aircraft Spruce lists a CM-4S (right) and a CM-4B (left) but no CM-4M or CM-4MS and the Van's store has no description. Thanks.

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Part number mix up, or old numbering system?

Aurora seems to use the "S" at the end for a stud added to a standard bearing.

http://cad.aurorabearing.com/item/a...uds-general-purpose-economy/cm-4s-2?plpver=10

Looking at old RV-6 plans Vans added a "MS" - possibly for 'male stud/shank' to the CM-4 part number.

I would stick with the current manufacturer's part number that Spruce sells.

Bearings

David,

Just confirming that Gil is correct. The upper rod end bearings are the standard looking ones and attach into the flap actuators in the cockpit. The lower rod end bearings do have a stud sticking out to the side. The lower stud bearings don't care if they are left or right, just mount them with the stud outboard to attach to the inner mounting point on the flap. CM-4M on top, CM-4S on the bottom.

Many thanks but those answers actually created another question. If the upper rod end bearing is the no-stud version, Aircraft Spruce lists the part as an MM-4 (or maybe a GMM-4M-470) rather than a CM-4 or, even more confusing, CM-4M as shown in my plans (RV-8/8A DWG 80).

Hangar 1271 said:

Many thanks but those answers actually created another question. If the upper rod end bearing is the no-stud version, Aircraft Spruce lists the part as an MM-4 (or maybe a GMM-4M-470) rather than a CM-4 or, even more confusing, CM-4M as shown in my plans (RV-8/8A DWG 80).

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Precision vs. Economy.

The two spec sheets are here -

http://cad.aurorabearing.com/item/a...ends-general-purpose-economy/cm-4-2?plpver=10

http://cad.aurorabearing.com/item/a...ends-general-purpose-precision/mm-4?plpver=10

However, the CM one has a much larger permissible misalignment angle which is probably good in the flap drive application. This seems to be based on the "H" dimension, the only real difference between the two parts.

Thanks for the information and for doing it so quickly.