Thanks Buly,

So, Pitch"  = MPH x12 x 5280

                   RPM x 60

I figure 12 (inches in a foot) and 5280 ( feet in a mile) and 60 ( minute in an hour).

So the top line is converted into inches per minute and the bottom line RPM.

 

So, Pitch " = inches per minute

                    RPM

 

Does that look right to you ?

George ( down under)

 

 

Thanks George. my mistake was that i did not convert it to MPH.

I was also given the formula for cruise speed:

Pitch" x RPM x 60  = MPH

       12 x 5280

Buly

On Dec 21, 2005, at 4:39 PM, george lendich wrote:

Buly,

Looking at the formula given by members on this list, 2 out of 3 were spot

on with Hoverhawk and the third was close.

Examples:

1. Prop Dia x 3.1416x RPM/ 720 - Correct!

2. Prop RPM x Dia x .00436 - Correct ( 3.14/ 720 =.00436)

3. 3.14 x 64 {given prop dia} ( 5500/2.17 {given RPM})= 508346/707 -

slightly incorrect ( as compared to the other 3 examples, which include

Hoverhawk)

i.e 3.14/ 707 = .004809 whereas all the others are 3.14/ 720 = .00436.

Now that I have that sorted - can someone tell me how to calculate pitch,

easily!!

George ( down under)

Thanks Perry. This makes me feel much better. Looks like the formulas

given to me were not good.

Buly

On Dec 19, 2005, at 2:00 PM, Perry Casson wrote:

I think your math is off a bit - Here's a online calculator http://

www.hoverhawk.com/propspd.html

I think 6900 puts a 72" prop close to  mach 0.9 but I've never ran

mine above 6500

Perry Casson

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Buly

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Bulent "Buly" Aliev

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