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Rod end bearings...p. 11-07& p. 44-05

Tony_T

Well Known Member
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Rod end bearings...p. 11-07 & p. 44-05

There is a new thread in General Discussion that raises the issue of rod end bolts not being correctly tight on the bearings so that the bearings do the work.

During an ACI in May, I found two places on the 12 where bolts supplied in the kit are slightly too long and when torqued bottom out on the threads before the bearing center is clamped and is actually working.
1. The AST pushrod end bearing AN3-10A bolt:
i-5WTQv7z-M.jpg

I found this to be true on my 12 and one other flying 12 that I checked.

2. The An3-14A bolt furnished with the auto pilot kit to attach the roll servo pushrod, note the amount of threads showing:
i-DtsJjtq-M.jpg

I emailed Van's about this one in May, so it may have been corrected since then. There was a drawing change in May, prior to my email, but does not address the issue. I have not checked this on another plane to verify, maybe someone building who has easy access to the roll autopilot pushrod could check and report.
On both of these I installed one additional washer to get the bolts to tighten on the bearings.

I should have posted about this earlier, sorry :eek:. The AST bolt is easy to check, the autopilot bolt, less easy but not too bad to get to.

Tony
 
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I've always used Van's call out on bolts and rivets lengths as a guide, adjust as required to ensure correct fit/clamp up etc..
 
There is a new thread in General Discussion that raises the issue of rod end bolts not being correctly tight on the bearings so that the bearings do the work.

i-DtsJjtq-M.jpg

I emailed Van's about this one in May, so it may have been corrected since then. There was a drawing change in May, prior to my email, but does not address the issue. I have not checked this on another plane to verify, maybe someone building who has easy access to the roll autopilot pushrod could check and report.
On both of these I installed one additional washer to get the bolts to tighten on the bearings.

I should have posted about this earlier, sorry :eek:. The AST bolt is easy to check, the autopilot bolt, less easy but not too bad to get to.

Tony

Shouldn't there be a larger washer on the bolt head to prevent the rod end from coming off if the bearing wears out of the fitting ?
 
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Shouldn't there be a larger washer on the bolt head to prevent the rod end from coming off if the bearing wears out of the fitting ?

The large washer (5702-475-48 Z3) under the head of the bolt is there, look carefully.
 
Yes, I did see that washer, it just looks like a small washer that isn't big enough to prevent it from falling through. I thought it needed to have a larger diameter washer there as the photo makes it appear as if it is too small.
 
Isn't that bolt upside down anyway? Or is the photo not oriented right? Also isn't more than two threads showing past the nut a No No.
 
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Isn't that bolt upside down anyway? Or is the photo not oriented right? Also isn't more than two threads showing past the nut a No No.

Minimum is 1 thread, no max as long as the nut has not run out of threads and the assembly provides proper clamp-up.
 
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What else is wrong...

Isn't that bolt upside down anyway? Or is the photo not oriented right? Also isn't more than two threads showing past the nut a No No.

The photo is shot straight down; the bolt is horizontal.

The one thing no one has mentioned is that the torque seal is incorrectly applied. It should straddle the nut and the structure so that if the whole bolt and nut are turning the issue would be caught by an ACI. Right?:eek:

The amount of threads showing is definitely a give-away that the nut has bottomed out and the clamp up of the joint is questionable.

The point of the original post was to alert us RV-12ers who are a bit spoiled by the excellent plans and are going by the ELSA mantra that you must build according to the plans and not change anything. Therefore, most of us are probably trusting that the plans are 100% correct as we build along, probably not realistic.

Tony
 
Tony, I checked my AST rod end bolt yesterday and sure enough, it was bottomed out on the threads as you reported! I added a washer for a temporary fix and will replace the bolt (and check the one on the servo as well) at Condition Inspection time in January.

John
 
CAUTION: Bolts are not "tight" if they still freely spin in the assembly, adjust the bolt grip length or add up to 2 washers as required. Chances are if more than 4 threads are showing the bolt is to long and/or you need to add washers to adjust.

From 43-13:GRIP LENGTH. In general, bolt grip
lengths of a fastener is the thickness of the
material the fastener is designed to hold when
two or more parts are being assembled. Bolts
of slightly greater grip length may be used,
provided washers are placed under the nut or
bolthead. The maximum combined height of
washers that should be used is 1/8 inch. This
limits the use of washers necessary to compensate
for grip, up to the next standard grip size.
 
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THANKS Tony!! Van's has NOT corrected the bolt length for the autopilot rod end bearing for roll control. I found the same a day ago when I was installing the foll servo and the associated linkage. The nut bottoms out on the AN3 bolt shoulder. I added a second washer under the nut.

Thought others may have noticed, and, I was right!

Hopefully Scott will take note. I plan on submitting a report to Van's. Will also check the trim tab rod end for the same problem.

Also, DO NOT UNDERSTAND why Van's specifies a AN364 (thin) nut here. There IS NOT a clearance issue and would think and AN365 (normal) nut would provide additional friction for this VERY CRITICAL application. The AN364 (thin) nut is specified on both flaperon rod end bearings.
 
Confirm on AST

Re: 11-04, Dwg Rev 0 was shipped with kit no. 682. Step 3, Figure 3 calls out AN525-8R8 for joining the AST segments. The unthreaded portion of the shank extends clear of the parts as mentioned in this thread. I substituted -7R7 which seems to be a better fit. I verified that there are no threads at the shear plane.
 
....
Also, DO NOT UNDERSTAND why Van's specifies a AN364 (thin) nut here. There IS NOT a clearance issue and would think and AN365 (normal) nut would provide additional friction for this VERY CRITICAL application. The AN364 (thin) nut is specified on both flaperon rod end bearings.

The thin nut is the correct part for bolts loaded in shear like these.

I imagine that Vans used them to save an ounce or two on the empty weight.

The friction locking of the thin and thick nuts is provided by the nylon insert and is identical for both nuts.
 
Thanks Gil. Do not quite understand why a thin nut is better in shear than a thick nut. Maybe elaborate. Seems counter intuitive. Believe you that the thin has the same gripping/friction power of the thick.
 
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