Re: Re: History of VP? [1 Attachment]

From: <Warthodson_at_aol.com>
Date: Tue, 13 Dec 2011 09:28:55 -0500 (EST)

John,
Thanks for the drawing & the explanation. I have never built a VP prop mechanism, but am intrigued by the concept & building one is on my very long "model airplane To Do list". Without your explanation & excellent drawing, I doubt that I would have had a clue how this device was intended to work. Torque burners also interest me. Compared to VP props they are a simple concept so it surprises me that they are prohibited from use in some of our model classifications in the USA. Are torque burners used in the UK?
Gary


-----Original Message-----
From: John Barker <john.barker783_at_ntlworld.com>
To: Indoor_Construction <Indoor_Construction_at_yahoogroups.com>
Sent: Tue, Dec 13, 2011 7:37 am
Subject: Re: [Indoor_Construction] Re: History of VP? [1 Attachment]


 

[Attachment(s) from John Barker included below]
 


Gary
I have not seen any response to your request for a photocopy from Zaic’s 1937 Year Book. I have a copy of the Model Aeronautic Encyclopedia vol1 which includes stuff from earlier YBs and on p81 there is a sketch of R. Hammer’s VP arrangement. The drawing of the working part is not much more than half an inch high so I did not think it would scan very well. I peered at it for a while through my loupe and made a larger sketch which I hope may be of some use. I have stayed with Frank’s drawing as closely as possible although I have given the wires some thickness to suit the larger size (in the original the wires were all drawn as single lines). I don’t understand what the arrows indicate and I certainly don’t understand the little circles on the pitch changing arms! The wire hinges (which I have drawn in blue) are just a single thin line in the original. Whether they are torsion wires or whether they pivot in some tubes I do not know.
Operation would seem to be straightforward. One would expect the propeller blades to have a high angle near the root such that, looking at the top blade in the sketch, the trailing edge would be nearer than the leading edge. If the motor was wound tightly the spring would compress, the ‘U’ shaped wire would move backwards pushing the trailing edge of the blade further in and increasing the pitch. However I have never seen much correlation between the tension and the torque in a motor so I would not expect the device to have many followers.
You also asked about Louis Garami’s ‘Torque Burner’. There is a short wire fixed to the motor stick, about 35% back and pointing downwards. The motor is made in two parts, a short front part and a long rear part joined by a wire ring. After the motor is wound the wire ring is slid onto the wire on the motor stick. The model flies on the front part of the motor until the tensions and torques in the two parts of the motor equalize, at which point the ring drops off the wire and the rear part of the motor comes into play.
John
Received on Tue Dec 13 2011 - 06:29:07 CET