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Author Topic: 1949 Fox 35 Stunt problem???  (Read 863 times)

Offline frank mccune

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1949 Fox 35 Stunt problem???
« on: October 06, 2018, 10:42:43 AM »
      Hi All:

       Whenever I tighten a prop to this engine, the drive washer gets pushed into the front of the case causing a severe bind.  The prop can only be turned with great difficulty.  The prop drive is tapered to fit a mating surface on the shaft that is also tapered.  Now, how to solve this problem.

        I guess that I could remove a bit of the nose on the crankcase or make another drive washer with a smaller tapered section.  Not having a lathe, I think I am limited to shortening the nose.  Or find a newer crankshaft that has the splines. Is possible?


        Suggestions as to what the taper was on these early crankshafts?

                                                                                                                                                  Be Well

                                                                                                                                                  Frank McCune


                                                                                                                                               
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Online Dan McEntee

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Re: 1949 Fox 35 Stunt problem???
« Reply #1 on: October 06, 2018, 11:56:55 AM »
    You could square off the end of the crank case to make sure it is square, and then remove material from the BACK of the prop drive washer. When you see that you have some satisfactory clearance, see how it tightens up. If you have clearance still, you can lap the drive washer to the crank shaft taper with fine lapping compound.  Mount the engine in a test stand, mount a prop on it, take the glow plug out, and check how the prop runs out at this point. If the prop doesn't run straight, then the tapers are not square and straight. This is about the only thing I think you can do with out a lathe and some technical help. You can look for a similar parts engine on eVilBay. A later model crank and drive washer may work but may have to be fitted also.
  Good luck and have fun,
  Dan McEntee
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Online Brett Buck

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Re: 1949 Fox 35 Stunt problem???
« Reply #2 on: October 06, 2018, 12:44:43 PM »
Quote from: frank mccune on October 06, 2018, 10:42:43 AM
      Hi All:

       Whenever I tighten a prop to this engine, the drive washer gets pushed into the front of the case causing a severe bind.  The prop can only be turned with great difficulty.  The prop drive is tapered to fit a mating surface on the shaft that is also tapered.  Now, how to solve this problem.

        I guess that I could remove a bit of the nose on the crankcase or make another drive washer with a smaller tapered section.  Not having a lathe, I think I am limited to shortening the nose.  Or find a newer crankshaft that has the splines. Is possible?


        Suggestions as to what the taper was on these early crankshafts?

   Dan's suggestion is probably a good one. A non-lathe "fix" would involve filing or grinding *the case* to shorten the bearing section, but that is offensive on multiple levels. That's probably what Duke would have done. It might only take .005 or so, but, still.

     As an aside - how the heck many airplanes do you have, anyway? You have them for 46SF, Foxes, McCoys, apparently, in endless variation.  This is not at all critical, I am just amazed at how you find the space or time to build or acquire them all.

     Brett
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Offline RandySmith

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Re: 1949 Fox 35 Stunt problem???
« Reply #3 on: October 06, 2018, 02:33:56 PM »
Quote from: frank mccune on October 06, 2018, 10:42:43 AM
      Hi All:

       Whenever I tighten a prop to this engine, the drive washer gets pushed into the front of the case causing a severe bind.  The prop can only be turned with great difficulty.  The prop drive is tapered to fit a mating surface on the shaft that is also tapered.  Now, how to solve this problem.

        I guess that I could remove a bit of the nose on the crankcase or make another drive washer with a smaller tapered section.  Not having a lathe, I think I am limited to shortening the nose.  Or find a newer crankshaft that has the splines. Is possible?


        Suggestions as to what the taper was on these early crankshafts?

                                                                                                                                                  Be Well

                                                                                                                                                  Frank McCune


                                                                                                                                               

Frank 

Discounting  making A  new  drive washer, I would  just file the front of the  case  down, it should only take  5 to 10 thous  for  the clearance  you need, I would  suggest  that  you   do not  turn down the  back of the  taper drive washer, the case will be  a better  idea

Randy
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Offline Al Ferraro

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Re: 1949 Fox 35 Stunt problem???
« Reply #4 on: October 06, 2018, 03:01:56 PM »
With the prop and drive washer off, screw the nut back on and pull the crank forward. You should see the front end of the crank come out of the case  approximately .020. If get the .020 out the front then you probably would need a new drive washer.  If you don’t get it then you must have dried caster or some other kind of foreign material in front of the counter weight on the crank.
Al
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Online Brett Buck

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Re: 1949 Fox 35 Stunt problem???
« Reply #5 on: October 06, 2018, 04:14:41 PM »
As previously mentioned, Randy and I *do not* have a hotline over which we consult on these posts! There is no conspiracy to pile on.

    Brett
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