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Determining Center of Firewall?

 
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Michael Valentine



Joined: 09 Jan 2006
Posts: 108

PostPosted: Tue Apr 10, 2007 7:05 pm    Post subject: Determining Center of Firewall? Reply with quote

Listers - how does one go about finding the center of the firewall? My firewall came with two tooling holes pre-drilled. I could obviously just draw a line between them. But, when I stick my square on the bottom edge, the holes are not perfectly aligned - the top hole is approximately 1-1.5mm off the line if I center the lower hole. The flanged bottom edge is not a perfect line itself, so I'm not sure it is the best place to square, but there are no other options. Also, in terms of side-to-side measurement, the darn thing is curved so it is tough to simply measure a centerline that way.

I'm sure I'm being dumb, but suggestions appreciated!

Michael in NH
Making progress on the fuse...601XL

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planecrazydld(at)yahoo.co
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PostPosted: Wed Apr 11, 2007 2:08 am    Post subject: Determining Center of Firewall? Reply with quote

one way to acheive a near "average" centerline:
  1. Cut out a cardboard pattern that will fit precisely inside the flanges of the firewall blank from bend radius tangent to bend radius tangent. Perhaps some odd shaped holes in the cardboard near the edges that can be traced with a sharpie for matching positioning later?
  2. Mark or cut the existing "tooling holes" holes in the cardboard from the firewall
  3. Then turn over the cardboard and re-trim to fit as well as possible. Trace the odd shaped hole in the cardboard on the firewall with a sharpie again to allow repositioning later.
  4. Re-mark or cut the hole locations in the cardboard.
  5. Find the center between each set of holes in the cardboard and drill a 1/16" pilot hole in the cardboard there.
  6. Replace the cardboard in the firewall and position with that set of alignment marks. Make a sharpie mark through the 1/16" holes in the cardboard.
  7. Flip the cardboard and repeat.
  8. Remove the cardboard.
  9. Find the center between each pair of pilot hole markings: there is the centerline.
Note that you can do this even if there are no pilot holes to transfer from teh part. The greater the distance between the 1/16" pilot holes in the cardboard, the greater the precision of this technique to find the center of a non symmetrical part.

Michael Valentine <mgvalentine(at)gmail.com> wrote:[quote] Listers - how does one go about finding the center of the firewall? My firewall came with two tooling holes pre-drilled. I could obviously just draw a line between them. But, when I stick my square on the bottom edge, the holes are not perfectly aligned - the top hole is approximately 1-1.5mm off the line if I center the lower hole. The flanged bottom edge is not a perfect line itself, Looking for earth-friendly autos?
Browse Top Cars by "Green Rating" at Yahoo! Autos' Green Center. [quote][b]


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barcusc(at)comcast.net
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PostPosted: Wed Apr 11, 2007 5:47 am    Post subject: Determining Center of Firewall? Reply with quote

Michael,

I had the same problem, the top hole was way off. It took a lot of fussing with it to get the center line, I basically had to ignore the top tooling hole and the bottom flange was no where near straight. I assembled everything and mounted it to the cabin floor, that is when I noticed a hairline crack in the flange near the top motor mount hole. I called Zenith, they seem surprised but really didn't give me any flack. The replacement is far superior to the old one, especially the bottom flange, it is straight across with the back angle pretty close. I strongly suggest you look very close for cracks so you don't waste as much time as I did. I have had other problems with parts but I have to admit their response was always good and the replacements usually arrived within three or four days.

Clyde Barcus
601 XL, Continental Powered
Wings, Tail & Engine Complete
Working on Fuselage

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PostPosted: Wed Apr 11, 2007 6:04 am    Post subject: Determining Center of Firewall? Reply with quote

I'm not sure if I did it correctly but I found the widest point and marked the middle (side to side). Then I intersected that mark with a square aligned with the bottom edge of the firewall and drew that vertical line to be used as the centerline.

Dred

---- Michael Valentine <mgvalentine(at)gmail.com> wrote:
Quote:
Listers - how does one go about finding the center of the firewall? My
firewall came with two tooling holes pre-drilled. I could obviously just
draw a line between them. But, when I stick my square on the bottom edge,
the holes are not perfectly aligned - the top hole is approximately
1-1.5mmoff the line if I center the lower hole. The flanged bottom
edge is not a
perfect line itself, so I'm not sure it is the best place to square, but
there are no other options. Also, in terms of side-to-side measurement, the
darn thing is curved so it is tough to simply measure a centerline that way.

I'm sure I'm being dumb, but suggestions appreciated!

Michael in NH
Making progress on the fuse...601XL

do not archive


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Ron Lendon



Joined: 10 Jan 2006
Posts: 685
Location: Clinton Twp., MI

PostPosted: Wed Apr 11, 2007 5:29 pm    Post subject: Re: Determining Center of Firewall? Reply with quote

Dred,

That's the way I would do it also. KISS


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dredmoody(at)cox.net
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PostPosted: Wed Apr 11, 2007 6:18 pm    Post subject: Determining Center of Firewall? Reply with quote

Yup. In hindsight, I should have advised that if the firewall bottom flange is not perfectly even, you can square to its average by setting both the firewall and the square on a nice flat surface and you'll be very close. Trying to set the square directly to an undulating bottom flange could be frustrating.

Dred
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