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General control line discussion => Open Forum => Topic started by: Ara Dedekian on November 22, 2015, 05:47:07 PM
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I have a neighbor, not a modeler, but a really cool guy just the same. Merrill is a sailor, marine surveyor, Jazz bassist, machine designer, mechanical engineer and machinist. He helped me rebuild a floor model drill press rescued from the dump by machining missing parts. I went to him when I learned of Fox engines demise for advice on making my own Fox 35 needle valves. Since the pitch on the Fox needle is 3/48, could I make one out of a 3/48 screw?
Below is Merrill's version of a Fox needle made from a Class 3, 3/48 socket head screw based on the sample I left him.
The brass end is knurled and pressed on, adjusted with a ball driver long enough to clear the prop. The flat was ground down with a Dremel tool secured to the lathe and the workpiece fastened to the toolholder, set to a 4 degree taper.
As expected, it worked great on the one flight, so far, of the BiSlob. I could land inverted all day with a profile and not worry about its breaking.
My next adventure was a botched RC landing which bent the crankshaft on my Supertigre G90 just ahead of the front bearing. Supertigre is no more, as are any crankshafts. I was able to miraculously straighten the crank to within .002" using the 3' mandrel pictured below inserted into the rear ID of the crank and used as a lever. With prop nuts on the threads and secured in a vice or chuck, you can gradually straighten it by pulling on the mandrel and checking the runout on a flat surface with a dial indicator. It runs well again without any vibration. The better news is that the mandrel came out of my scrap box as is; it couldn't have fit better if it was custom made! I wonder if a Fox 35 case would hold up to crank bending forces.
Ara
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The last Fox.35s produced had a tapered needle. You ought to try one of those if you are looking to make a few more. I think guys have just ground the old ones to a taper legth to match the flat and they worked fine, allowinga more fine adjustment of the needle.
Thanks for the photos.
Dan McEntee