Rear throttle linkage and trim cable holes

[kens_cockpit]

http://img141.imageshack.us/img141/3...bushinghr9.jpg

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http://img409.imageshack.us/img409/1...bushingmj7.jpg

http://img224.imageshack.us/img224/1...bushingsb5.jpg

I've attached some pictures showing the mess I made of these holes. I took photos with the bushing for the trim cable in and out to give some perspective.

What do I do about this? My email to Vans support is as follows but I'ld appreaciate the thoughts of people on this forum. Thanks.

The bottom part of the large irregularly shaped hole is for the throttle linkage to the rear throttle assembly. The top part of that hole in which the bushing is located is for the manual trim cable. The bottom small hole is just a mistake I made when I started cutting for the rear throttle linkage

I made a real mess of the holes for the linkage. Now I?m paying the price for that.

You will also note in the photos taken from the rear a rather nasty wound from the dremel running away up the back of the F804C when I was cutting the holes for the throttle linkage. I can smooth that out but it has created a line of thinner material and presumably some potential weakness in that part.

You will also see the trim cable hole goes right up to and actually takes a little bit of the edge of the plate nut for the screw holding the throttle quadrant on. I?m not so concerned about that because I assume once the screw is in that will be secure enough.

However, it seems to me this is a pretty important structural part because the wings attach immediately below here! And I am thinking I might need to add some strength to it after making such a mess of it.

I accept you do not have any structural testing to rely on for this situation and all of the usual caveats. I suppose I?m interested in knowing what you would do in this situation (aside from not getting into it in the first place!). Would you just leave it or would you do something to add some strength here?

I thought I might do the following:

1. Drill out the nutplates for attaching the throttle quadrant
2. Cut a piece of .040 sheet aluminum to cover the holes plus about an inch (or 2?) at the top and bottom of the messy holes. I would keep the sheet narrow enough so that it didn?t cover the holes for the F804NPP. That would be to ensure that no extra grip length is required of the rivets attaching the F804NPP to the F804C. I suppose I could just get rivets with a longer grip length to be sufficient for the thickness of both the F804C and the ?strengthening? aluminum sheet.
3. Use AN426AD3 rivets to join the sheet to the F804C on the inside. I?m not sure how many and at what spacing and would appreciate some guidance.
4. Remake neater holes for the trim cable and throttle linkage to the rear.


Can you please give me some guidance here?


Ken Stanton
8QB Fuse wiring and cables etc.

[kens_cockpit]

Vans said to make a doubler so I went out and did that today. Of course that wasn't as straight forward as I anticpated either but I think it will be functional.

[dan]

Ken,

I know this doesn't help you now, but next time you might invest in a Greenlee knockout punch. Makes a nice clean hole!

[AntiGravity]

Originally Posted by dan

Ken,

I know this doesn't help you now, but next time you might invest in a Greenlee knockout punch. Makes a nice clean hole!

Hi Dan, what size punch(es) do you recommend, and where do you purchase them from? Are they expensive?

[Mike S]

Jeff, electrical supply house for the Greenley punches. Or, if you know any old time electricians, maybe you can borrow them.

Yes, a bit pricy, but well built tools made to last, and in steel at that.

A step drill, "Unibit" is also a good choice for sheet metal.

Large, round holes in sheet metal are not as easy at most folks think.

Mike

[AntiGravity]

Thanks Mike,

After some searching I found them supplied by RS Components here in NZ. Like you sid, not cheap! Of course, RS isn't known for keen pricing, so maybe I can find some elsewhere; I'll see if I can get one of two of the bigger sizes that the unibit can't touch (like 2?" for the smaller panel instruments maybe).

Cheers,

[Mike S]

Jeff, there is a punch available that is specifically for instruments, double sided to make both 2 1/4, and 3 1/8.

I would think you can find one to borrow from another builder in your area.

Mike

[AntiGravity]

Hi Mike,

we're a little thin on the ground with local builders here in NZ. We might club together and joint buy some of the more expensive tools that will only see little use during any one project. Good way to spread the cost.

Cheers,