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Engine restrictions with M type hub or 2.5" prop extension

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agent4573

Well Known Member
If you want to run horizontal induction and the Sam James cowl you need either an M type hub or a standard hub with a 2.5" prop extension. Prop supplier has said this doesn't impose any restrictions, engine supplier (Aerosport performance IO-375) isn't saying anything. He forwarded it to the tech department and a month later still no reply. Anyone running a Lycoming or clone with the Sam James long cowl care to chime in with some knowledge?
 
Call Hartzell they can help you with M hub. Look at the VAF Forum Prop section. I posted a Application guide.... I would not recommend a separate bolt on extension for a constant speed prop. Those are for fixed pitch, but up to you.
 
I run a James extened cowl with a Saber 2.25 extension and a CS hartzel prop. But my engine uses a carb. Saber makes an extension just for CS props. The extension bolts to the engine flange and the prop bolts to the extension. The clocking is off or moved half a lug distance but no issues with that.
I do not do acro so no issue for me but I have heard the extension setup could be a possible issue.
 
I'm running an IO-320 with a James cowl, Hartzel prop and a Sabre 2.25 extension, no problems and its been about 15 years. I am going to run the same setup on my RV8 also.
 
The answer may well be dependent on the prop blades - aluminum/composite/mass specifications including specific crankshaft prop flange dimensions/design. It is more than G loading, it includes rate of change in rotation about the X, Y, Z axes of the engine/airframe.

The best answer comes from the engine manufacturer and/or the prop engineering department.

This has been thrashed here before.
 
BillL said:
The best answer comes from the engine manufacturer and/or the prop engineering department.
Click to expand...

It sure does. But when companies refuse to answer technical questions about their products, you take other measures to find information. I've looked in the prop section and very few people are running the high compression 375, so there isn't much info there. Quiet a few people are using the sam James cowl though, was hoping to find a wider audience with some experience.
 
agent4573 said:
It sure does. But when companies refuse to answer technical questions about their products, you take other measures to find information. I've looked in the prop section and very few people are running the high compression 375, so there isn't much info there. Quiet a few people are using the sam James cowl though, was hoping to find a wider audience with some experience.
Click to expand...

Link sent via your web site contact.
 
I'm running the Saber 2.25" extension and Whirlwind 200RV prop on my IO360 with Sam James cowl. Whirlwind advised that they knew of no RPM restrictions but thought that keeping standard 2100-2300 caution range was a good idea, no extended operation there.
 
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