kram

My Feedback: (7)

I know this has been discussed a lot before.

I have a couple of new (5 tanks through them) OS 1.20-P's.

I would like them to turn 15 X 10 APC's for the airframe they're in (old Art Johnson P-38)

I'm a little disappointed at 8,400 RPM, although they seem to run well, don't heat up, and that should be fast enough for the airspeeds I need.

Fresh Cool Power 15% 4S fuel.

Big Question: Is that so slow it will hurt the engines?

I could back down to 15 X 8's, but heck, my older OS .91-P's turn 15-8's at 8,800.

The 1.20 manual doesn't actually say what max and min RPM's should be.


Thanks,


mt

jaka

Hi!
It's simple!
If the engines sound alright...it's just fine! Othervise use the 15x8 APC!

rcdude7

My Feedback: (264)

8.4k on a apc 15X10 is good, I would have expected less on that engine.

rambler53

My Feedback: (494)

3rd that vote. Stick with the 15X10.

cutaway

Measure it again after 2 hours running time.

kram

My Feedback: (7)

Thanks for all the input.

Since that speed, that prop gives me a theoretical 82 mph, probably more with unloading in the air, my only concern is that it might hurt the engines somehow.

I have not received any negative opinions to that effect.

Thanks,


mt

Kostas1

Your engine needs to be broken in more.

8.8k rpm is good for only 5 tanks of fuel burnt.

I'd use a 16x6 or 16x8 for the first flights though. That "10in." pitch sounds too much IMO.

Kweasel

My Feedback: (29)

I got 8400 with that prop on a non pumped 120 Surpass and 8600 with my early pumped 120 Surpass-1. 15% Omega.

blw

My Feedback: (3)

There is no way to predict how much an engine will unload. 1000 is usually a safe figure.