Joy,
You are probably right about the construction of the plate, I don't know.
What I meant is front plate separation usually comes from an improper hitch
rating and stiff tow vehicle suspension that is transferred to the coach A
frame assembly. The radial tires might soften the transfer of energy from
the road to the plate (and everywhere else for that matter), however
small??? I am really more concerned about working rivets and the holding
tanks from a stiff suspension/tire.
The part about equalizer hitch rating, though, I have to disagree with you.
The bars used to distribute the weight need to flex and not be over-rated.
Your right that the root cause is probably moisture but "All airstreams
leak", or eventually will, so stiff equalizer bars only compounds the
problem. We can dip our entire coach in Vulkem, and water will find it's
way back in!
Thanks for taking the time to respond in detail about the plates. I learned
something and I'm headed for my caulking gun.
Randy
>
> Hi All,
>
> I don't get it about "front plate" protection and front plate separation
> that can be the result of using radial tires vs.. bias ply.
>
> The only thing that I can imagine that could cause the front plate to
> separate from the frame is flexing of the "A" frame with the pivot point
> located well behind the front plate. This assumes that the plate is the
> angle iron that extends about 9 inches up behind the outer skin and has a
> double row of rivets to bond it to the skin. The foot of the angle iron
> extends about an inch under the floor, inside the aluminum "U" channel
that
> secures the upper structure to the floor/frame with rivets and bolts.
(see
> small attached sketch)
>
> I can imagine that the reason for the separation does not have anything to
> do with tires or the equalizer hitch assembly. I've noted severe
corrosion
> (rust) of the washers that secure the rivet heads (both top and bottom)
that
> bind the upper body to the frame. I recall that there are 5 rivets.
> Additionally, there are about five 1/4 X 20 X 3 inch bolts that secure the
> floor to the frame in the same vicinity. The ten bolts/rivets pass
through
> the foot of the angle iron that may be the referenced "front plate". If
> this the point of separation, the flex may contribute, but the root of the
> problem is failure of the fasteners from corrosion.
>
> I've noticed a similar problem with pop-type rivets where the pull stem is
> steel in an aluminum rivet. The corrosion eventually causes the rivet to
> fail (these hold the trim strip and banana curve and most of the belly
pan).
> I have NOT noticed any deterioration of the "buck-type" rivets that are
used
> through out the A/S to fasten aluminum to aluminum. However, the vertical
> section of the angle IRON is riveted to the aluminum skin with aluminum
> rivets. It's possible that electrolysis could compromise the double row
of
> rivets.
>
> It seems that the specific point of separation must be identified. Either
> the vertical plate or the foot under the floor. It's logical that once
the
> fasteners are weakened in either location, the soft aluminum would
> eventually fail. Same seems true for the rivets that bind the aluminum
"U"
> channel to the floor/frame. If the rivets through the foot of the angle
> iron are compromised by corrosion, it is most assured that the floor is
> rotted and soft. This would allow the foot to move and eventually cause
> failure of the rivets.
>
> All this said, it's strictly my opinion that tires and flexing of the "A"
> frame may contribute to separation of the "plate" (assuming I've properly
> identified what the plate is); however, the cause is corrosion from water
> where it shouldn't be. To me, this makes caulking of the banana curve
seam
> under the trim strip and other seams around the "A" frame cutouts a
critical
> owner maintenance task. Much like maintenance caulking roof openings.
>
> I noted the severe corrosion of these fasteners in both the front and rear
> of my '69 Safari when I opened the inner skin to replace sections of
> flooring. Associated with this corrosion was near total disintegration of
> the floor pinched between the frame/angle iron/aluminum "U" channel.
>
> It seems that once the rivets/fasteners are compromised, protecting the
> "plate" by taking it easy only delays a future catastrophe. My choice is
to
> be sure the fasteners are not subjected to the elements that cause
corrosion
> and floor rot. I would advise A/S restorers to pay particular attention
to
> these fasteners.
>
> The small sketch is attached to show the rear connection; however, it is
> nearly identical to the front connection and might help visualize what I
> tried to describe.
>
> Joy
>
>
>
>
>
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