Frankenstein Hartzell c/s Prop - seeking opinions

[QuixoteAg]

Still trying to figure out my options here with my project.

Here is my setup:

RV6
IO-360-A4Jc (O360a4j with Bendix fuel injection & hollow crank)

Hartzell HC-C2YL-1BF/F7663-4 (the one for an O-320)

I asked Hartzel if i could simply swap out the Hub for one that would fit my blades and work on an IO-360 and their response

"This makes perfect sense, by swapping the hub it would be possible to save the blades. I’ve done some digging here on your behalf and tried to see if it would be possible. By moving from the 320 to the 360 you would be moving from the L flange to a hub with a “K” or “R” flange and that would change the hub and you’d be able to keep your blades. With that being said, Hartzell currently does not make an application which has the K or R flange hub with the F7663-4 blades. Please see the attached type certificate data sheet P920 (page 8 specifically). You’ll note that the only approved data we have for the 7663 blade is on lycoming 290, 320, and IO-320 engines.

Although it would be technically possible to swap the hub out and use the old blades (should function just fine), we do not have a model of propeller supported with data to support the vibrational loads associated with the new higher horsepower engine using these blades."

I believe I'm dealing with the same RPM's on the 360 vs the 320 @ 2700 but and similar MP - is it just a 'power' going to the blades issue that would cause vibrations?

Thoughts / advise?

 

[Freemasm]

That's pretty old tech you're dealing with. As usual, it comes down to $. I'd personally go with one of the newer "non-legacy" OEM designs. There are plenty of reviews here. If that's not in your budget, the aforementioned, slightly older, still wonderfully performing, used models come up for sale here. Lots of options but the one you're pursuing screams "caution" to me.

You're going ot get a lot of opinions here. Give a collective listen.

 

[TParker]

I believe I'm dealing with the same RPM's on the 360 vs the 320 @ 2700 but and similar MP - is it just a 'power' going to the blades issue that would cause vibrations?

Sort of, it's not just a power increase. The dynamics of the rotating system between the combustion and the propeller are different enough that, from Hartzell's standpoint, it's a different engine design that needs to be tested separately; and it's the same in both directions, in that we don't use data from a 360 to say a 320 is "ok". We haven't tested this particular potential combination, which means it's unknown; so it may be safe, it may be unsafe, it may need an operating restriction in order to be safe. Manual 193, Volume 2 on our website has some additional background on this topic.

The other factor, and the reason we haven't tested the combination of a two blade 7663() propeller and 360 engines, is that the blade was designed for the lower power engines, and we have different blades that are designed for the increased power of the 360 that perform better with that engine.

 

[jcarne]

Sort of, it's not just a power increase. The dynamics of the rotating system between the combustion and the propeller are different enough that, from Hartzell's standpoint, it's a different engine design that needs to be tested separately; and it's the same in both directions, in that we don't use data from a 360 to say a 320 is "ok". We haven't tested this particular potential combination, which means it's unknown; so it may be safe, it may be unsafe, it may need an operating restriction in order to be safe. Manual 193, Volume 2 on our website has some additional background on this topic.

The other factor, and the reason we haven't tested the combination of a two blade 7663() propeller and 360 engines, is that the blade was designed for the lower power engines, and we have different blades that are designed for the increased power of the 360 that perform better with that engine.

Straight from the horses mouth.

Personally I don't think I would play with it; too many unknowns. Just my opinion though. We all have different risk tolerance.

 

[QuixoteAg]

Thanks for the input Trevor! very much appreciated.

 

[QuixoteAg]

The plot thickens - the project that I purchased came with an engine - IO360 but the cylinders are from a 320 so it is only going to generate 150-160 HP so maybe it will work with the Prop ok better than trying to switch out the hub.

so the decision becomes buy a lycoming 320 and take a few steps back in the build but be able to use it with the prop that i have or stay with a frankenstein engine with the 320 prop...decisions decisions.