Vibration in a PA-18 105 with the std Conical Engine Mount

[cubscout]

As I recall, all of the Dave Johnson STC's had a mandatory yellow band on the tach, regardless of crank configuration, but Dave's (sadly) not around any more to put me straight again. Could've been another Blessing from the Friendly Aviatiion Agency. I think PennYann wound up with the paperwork from Dave's son-in-law, and fixed some of the chronic issues (fuel valve position, oil cooler position); you more knowledgeable folks pleas chime in here.

I believe the 8GCBC with the 1-200 HFA-41 is yellow-zone regardless of crank. Most are probably 0-360-C2A or C2E, if failing memory is correct. Don't have my Majic Lycoming Decoder Ring on, which crank on which dash engine....

 

[SuperCub MD]

I'm reasonably sure the PennYann allows either solid or hollow crank, and if a solid crank is used, no yellow arc is needed. It's been a while since I flew one, but I think the 8GCBC has a yellow arc. Anything with a constant speed prop needs a hollow crank. I'm not saying that there is anything wrong with the hollow crank. I would definately concider it on a 180 conversion to keep the weight down. The biggest drawback would be that the yellow arc would be exactly where I would want to cruise when flying formation with some slower aircraft, which would be a real pain.

 

[sj]

MD,

You are exactly right about the pain in the hollow crank redline. I finally had to drop 10 degrees of flaps to stay back with a citabria the other day, and keep out of the red arc. 2150 was too little, 2350 was too much...

According to my research, mine (apparently) is only restricted on the sensenich not the borer, does that sound right?

sj

 

[SuperCub MD]

SJ,
Is it a red or yellow arc? What exact model is your engine, as in dash #? and what prop? I think you mentioned a possibe CS prop for yours, so you probably have a hollow crank?

Maybe there are restrictions on the solid cranks with certain props too, each installation could be different...tough to keep all this stuff straight.

 

[sj]

MD,

I have a hollow crank (O360-C1G). Previous owner was hopeful that CC would purse the constant speed prop STC, not sure if that will happen now.

It is a red arc from 2150-2350. I know it applies to the sensenich, but not sure on the mccauley.

sj

 

[flyer]

doesnt it say not for extended periods of time. so flying for awhile should not be much of a problem. has anyone ever heard of a problem from flying in the yellow range in any airplane for a sensible amount of time.

 

[sj]

"avoid continous operation" is what it says, and it is a red arc (red means, "don't go there" in my book). Yellow is usually "caution" or "ok to go there some".

I'm sure there are lots of hollow crank engines that are not marked flying around out there at 2200 rpm everyday. You do notice the vibration on this one in the range.

sj