WHIRLWIND BLADES FOR SUBARU?

[EDMO 1078]

I took notice of the 2500 rpm limit on the Whirlwind blades - Got me to thinking - that usually gets me into trouble - Got out my calculator and punched in 2500 x 1.84 reduction drive ratio, and came up with the number of 4600 for my max engine rpm - that seems low? I can turn 5200 for takeoff - wonder if dialing in enough pitch to keep the rpm down would load the engine too heavy, and make takeoff longer? any comments?

Maybe with my reduction ratio, I will have to stay with Warp Drive blades?

ED in MO

Edited 7 Mar 2013 by Ed In Missouri

[akflyer 1427]

overloading the engine is generally not a good idea and leads to loss of performance in a big way, as well as shortened life span of said engine.

[EDMO 1078]

overloading the engine is generally not a good idea and leads to loss of performance in a big way, as well as shortened life span of said engine.

:BC:/>

Randy, what is your redrive ratio? How fast were you turning the Whirlwind blades?

Ed in MO

[SuberAvid 617]

Randy, what is your redrive ratio? How fast were you turning the Whirlwind blades?

Ed in MO

The stratus redrive is 2.2:1. The highest I turned them was 4800 rpm (at 17 degrees pitch) so well under the 2500 rpm limit on the blades. I think the best performance compromise was actually at the 22 degrees pitch and takeoff RPM was 4250. I think you could calculate the prop rpm from this and then back to your engine rpm with your ratio and you should be able to pitch your blades to turn under 2500 at climb out. I think you will not have a problem over reving them with your lower drive ratio and only 80 hp. You will have to run the blades pretty flat to get anything close to 2500 rpm at the prop.

[EDMO 1078]

The stratus redrive is 2.2:1. The highest I turned them was 4800 rpm (at 17 degrees pitch) so well under the 2500 rpm limit on the blades. I think the best performance compromise was actually at the 22 degrees pitch and takeoff RPM was 4250. I think you could calculate the prop rpm from this and then back to your engine rpm with your ratio and you should be able to pitch your blades to turn under 2500 at climb out. I think you will not have a problem over reving them with your lower drive ratio and only 80 hp. You will have to run the blades pretty flat to get anything close to 2500 rpm at the prop.

Thanks Randy,

I've got plenty of time to decide on the blades before getting to testing - maybe borrow some Warp Drive or buy used ones to do initial tests, and go to Whirlwind later? I've got a mile of concrete runway in the cleared flat farms in the river valley to do my testing.

Ed in MO

afterthought: I am not sure what HP I have until testing - the heads were milled and the big carb installed - Dont know if the cam has been reground - I could have 90 or 100 hp? I was told it turned 5700 until someone blew the crank bearings - got new or reground crank in it now, and dont plan on that many revs.

ED

Edited 11 Mar 2013 by Ed In Missouri