Irvine 72

I purchased 4* 60 with an Irvine 72. The engine appears to be new and high quality. Two short test flights yesterday revealed excessive vibration (1/2” side to side movement at the front of the fuselage). The prop is a 12-7 APC, which seems a little small. And yes I checked the prop balance.

What size prop and RPM is expected on an Irvine 72? What vibration level should be expected? If the vibration is normal the airframe will need reinforcing at the firewall and front of the fuselage.

Thanks.

Bill

I have a 72 on a Swallow pattern plane they are long stroke very stron engines, i would check the motor mount for the vibration and put a bigger prop
like a 13 x 7 or 14 x 6 let me check what am i using

Patrick,

Yes I would be interested in the prop size you are running. A long stroke engine with a small prop would be vibration prone. The motor mount is two-piece but appeared to me mounted securely. Took the engine and motor mount out anyway and am in the process of adding triangular stock at the firewall and forward fuselage sides as a precaution.

Thanks.

Bill

I am still searching for RPM and prop sizes for the Irvine 72 but have been unable to find anyone with actual experience with the engine. Prop sizes recommended on the Irvine web site are huge.

Bill

Bill, you'll get the most out of it treating as if it were a .91, in other words a 14x6 is perfect. 5% nitro is a must too.

a 14x6 prop is what I'm using on mine, great engine I don't recall my rpm's though, too many engines to try to remember them all, I guess I should start writing this stuff down.

Does 8100/8200 RPM sound like it is in the correct range for an Irvine 72? One of the recommended props is a 14-8, which is what is being tested.

Bill