Re: Rotor tip speeds!

[MrBonk]

There was a photo on the web somewhere of a large 4wd (no idea what
make/model) with a carbon main blade stuck in the door. Story apparently
went that the fellow was hovering next to the parking area when a blade grip
gave up and ejected the blade. Managed to puncture the door skin of the
car, so I wouldn't like your chances if it hit your body somewhere. Very
nasty!

MrBonk
www.mrbonk.com

"SRS" <sstuart@NOSPAM.glasscity.net> wrote in message
news:va3h6os7p9q0bd@corp.supernews.com...
> Question is, will the blade continue to shoot straight out at high
> speed, or more likely flutter from varying drags across the airfoil
> quickly loosing its momentum. Dunno, just a guess. And what of the poor
> heli with an incredible balance problem. Wouldn't want to get hit with
> those flying parts either!
>
> Steve w8an

[Bill Sheppard]

David wrote,

>It's surprising just how fast it's going. It
>could travel 129 yards in 1 Sec if there
>were no losses from turbulence, etc.

What you're calculating is the tangental, or linear velocity of the
blade tip. But the blade proper is moving much slower. If the blade were
to separate from the hub, its actual departure speed would be the
average of the base speed and the tip speed.
Still wouldn't want to be in the way of a wayward blade,
though.

Bill (oc)

[David]

Agreed, also centrifugal force effectly moves the centre of the mass towards
the tip. Whatever the speed, I would not want to be in its path.
David
"Bill Sheppard" <oldcoot@webtv.net> wrote in message
news:2057-3EA1EF21-138@storefull-2356.public.lawson.webtv.net...
> David wrote,
>
> >It's surprising just how fast it's going. It
> >could travel 129 yards in 1 Sec if there
> >were no losses from turbulence, etc.
>
> What you're calculating is the tangental, or linear velocity of the
> blade tip. But the blade proper is moving much slower. If the blade were
> to separate from the hub, its actual departure speed would be the
> average of the base speed and the tip speed.
> Still wouldn't want to be in the way of a wayward blade,
> though.
>
> Bill (oc)
>

[Beav]

"SRS" <sstuart@NOSPAM.glasscity.net> wrote in message
news:va3h6os7p9q0bd@corp.supernews.com...
> Question is, will the blade continue to shoot straight out at high
> speed, or more likely flutter from varying drags across the airfoil
> quickly loosing its momentum. Dunno, just a guess. And what of the poor
> heli with an incredible balance problem. Wouldn't want to get hit with
> those flying parts either!

When you've pulled a blade out of a brick wall, your question will be
answered :-)


--
Beav


Please note my E-mail address is "beavis dot original at ntlworld dot com"
(with the obvious changes)

Beavisland now lives at
www.beavisoriginal.co.uk

[All Thumbs]

I've seen a raptor 30 go in hard & come out with half a rotor blade (Carbon)
imbedded(Right through) on the needle valve. Still can't figure how that
happened. If I hadn't seen it, I won't have believed it.
The other tip flew about 100m..........



"Beav" <beavis.original@ntloxoworld.com> wrote in message
news:tgvoa.805$%21.663@newsfep4-winn.server.ntli.net...
>
> "SRS" <sstuart@NOSPAM.glasscity.net> wrote in message
> news:va3h6os7p9q0bd@corp.supernews.com...
> > Question is, will the blade continue to shoot straight out at high
> > speed, or more likely flutter from varying drags across the airfoil
> > quickly loosing its momentum. Dunno, just a guess. And what of the poor
> > heli with an incredible balance problem. Wouldn't want to get hit with
> > those flying parts either!
>
> When you've pulled a blade out of a brick wall, your question will be
> answered :-)
>
>
> --
> Beav
>
>
> Please note my E-mail address is "beavis dot original at ntlworld dot com"
> (with the obvious changes)
>
> Beavisland now lives at
> www.beavisoriginal.co.uk
>
>

[Steve Simpson]

> > > PS Try doing these calculations with a 10 x 6 prop at 16,000 RPM, and
then
> > > wonder if it's ever worth looking over a prop when it's running!

Another interesting exercise is to do the calculations on the ultimate in
piston engines planes; fighters from late WWII.

The limiting factor was the propeller tips going supersonic.

[David]

Yes, I know the US made 'Harvard' was renoun for this effect, the propellor
makes a loud cracking noise as the tips go supersonic, affects tip wear too
I understand.

The tips of a 9ft prop turning at 2300RPM just start going supersonic.

David

"Steve Simpson" <simpsons34@NIXcox.net> wrote in message
news:9Egqa.24$qc5.9@fed1read06...
> > > > PS Try doing these calculations with a 10 x 6 prop at 16,000 RPM,
and
> then
> > > > wonder if it's ever worth looking over a prop when it's running!
>
> Another interesting exercise is to do the calculations on the ultimate in
> piston engines planes; fighters from late WWII.
>
> The limiting factor was the propeller tips going supersonic.
>
>