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  #1  
Old 03-04-2018, 06:44 PM
mfleming's Avatar
mfleming mfleming is offline
 
Join Date: Sep 2016
Location: Joseph, Oregon
Posts: 304
Default -7 Elevator Bellcrank Install Issue

I'm installing the F-635 elevator bellcrank assembly on my -7 QB fuselage.

The quick builders drilled the ¼" bolt hole in the F-729A bellcrank rib and angle. They also drilled the hole in the F-728A bellcrank channel BUT did not drill the F-728B angle.

This seems like a critical hole to drill so the bolt is square with the structure.

My problem is how to drill through the angle and not get off center??

Here's the drawing.



Here's the channel with the ¼" hole but not in the angle.



I can get a long ¼" bit through the rib hole but the there's nothing to help stabilize the bit and prevent a misdrilled hole.

Any thoughts would appreciated.
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Michael Fleming
Joseph, OR
sagriver at icloud dot com

RV-7 Slider #74572
Started 11/2016
Empennage completed 11/2016 (sans fiberglass)
Ailerons and flaps completed 3/2017.
Wings completed 12/2017 (sans fiberglass)
Started on QB fuselage 01/2018
Donated and so should you
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  #2  
Old 03-04-2018, 07:22 PM
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wirejock wirejock is offline
 
Join Date: Oct 2005
Location: Estes Park, CO
Posts: 3,031
Default Drill bushing

Go to the hardware store. Buy one of each size brass tubing up to 1/4" OD.
Cut a length off each shorter than the bit that fits the smallest tube. Probably #41.
Insert them inside each other so the outer tube fits the hole. The inner tube holds the bit centered. Once you have the pilot hole, drill in incremental sizes up to 1/4".
Hope that helps.
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Donated 12/01/2017. Plus a little extra.
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  #3  
Old 03-04-2018, 07:36 PM
Simon Hitchen Simon Hitchen is offline
 
Join Date: Apr 2006
Posts: 251
Default Same idea

Use a square piece of aluminiun stock, drill the correct size hole through it using a drill press, clamp it in place between the rivets and use it as a guide. That’ll get you a square hole so to speak.
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  #4  
Old 03-05-2018, 10:49 AM
mfleming's Avatar
mfleming mfleming is offline
 
Join Date: Sep 2016
Location: Joseph, Oregon
Posts: 304
Thumbs up

Quote:
Originally Posted by wirejock View Post
Go to the hardware store. Buy one of each size brass tubing up to 1/4" OD.
Cut a length off each shorter than the bit that fits the smallest tube. Probably #41.
Insert them inside each other so the outer tube fits the hole. The inner tube holds the bit centered. Once you have the pilot hole, drill in incremental sizes up to 1/4".
Hope that helps.
Quote:
Originally Posted by Simon Hitchen View Post
Use a square piece of aluminiun stock, drill the correct size hole through it using a drill press, clamp it in place between the rivets and use it as a guide. That’ll get you a square hole so to speak.
Thanks for the advice...both methods sound good.
__________________
Michael Fleming
Joseph, OR
sagriver at icloud dot com

RV-7 Slider #74572
Started 11/2016
Empennage completed 11/2016 (sans fiberglass)
Ailerons and flaps completed 3/2017.
Wings completed 12/2017 (sans fiberglass)
Started on QB fuselage 01/2018
Donated and so should you
Reply With Quote
  #5  
Old 03-08-2018, 12:16 PM
mfleming's Avatar
mfleming mfleming is offline
 
Join Date: Sep 2016
Location: Joseph, Oregon
Posts: 304
Thumbs up Thanks for the help!

Quote:
Originally Posted by mfleming View Post
I'm installing the F-635 elevator bellcrank assembly on my -7 QB fuselage.

The quick builders drilled the ¼" bolt hole in the F-729A bellcrank rib and angle. They also drilled the hole in the F-728A bellcrank channel BUT did not drill the F-728B angle.

This seems like a critical hole to drill so the bolt is square with the structure.

My problem is how to drill through the angle and not get off center??

Here's the drawing.



Here's the channel with the ¼" hole but not in the angle.



I can get a long ¼" bit through the rib hole but the there's nothing to help stabilize the bit and prevent a misdrilled hole.

Any thoughts would appreciated.

Here's a look at how the troublesome hole was drilled.

I used a piece of ¼" OD copper tubing. One end was squared off so it would fit in the small lip of the hole in the F-728A channel. The ¼" tubing ID was perfect for a 3/16" drill bit.

So with the tubing in place, I had a nice square perfectly aligned jig.

Here's what it looked like just before drilling.



And the final F-635 assembly in place.

__________________
Michael Fleming
Joseph, OR
sagriver at icloud dot com

RV-7 Slider #74572
Started 11/2016
Empennage completed 11/2016 (sans fiberglass)
Ailerons and flaps completed 3/2017.
Wings completed 12/2017 (sans fiberglass)
Started on QB fuselage 01/2018
Donated and so should you
Reply With Quote
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