Re: Re: Re: [indoor construction] VP or VD

From: Nick Ray <lasray_at_gmail.com>
Date: Mon, 23 Oct 2006 20:17:14 -0400

In order to keep a constant P/D you would need to have a V/P mechanism
along with a mechanism for folding of the Prop. Right? I know you
could have one mechanism for doing both things but I can not get my
brain around this I'm going to break it into parts.

First the change in P is a function of radius of the prop. So if we
use a prop that changes gradually the we model it with a one to one
function of torque vs. radius of the prop. That calculation could come
from modeling the rate of change of the spring based on a given
preload. BUT every time you change the preload the rate of change in
diameter would change. The other way to figure this out would be to
test torque loads and then plot them on a curve and use that for
determining at which rate the prop would need to change pitch.

To find the pitches of the prop as per the given distances I think the
easiest thing to do would be to plot the pitches and 10-15 different
points throughout the changes in the prop diameter and then use a
regression line to come up with a spring that would match the needed
rate of change.

now... we'd need a mechanism that would do this... for that I pass for now...
Nick (some one point out the points were I'm wrong if you see any)

On 10/23/06, Bill Gowen <b.gowen_at_earthlink.net> wrote:
>
>
>
>
>
>
> Slobodan
> Jim Richmond seems to do very well with a folding VD prop. For me the
> folding mechanism is too complicated and the sliding spar mechanism is too
> heavy. Even the sliding spar mechanism is difficult to keep working
> reliably.
>
> I'm sure that someone could work out a way to keep a constant P/D ratio but
> I think it would be very difficult. I looked at the increased pitch as a
> bonus in my props - like I was getting VD and VP all at the same time.
>
> ----- Original Message -----
> From: Slobodan Midic
> To: Indoor group
> Sent: Monday, October 23, 2006 3:13 PM
> Subject: [Indoor_Construction] Re: [indoor construction] VP or VD
>
> Thank you Bill and Nick,
>
> You have right, at known constructions of VD prop, that means at folding VD
> system and at sliding VD system, you have only translation movement the
> prop blades near to prop axis, and "the P value isn't constant", nor P/D
> value also. But if the progressive movement of blade is combined with some
> blade rotation in the same time for some angle round the blade spars, at
> some predetermined low, maybe can you achieve, P/D=Const., during changing
> the prop diameter. I don't have the solution for that VD prop, that is
> something imaginary, but it can be solve, only the question is, have this
> some sense or not. My impression was that VD prop have better potential for
> flying with optimal prop efficiency at different working regimes than at VP
> props, and maybe is that criterion P/D=Const.
>
> I excuse to the group with my hypothetical questions, maybe it is not
> interesting ....
>
> Thank you,
> With compliments,
> Slobodan Midich, dipl.ing.
>
> [Non-text portions of this message have been removed]
>
>
Received on Mon Oct 23 2006 - 18:03:17 CEST