Re: Re-Pitching the Ikara Prop

From: Bill Gowen <b.gowen_at_earthlink.net>
Date: Tue, 13 Nov 2007 16:12:01 -0500

I don't know what your normal practice is for the prop shaft and bearing. If you're using the standard Ikara bearing then the first thing to do is to replace this part of the system. Here's the way I do it. There are pictures in the photo section under "Ikara prop shaft modification".

Take a Harlan penny plane bearing and drill out both the front and back hole to about .022". If you have numbered drills, a #74 is .0225" and is perfect for this job. Be careful doing this because the bearing will be weak if you drill the hole too large.

Cut the old prop shaft with wire cutters and throw away the shaft, bead and bearing. Make a new .020" wire prop shaft that will be glued into the prop hub. This shaft will have a small 90 degree hook on the front and whatever rubber hook you like on the back. You'll have to bend the front hook after the shaft is in the prop. Make sure that the shaft is long enough for the rubber hook to clear the rear of the bearing. The second picture shows holding the prop shaft with a set of pliers where the front bend will be. Bend the hook in the shaft and cut off the excess wire. Align the hook the way you want it and put a tiny drop of thin CA in the hole to hold the shaft in. When this cures you can fill up around the prop shaft with CA making sure none is on the part of the shaft that goes thru the bearing. Also glue all around the bend in front of the prop. I usually cut off some of the excess plastic in front of the prop but it's really not necessary with the current rules to worry about that little bit of weight.


With your prop prepared this way it will work in Tim's pitch gauge without any mods to the gauge. Also, there will be no free play between the prop and the prop shaft so whatever adjustments you make to the pitch, tracking and balance won't change from the prop wobbling on the shaft.

In the movie clip the blue stuff that looks like 3M masking tape is 3M masking tape! It's there to protect the prop blade from the heat. The blades will melt before the spar if you get them hot. This is not desirable.

I'm not sure what's going on with your prop spar. If you use an anchored prop shaft like I described above and set both blades to track the same and to have the same pitch then the spar should not be a problem whatever it's shape.


  ----- Original Message -----
  From: calgoddard
  To: Indoor_Construction_at_yahoogroups.com
  Sent: Tuesday, November 13, 2007 2:47 PM
  Subject: [Indoor_Construction] Re-Pitching the Ikara Prop


  Bill:

  You are right, your video clip is still in the files section.

  I gather that is Tim Goldstein's prop pitch gauge. Do I need to make
  any modifications to that gauge to use your re-pitching technique or
  do I need to make a special thrust bearing, etc.?

  What is the blue material on the prop in the video clip? Is this some
  sort of heat shield or is it a reinforcement?

  It looks like a piece of 3M blue masking tape. Is it needed?

  What do you do if one prop spar is not perpendicular to the motor
  shaft? We have an Ikara prop that looks like one prop spar is canted
  forward maybe five degrees. Could this be responsible for the shudder
  in the stablizer?



   

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Received on Tue Nov 13 2007 - 13:12:05 CET