|
|
In a message dated 3/1/2003 6:49:59 PM Central Standard Time, Brent@regandesigns.com writes:
If a threaded joint is creaking then it IS moving, and movement at a
threaded interface is always bad.
Brent,
Thanks for the info. Every reference I have seen to torque related to a specific bolt grade (AN, MS or SAE) varies differently with phrases such as "when threads lubricated with #10 oil" or "dry, with a plain nut." Frankly, this is why Matt (?) and I like our motorcycle maintenance manuals since the torque is specified for the particular application (handle bar riser bolt, axle nut, etc.). This is similarily provided in the Lycoming engine maintenance manual. Another example is the Hartzell prop hub case bolts to which we attach or spinner backplates. These bolts are not torqued to the general bolt value, but to 22 lb ft, specific to that application. A "torque" value is useful in these situations since they indirectly refer to a specific tension or pressure under which the joined parts should be held.
I do not believe it is the bolt, thread or nut that is "creaking", but the gear pivot plate to glass interface (under which is Phenolic (front) or aluminum (rear)). If these plates are not secured firmly enough (each via four AN4 bolts), they seem to move enough to "creak" when under shear stress. Maybe the bolt holes aren't perfect. This is afterall, a "homebuilt" fashioned with simple tools (per kit plane advertisements).
It would be useful if construction manuals contained such "torque" values since the designing engineer should know the compressability of materials, max shear loads, surface frictions , etc. At least we could be within the range of fastener reasonableness rather that having to rely on "Gut und Tite."
Scott Krueger
N92EX
|
|