HELP

[Sonnyj]

G'Day Ya'll
Got a guick question. I need to figure out what the tip speed is on my prop. Here awhile back, I seem to remember Ted and Russ havin this discussion, but I cain't find it. Could some one please direct me to it, or just give me the formula again?
Thanx
Sonny

[BeefBear]

Sonny, You need to know the rpm and the circumference of your prop.

So if you have a 72" prop Circumference is 226.19, 70" prop Circumference is 219.91" and 68" prop has a cricumference of 213.62"

Divede Circumference by 12 and multiply the result by current RPM and bingo.. there she be. :dance: :friday:

Ted

[russ]

Bet that never came from a reliable source............aye what

Hey sonnyi................let me know if you want the real equation...............from me 25 yr old diary..........spot on.........guaranteed

By the way................xmas cheers :cheers:

[bones]

Hey sonnyi................let me know if you want the real equation...............from me 25 yr old diary..........spot on.........guaranteed
If any one is wondering why he keeps referring to this dairy that he uses all the time its because Russ suffers from a disease called CRAFT(Cant Rememeber A F*cking Thing)... :moon:
I think thats one to me Russ :joy: :rockon:

[russ]

just gave you one of them nega things......................cheers :pistoles: [ "mudy"]

[hoody]

i think thats one each to bones-mudcrab and russel-coit,


hey russ, you cant just post it or give it to rotor so it can be filed as a reference or somthing???

a place for such info would be good, like that other formula to calc relative air density.

[Sonnyj]

Thanx Gents :peace:
I preciate it.
Ted ( sracthin me head ) 51 x 3.14 =160.14 divided by 12 =13.345 x4000 =53380. Wot is 53380? :question2: FPS? FPM? MPH?
Thats a great idea Hoody heres to ya :beer:
Yea Russ, post the formula, if you can remember where ya put the diary :cheers:
That way I can put it my diary------if I can find it :crazyas:
Bones, I suffer from the same thing, only they call it CRS here,caint remember S--t. :confused:
Cheers
Sonny

[bones]

Kick it to me, Kick it to me, righto here it is in english for ya sonny
tip speed = dia in inches x 3.1412 =* y
y then divided by 12, then x by prop rpm= y2
y2 divided by 60 will give you your tip speed in ft per sec

I think not sure about this one thou, the max tip speed is about 950 ft per sec some where around that mark anyway.... :paper:


Thank you, thank you orr you guys are to generous, ok stop clappin now..... :yes:

[bones]

So Sonny if i'm guessin right your runnin a 51 " prop at 4000 prpm, if so your tip speed is;
51 x 3.1412 = 160.201* *- which is your circumference of your prop swing in inches
160.201 / 12 =13.350* *-which the same in ft, 13.350 x 4000 = 53400.40* - which is your tip speed in ft per hr
53400.40* / 60 = 890.00* ft per second
that speed is more than acceptable, the higher you go the more noise the prop makes...

[russ]

Hey..........mudy. I'll kick ya................inya bawls :moon:

I'm tryin to find me trusty 25 yr old diary..................misplaced it sumwhere.................shyte :cheers:

[russ]

OK guys.........stop panakin.........found me diary, geez where's me glasses now..............hangon......... :crazyas:

[BeefBear]

Bones theres something odd about your formula.

51 x 3.1412 = 160.201 - which is your circumference of your prop swing in inches
160.201 / 12 =13.350 -which the same in ft, 13.350 x 4000 = 53400.40 - which is your tip speed in ft per hr
53400.40 / 60 = 890.00 ft per minute

Prop diameter by Pi = Circumference. Divide by 12 to bring Circumference to ft untis. Multiply by rpm and that should be it Right. Got to be since we are now talking circumference in feet and Reveloutions Per Minute, so where does the divide by 60 come in to effect?


Ted

[Aussie_Paul]

The 60 comes in at the end to get the answer in feet per second, not feet per minute. It is feet per second that is used re prop tip speed.

I got 890.233333 feet per second.

I divided 51" by 12 to get feet. Then I multiplied that figure by pi 3.142. Then I multiplied that figure by 4000 prop rpm, and devided the answer by 60 to bring it from feet per minute to feet per second.

Clear as mud to me!!!!

Aussie Paul. :mrhappy

[BeefBear]

Paul, I under stand the reasoning behind the formula. The point I was making to Bones is that if we were already in ft for circumference and had our RPM then the outcome already had to be in feet per minute.


The use of Pi being 3.142 is also under question as 3.14159 is far more accurate.


Ted

[bones]

hmmm, well there ya go Sonny, if you can make sense of all that your better than me and i started it...... :blahblah:
Sorry Ted a small typo, fixed now, i had it right in the first one :fingers:

[Sonnyj]

Hey guys
Yep I think I got it, I'll put it the jurnal if my wife can remember where I put it. :chuckel:

One thing thow, pie r not square. Cornbread r square, pie r round. :yikes:

All kiddin aside, thank you all, :cheers:

And Merry Christmas to all and a happy new year. You too Bones. :peace:

Best wishes
Sonny

[Aussie_Paul]

Paul, I under stand the reasoning behind the formula.* The point I was making to Bones is that if we were already in ft for circumference and had our RPM then the outcome already had to be in feet per minute.


The use of Pi* being 3.142 is also under question as 3.14159 is far more accurate.


Ted


Hi Ted, if you can tell the difference in efficiency between using the accepted pi 3.142 and the correct pi of 3.14159, you are definately a better man than I. That's probably true anyway!!!

I may be completely wrong BUT I was under the impression that all prop info in relation to tip sped was in feet per second, but as I say I may be completely wrong. Feet pr minute are extremelly larg figuers to have to work with. 891 feet per second is 53460 feet per minute. Much more unweildly I would have thought, BUT I may be completely wrong.

I started doing these type of figures back in 1982 when I wanted the tip speed of my 53" VW prop to be about the same as my fathers 72" on his 160 hp Lycoming.

I was nieve back then and worked with MPH, BUT then found evryone used feet per second, so I change to the '/second.

Aussie Paul. :)

[bones]

And Merry Christmas to all and a happy new year. You too Bones. :peace:

Best wishes
Sonny
[/quote]
Ok i'll bite Sonny WHY the hell was I singled out of the crowd as a SPECIAL one to be mentioned by meself, hmmmm me thinks there is gonna be a little bits of war over this one.. :pistoles:

[BeefBear]

Paul, It isn't a case of whether I can tell the difference of effeciency between 3.142 and 3.14159. Its simply that. should you use the corrected figure any data that you extrapolate, is then more than capable of withstanding scrutiny by others who may be intereted in using your data or your formulas. In Mark's case it was a typo, but when you then used the incorrect figure it shows that either you didn't know the correct figure or you're happy to be considered mathematicly challanged.

Ted

[Sonnyj]

Howdy Mark
Especially you, becouse sittn there with your leg in a cast, has to take a little fun out of the holidays for you, no malice intended Mate. :cheers:

Merry Cristmas, and GET WELL SOON.

Cheers
Sonny

[Mitch]

Merry XMas to you all and to Rotor for providing such a great forum and alternative. :cheers: :cheers: :cheers:
I'm with Sonny Bonsey ole Mate....get well soon.
Sonny tell Barbara and the family all the best from me.
Cheers Bro.
Mitch.

[bones]

She's all good Sonny, legs out of the brace, walkin without crutches all be it with big limp, was goin for a fly today be got FORCED to have a drink, or three so thats out the window now, nothing taken the wrong was only shit stirrin, have a good one talk to yous all latter