100 hp...efi...air cooled...80kg.....read on

[russ]

Mite interest some........

Homebuilt Aviation

efi....twin ign...2plugs...torque and hp.......sounds real good for a gyro maybe.
[with redrive too]

[BeefBear]

I note it spins at 2750 rpm. Given that, what would be the tip speed if you ran a 68" prop?

Ted

[russ]

Buggered if I know.........next question :yikes:

[BeefBear]

Hmmm..... really?? OKay, are you really an instructor??? May I remind you Mr. Cook that you are the Instructor and I'm the student.... :mrgreen: and you are supposed to know these things just in case I should ask :cheers: hehehe

Lets see... 2750 rpm x 68" prop..... err.... ((2X3.14159x34)/12)x2750= 48931.66'/min. You know Russ , if you were going that fast you even beat the photo cameras. :raving:

So back to them figures, that'll be (48931.66x60)/5280=556.04 miles an hour.

What's our maximum allowable tip speed?

Ted

[russ]

Ok smart arse... :mrhappy: let me try........
to get prop diameter...............................850x12x60 divided xmax rpm dividedx3.1416= diameter
to get prop pitch..................max airspeedx1056 divided x max rpm = pitch

eg........my max rpm is to be, let's say......3500
my max airspeed to be................90

useing the above guide........my prop diam is to be 55.6"
my prop pitch is to be 27.15


Now I could be wrong here.........would'nt be the first time

[russ]

Sorry forgot this bit...........
Prop speed.....

You have worked out your prop diameter........so useing this method,
201655 divided by diam of prop...........gives you the MAX you spin that prop,

I think the max recomended tip speed is Mark .83 or 600 mph at the tips

:cheers:

[BeefBear]

Russell, Somewhere a long time ago, possibly on the American forum, I thought I read 585mph.... but anyway 600 is close enough.

One other thing I noticed with the engine is that its swinging a normal plane prop. Why can't we? Is it to do with the lack of substantial engine mounting capability?

Tosser

[russ]

Well, to be honest.......I got the info from my diary, and this info was dated december 1985, got it from an ozy prop manufacturer "Bob Morton"........yea, 20 yrs ago.......phew

so go ezy on them questions........I'm running out of answers here

[bones]

Actually Russ it's find the prop rpm then divide it by 201655 to give the max dia;
201655 divided 2750 =73.32, so a 72" prop would be fine, just a note this figure works the other way too, ie if you wanted to spin a 70" prop for eg;
201655 divided 70 = 2880.78, so the max rev the prop can spin is 2880prpm.
Can i come to the front of the class, can i, can i???? :blahblah: :pelvic_thrust2:

[russ]

NO........stay down the back yar mongrel.....need long range practice at throwing me chalk. [smart arses.....hate em, could be why I hate me self sometimes] :peace:

[BeefBear]

Sack the Instructor...... Vote for Bones.... :joy:

Any one who has a 20 year diary still in use hasn't got a life!!!!!!

[russ]

yea......another 20yrs from now, it'll have 40 yrs of wealth to call back on.......Grrrrrrrrrrrrr

Hey...it's still winter up in your mountains, crawl back into your cave, and hybernate a bit more :shiver: :cheers:

[BeefBear]

Russell, it was -5 the other morning. Air was still, would have been as smooth as silk...... why don't you come down and try it ya Tosser. :drunk:


Like most winter days it rose to a very pleasant 21 degreees for an hour. Should be more of it. Oh dear, I just thought of the real reason why Birdy doesn't fly high. His famous thongs would freeze!! :mrhappy: