Thanks for your replies Dan and John. It is strangely comforting to know I am not alone. I wonder how many other C-85/C-90's out there have some vibration in that range? Any AP/AI's on this forum familiar with vibration issues at 21-2300 R's?? Is it indeed common to the engine?
Craig --- In [email protected], "Dan Caliendo" wrote: >Craig, >I have a newly acquired 415C with C-90 that has the same problem. >Real smooth at 2400 rpm or >1800 rpm, some vibration between those ranges with a concerning >amount of vibration at 2100 to 2300 >as in your case. My prop was installed "according to the book"; but >the guys on tech site say it should >stop at the 2 o'clock position (viewed from pilots seat)...mine stops >at the 10 to 11 o'clock position. >I would be very interested in whether the dynamic balance helps and >what position your prop is >currently stopping at. (I asked the same question 2 or 3 months ago >so you might look at the archives >for the answers I got. (I've about told you everything they said >except that others have same problem and >just avoid those rpm settings.) >Dan C > --- In [email protected], "john brier" wrote: > >Hi, I went through the same drill with my C-90 in my Forney, N26C. >New mounts, had prop rebuilt, measured the shaft for the correct >angle, did it all. Then I had dynamic balance done ($300.00 five >years ago) and not a thing changed. Also tryed another prop, tryed >reindexing mine and nothing worked. I then gave up and just fly the >plane. > >My vibration grows more intense as I bring the power back reaching a >peak about 2300 rpm. Then right at 2200 +- 25rpm it reaches the sweet >spot and that is the best it will do. Used to worry me a lot, but >have put about 300 hours on the plane (1450 SMOH) with no problems. >It is just very very annoying. > >Let us know if you have any luck. --- In [email protected], "cpetemn" <[EMAIL PROTECTED]> wrote: > > I have noted on my recently acquired 415C, that the C-85 has a > moderate amount of vibration between 2100-2300 RPM. We re-positioned > the prop to the proper position on the hub, but no difference. The > motor mounts are good and there doesn't seem to be a lot of filing > that would put the prop out of balance. The next step would be dynamic > balancing. But, is there any known inherent vibration in the C-85's in > that rpm range? Any other thoughts? > > Craig > N87018 >
