Re: F1M VP spring question

From: William Gowen <wdgowen_at_gmail.com>
Date: Fri, 07 Sep 2012 11:50:32 -0400

FWIW at some point in time I changed my spring to 5 turns of .013" wire.
The anchorage points are 180 degrees apart and the spring "unwinds" when
going to high pitch. I'm not too clear about this but I think it *might*
be better to have the spring "unwinding" when the prop is coming off
high pitch to reduce friction.

On 9/7/2012 12:39 AM, Tapio Linkosalo wrote:
>
>
> So, in order to reset my new VP for F1M, I had a spring winding session
> yesterday. The original spring was something like 7 turns of 0.3mm
> (0.012") around a 1.5mm (0.06") mandrel, but this seemed to be too soft.
> The pitch only started to reduce halfway into the flight, and then went
> to bottom setting rapidly.
>
> Looking at Bill's notes, I changed to 0.4mm (0.016") wire and 3 turns
> around the same mandrel. However, this seemed way too stiff, with
> practically no pre-tension I got the change to happen at reasonable
> torque, but then the VP did not go to bottom stop at all but was left
> hovering inbetween the stops. No good, too hard a spring. So eventually
> I went back to the thinner wire and a thinner (1.2mm, 0.047") mandrel.
> At 3 turns and 90 degrees pre-tension this seemed to work better.
> Tomorrows trimming session will show if this spring is any harder than
> the old one.
>
> A question, however. I seemed to have hard times bending the spring so
> that it did not flip sideways. The old one with more turns took better
> support from the shaft tube, but the new was so flat that it did not
> support, and often it turned to the side. I tried bending the bottom
> with a slot that goes around the cross bar so that it would support
> there from flipping, but it was not too successful. Making a deeper hole
> in the adjustment screw gave better support. But is there something in
> the spring geometry that I have not realized, something that would make
> it inherently stable instead of unstable, locations of the support point
> for instance?
>
> -Tapio-
>
>
Received on Fri Sep 07 2012 - 08:50:40 CEST