Can anyone ID this engine component?
 

It's part of a common governor system fitted to many planes that have the
prop pitch set by a system using oil pressure to move a piston in the prop
hub.

What is that large disk for?
It looks like it is attached to the manual speed control shaft.
http://www.b3tards.com/u/57a418c694b...roppitch22.jpg

Looks to me like it's simply a wheel to adjust the governor with, notice how there is a pin on the bottom to lock it in place (and the corresponding holes in the wheel).

After actually reading the article I realize the above statement is entirely wrong and I shall now STFU

But it's attached to the mechanism the pilot uses to change the prop pitch.
Why would you want to lock that in place?

Would it be a maintenance thing or would it be locked in flight?

Check out this site:

http://www.enginehistory.org/Propell...ors/hydgov.htm

Depending on the mechanism, you probably have to lock it in place?

yes, that is where my image is from, but it doesn't explain the purpose of the large disk.

Possibly the "pin" is actually a spring loaded ball detent, which would act like a friction to hold the selected position

Ahhh! Now that makes sense.
That would suggest that planes with this system would, in effect, have a
limited number of prop pitch settings (as many as holes on the disk).

If it's a governor for a constant speed unit you don't directly set the prop pitch through any setting. What your actually setting is the RPM. The CSU sets the prop pitch to what ever it needs to maintain the RPM at a given throttle setting if it can (any where between coarse and fine).

It's hard to see but if you look at the cut away diagram on the link, the disk is attached to the "speed control shaft" (No 1 on the diagram, but then again my eyes are dim and weak with old age)

(quote)
That would suggest that planes with this system would, in effect, have a
limited number of prop pitch settings (as many as holes on the disk).



It appear's that the setting was in increment value of five (5)

The holes are more likely to be for attaching and adjusting the linkage, the fact that there's so many of them is to adjust movement set by the throttle.

The position of this set the props rpm limit and the governor controls the overspeed/underspeed condition of the propeller.

The holes are not related to the pitch angles


"The propeller governor maintains a constant engine speed by controlling propeller pitch. Engine speed is selected by a cockpit control connected to the governor speed control shaft."


EDit

Shoshi Tiger had explained it well enough.