I can fill in some of the details regarding VP development in the early 90's by Bob Randolph and myself.
Beginning after the 1988 World Champs, where Cezar Banks debuted his VP design, Bob Randolph and I began building Cezar's design and flying it a lot in Cat I and Cat II sites. The early versions used a 0-80 nylon screw for high pitch adjustment and either had no preload adjustment, or used a wooden wedge under the preload spring arm. We found that the wedge was unsatisfactory.
In Cezar's earliest versions the spring and vp "yoke" were all made of a single piece of wire, a tricky bending and soldering operation. Randolph began experimenting with separate yokes and ways to secure them to the prop shaft. He eventually settled on a wire yoke similar to what John Kagan now uses after trying wood, plastic, carbon, etc. secured by CyA or epoxy.
I eventually arrived at a soldered metal yoke and both of us began using the 00-90 adjustment screws. We were able to set a variety of low ceiling records with these models.
I believe that Cezar Banks often flew an alternate design during much of the 90's instead of the one we associate with him. It did not use a coil spring, but utilized the bending of the prop shaft.
--Steve Brown
--- In Indoor_Construction_at_yahoogroups.com, "ray_harlan" <rbharlan@...> wrote:
>
> The earliest concept of a VP for indoors that I know of is on p. 74 of the '37 Zaic yearbook (same page as the torque burner). It is by R Hammer and uses a compression spring and bent wires through the prop hub to effect what looks to be decreased pitch with increased motor tension. Perhaps Zaic didn't draw it correctly.
>
> However, the real pioneer of workable VP props was Jeff Annis. He puplished the paper "Torque Variable-Pitch Propeller" in the 1975 NFFS Symposium. It shows a mechanically workable design employing the torsion spring characteristics of the prop shaft. He had tested it prior to publication and had found 15-30% better duration over a flaring prop in low ceilings.
>
> It took quite a while to lead to better designs of the VP prop. The Brits tried at the '80 WCh, using essentially the Annis design, but couldn't get it working well (see Aug. '82 INAV). Jim Richmond introduced his VD prop in'84 in Chicago and used it at the '84 WCh where he won the contest with it. After a flurry of activity with VD props, only two fliers were successful with them - Jim Richmond and Rich Doig. Attention returned to VPs. Ron Higgs tried one with a spiral spring in '85 and set a Cat I world record. At this point my collection of INAV is a bit thin. In Dec '90 Bob Randolph set a Cat I record with a VP prop that looks much like the classic Banks/Brown design. The prop doesn't use a preload adjust screw, just a high limit screw (May '91 INAV). I don't know who was first. I thought it was Cezar Banks who finally developed a compact wound torsion spring design. Steve Brown made the technology accessible with his excellent article on how to build a VP in the Oct '96 issue of INAV. The current VP designs are only small variants of this design.
>
> Ray
>
> --- In Indoor_Construction_at_yahoogroups.com, Tapio Linkosalo <tapio.linkosalo@> wrote:
> >
> >
> > Who did invent / introduce the spring-loaded VP system to indoor flying?
> > A friend asked this during the Finnish Champs yesterday, and I had to
> > confess that I did not know. I recall seeing pictures of Joachim
> > Löffler's F1B (wakefield) hub from the 1960's, using that mechanism
> > where torque on one bar and prop on another produce the blade twist. The
> > first picture of an indoor adaptation I have seen is the Richmond (?)
> > drawing in INAV in the 80´s I think, but that seems to be a
> > well-established concept already, so the initial use has been before that?
> >
> >
> >
> > -Tapio-
> >
>
Received on Wed Dec 07 2011 - 10:44:05 CET
This archive was generated by Yannick on Sat Dec 14 2019 - 19:13:46 CET