Last update: 13/4 2009 Design by Henning Forbech Here are some photos and an interactive 3D model of the shut-off system that I have been working on this winter. The system has now been tested and it is ready for use in competitions. The system is mainly an update of my 2007 design. Most of the parts and functions are the same but there are a couple of changes and some new functions. 3D interactive model: eDrawing (5 Mb exe-file). Same file in a zip file (5 Mb zip-file).		Henning Forbech
First system at a test flight The biggest change is that the spring activation from 2007 has been replaced by a new swing arm activation. This small swing arm will force the shut-off open when the arm is turned towards the inboard wing. The force from the spring will keep the swing arm in this position as long as the line tension is low. When the line tension gets higher than 10 N the swing arm will be free to move. If the model is held with the nose up by the pitman (for starting the engine) the pilot pull the lines hard enough to release the spring, the swing arm will only move to a position backwards. When the line gets to a lower tension again the swing arm will still block the shut-off. This prevents the system from arming and shutting down by a short jerk on the lines. Shutting off on these unattended jerks was one of the biggest problems in the 2007 design. With the 2009 design the mini swing arm must be in a position backwards/outboard before the spring can pinch the fuel line. It takes 10 N of line tension AND 2 g centripetal acceleration to activate the system. Close-up photos of the mini swing arm The main spring and the base plate have been turned around and is now flying "backwards". The safety wire has been moved from the top to the bottom of the model. On the 2007 design the mix of safety wire, fuel lines and streamer string sometimes confused the pitmen. From the production 30 shut-offs in production Parts for the 2009 shut-off First test flight at Munich, Germany, Marts 7. 2009. Lothat Hentzel, Johan Schwarz and Rudi Königshofer Test flight i Aalborg, Denmark, April, 3. 2009
ViKo Models now has a shut-off system for sale. A system very close to this design. More info here.		Viko Models

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Shut-off start - F2D.dk