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  #1  
Old 03-19-2017, 06:49 PM
flyindoorman flyindoorman is offline
 
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Default TruTrak Autopilot shear pin

I have a TruTrak autopilot that has sheared the screw off there are three holes in the disk. how do I rotate to get another hole to line up? Did not want to just twist it and cause damage?
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  #2  
Old 03-19-2017, 10:02 PM
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Jesse Jesse is offline
 
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First of all, you have to remove the head of the sheer screw.

The easiest way is to just loosen the center screw a little bit and hold the "drum part" and rotate he arm until the next hole lines up. Install the new sheer screw and tighten the center screw. If you can't easily loosen the center screw, or it's a nut, you can still turn he "drum" separate from the arm to line up the next hole. If you couldn't, then the auto pilot would still work normally, which would mean that the sheer screw may not actually be steered.

If neither of these works, remove the center screw or nut and separate the arm from the drum. Install a sheer screw in a new hole, rotate the drum until it can line up with the hole in the arm and reassemble.

Make sure not to overtighten the sheer screw, and it's not a bad idea to use a little blue loctite on the sheer screw. If you overtighten you may weaken the sheer screw and it will sheer much more easily than it should.
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  #3  
Old 03-20-2017, 03:16 AM
flyindoorman flyindoorman is offline
 
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Jesse,
Thanks for your reply. The head of the shear screw fell out but the drum will not rotate.
I tried a little pressure with pliers but didn't want to damage it. Should it rotate freely ?

Thanks again
Randy
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  #4  
Old 03-20-2017, 05:47 AM
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Jesse Jesse is offline
 
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Quote:
Originally Posted by flyindoorman View Post
Jesse,
Thanks for your reply. The head of the shear screw fell out but the drum will not rotate.
I tried a little pressure with pliers but didn't want to damage it. Should it rotate freely ?

Thanks again
Randy
If part of the sheer screw is sticking out of the hole, meaning it broke the head of the sheer screw, but the shaft of the screw is still catching the arm, then it may not rotate freely. I saw one the other day that allowed about 20 degree of motion before it caught. In this case you may need to remove the arm, file off the part of the sheer screw sticking out of the hole, then rotate to the next hole. Of course, if there is enough sticking out that you can grab it with plyers and remove, then you can reuse the same hole.
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  #5  
Old 03-20-2017, 06:08 AM
flyindoorman flyindoorman is offline
 
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It broke off up inside the hole a bit. I removed the center screw and the drum will not rotate with pliers feels bound up. I'm guessing that this drum should rotate freely?
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  #6  
Old 03-20-2017, 08:14 AM
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Jesse Jesse is offline
 
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As I said in the email, it should move freely. Remove the connector from the back of the TruTrak programmer in your panel or from he back of the servo and see if it starts to move freely. If not, it's a bad servo and needs to be replaced or rebuilt.

Also, as mentioned in the email, this is the exact situation requiring a sheer screw.
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RV Hotel (hangar, room, car) at X35 in north FL

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Dynamic Prop Balancing, Prebuy Inspections, Condition Inspections, Repairs and Mods, Injector Tuning, Airframe, Engine, Panel Upgrades, Ferrying, etc.
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  #7  
Old 03-20-2017, 03:25 PM
flyindoorman flyindoorman is offline
 
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Jesse
It did what it was designed. I ordered a replacement servo this morning. Thanks again for your help I really appreciate it.

Randy
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