can someone finish this
prop x rpm x 0.0009469 x slip
|
Originally Posted by crayolacrazy
(Post 3710040)
prop x rpm x 0.0009469
|
Originally Posted by crayolacrazy
(Post 3710040)
prop x rpm x 0.0009469 x slip
|
Originally Posted by crayolacrazy
(Post 3710040)
prop x rpm x 0.0009469 x slip
|
Originally Posted by crayolacrazy
(Post 3710040)
prop x rpm x 0.0009469 x slip
ANSWER: NO, we can't finish this? :cartman: We give up..... what's the answer? Thanks, Tim Bostic Hoss Marine Props |
Speed = (RPM/GearRatio)/60 * (Pitch/12) * slip * 0.68
Where Speed in mph RPM in rev/min Pitch in inches If you take all the constants together, that gives you 0.00944, which is just rounding errors different from what was originally posted. The original post was missing the gear ratio factor. |
Originally Posted by Tim Bostic
(Post 3713415)
ANSWER: NO, we can't finish this? :cartman:
We give up..... what's the answer? Thanks, Tim Bostic Hoss Marine Props |
Originally Posted by crayolacrazy
(Post 3715254)
this was a formula to figure out speed and slip 31pitch x 5800 rpm x 0.0009469x 0.90 slip devided by gear ratio 1.50= 102 mph .. I can hit 100. 0.90 is 10% slip so my slip is about 11.5% after posting this question I remembered the fomula ,I have not use for sometime and Im getting old HA HA
RPM/gear ratio * pitch / 1056 = Theoretical Speed Actual Speed / Theoretical Speed = Slip So using your info: 5800/1.5 = 3,866.66 prop rpm 3,866.66 * 31 = 119,866.66 (inches per minute) 119,866.66 / 1056 = 113.51 (converts to miles per hr)(Theoretical speed) 100 / 113.51 = 88.1% efficiency or 11.9% slip I use this formula because I can remember it (I'm getting old too!! haha) and do it on my phone while I'm at the lake testing props. This works good when you are doing back to back COMPARISONS on props. You have to assume the speed is accurate.... the rpm is accurate.... and the pitch is accurate?????..... if any of the info is in error, then your answer is off too. I use GPS, calibrated tach, and actual prop pitch. When testing new designs, I have a "shop" prop that I run first to verify engine performance and conditions.... then test the new props. If testing lasts most of the day, I'll finish with a final run with the "shop" prop to verify that nothing had changed throughout the day. Thanks, Tim Bostic Hoss Marine Props |
Originally Posted by Tim Bostic
(Post 3715283)
Here's the formula that I use:
RPM/gear ratio * pitch / 1056 = Theoretical Speed Actual Speed / Theoretical Speed = Slip So using your info: 5800/1.5 = 3,866.66 prop rpm 3,866.66 * 31 = 119,866.66 (inches per minute) 119,866.66 / 1056 = 113.51 (converts to miles per hr)(Theoretical speed) 100 / 113.51 = 88.1% efficiency or 11.9% slip I use this formula because I can remember it (I'm getting old too!! haha) and do it on my phone while I'm at the lake testing props. This works good when you are doing back to back COMPARISONS on props. You have to assume the speed is accurate.... the rpm is accurate.... and the pitch is accurate?????..... if any of the info is in error, then your answer is off too. I use GPS, calibrated tach, and actual prop pitch. When testing new designs, I have a "shop" prop that I run first to verify engine performance and conditions.... then test the new props. If testing lasts most of the day, I'll finish with a final run with the "shop" prop to verify that nothing had changed throughout the day. Thanks, Tim Bostic Hoss Marine Props |
All times are GMT -5. The time now is 05:04 AM. |
Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.