Originally Posted by
1200SportsterRider
The go to prop for the MVVS 77 is a 14 x 7, it is a torquer and will idle at 1,000 rpm when so equipped. I had an MVVS 61/LS, not officially called a long stroke but was one. I tried a 12 x 5 Grey Graupner, it shook a Bruce Tharpe Venture 60 like a rag doll. A 13 x 6 cured all of that.
SportsterRider, I think you are on to something.........
I was still waiting for my 14 x 7 to arrive, so I did some prop load factors (14 x 14 x 7 = 1372 and 15 x 15 x 6 = 1350) and so I balanced a 15 x 6 and put it on the engine this afternoon, 53 F, high humidity. Same fuel, plug etc as before. That serious vibration around 2800 rpm was
greatly reduced. While impossible to document, it seemed the vibration, tho reduced, was still there...you could feel it while siting behind the engine on the deck (to which the test stand was attached).
,
Reliable idle 2100 rpm. I did not try to find the top end though had it up to 7300
.
But I was reminded of what Ice said to Maverick after they had taken care of the Libyan Migs and returned to the carrier: "Maverick........you'r STILL dangerous"
I began flying glow engines in 1954, and I have never experienced the kind of vibration as demonstrated by this engine. I am lerry of this engine, it is "still dangerous", and absent finding a fix,
I will put something which runs normally in my brand new Dalotel.