Tip Speed Calculator

[Mart61]

Morning All

I've seen a few discussions on various threads relating to blade tip speeds in MPH.

For those of you that are interested, I've attached a little Excel spreadsheet that you can use to calculate your blade tip speed.

Just enter the disc diameter in millimetres and head speed RPM and the maths is done for you, as if by magic!

[Tom Burgess]

Huh? so the tips of the blades on my Aurora are only doing 320ish MPH at 1950?

[J-S-Q]

Huh? so the tips of the blades on my Aurora are only doing 320ish MPH at 1950?

Sounds about right I'd say.

[Tom Burgess]

Sounds about right I'd say.

I thought it would be much quicker than that

[Mart61]

I think I got the maths right but, if I've made an error, please do let me know and I'll make the corrections.

[Steve]

Don't forget, disc diameter isn't just two times the blade length - you have to add the hub and blade grip assembly dimension as well.

So for a 600mm set of blades, the disc diameter would be (2 x 600) + 100ish = 1300mm. i.e. not just 1200mm.

I don't have a heli in front of me so am guessing at the middle dimension, but I'm sure you'll all get the jist.

[unwind-protect]

Sounds about right I'd say.

Indeed; google is your friend:

http://www.google.co.uk/search?q=(80cm+*2*+pi+*1800+per+minute)+in+miles+p er+hour

where 80cm is the disk radius (approx blade length), and 1800 is the rpm.

[Mart61]

I took my disc diameter from the Align build manual - 970mm. I've not actually measured it to see if it was right.

[Janek]

320mph is pretty fast, just double'ish the head speed and you'll have a flying bomb when the tips exceed the speed of sound

[Steve]

It's not hard to get a 40 size aero engine to swing a 10" prop at 15,000 rpm or more, and it will speed up significantly in a dive.

That gives tip speeds in excess of 440mph.

[SRH990]

I seem to remember reading somewhere that full size heli's blade tip speed is around the 300mph mark. I calculated my 700 at around 320mph too, then worked out the Beam E4, only 200mph or so!