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[rebel-builders] Question of Rebel Datum location/ Cof G ran

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Wayne G. O'Shea

[rebel-builders] Question of Rebel Datum location/ Cof G range

Post by Wayne G. O'Shea » Sun Feb 19, 2012 8:35 pm

Okay.. so todays investigation.. just to make it all into real thick mud.

The Spring LEAF gear... without any extreme regard for measuring accuracy...
with a leg on the work table, the axle centerline appears to be 7/8" AHEAD
of the door post center line!

Bungee style gear the axle center line should = the door post center line
unless you've jammed that LG-13 against the main leg so hard that you've
forced it forward.

I have 3 Rebels here in the hangar/shop and an Elite as well... with very
little difference between them in leading edge to door post distances. The
average is that the leading edge of the wing is ~ 3/4" AHEAD of the door
post center line (door post c/l is what MAM originally used as the datum as
it matched the main wheel center line).

So on a Bungee Gear Rebel the axle center line = the center of the door post
and they are 3/4" AFT of the wing leading edge.

On a Spring Gear Rebel the axle center line does not = the door post
centerline and the axle center line is 1/8" AHEAD of the leading edge.. or
7/8" ahead of the door post.

Now this wing leading edge to door post center line is variable...
considering you shim the front wing attach to make up for where the rear
attach puts the wing. I've seen a lot of Rebel and rarely two have been the
same. Some have the front wing attach up tight against the forward edge of
the carrythru and some are almost centered in the carrythrough with spacers.
So the only real conclusion here is that everyone has to determine their own
range based on what you want to use as the datum point and where your wing
leading edge sits!

I didn't pull the fairings off on of the birds to see what the spacing was..
but if memory serves me correctly I have 3 washers spacing mine AFT on the
front attach.. so with the LEdge currently 3/4" (.75) ahead of door post
c/line + 3 x .063 = 0.939" would be the maximum I could get my leading edge
ahead of the axle center line if I removed the spacers and jammed it tight
to the front inside face of the carrythru tube. Now someone that didn't pull
their leading edge quite as tight during wing build might even get it to
work out to where Darryl quoted 1.15"

In the end... you guys are worrying tooooo much about this. :O)

Wayne

----- Original Message -----
From: "Gary Gustafson" <gargus@comcast.net>
To: <rebel-builders@dcsol.com>
Sent: Sunday, February 13, 2011 12:30 PM
Subject: RE: [rebel-builders] Question of Rebel Datum location/ Cof G range

When my measurements were done by the two mechanics, they
leveled the plane by putting 3' bubble levels on the bottom
of each door frame. Since scales were under each wheel, it
was easy to drop a plum bob from the leading edge of the
wing right next to the axle and measure the horizontal
distance from the axle (which in my case the axle was in
front of the wing).

However I have to agree with Wayne that it is a physical
impossibility to have the axle in front of the leading edge
due to the way the plane is built and if things are
perpendicular. So I have to conclude that, in my case, the
level was not really level or that the level was not in
solid contact with the door sill. However, that is a lot of
inches to make up (raising tail another almost 5" to get
plumb bob line 1.15" in front of the axle center). Looks
as if I am not the only one with a measurement problem.
ROFLOLAE (Rolling on floor, laughing out loud, and embarrassed)

Thanks for keeping me straight and hopefully out of trouble.



-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com] On Behalf Of
Wayne
G. O'Shea
Sent: Saturday, February 12, 2011 10:19 PM
To: rebel-builders@dcsol.com
Subject: Re: [rebel-builders] Question of Rebel Datum location/ Cof G
range

as an adendum to that.. with Spring Gear.. bolt flange for axle may be
slightly forward of the door post centerline due to the taper cut of the
leaf. I have a set in the shop I'm gonna verify that on tomorrow. Even if
it

is I can't see it being forward of the leading edge of the wing.

I know for fact that Gary has the bungee style gear though.. and it is
definitely centered on the door post.

----- Original Message -----
From: "Wayne G. O'Shea" <oifa@irishfield.on.ca>
To: <rebel-builders@dcsol.com>
Sent: Saturday, February 12, 2011 9:44 PM
Subject: Re: [rebel-builders] Question of Rebel Datum location/ Cof G
range

That's interesting Ron.. considering the cabin bottom below the door sill
is
to be level for weighing.. and the door post is perpendicular to the
cabin
bottom.. and the axle should be on the center line of the door post.. and
the door post is behind (aft of) the wings leading edge.

Wayne

----- Original Message -----
From: "Ron Shannon" <rshannon@cruzcom.com>
To: <rebel-builders@dcsol.com>
Sent: Saturday, February 12, 2011 9:27 PM
Subject: Re: [rebel-builders] Question of Rebel Datum location/ Cof G
range

On 254R, with spring gear and 8.00x6.00 Carlisle turf tires, the center
of
the axle was 0.5" forward of a plumb bob dropped from the leading edge.

Ron
N254MR


On Sat, Feb 12, 2011 at 4:03 PM, Wayne G. O'Shea
<oifa@irishfield.on.ca>wrote:


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